AQA BIOL5 ~ 17th June 2013 ~ A2 Biology

Can someone plz explain question 4cii after chapter 16 where it says give the sequence of the shortes DNA fragment produced in tube 2 thx

advantages and disadvantages for both in vivo and in vitro gene cloning??

Nvm i'm wrong can someone answer this too.


Posted from TSR Mobile

How can you determine when fertilisation is most likely to occur? When there is high level of progesterone, so the uterus lining is available for a fertilised egg to be embedded?

How can you determine when fertilisation is most likely to occur? When there is high level of progesterone, so the uterus lining is available for a fertilised egg to be embedded?

Actually i worked it out.

Find the complementary strand of DNA to this sequence and then the shortest strand will be up to the first C in the complementary strand.

because tube 2 has cytosine terminator.


Posted from TSR Mobile

im a bit stuck on transcription and translation... anybody got a bullet point form of what happens that has enough content in that i could learn from? or a decent youtube vid?

im a bit stuck on transcription and translation... anybody got a bullet point form of what happens that has enough content in that i could learn from? or a decent youtube vid?

Transcription:
- Occurs in the nucleus
- DNA stands are split by hydrogen bonds being broken by DNA helicase
- One of the strands acts as a template
- Individual RNA nucleotides align next to the template according to specific base pairing
- The difference being uracil replaces thymine
- RNA nucleotides are joined together by RNA polymerase
- This creates a strand of pre-MRNA which undergoes splicing (removes introns and joins together exons) and leaves through a nuclear pore to the cytoplasm to attach to a ribosome to undergo translation.

Translation:
- Occurs in a ribosomes in the cytoplasm
-Sequence of codons on mRNA is used to determine the sequence of amino acids in a polypeptide and works by:

- Each tRNA molecule has 3 exposed bases called an anti-codon.
- tRNA with the anticodon complimentary to the first mRNA codon will move towards the mRNA strand bringing along the specific amino acid
- Other tRNA join in order determined by mRNA
- Amino acids join together by peptide bonds which require ATP.
- tRNA then begins to move away, leaving behind the amino acids. It collects another amino acid of the same kind so it can be reused.
- This continues until all codons have been read and it reaches a stop codon, and a specific polypeptide is then produced from the sequence of amino acids.
- The polypeptide then folds into secondary/tertiary structures.

FEel free to ask more if something doesnt make sense

In-vivo Cloning:

Advantages:
- Can produce mRNA, proteins and DNA.
- Able to modify the produced proteins/dna/mrna
- Relatively cheap
- Can use large fragments

Disadvantages:
- Slow
- Doesn't produce that much

In-vitro cloning

Advantages:
- Very fast
- Can produce lots of fragments

Disadvantages
- Expensive equipment
- Can only use small fragments
- can only produce DNA.

Simple revision cards I made for them. Some people say its helicase that breaks the H bonds, this is true in semi-conservative replication but for transcription my textbook just says it starts when RNA polymerase attaches to the DNA, and the H bonds break, doesn't specify helicase so you should be fine with or without it

Hope they help


Posted from TSR Mobile

is that the bare minimum that needs to be known? theres always extra stuff in textbooks and half the teachers notes never make any sense !! you are a geenius

I've taken 2 past papers, got 52/75 and then 61/75 without the essays. If I did like a low-average score essay would this be enough to get me an A? I've barely revised at all for the essay :/

I've taken 2 past papers, got 52/75 and then 61/75 without the essays. If I did like a low-average score essay would this be enough to get me an A? I've barely revised at all for the essay :/

This is from my class notes

Textbooks just waffle on sometimes so :P