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Chapter 8

A level Biology Chapter 8 - DNA , genes etc

QuestionAnswer
Describe how mRNA is produced in the nucleus of a cell? [6 marks] DNA helicase unwinds sections of DNA reveals exposed nucleotides Strand acts as a template for RNA nucleotides to line up along DNA exposed bases Make RNA strand with complementary base pairing U replaces T RNA polymerase moves along joins up nucleotides
Role of ribosome in translation? Ribosome attaches to mRNA strand. tRNA with a complementary anticodon attaches to the codon on the mRNA. Ribosome moves along mRNA strand allowing tRNA molecules to bind to codons. Peptide bonds form between the amino acids.
Definition of degenerate? More than one triplet can be used for each amino acid.
Non overlapping definition? Each base is only used once.
Why is genetic code described as being universal? Same triplet and amino acids used for every organism.
Explain how organic bases help to stabilise the structure of DNA? Between organic bases there is hydrogen bonds between complementary bases in 2 strands. There is lots of hydrogen bond and therefore these provide strength.
The use of Stop codons? Stop translation and detach the chain
Advantage of showing genetic code as bas sequence of mRNA rather than triplets of DNA? no introns. DNA has 2 strands (dunno which strand to use) however mRNA only has 1 strand.
What is meant by a gene? A length of DNA; that codes for a single protein
Explain how a change in a sequence of DNA bases could result in a non-functional enzyme. Base substitution = change in amino acid produced; Different primary structure and therefore change in tertiary structure too; change in shape of active site. substrate no longer fits; enzyme substrate complex not formed; enzyme doesn't work.
During which part of the cell cycle are gene mutations most likely to occur? Interphase because its when DNA replication happens and is longest part of cycle.
Give two structural differences between a molecule of mRNA and tRNA? mRNA is single stranded with no H bonds but tRNA has a clover leaf shape with H bonds. mRNA has codons but tRNA has anticodons.
Compare and contrast the DNA in eukaryotic cells and prokaryotes? Eukaryotes = Has introns, Is linear, is longer, associated with histones, Prokaryotes = No introns, Circular, Shorter, not associated with histones. Similarities = Nucleotide structure is identical, Nucleotides joined by phosphodiester bonds.
Created by: ksatti12
 

 



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