I need to know/understand the material though, bc the mark schemes won't help with application based questions but yes, I plan on doing that later- I have 12 hours, so there's still enough time.(Original post by ozzie2)
Maybe you should try to learn some mark schemes for papers if you don't have enough time to do them, it's not the best way of revision but it may be a faster way and you get a feel for the exam in a shorter time.
AQA Biology Unit 2 with Anon_98.
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- 07-06-2016 01:05
- 07-06-2016 01:14
Properties of triplet code?
Degenerate = each AA has more than one triplet code, non-overlapping = each base is read only once, stop codes = occur at end of sequence – do not code for an AA
How does a mutation lead to a non-functional enzyme?
Alright, so like before:
-change in base sequence
−change in sequence of triplet codes
−change in sequence of AAs
BUT THEN that means that there is a ..
−change in primary structure
−change in tertiary structure
−change in active site shape
−substrate no longer complementary
−can no longer form enzyme-substrate complex
Okay so if there's a mutation, that alters the base sequence which alters the sequence of triplet codes and therefore the amino acid sequence too. But since the primary structure is made up of a sequence of amino acids that changes, and the primary structure makes up the tertiary so that changes and the active site changes shape, the enzyme is no longer complementary to the substrate which means an enzyme substrate complex caanot form which is why the enzyme cannot function. hm.
- 07-06-2016 01:22
What is a chromosome?
Formed during interphase - made of 2 identical chromatids joined by a centromere (carries 2 copies of the same DNA molecule)
A chromosome is formed during INTERPHASE.
Interphase is where the chromosome is formed.
It's made up of two identical chromatids joined together by a centromere.
That is two identical chromatids.
2 identical chromatids + centromere.
Okay, so a chromosome is formed during interphase and it's made up of 2 identical chromatids which are joined by a centromere. Hm. yes.
- 07-06-2016 01:24
It looks like thisssssssssss:
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- 07-06-2016 01:25
What is a homologous pair of chromosomes?
a pair of chromosomes, 1 from mother, 1 from father, carries same genes but different alleles – there are 23 pairs
Okay, so a homologous chromosome is literally just a pair of chromosomes. 1 from mommmmmmmmmmmmmmy and one from father. They carry the same genes but different alleles and there are 23 pairs. Cool.
- 07-06-2016 01:27
What does cell cycle (mitosis) produce?
2 genetically identical cells, diploid (full set of dna)
So the cell cycle produces two genetically identical cells. Diploid. Which is a full set of DNA.
Two genetically identical cells.
The cell cycle produces two genetically identical cells.
- 07-06-2016 01:30
- 07-06-2016 01:31
Benefit of Mitosis?
Growth and repair of tissues.
Just growth and repair.
The benefit is that it provides the growth + repair of tissues.
- 07-06-2016 01:32
Ohmyg, the battery's going to die.
- 07-06-2016 01:35
Okay, we're back lol. But ew, I had to change spots + I was pretty comfortable. *criiiiiiiiiiiiiiiiiiiiii*
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- 07-06-2016 01:36
- 07-06-2016 01:40
Stages of Cell Cycle?
There are three stages of the cell cycle and it goes like:
So, the three stages of the cell cycle are Interphase, Mitosis and Cytokinesis.
lol. :'3Last edited by Anon_98; 07-06-2016 at 01:43.
- 07-06-2016 01:41
- 07-06-2016 01:46
G1: protein synthesis
S: DNA replication
G2: organelle synthesis
Alright, so within interphase you have 3 stages and they are G1 phase, S phase and the G2 phase.
G1 is protein synthesis, then S is DNA replication then G2 is organelle synthesis.
Okay, so we have protein synthesis on the left, then DNA replication in the middle then organelle synthesis.
P synthesis -G1
Replication - S
O synthesis - G2.
- 07-06-2016 01:59
Prophase: dna coils to form chromosomes, nucleus breaksdown, spindle fibres form
Metaphase: chromosomes line up in middle of cell and attach to spindle fibre via centromere
Anaphase: spindle fibres pull, centromere splits, sister chromatids move to opposite sides
Telophase: chromatids uncoil, nucleus reforms (left with 2 identical nuclei)
Prophase, Metaphase, Anaphase, Telophase.
Please Make Anon ..Tall?
Right, so we have Prophase first and the DNA coils to form chromosomes then the Nucleus breaks down then the spindle fibres form.
So DNA coils = forms chromosomes = nucleus breaks down = spindle fibres form.
The DNA coils to form the chromosomes then the nucleus breaks down and the spindle fibres form. Okay.
Then we have Metaphase and chromosomes line up in middle of cell and attach to spindle fibre via centromere. So they just walk across and all line up into the middle of the cell and attach themselves to the spindle.
Line up + attach. Okay.
Then we have Anaphase - and this is when the spindle fibres pull, centromere splits, sister chromatids move to opposite sides.
So the spindle fibres pull, the centromere splits and the sister chromatids move to the opposite sides. The fibres pull the centromere splits + they split apart. Pull, Split, Move. Okay.
Finally we have Telophase.chromatids uncoil, nucleus reforms .
Alright so let's go again, overall:
The DNA coils + forms the chromosomes, the nucleus breaks down + the fibres form.
THEN, the chromosomes all walk up to the middle of the cell and the line up and attach themselves. Well, they don't really walk up lmao but they basically go to the middle.
THEN the spindle fibres are like "nooo" and they pull, which causes the centromere to split and the sister chromatids move to opposite sides of the cell.
THEN the chromatids uncoil and the nucleus reforms.
- 07-06-2016 02:01
What happens to DNA mass in mitosis?
Okay so the mass of the DNA halves in mitosis.
In Mitosis, the mass of DNA halves.
- 07-06-2016 02:03
What happens to Chromosome number in mitosis?
Stays the same
The chromosome number in Mitosis stays the same.
Basically nothing happens.
- 07-06-2016 02:04
Okay so I think mitosis is now done + stuff.
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- 07-06-2016 02:13
What does Meiosis produce?
produces gametes, 4 genetically different cells, haploid (half the dna)
Haploid. = MEIOSIS.
How does Meiosis produce variation?
Crossing Over and Independent Assortment.
Okay, so variation is produced bc by crossing over + independent assortment.
What is crossing over?
Occurs in Prophase I of Meiosis I, homologous pairs of chromosomes wrap around each other and swap equivalent sections of chromatids – produces new combination of alleles.
Alright, so it happens in Prophase I of Meiosis I and yeah.
What is independent assortment?
in Anaphase I of Meiosis I – the homologous pairs of chromosomes separate, in Anaphase II of Meiosis II – the chromatids separate.
Independent assortment produces a mix of alleles
Okay so it happens in Anapahse both in I and 2 when the chromosome pairs separate and when the Chromatids separate.
- 07-06-2016 02:15
Difference between Metaphase I and Metaphase II?
Metaphase I = homologous pairs line up in centre of cell (23 pairs),
Metaphase II = single chromosomes line up in middle of cell (23 chromosomes at this stage)
Alright, so with Metaphase I, the pair line up in the centre whereas with II it's the single chromosomes that line up. Not the homologous pairs bc they've basically been split up.