4.2 TRANSCRIPTION AND TRANSLATION

Question 1

describe how mRNA is formed by transcription in eukaryotes

Answer 1

1. hydrogen bonds break between complementary base pairs so strands of DNA separate
2. only 1 DNA strand acts as a template
3. RNA nucleotides complementary base pair with exposed bases on template strand
4. so uracil with adenine, adenine with thymine and cytosine with guanine
5. RNA polymerase catalyses condensation reactions between RNA nucleotides to form phosphodiester bonds
6. forming pre-mRNA
7. introns spliced out of pre-mRNA to form mRNA

Question 2

describe how a polypeptide is formed by translation of mRNA

Answer 2

1. mRNA associates/binds to ribosome
2. ribosome moves to the start codon
3. complementary tRNA anticodon binds via complementary base pairing to mRNA codon
4. tRNA brings a specific amino acid
5. peptide bond forms between amino acids in a condensation reaction
6. via the action of RNA polymerase
7. amino acids join using ATP
8. tRNA molecule detatches
9. ribosomes can attach to 2 codons at once
10. ribosome moves along to next codon to form the polypeptide

Question 3

what is the proteome of a cell

Answer 3

the range/number of different proteins the genome can code for

Question 4

structural differences between an mRNA and tRNA molecule

Answer 4

1. mRNA has linear shape whereas tRNA has clover leaf shape/tRNA has hydrogen bonds between complementary base pairs whereas mRNA doesn’t
2. tRNA has an mRNA binding site whereas mRNA doesn’t
3. mRNA has more nucleotides/ is longer than tRNA
4. mRNA has codons whereas tRNA has anticodons