8.2

Question 1

What is the basic process of polypeptide synthesis?

Answer 1

1. DNA provides instructions
2. A complimentary part of the sequence of bases provided by the DNA is formed as pre-mRNA
   3.pre-mRNA is spliced to form mature mRNA
3. mRNA is used as a template to which complementary tRNA molecules attach to the amino acids they carry and are linked to form a polypeptide.

Question 2

what are the three types of RNA?

Answer 2

1. mRNA: messenger
2. tRNA: transfer
   3.rRNA: ribosomal

Question 3

what is mRNA? What is its structure? (6)

Answer 3

1. mRNA is used as a messenger to transfer the genetic code from the nucleus to the ribosome
2. mRNA is complementary to the DNA it codes for
3. single-stranded
4. associates with ribosomes
5. contains ribose not deoxyribose
6. it has uracil instead of thymine.

Question 4

what is transcription?

Answer 4

The process in which an RNA sequence is produced from a DNA template using the enzyme RNA polymerase

Question 5

describe the process of transcription (5 points)

Answer 5

1. DNA helicase breaks hydrogen bonds between the complementary bases on the DNA strand causing the two DNA strands to separate
2. The enzyme RNA polymerase binds to the DNA at the start of a gene
3. Free complementary RNA nucleotides found in the nucleus are exposed to one of the two DNA strands (antisense/template) from a 3prime to a 5prime direction
4. RNA polymerase joins nucleotides on the exposed template strand to form pre-mRNA
5. pre-mRNA is spliced to form mature mRNA before it is transported to the ribosomes

Question 6

why can’t DNA directly travel to the ribosomes? (2)

Answer 6

1. DNA is too large to pass though the nuclear pore
2. DNA might be degraded in the cytoplasm due to the presence of enzymes

Question 7

what are introns? what are exons?

Answer 7

Introns are the non-coding regions on the DNA strand.
Exons are the coding regions on the DNA strand.