Week 3- Chromosomes, Genes and DNA

Question 1

Sickle cell anaemia

Answer 1

• Chromosome 11

- Single base substitution: A –> T at 7th position

Question 2

Cystic fibrosis

Answer 2

• Chromosome 7
• Transmembrane chloride channel
• 3 base pairs CTT deletion between 5th and 6th position
• Single amino acid deletion: phenylalanine, misfolded protein

Question 3

Polynucleotides

Answer 3

Linear polymers of nucleotides

Question 4

Nucleoside

Answer 4

Base plus sugar

Question 5

Types of nitrogenous bases:

Answer 5

1. Purine - 2 ring structure (Adenine, Guanine)

2. Pyridimine - single ring (Cytosine, Thymine, Uracil in RNA)

Question 6

Two types of chromatin structure

Answer 6

1. Euchromatin: light grey, beads on a string, genes expressed
2. Heterochromatin: solenoid, 30 nm fibre, genes not expressed, dark-grey

Question 7

Chromatin

Answer 7

DNA/protein complex that forms a chromosome

Question 8

Length of spermatogenesis

Answer 8

Approximately 48 days

Question 9

Length of oogenesis

Answer 9

Approximately 12 to 50 years

Question 10

Consequences of faulty meiosis

Answer 10

1. 1/3 of all identified miscarriages
2. Infertility
3. Mental retardation

Question 11

Uses of mitosis

Answer 11

1. Growth
2. Cell replacement
3. Wound healing
4. Embryological development
5. Asexual reproduction

Question 12

RNA primer

Answer 12

Short-double stranded region of RNA base-paired to DNA template; free hydroxyl group on 3’ end of template which allows for addition of nucleotides

Question 13

Telomeres

Answer 13

Comprises of non-coding DNA plus proteins located at the ends of linear chromosomes;

• maintain structural integrity of chromosomes, preventing attack by nucleases
• several thousand tandem repeats