3.4.2 DNA and protein synthesis

Question 1

where does transcription occur in a cell?

Answer 1

Nucleus

Question 2

Name the enzymes involved in transcription and explain their function

Answer 2

DNA helicase - Unwinds DNA
RNA polymerase - Adds complementary nucleotides

Question 3

What happens when the RNA polymerase attaches to the DNA at the start codon?

Answer 3

H bonds between DNA strands break

Question 4

what happens when RNA polymerase reaches a stop codon?

Answer 4

• stops producing mRNA
• detaches from DNA

Question 5

what is a codon?

Answer 5

a triplet of bases which codes for an amino acid

Question 6

explain why the term degenerate is used to describe the DNA code

Answer 6

multiple codons code for the same amino acid

Question 7

what is the product of translation?

Answer 7

polypeptide chain (protein)

Question 8

where does translation take place?

Answer 8

ribosome

Question 9

describe the structure of tRNA

Answer 9

amino acid binding site
anti codon
clover leaf shape

Question 10

what is an anti codon?

Answer 10

the complimentary triplet on tRNA to a codon on mRNA

Question 11

which part of tRNA binds to the mRNA?

Answer 11

anti-codon binding site

Question 12

what are the stop and start codons for?

Answer 12

triplets to tell the cell to stop or start the production of a protein

Question 13

what are the 2 main functions of DNA?

Answer 13

carry genetic code
and instructions for making proteins

Question 14

What happens during transcription?

Answer 14

RNA polymerase converts DNA to mRNA by creating a complimentary strand

Question 15

what happens to mRNA after it leaves via the nuclear pore?

Answer 15

binds to ribosome on the RER

Question 16

What happens at the RER?

Answer 16

translation of mRNA into a polypeptide

Question 17

what 2 enzymes are involved in the semi- conservative replication of DNA?

Answer 17

DNA helicase
DNA polymerase

Question 18

what is the genome?

Answer 18

The complete set of genetic information contained in cells of an organism

Question 19

what is the proteome?

Answer 19

The complete set of proteins that can be produced by a cell

Question 20

Describe the structure of messenger RNA (mRNA).

Answer 20

A long, single strand. Its base sequence is complementary to the DNA it was transcribed from.

Question 21

suggest the advantages of using mRNA rather than DNA for translation.

Answer 21

• shorter & contains uracil = breaks down quickly so no excess polypeptide forms
• single-stranded & linear = ribosome moves along strand & tRNA binds to exposed bases
• contains no introns

Question 22

what is produced by transcription?

Answer 22

mRNA

Question 23

outline the process of transcription.

Answer 23

• DNA uncoils into two strands with exposed bases. One used as a template.
• free nucleotides line up next to their complementary bases, and are joined together by RNA polymerase

Question 24

what happens to mRNA after transcription?

Answer 24

In eukaryotic cells, pre-mRNA must be spliced to remove introns, leaving only the coding regions. Then it moves out of the nucleus and attaches to a ribosome.

Question 25

outline the process of translation.

Answer 25

• the anti-codon of tRNA attaches to complementary bases on the mRNA.
• Amino acids bonded to tRNA form peptide bonds, continuing to form a polypeptide chain until a stop codon is reached
• process requires ATP