Structure and Replication of DNA

Question 1

What is DNA

Answer 1

Polymer of 4 different nucleotides, arranged in a repeating fashion

Question 2

Each nucleotide consists of

Answer 2

alternating deoxyribose sugar and phosphate sections with one of 4 bases attached to sugar

Question 3

amino acid

Answer 3

sequence of 3 bases, amino acids are assembled to produce a particular protein

Question 4

Structure of DNA

Answer 4

Anti-parallel double-stranded helix held together by complementary base pairs

Question 5

Sugar phosphate back bone structure

Answer 5

5’ end at phosphate

3’ end at deoxyribose end

Question 6

5’ end

Answer 6

phosphate

Question 7

3’ end

Answer 7

deoxyribose

Question 8

what does DNA store

Answer 8

Genetic information

Question 9

Base sequence forms

Answer 9

Genetic code

Question 10

Genotype is determined by

Answer 10

Sequence of bases

Question 11

Need for DNA replication

Answer 11

Make identical copy

Question 12

Requirements for DNA replication

Answer 12

Original DNA template

Free nucleotides

DNA polymerase

Primers

Ligase

Question 13

DNA polymerase

Answer 13

Enzyme that adds new nucleotides to growing strand of DNA

Question 14

Primers

Answer 14

Short sequence of nucleotides that bind to 3’ end of template DNA allowing DNA polymerase to add free DINA nucleotides

Question 15

Stage 1 DNA replication

Answer 15

DNA unwound and unzipped

-helix unwounded
-special molecules break weak hydrogen bonds between bases
- process occurs at several locations on a DNA molecule

Question 16

Stage 2 of DNA replication

Answer 16

DNA polymerase adds free DNA nucleotides to 3 end of primer

Question 17

Leading strand

Answer 17

synthesised continuously DNA polymerase adds to 3’ ended strand

happens in 5’ to 3’ direction

Question 18

Lagging Strand

Answer 18

synthesised in fragments

nucleotides cannot be added to 5’ end because DNA polymerase can only add in a 5’ to 3’ direction.

fragments sealed together by enzyme ligase

Question 19

Stage 3 DNA replication

Answer 19

new strand twists to form double helix - each identical to original

Question 20

Polymerase Chain reaction

Answer 20

Technique used for amplification of DNA in vitro

easy and cheap

Question 21

PCR and DNA

Answer 21

PCR amplifies DNA using complementary primers for specific target DNA sequence

Question 22

What is PCR used for

Answer 22

DNA for criminal investigations

Settle paternity suits

Diagnose genetic disorders

Question 23

Requirements for PCR

Answer 23

DNA

Complementary primers

Thermal cycler

Heat tolerant polymerase

Supply of nucleotides

Question 24

PCR process

Answer 24

1. Heated 92-98 degrees to denature and separate strands
2. cooled to 50-65 degrees to allow primers to bind to target DNA
3. Complementary primers added
4. Heated 70-80 degrees - heat tolerant DNA polymerase added
5. Repeated cycles of heating and cooling amplify target region of DNA

Question 25

Thermal cycler allows process to be

Answer 25

automated

continually denatured and replicated