Unit 1- Structure And Replication of DNA

Question 1

Describe a nucleotide

Answer 1

A repeating unit that makes up DNA. Consists of a deoxyribose sugar a phosphate and a base.

Question 2

Describe the sugar phosphate backbone.

Answer 2

Nucleotides are arranged so that The phosphate (5’ end) of one nucleotide connects to the deoxyribose sugar (3’ end) of another nucleotide connect in one direction 5’ end to 3’ end.

Question 3

Describe the structure of DNA.

Answer 3

Strands are joined together by complementary base pairing. Bases join by hydrogen binds connecting each backbone forming a double stranded helix and is antiparallel.

Question 4

Where does DNA replication take place?

Answer 4

The nucleus.

Question 5

Describe the process of DNA replication.

Answer 5

1. The double helix is unwound.
2. Hydrogen bonds break forming 2 single strands.
3. DNA polymerase (enzyme) needs a primer (short strand of nucleotides) to be present on the 3’ end of the template strand.
4. DNA polymerase adds free nucleotides using complementary base pairing to the deoxyribose sugar (3’) end of the DNA strand being replicated.
5. Strong chemical bonds form between the nucleotides forming a sugar phosphate backbone.
6. DNA polymerase can only add DNA nucleotides to the 3’ end of the new strand.
7. Therefore DNA polymerase can add nucleotides in one direction.
8. Resulting in the leading strand being replicated continuously and the lagging strand being replicated in fragments.
9. DNA ligase (enzyme) joins fragments of DNA resulting from the replication of the lagging strand.
10. A newly formed daughter molecule of DNA winds into a double helix.

Question 6

Describe PCR

Answer 6

Polymerase Chain Reaction amplifies DNA using complementary primers for specific target sequences.

Question 7

Describe the process of PCR

Answer 7

1. DNA is heated to 92-98 degrees to separate the strands.
2. DNA is then cooled to 50-65 degrees to allow primers to bind to target sequences.
3. DNA is heated to 70-80 degrees for heat tolerant DNA polymerase to replicate the region of DNA.

Question 8

What are the applications of PCR?

Answer 8

Amplifying DNA can help solve crimes, settle paternity suites or diagnose genetic disorders.