Storing and Using Genetic Information

Question 1

DNA replication is said to be

Answer 1

• Semi conservative

- Bi directional

Question 2

What does semi-conservative mean?

Answer 2

• Each half of DNA molecule is old, the other is new

Question 3

What does bi directional mean?

Answer 3

Strands are created in opposite directions

Question 4

What enzyme unzips the double helix?

Answer 4

DNA Helicase

Question 5

What enzyme adds new nucleotides?

Answer 5

DNA Polymerase

Question 6

In which direction is the new strand formed? C’what to C’what?

Answer 6

C’5 to C’3

Question 7

What happens with the other strand?

Answer 7

• It first attaches a primer

- Then a polymerase enzyme adds nucleotides

Question 8

What is the role of DNA ligase in the formation of the lagging strand?

Answer 8

• Joins fragmented segments together

Question 9

What are the discontinued fragments called before the action of DNA ligase?

Answer 9

Okazaki fragments

Question 10

What is a sequence of 3 bases called?

Answer 10

Codon

Question 11

What is the term given to the fact that a codon can refer to more than 1 amino acid?

Answer 11

Degenerate

Question 12

What is the start codon?

Answer 12

Methionine

Question 13

How does the sequence of codons stop?

Answer 13

A stop codon is in the sequence

Question 14

What happens after the sequence is transcribed?

Answer 14

Alternative splicing of exons to leave only introns

Question 15

What is attached to the mRNA to stop it from being broken down by enzymes?

Answer 15

• A cap is attached to the 5’ end

- A tail is attached to the 3’ end

Question 16

Where does translation occur in the cell?

Answer 16

Endoplasmic reticulum

Question 17

What is the first step in translation?

Answer 17

• Attachment of a small ribosomal subunit to the mRNA

Question 18

What happens in step 2

Answer 18

• Specific tRNA molecule carrying methionine binds to the corresponding codon on the mRNA

Question 19

What happens in step 3

Answer 19

The large unit of the ribosome joins the smaller one and the tRNA, the tRNA occupies the P section of the binding sites

Question 20

What happens in step 4

Answer 20

• Another tRNA comes along carrying the next amino acid

- It binds to the A site

Question 21

What happens as the ribosome moves along the code?

Answer 21

The tRNA in the P site leaves and the one in the A site takes its place

Question 22

What happens when the process reaches a stop codon?

Answer 22

The process stops and the polypeptide is released