Structure and replication of DNA

Question 1

What is DNA?

Answer 1

A nucleic acid

A macromolecule

Question 2

What is DNA made of?

Answer 2

Two polynucleotide chains

Question 3

What is each polynucleotide made up of?

Answer 3

Many nucleotides

Question 4

What does a nucleotide consist of?

Answer 4

5-carbon sugar (deoxyribose)
Nitrogen containing base
Phosphate group

Question 5

Name the four bases

Answer 5

Adenine
Thymine
Cytosine
Guanine

Question 6

What is a nucleoside?

Answer 6

Sugar + base

Question 7

What is the bond between the sugar and the base?

Answer 7

A glycosidic bond

Question 8

What is the bond between the sugar and the phosphate?

Answer 8

A phosphodiester bond

Question 9

Why is DNA described as anti-parallel?

Answer 9

The two strands run parallel to each other but in opposite directions

Question 10

How many hydrogen bonds are there between adenine and thymine?

Answer 10

Two

Question 11

How many hydrogen bonds are there between cytosine and guanine?

Answer 11

Three

Question 12

Which two bases are purine?

Answer 12

Adenine

Guanine

Question 13

Which two bases are pyramidine?

Answer 13

Cytosine

Thymine

Question 14

How does a purine base differ from a pyramidine base?

Answer 14

Purine bases have two rings

Pyramidine bases have one ring

Question 15

What is the major groove?

Answer 15

The space between two turns of the double helix

Question 16

What is the minor groove?

Answer 16

The space between two strands of DNA

Question 17

What is meant by the 5 prime end?

Answer 17

The 5 carbon sugars are asymmetrical

The side the 5th carbon is found is the 5 prime end

Question 18

Describe asexual reproduction in prokaryotes

Answer 18

Entire genome in one circular chromosome
The chromosome replicates once
Two chromosomes migrate to opposite ends of the cell
Cell divides
Daughter cells have 1 chromosome each

Question 19

Describe asexual reproduction in eukaryotes

Answer 19

DNA replicates during S phase
Gene expression occurs in G1 and 2
Nuclear division occurs in mitosis
Cell division occurs at the end of mitosis

Question 20

Why is DNA replication described as semi-conservative?

Answer 20

The strands separate

A new strand is made using an old strand as a template

Question 21

Which is the first enzyme involved in DNA replication?

Answer 21

Helicase unwinds the double helix DNA

Question 22

Which is the second enzyme involved in DNA replication?

Answer 22

Single-strand binding protein binds to and stabilises the single strand to keep DNA unwound

Question 23

Which is the third enzyme involved in DNA replication?

Answer 23

DNA primase adds ribonuceloside triphosphate to synthesise and RNA primer

Question 24

What is the fourth enzyme involved in DNA replication?

Answer 24

DNA polymerase proceeds in a 5’ to 3’ direction

Question 25

What rate does DNA polymerase work at?

Answer 25

1000 bases a second

Question 26

What 3 things does DNA polymerase rely on?

Answer 26

Template Primer All 4 nucleotides

Question 27

What is the fifth enzyme involved in DNA replication?

Answer 27

Exonuclease removes nucleotides from the end of a DNA strand | Has a 5' to 3' and 3' to 5' version

Question 28

What is the sixth enzyme involved in DNA replication?

Answer 28

Ligase joins ends of single DNA strands by making new phosphate bonds

Question 29

How does RNA differ from DNA?

Answer 29

Single stranded | Uracil instead of thymine

Question 30

What is the name given to the adding of nucleotides by DNA polymerase?

Answer 30

Elongation

Question 31

What does exonuclease remove?

Answer 31

The RNA primer

Question 32

What names are given to the two strands?

Answer 32

Leading and lagging

Question 33

What causes differences in the two strands?

Answer 33

DNA polymerase has to work 5' to 3'

Question 34

What happens to the lagging strand?

Answer 34

It is fragmented | These fragments are called Okazaki fragments

Question 35

How many origins of replication are there in prokaryotes and eukaryotes?

Answer 35

Prokaryotes have one | Eukaryotes have many

Question 36

What is the seventh enzyme involved in DNA replication?

Answer 36

Gyrase relaxes supercoils produced when the molecule is twisted during replication Also facilitates unwinding at the beginning

Question 37

What is the eight enzyme involved in DNA replication?

Answer 37

Telomerase uses a short RNA template to add short DNA repeats to the short ends of linear chromosomes when the last primer is removed using RNA template

Question 38

What is the name given to the point at which the double strand splits?

Answer 38

Replication fork