Structure and Replication of DNA

Question 1

What does DNA stand for?

Answer 1

Deoxyribose Nucleic Acid

Question 2

What does DNA consist of?

Answer 2

2 strands of repeating units called Nucleotides

Question 3

What are nucleotides composed of?

Answer 3

Deoxyribose Sugar (D), Phosphate (P) and a Base (B)

Question 4

What forms a Sugar-phosphate Backbone?

Answer 4

A strong chemical bond forms between the phosphate group one of nucleotide and the deoxyribose of another

Question 5

Bases on each strand of nucleotides are joined together by what?

Answer 5

Weak hydrogen bonds, forming bases pairs

Question 6

What are the base pairs?

Answer 6

Adenine - Thymine

Cytosine - Guanine

Question 7

What does the base sequence form?

Answer 7

The organisms genetic code

Question 8

What structure does DNA have and what does it mean?

Answer 8

It has a Antiparallel structure meaning the 2 strands run in opposing directions with one end bearing the deoxyribose 3’ end and the other the phosphate 5’ end

Question 9

The two strands twist into what?

Answer 9

A double helix

Question 10

What is DNA replicated by?

Answer 10

A polymerase (this is prior to cell divison)

Question 11

What is the requirements for DNA replication?

Answer 11

DNA Template
Primers (short strand of nucleotides which binds to 3’ ends)
Nucleotides
Enzymes (DNA polymerase and sometimes ligase)
ATP

Question 12

What happens during DNA replication?

Answer 12

DNA unwound and hydrogen bonds between bases break to form 2 template strands. The primer must bond to 3’ end to start replication. The DNA polymerase adds new complementary nucleotides to the template strands from the primer onwards so replication can only occur from the 3’ end of the parent strand

Question 13

What happens to the leading strand?

Answer 13

Replicates continuously

Question 14

What happens during lagging strands?

Answer 14

New nucleotides can only be added to 3’ end so is replicated in fragments with many primers

The fragments are joined together with ligase

Question 15

What does PCR do?

Answer 15

Amplifies DNA using complementary primers (short strands of nucleotides) which are complementary to specific target sequences at two ends of the region of DNA to be amplified

Question 16

What happens during PCR?

Answer 16

Repeated cycles of cooling and heating amplify the target region, DNA is heated to between 92 and 98C to separate strands. It is then cooled to between 50 and 65C to allow primers to bind target sequences. It is then heated to between 70 and 80*C for heat tolerant DNA polymerase to replicate the region of DNA

Question 17

What is PCR used for?

Answer 17

Help to solve crimes, settle paternity suits and diagnose genetic disorders