protein synthesis

Question 1

where are proteins created?

Answer 1

on ribosomes

Question 2

give an overview of transcription

Answer 2

1. RNA polymerase attaches to a start codon on the gene
2. DNA helicase breaks the H bonds between bases on the double helix so the molecule unwinds and bases are exposed.
3. Free RNA nucleotides are attracted to exposed bases and line up to the complementary base.
4. RNA polymerase forms sugar phosphate bonds between nucleotides, forming the mRNA strand
5. Once modified, the mRNA leaves the nucleus

Question 3

what happens between transcription and translation?

Answer 3

splicing

Question 4

explain what happens when the mRNA is spliced

Answer 4

Following transcription, pre-mRNA has to be modified to become mRNA so that is can go through translation. The introns (non coding) are spliced out, leaving only exons on the strand

Question 5

which strand is mRNA complementary to?

Answer 5

template

Question 6

in a eukaryotic cell, transcription results in pre-mRNA but in prokaryotes mRNA is produced directly. Explain why

Answer 6

DNA in eukaryotic cells contains non coding regions/introns that must be spliced

Question 7

give 2 differences between the structure of mRNA and the structure of tRNA

Answer 7

1. tRNA is clover leaf, mRNA is a single strand
2. tRNA contains paired bases mRNA doesn’t

Question 8

where does translation occur?

Answer 8

at the ribosomes

Question 9

give an overview of translation

Answer 9

1. the mRNA attaches to a ribosome in the cytoplasm
2. the ribosome attaches to the start codon on the mRNA
3. a tRNA molecule with complementary anticodon to the start codon binds to the mRNA. It brings an amino acid with it
4. the ribosome moves along to the next codon, it can fit 2 at a time.
5. The 2 tRNA molecules are joined by a peptide bond. Requires ATP
6. this continues until the ribosome reaches a stop codon so it detaches and translation ends.

Question 10

what is the specific starting amino acid on the tRNA molecule in translation

Answer 10

methionine

Question 11

where does the polypeptide chain go after translation?

Answer 11

to the Golgi body for folding and modification

Question 12

what is the role of RNA polymerase in transcription?

Answer 12

forms sugar phosphate bonds between nucleotides to form mRNA

Question 13

what enzyme converts mRNA into cDNA?

Answer 13

reverse transcriptase