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myah_94
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This is an AQA Biology AS unit 2 thread

Post anything...ask questions etc
P.s I would start studying+revising now

Here are some revision sites:
http://www.mrothery.co.uk/
http://getrevising.co.uk/ (you will have to sign up, won't take long)
http://www.s-cool.co.uk/a-level/biology

Past papers:http://web.aqa.org.uk/qual/gce/scien...-materials.php
Take a look at the 'reports on the examinations' as well

I strongly recommend the CGP book
http://www.amazon.co.uk/Level-Biolog...der_1847624235
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Flying Cookie
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The triplet code is based on the fact that 3 consecutive nucleotide bases in DNA (adenine, guanine, cytosine or thymine) code for one amino acid which is the building block of all proteins.

So the sequence ACCGTC may code for 2 amino acids. Note that there is no overlap in reading the sequence.

Do you have a particular question?
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myah_94
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(Original post by Flying Cookie)
The triplet code is based on the fact that 3 consecutive nucleotide bases in DNA (adenine, guanine, cytosine or thymine) code for one amino acid which is the building block of all proteins.

So the sequence ACCGTC may code for 2 amino acids. Note that there is no overlap in reading the sequence.

Do you have a particular question?
thnx for replying
i'm a bit confused as to why three bases code for one amino acid..there's 4 bases
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Flying Cookie
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(Original post by myah_94)
thnx for replying
i'm a bit confused as to why three bases code for one amino acid..there's 4 bases
There's no compelling reason why three bases code for an amino acid, and there's 4 bases... It's something rooted in biochemistry really. Well, for starters, there must be 4 bases because they are each coupled up with another due to their complementary shapes, so A-T and C-G makes sense... I guess the reason 3 bases code for an amino acid is because it's the minimum number which generates enough combinations to cover all potential amino acids reliably.
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myah_94
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(Original post by Flying Cookie)
There's no compelling reason why three bases code for an amino acid, and there's 4 bases... It's something rooted in biochemistry really. Well, for starters, there must be 4 bases because they are each coupled up with another due to their complementary shapes, so A-T and C-G makes sense... I guess the reason 3 bases code for an amino acid is because it's the minimum number which generates enough combinations to cover all potential amino acids reliably.
it sort of makes sense, im just overthinking it
thanks again
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sahdiya
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Hi I'm stuck on what I need to know about haemoglobin


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myah_94
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i haven't got up to that yet...i'm assuming you need to know all of it
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myah_94
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(Original post by sahdiya)
Hi I'm stuck on what I need to know about haemoglobin


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i haven't got up to that yet...i'm assuming you need to know all of it
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Shinusuke_Akki
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Hello everyone, I'm in the process of slowly writing up biology notes on the AQA AS Biology Unit 2 (for the exam in June 2013) would anyone be interested in these notes? I'd be quite happy to post them here if they would be of use to anyone ^^ (As an example of my notes here's my OCR AS Physics Unit 2 G482 thread - if you are taking physics too feel free to check it out http://www.thestudentroom.co.uk/show...299&p=41138935) Nice to meet you all, I hope we can all help each other understand our biology lessons better together ^^
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Neon-Soldier32
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(Original post by myah_94)
thnx for replying
i'm a bit confused as to why three bases code for one amino acid..there's 4 bases
One triplet would have been bred in through evolution.

There are 20 amino acids. If one base coded for an amino acid then there would be 4 to the power 1 - 4 - available amino acids. If 2 bases coded for an amino acid then there would be 4 to the power 2 - 16 - possible bases. However, there are 20 amino acids in total. So 3 bases for an amino acid mean 4 to the power 3 - 64 - possible amino acids can be coded for.

However, there are only 20 amino acids so more than one triplet codes for the same amino acid. This is said that DNA is degenerate.

Other important features of DNA are that it is:
- Universal across (for AQA spec) all organisms

Also, there are 4 bases as DNA has a double helix shape that runs anti-parallel i.e. on one chain the 5th carbon in the deoxyribose sugar is facing upwards but on the opposite chain the 3rd C is facing up.

There are 4 nucleotide bases as one strand of DNA is a template strip to which a 'coding' strip is produced. This coding strip codes for the polypeptide. 2 nucleotide bases have to be complementary to each other for this mechanism to work.

Pyrimidines have one C and N ring and are thymine and cytosine
Purines have two C and N rings are are guanine and adenine.

Complementary bases have to have 3 rings in total and hence cytosine (one ring) is complementary to guanine (two rings) and the two form two (I think) hydrogen bonds with each other. Also cytosine and guanine are complementary.

I know you didn't exactly as this, but it's good for me to revise it by writing it out.
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myah_94
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(Original post by Shinusuke_Akki)
Hello everyone, I'm in the process of slowly writing up biology notes on the AQA AS Biology Unit 2 (for the exam in June 2013) would anyone be interested in these notes? I'd be quite happy to post them here if they would be of use to anyone ^^ (As an example of my notes here's my OCR AS Physics Unit 2 G482 thread - if you are taking physics too feel free to check it out http://www.thestudentroom.co.uk/show...299&p=41138935) Nice to meet you all, I hope we can all help each other understand our biology lessons better together ^^
Hi yess pleaseee...notes would be great help
me too
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myah_94
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(Original post by Neon-Soldier32)
One triplet would have been bred in through evolution.

There are 20 amino acids. If one base coded for an amino acid then there would be 4 to the power 1 - 4 - available amino acids. If 2 bases coded for an amino acid then there would be 4 to the power 2 - 16 - possible bases. However, there are 20 amino acids in total. So 3 bases for an amino acid mean 4 to the power 3 - 64 - possible amino acids can be coded for.

However, there are only 20 amino acids so more than one triplet codes for the same amino acid. This is said that DNA is degenerate.

Other important features of DNA are that it is:
- Universal across (for AQA spec) all organisms

Also, there are 4 bases as DNA has a double helix shape that runs anti-parallel i.e. on one chain the 5th carbon in the deoxyribose sugar is facing upwards but on the opposite chain the 3rd C is facing up.

There are 4 nucleotide bases as one strand of DNA is a template strip to which a 'coding' strip is produced. This coding strip codes for the polypeptide. 2 nucleotide bases have to be complementary to each other for this mechanism to work.

Pyrimidines have one C and N ring and are thymine and cytosine
Purines have two C and N rings are are guanine and adenine.

Complementary bases have to have 3 rings in total and hence cytosine (one ring) is complementary to guanine (two rings) and the two form two (I think) hydrogen bonds with each other. Also cytosine and guanine are complementary.

I know you didn't exactly as this, but it's good for me to revise it by writing it out.
lovely explanation, thanks
C and G is 3 hydrogen bonds
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Shinusuke_Akki
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(Original post by myah_94)
Hi yess pleaseee...notes would be great help
me too
When I'm done typing them up I'll pop 'em up here then.

My first set of notes will be on the following: Variation, DNA Structure, The Triplet Code, DNA Chromosomes, DNA Replication, Mitosis. Meiosis & Genetic Variation and finally The Cell Cycle

I'm still trying to sift through my work and text books but when I've finished typing up a good set of notes I'll let you know.

Further note: If you'd like I can post each of those sub topics up as I write them, if not I'll wait till I have the full notes copied up.
Current progress of writing up notes: (5/8)
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myah_94
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(Original post by Shinusuke_Akki)
When I'm done typing them up I'll pop 'em up here then.

My first set of notes will be on the following: Variation, DNA Structure, The Triplet Code, DNA Chromosomes, DNA Replication, Mitosis. Meiosis & Genetic Variation and finally The Cell Cycle

I'm still trying to sift through my work and text books but when I've finished typing up a good set of notes I'll let you know.

Further note: If you'd like I can post each of those sub topics up as I write them, if not I'll wait till I have the full notes copied up.
Current progress of writing up notes: (5/8)
please would you post the sub topics you've done, i'd really appreciate it
thanks
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Shinusuke_Akki
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(Original post by myah_94)
please would you post the sub topics you've done, i'd really appreciate it
thanks
Will post in just a moment am just typing up a small paragraph first, I'll then keep adding to that post as I get more typed up so check back occasionally, I'll put a 'The End' at the end to let you know when its all up - This section of notes refers to sections 3.2.1 , 3.2.2 & 3.2.5 of the AQA specification available for free here: store.aqa.org.uk/qual/gce/pdf/AQA-2410-W-SP.PDF
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Part 1 - Variation, DNA, The Triplet Code, Chromosomes, DNA Replication, Mitosis, Meiosis, The Cell Cycle
Refers to sections 3.2.1 , 3.2.2 & 3.2.5 of the AQA specification available for free here: store.aqa.org.uk/qual/gce/pdf/AQA-2410-W-SP.PDF

VARIATION
Variation between different species is known as Interspecific Variation.
Variation within a species is known as Intraspecific Variation.

Sampling
In biology when measuring large amounts of highly variable data sampling is used to ensure more understandable data. Sampling is when a number of individuals are taken as a sample group of the population and are used to represent it. There are two main disadvantages to sampling but both can be overcome by taking certain precautionary measures:
Sampling Bias is when a selection of samples may be intentional or accidentally biased due to human selection. This can be avoided by using random sampling.
Chance is when the individuals selected (even when using random sampling) are not representative of the population. This can be avoided by using a large sample size (to reduce the probability of freak pieces of data affecting the samples) and using statistical analysis (to help determine whether variation is a result of chance or external factors).

Genetic Differences
Different genes cause organisms to have distinct genetic differences (e.g. blood type determined by a single gene). Mutations can occur causing changes to the genes and chromosomes passed on to the next generation. Both meiosis (which forms different gametes) and the fusion of gametes (when a random gamete from each parent is fused together forming a new variation) lead to gene differentiation.

Environmental Variation
Environmental Variation is when factors of variation are affected by the environment giving continuous grades of variety e.g. height - dependent on food availability in the organisms environment despite a predetermined gene indicating a general height.


DNA STRUCTURE
DNA
The shape of a DNA (Deoxyribonucleic Acid) polymer is known as a double helix. DNA contains information in the form of the genetic code which is responsible for inherited characteristics. There are 3 basic components that combine to form nucleotides (the monomers of DNA).

Nucleotide Structures
An individual nucleotide is made of a deoxyribose sugar, a phosphate group and an organic base.
There are 4 bases; Thyamine and Cytosine are single-ring bases whilst Adenine and Guarine are double-ring bases.
The 3 components that make up a nucleotide are joined by a condensate reaction. A single nucleotide is called a mononucleotide. Mononucleotides are joined in a condensate reaction (to form a dinucleotide); they are joined between the deoxyribose sugar of one and the phosphate group on the next.
https://twitter.com/shinusuke_akki/s...503425/photo/1
2 mononucleotides form a dinucleotide, more than 2 joined together form a polynucleotide.

DNA Structure
DNA is composed of 2 long strands of nucleotides (polynucleotides); joined by condensate reactions between complementary bases forming hydrogen bonds between the strands.

Base Pairing
Double-ring bases have longer molecules than single-ring bases, therefore a double-ring base will only form combine with a single-ring base so that all the connections between the 2 strands are the same length. Thyamine(T) only pairs with Adenine(A); Cytosine(C) only pairs with Guarine(G) they are known as having complementary bases. Thyamine and Adenine join by condensate reaction forming 2 hydrogen bonds; Cytosine and Guarine form 3.


THE TRIPLET CODE
Genes
A gene is a section of DNA that codes for a polypeptide. It is made up of a sequence of DNA bases; the specific sequence of bases is what codes for the poly peptide (determined by its primary structure - the unique amino acid sequence that makes a polypeptide). DNA controls the shapes of proteins (including enzymes and hormones etc.) as its genes code for the primary structure of polypeptides which in turn determines the poly peptides tertiary structure.

The Triplet Code
The triplet code determines the sequence of amino acids to be produces which creates a specific polypeptide. There are 20 amino acids that occur in proteins A single base has 4 possible combinations; AT, TA, CG, GC. It takes 3 sets of bases to code for an amino acid - giving the triplet code.
e.g. AUG (also known as the initiation code) produces the amino acid Methionine - every code starts with this as it indicates where translation from code to protein begins.
3 sets of bases give (4 x 4 x 4) 64 possible code combinations, as there are only 20 amino acids some of these code combinations must result in producing the same amino acid and this is why the code is known as a degenerate code.
Introns are sections in a DNA which don't code for amino acids, they are known as non-coding sequences and are the opposite of exons (sections of DNA that do code for amino acids). Introns are not transcribed in the transcription process.

Alleles
A gene is a section of DNA that codes to form a specific sequence of bases giving an organism a type of characteristic e.g. eye color. An allele is the specific characteristic and therefore is the code that the gene codes for e.g. blue eyes.
Organisms inherit alleles from both parents, they can be the same or different. In the case where there are two different alleles they will both code for different polypeptides and a different sequence.

Locus
The locus of a gene is its location on a chromosome or a DNA molecule.

DNA & CHROMOSOMES
DNA in eukaryotic cells form linear molecules which form structures called chromosomes.
DNA in prokaryotic cells are small and form circles called plasmids - they don't form chromosomes.

Chromosome Structures
Chromosomes are only visible when a cell divides. They have 2 threads called chromatids which join together at the centromere. A chromosome contains 1 molecule of DNA. DNA is wrapped around protein molecules forming a DNA-protein complex, which is coils and then folds to form loops, the loops further coil and condense to form the chromosome.

Homologous Chromosomes
2 gametes each provide a set of chromosomes when forming a new organism and so the new organism's chromosomes occur in pairs. The first formed cell has the chromosomes directly from the parent cells (the maternal and paternal chromosomes)and after that the cells duplicates also have homologous pairs (also duplicates of the originals).
The total number of chromosomes are known as the diploid number. e.g. Humans have 46 chromosomes and so have 23 homologous pairs.


THE CELL CYCLE

DNA Replication
When a cell divides, firstly the DNA is replicated (known as interphase) which ensures that both the daughter cells retain all the original genetic information. DNA is replicated when the original strand of DNA is split by DNA helicase (which breaks the hydrogen bonds between the complementary bases) into 2 strands of DNA. As the DNA is split free activated nucleotides join to their complementary bases which is catalyzed by DNA polymerase (the bottom 3 nucleotides). When all the nucleotides on both strands are joined with their complementary nucleotides, 2 complete and identical polynucleotide chains are formed. This method of replication is known as semi-conservative replication.
Once the DNA has been replicated (interphase) nuclear division occurs as either mitosis or meiosis, which is then followed by cell division, producing the daughter cells.
Mitosis produces 2 daughter nuclei that have identical DNA and number of chromosomes as the parent nucleus.
Meiosis produces 4 daughter nuclei, with half the number of chromosomes the parent possessed. The 4 daughter cells that are then produced are gametes (e.g. Sperm and Egg cells).

Mitosis
Mitosis is necessary for the growth of organisms and in particular from haploid cells (produced by the fusion of the organisms parents diploid cells) - the replication of the cells to produce identical cells, ensures the new organism carries the features held within the coding of the original haploid cells - these features were inherited from its parents.
After Interphase (Phase 0), which includes both the cells normal activity and DNA replication, the first phase of mitosis occurs.
Phase 1 - Prophase - Chromosomes become visible, the nuclear envelop disintegrates and the nucleolus disappears.
Phase 2 - Metaphase - Spindle fibers form and arrange the chromosomes along the center of the cell.
Phase 3 - Anaphase - Spindle fibers contract causing the 2 chromatids of each chromosome to be separated to opposite poles of the cell.
Phase 4 - Telophase - The chromatids at both poles become unclear, the nuclear envelope and nucleolus reform and the spindles disintegrate.
The cell then divides between the nuclei producing the 2 new daughter cells.

Meiosis
In meiosis the cells nucleus divides twice. Meiosis is important in the production of genetic variation. Variation is caused with 'Crossing Over and Genetic Recombination' (see below) and with 'Independent Segregation - when the homologous line up, which way the pairs line up (which side the paternal/ maternal line up on) is random and hence which chromosome from each pair the daughter cell also receives is random. As the pairs have the same genes but different alleles, when separated the daughter cells receive one of many different genetic combinations.
Division 1 - Homologous chromosomes pair up and and their chromatids wrap around each other, when they twist the tension may cause parts of them to break, swap and rejoin to the chromatid on the other chromosome of the pair. (This 'crossing over' and 'recombination' causes genetic combinations to be made and hence gives the offspring variation)
Division 2 - The chromatids in each daughter cell are separated. The cells both separate producing 4 haploid cells, each with half the number of chromatids than the original cell.

The Cell Cycle
The cell cycle has 3 stages:
Stage 1 - Interphase - The majority of the cell cycle where the cell undertakes it's normal activities:
‣ G1 - First Growth Phase - Proteins for cell organelle synthesis are produced.
‣ S - Synthesis Phase - DNA is replicated.
‣ G2 - Second Growth Phase - Cells organelles grow and divide whilst energy is stored.
Stage 2 - Nuclear Division - The cells nucleus divides, in either mitosis (producing 2 nuclei) or in meiosis (producing 4 nuclei)
Stage 3 - Cell Division - The cell then divides producing the same number of cells as nuclei produced in the previous stage.
Note: Cancer is a category of diseases, where there is damage to the gene that controls the cell cycle and mitosis, which results in a growth disorder of the cells. Tumors are where groups of cells which have growth disorders continuously grow.


GENETIC COMPARISONS
DNA determines the proteins (and enzymes) of an organism and hence its characteristics. Evolutionary relationships between species can be found by comparing the DNA of organisms.
Mutations results in changes to the DNA bases and so new species are created. The first generation of a new species will have more similar DNA that the species after several generations; so organisms with more similar DNA are more closely related.

DNA Hybridisation
DNA hybridisation is a method used to determine the similarities between DNA.
If DNA is heated the hydrogen bonds between complimentary bases break and the 2 DNA strands separate, when cooled over time DNA will reform.
2 species DNA are extracted, purified and cut into sections. 1 of the species DNA is marked or dyed, then mixed with the other species. The DNA strands are separated by heating, then cooled, allowing strands to join at complimentary bases. This can be with a strand from each species (hybridisation). The temperature is now increased in stages in an attempt to separate the Hybrid strands. At each stage, the amount the 2 strands are still connected is measured. The more complimentary bases, the more hydrogen bonds connecting the hybrid strands and the more difficult it is to separate them.
The higher temperature needed to separate the hybrid strands, the closer the 2 species are related.

DNA hybridisation has been used by the Royal Botanical Gardens, Kew to devise it's a new classification (the phylogenetic tree) for the families of flowering plants.

DNA codes for the sequence of amino acids (secondary structure) of proteins. The the amino acids sequence for a protein can be found for 2 different species and the similarities between them counted to find how closely they are related.
Proteins of different species can be compared using immunology, where the antibodies of 1 species will respond to the antigens of another.
Serum 1 extracted from species 1 is injected into species 2.
Species 2 produces antibodies (A) to the antigen sites (a) from serum 1.
Serum 2 is extracted from species 2.
Serum 2 produces antibodies (A).
Serum 3 extracted from species 3 is mixed with serum 2.
The antibodies (A) from serum 2 will respond to any antigens similar to antigens (a), which forms a precipitate.
Species with more similar antigens would form more precipitate, indicating that they are more closely related.

THE END OF PART 1/5
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myah_94
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(Original post by Shinusuke_Akki)
Part 1 - Variation, DNA, The Triplet Code, Chromosomes, DNA Replication, Mitosis, Meiosis, The Cell Cycle
Refers to sections 3.2.1 , 3.2.2 & 3.2.5 of the AQA specification available for free here: store.aqa.org.uk/qual/gce/pdf/AQA-2410-W-SP.PDF

VARIATION
Variation between different species is known as Interspecific Variation.
Variation within a species is known as Intraspecific Variation.

Sampling
In biology when measuring large amounts of highly variable data sampling is used to ensure more understandable data. Sampling is when a number of individuals are taken as a sample group of the population and are used to represent it. There are two main disadvantages to sampling but both can be overcome by taking certain precautionary measures:
Sampling Bias is when a selection of samples may be intentional or accidentally biased due to human selection. This can be avoided by using random sampling.
Chance is when the individuals selected (even when using random sampling) are not representative of the population. This can be avoided by using a large sample size (to reduce the probability of freak pieces of data affecting the samples) and using statistical analysis (to help determine whether variation is a result of chance or external factors).

Genetic Differences
Different genes cause organisms to have distinct genetic differences (e.g. blood type determined by a single gene). Mutations can occur causing changes to the genes and chromosomes passed on to the next generation. Both meiosis (which forms different gametes) and the fusion of gametes (when a random gamete from each parent is fused together forming a new variation) lead to gene differentiation.

Environmental Variation
Environmental Variation is when factors of variation are affected by the environment giving continuous grades of variety e.g. height - dependent on food availability in the organisms environment despite a pre-determined gene indicating a general height.


DNA STRUCTURE

DNA
The shape of a DNA (Deoxyribonucleic Acid) polymer is known as a double helix. DNA contains information in the form of the genetic code which is responsible for inherited characteristics. There are 3 basic components that combine to form nucleotides (the monomers of DNA).

Nucleotide Structures
An individual nucleotide is made of a deoxyribose sugar, a phosphate group and an organic base.
There are 4 bases; Thyamine and Cytosine are single-ring bases whilst Adenine and Guarine are double-ring bases.
The 3 components that make up a nucleotide are joined by a condensate reaction. A single nucleotide is called a mononucleotide. Mononucleotides are joined in a condensate reaction (to form a dinucleotide); they are joined between the deoxyribose sugar of one and the phosphate group on the next.
pic.twitter.com/77J3VjSZ
2 mononucleotides form a dinucleotide, more than 2 joined together form a polynucleotide.

DNA Structure
DNA is composed of 2 long strands of nucleotides (polynucleotides); joined by condensate reactions between complementary bases forming hydrogen bonds between the strands.

Base Pairing
Double-ring bases have longer molecules than single-ring bases, therefore a double-ring base will only form combine with a single-ring base so that all the connections between the 2 strands are the same length. Thyamine(T) only pairs with Adenine(A); Cytosine(C) only pairs with Guarine(G) they are known as having complementary bases. Thyamine and Adenine join by condensate reaction forming 2 hydrogen bonds; Cytosine and Guarine form 3.


THE TRIPLET CODE

Genes
A gene is a section of DNA that codes for a polypeptide. It is made up of a sequence of DNA bases; the specific sequence of bases is what codes for the poly peptide (determined by its primary structure - the unique amino acid sequence that makes a polypeptide). DNA controls the shapes of proteins (including enzymes and hormones etc.) as its genes code for the primary structure of polypeptides which in turn determines the poly peptides tertiary structure.

The Triplet Code
The triplet code determines the sequence of amino acids to be produces which creates a specific polypeptide. There are 20 amino acids that occur in proteins A single base has 4 possible combinations; AT, TA, CG, GC. It takes 3 sets of bases to code for an amino acid - giving the triplet code.
e.g. AUG (also known as the initiation code) produces the amino acid Methionine - every code starts with this as it indicates where translation from code to protein begins.
3 sets of bases give (4 x 4 x 4) 64 possible code combinations, as there are only 20 amino acids some of these code combinations must result in producing the same amino acid and this is why the code is known as a degenerate code.
Introns are sections in a DNA which don't code for amino acids, they are known as non-coding sequences and are the opposite of exons (sections of DNA that do code for amino acids). Introns are not transcribed in the transcription process.


DNA & CHROMOSOMES
DNA in eukaryotic cells form linear molecules which form structures called chromosomes.
DNA in prokaryotic cells are small and form circles called plasmids - they don't form chromosomes.

Chromosome Structures
Chromosomes are only visible when a cell divides. They have 2 threads called chromatids which join together at the centromere. A chromosome contains 1 molecule of DNA. DNA is wrapped around protein molecules forming a DNA-protein complex, which is coils and then folds to form loops, the loops further coil and condense to form the chromosome.

Homologeous Chromosomes
2 gametes each provide a set of chromosomes when forming a new organism and so the new organism's chromosomes occur in pairs. The first formed cell has the chromosomes directly from the parent cells (the maternal and paternal chromosomes)and after that the cells duplicates also have homologous pairs (also duplicates of the originals).
The total number of chromosomes are known as the diploid number. e.g. Humans have 46 chromosomes and so have 23 homologeous pairs.

Alleles
A gene is a section of DNA that codes to form a specific sequence of bases giving an organism a type of characteristic e.g. eye colour. An allele if the specific characteristic and therefore code that the gene codes for e.g. blue eyes.
Organisms inherit alleles from both parents, they can be the same or different. In the case where there are two different alleles they will both code for different polypeptides and a different sequence.


DNA REPLICATION

When a cell divides, firstly the DNA is replicated (known as interphase) which ensures that both the daughter cells retain all the original genetic information. DNA is replicated when the original strand of DNA is split by DNA helicase (which breaks the hydrogen bonds between the complementary bases) into 2 strands of DNA. As the DNA is split free activated nucleotides join to their complementary bases which is catalyzed by DNA polymerase (the bottom 3 nucleotides). When all the nucleotides on both strands are joined with their complementary nucleotides, 2 complete and identical polynucleotide chains are formed. This method of replication is known as semi-conservative replication. Once the DNA has been replicated (interphase) nuclear division occurs as either mitosis or meiosis which is then followed by cell division giving the 2 cells.
thankyou!
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Shinusuke_Akki
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Ok added lots more to Part 1 - Genetics and Variation covering sections 3.2.1, 3.2.2, 3.2.5 of the AQA specification and have finally added a little of 3.2.9 in references to topics on genetic comparisons, DNA and proteins.

Later on this week I'll be trying to add Part 2 - Further Variation, Part 3 - Plants (we took a sudden turn in what we were learning and quickly looked a lot at plants, not saying much but just that I noted it after we were given some assessment dates, I am not promising nor am I stating anything, only saying this section might be worth looking over, if my suspicions on teachers behavior are anything to go by... but yeah then I'll post on Part 4 - Other organisms. The Final Part will be Part 5 on Adaption, Selection and Biodiversity. I've not checked out this bit yet and so Part 4 and 5 may not be posted until after this week but then that should be EVERYTHING!!!! *takes in a deep breath* So... who's looking forward to June 3rd? ^^ Oh yeah and results day on March 7th? :/
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(Original post by sahdiya)
Hi I'm stuck on what I need to know about haemoglobin


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I'll cover that in part 4 first thing, sorry I'd of written about all this sooner but ironically college prevents my learning and hence note writing... :/
If I get the chance I'll try to post about hemoglobin before the weeks over ^^
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(Original post by Shinusuke_Akki)
Ok added lots more to Part 1 - Genetics and Variation covering sections 3.2.1, 3.2.2, 3.2.5 of the AQA specification and have finally added a little of 3.2.9 in references to topics on genetic comparisons, DNA and proteins.

Later on this week I'll be trying to add Part 2 - Further Variation, Part 3 - Plants (we took a sudden turn in what we were learning and quickly looked a lot at plants, not saying much but just that I noted it after we were given some assessment dates, I am not promising nor am I stating anything, only saying this section might be worth looking over, if my suspicions on teachers behavior are anything to go by... but yeah then I'll post on Part 4 - Other organisms. The Final Part will be Part 5 on Adaption, Selection and Biodiversity. I've not checked out this bit yet and so Part 4 and 5 may not be posted until after this week but then that should be EVERYTHING!!!! *takes in a deep breath* So... who's looking forward to June 3rd? ^^ Oh yeah and results day on March 7th? :/
not looking forward to June 3rd lol
woah go on then, someone's doing well!
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