biology test 07/03

Question 1

What is the type of bond between complementary base pairs?

Answer 1

hydrogen

Question 2

What is the type of bond between adjacent nucleotides in a DNA strand

Answer 2

Phosphodiester

Question 3

What is the type of bond between

Question 4

Describe the structure of DNA (5)

Answer 4

• polymer of nucleotides
• Each nucleotide formed from deoxyribose, a phosphate (group) and an organic/nitrogenous
• Phosphodiester bonds between nucleotides
• Double helix held by hydrogen
• Hydrogen bonds between adenine, thymine and cytosine,

Question 5

Describe how a phosphodiester bond is formed between two nucleotides
within a DNA molecule

Answer 5

Condensation reaction
Between phosphate and deoxyribose
Catalysed by DNA polymerase

Question 6

Name the protein associated with DNA in a chromosome

Answer 6

histone

Question 7

In the process of semi-conservative DNA replication, the two strands within
a DNA molecule are separated. Each then acts as a template for the
formation of a new complementary strand.
Describe how the separation of strands occurs.

Answer 7

DNA helicase
Breaks hydrogen bonds between base pairs

Question 8

Describe the role of DNA polymerase in the semi-conservative replication
of DNA.

Answer 8

1. Joins adjacent DNA nucleotides
2. Catalyses condensation reactions
3. Catalyses formation of phosphodiester bonds between adjacent nucleotides

Question 9

Name the two scientists who proposed models of the chemical structure of
DNA and of DNA replication

Answer 9

Watson and Crick

Question 10

DNA nucleotide

Answer 10

o. |base|
. /
/\
| |
__

Question 11

What features of DNA are important in semi-conservative replication?

Answer 11

1. Weak hydrogen bonds between bases allow two strands to separate
2. Two strands, so both can act as templates
3. Forming phosphodiester bonds;

Question 12

Describe binary fission in bacteria.

Answer 12

1. Replication of (circular) DNA
2. Replication of plasmids
3. Division of cytoplasm to produce daughter cells

Question 13

Describe the stages of mitosis

Answer 13

During prophase
1. Chromosomes condense
2. Chromosomes appear as two sister chromatids joined at the centromere
During metaphase
3. Chromosomes line up on the equator
4. Chromosomes attached to spindle fibres by their centromere;
During anaphase
6. The centromere divides;
7. Sister chromatids pulled to opposite poles
During telophase
8. Chromatids become thinner.

Question 14

How do HIVs replicate?

Answer 14

1. Attachment proteins attach to receptors on helper T cell
2. Nucleic acid/RNA enters cell
3. Reverse transcriptase converts RNA to DNA
4. Viral protein produced;
5. Virus particles assembled and released from cell

Question 15

Give two types of cell, other than pathogens, that can stimulate an immune response

Answer 15

1. Cells from other organisms/transplants;
2. Abnormal/tumour cells
3. Cells infected by virus;

Question 16

What is a monoclonal antibody?

Answer 16

Antibodies with the same tertiary structure