Structure & Replication of DNA

Question 1

What does DNA consist of

Answer 1

Two strands of nucleotides twisted into a double helix

Question 2

What do DNA nucleotides contain

Answer 2

Deoxyribose sugar, phosphate and a base (Adenine, Thymine, Cytosine or Guanine)

Question 3

Deoxyribose has a base attached to

Answer 3

It’s carbon 1, and a phosphate attached to its carbon 5 (this forms the 5’ end)

Question 4

What is the DNA sugar-phosphate backbone held together by

Answer 4

Strong chemical bonds

Question 5

The 2 DNA strands are antiparallel

Answer 5

With deoxyribose sugar and phosphate at 3’ and 5’ ends of each strand

Question 6

Adenine pairs with

Answer 6

Thymine

Question 7

Cytosine pairs with

Answer 7

Guanine

Question 8

What is the genetic code formed by

Answer 8

The base sequence of DNA (the order of bases)

Question 9

What do chromosomes consist of

Answer 9

Tightly coiled DNA packaged around bundles of protein

Question 10

What must happen before a cell divides

Answer 10

The DNA must be replicated

Question 11

DNA is replicated by

Answer 11

The enzyme DNA polymerase

Question 12

Replication of the DNA template strand with the 3’ end is

Answer 12

Continuous and forms the “leading strand”

Question 13

DNA chain of nucleotides can only grow by

Answer 13

Adding nucleotides to its 3’ end

Question 14

What does DNA polymerase bring about the formation of

Answer 14

The sugar–phosphate bonds between individual nucleotides

Question 15

What does the enzyme ligase do

Answer 15

Joins fragments of DNA together to form the “lagging strand”

Question 16

Requirements for DNA replication:

Answer 16

DNA, primers, enzymes, DNA nucleotides and ATP

Question 17

What end of the DNA strand is the deoxyribose on

Answer 17

The 3’ prime end

The phosphate is on the 5’ end

Question 18

What is a DNA primer made of

Answer 18

A short sequence of nucleotides which binds to the 3’ end of the template DNA strand

Question 19

Replication of the lagging strand is

Answer 19

Discontinuous as this strand starts with the 5‘ end

Question 20

What happens during the first stage of DNA replication

Answer 20

The DNA double helix unwinds and the weak hydrogen bonds between bases break

Question 21

Why are primers required

Answer 21

To create an existing chain for DNA polymerase to add DNA nucleotides to

Question 22

What is polymerase chain reaction (PCR)

Answer 22

A technique used to create many copies of a piece of DNA

Question 23

What does PCR use

Answer 23

Complimentary primers for specific target sequences to “amplify” the DNA

Question 24

Firstly DNA is heated

Answer 24

To between 92 and 98°C to separate the DNA strands

Question 25

Next the DNA is cooled

Answer 25

To between 50 and 65°C allowing primers to bind to target sequences

Question 26

Finally DNA is heated

Answer 26

To between 70 and 80°C for heat-tolerant DNA polymerase to replicate the region of DNA

Question 27

What does the PCR technique help

Answer 27

Solve crimes, settle paternity disputes and diagnose genetic disorders