polypeptide synthesis

Question 1

stages of protein synthesis

Answer 1

1. transcription of gene in the nucleus, forms mRNA
2. processing of mRNA
3. translation of mRNA in ribosome, polypeptide chain is formed
4. modification of protein

Question 2

transcription

Answer 2

1. enzyme helicase breaks H bonds between the bases in specific region of DNA, strands separate

2.RNA polymerase binds to promoter region at 5’ end of antisense/template strand

3. RNA polymerase moves in 5’ to 3’ direction forming complementary mRNA strand with free RNA nucleotides
4. mRNA strand separates once formed, double-stranded DNA recoils behind it

5.once terminator region is reached, RNA polymerase detach, DNA no longer transcribed, mRNA leaves nucleus

Question 3

start codon

Answer 3

AUG, methionine

Question 4

similarities in DNA replication and transcription

Answer 4

DNA unwinds and unzips

Helicase enzymes

Template DNA

Complementary base pairing

Hydrogen bonds

Free, activated nucleotides

Polymerase enzymes

Question 5

differences in replication and transcription

Answer 5

Only a small section of DNA unzips during
transcription

Both strands act as templates in
replication; only one in transcription

RNA vs DNA free nucleotides

RNA polymerase vs DNA polymerase

Different helicase enzymes

Products are two new daughter strands
of DNA in replication and one mRNA
strand in transcription

mRNA leaves nucleus whereas the new
DNA strand remains bound to the
template strand

Question 6

tRNA

Answer 6

made in the nucleolus and leave via a nuclear pore to enter the cytoplasm. Here they become attached to a specific amino acid
single-stranded RNA polynucleotides that fold into a three-looped hairpin structure

Question 7

Translation

Answer 7

1. mRNA attaches to the ribosome at the start codon AUG, end of 3’
2. tRNA molecules contain anticodon that bind with complementary codon on the mRNA
3. ribosome moves along mRNA, complementary anticodon on tRNA will bind to mRNA codon, peptide bond forms between amino acids

4.another tRNA molecule enters ribosome carrying amino acid, fist tRNA is discharged from ribosome

5. polypeptide is released from ribosome and must undergo folding and further processing before use

Question 8

mutation

Answer 8

change in the amount or structure of DNA

Question 9

Genetic mutations

Answer 9

change in the base sequence of a gene, which can cause a change in the polypeptide chain.

It is caused by errors that occur during DNA replication.

The mutation rate in humans is low because there are enzymes that check the bases and correct any errors.

Mutations are random and spontaneous.

They can be harmful, are sometimes beneficial and often have no effect at all.