DNA and chromosomes

Question 1

State the 4 parts of the cell cycle

Answer 1

• G1 phase
• S phase
• G2 phase
• M phase

Question 2

What happens during the M phase

Answer 2

• mitosis (nuclear division)
• cytokinesis (cytoplasmic divison)

Question 3

Which phases does mitosis include?

Answer 3

1. prophase
2. metaphase
3. anaphase
4. telophase

Question 4

What happens during the S phase of the cell cycle?

Answer 4

DNA replication

Question 5

What happens during prophase?

Answer 5

• chromosomes condense
• mitotic spindles form

Question 6

What happens during prometaphase?

Answer 6

• nuclear membrane disintegrates
• spindles attach to kinetochores

Question 7

What happens during metaphase?

Answer 7

chromosomes align at equator

Question 8

What happens during anaphase?

Answer 8

• sister chromatids seperate
• pulled towards spindle poles

Question 9

What happens during telophase?

Answer 9

• chromosomes arrive at poles
• nuclear envelopes reform

Question 10

What happens during cytokinesis?

Answer 10

cytoplasm divides resulting in two genetically identical cells

Question 11

What do chemotherapy drugs target?

Answer 11

the S and M phases of the cell cycle, which rapidly kills replicating cells

Question 12

Which direction is DNA synthesised in?

Answer 12

5’ to 3’ end

Question 13

How is he accumulation of mutations prevented ?

Answer 13

• proof reading capacity of DNA polymerase during DNA replication
• excision repair systems act throughout cell life repairing DNA damage

Question 14

How do you characterise mutations?

Answer 14

• impact on individual or offspring (somatic or germ line)
• scale of mutation
  (chromosome or SNP)
• effect on normal function

Question 15

Describe what an SNP is?

Answer 15

• single nucleotide polymorphism
• single base chnage in DNA sequence
• no change in amino acid sequence

Question 16

What are monogenic genetic diseases?

Answer 16

• single gene disorders

Question 17

Give the 3 kind of monogenic genetic diseases and examples

Answer 17

• substitution (sickle cell anaemia)
• deletion (cystic fibrosis)
• insertion (huntington’s disease)

Question 18

Describe sickle cell anaemia

Answer 18

• single nucleotide substitution in HBB gene (beta chain of haemoglobin)
• misshapen blood cells do not survive as long and clog capillaries

Question 19

Describe cystic fibrosis

Answer 19

• abnormal mucus un lungs
• results in lung infections, difficulty breathing, digesting food
• impaired chloride transport

Question 20

Describe Huntington’s disease

Answer 20

• neurodegenrative disease
• uncontrollable muscle movements
• loss of memory and depression
• difficulties with speech and swallowing
• damage of nerve cells in areas on the brain

Question 21

What is the cause of Huntington’s disease ?

Answer 21

caused by increase in number of CAG trinucleotide repeats (encoding glutamine) in the Huntingtin (HTT gene)
- polyglutamine residues stick together creating a toxic product which causes neuron cell death

Question 22

What is the cause of cystic fibrosis?

Answer 22

70% have 3bp deletion in CFTR gene on chr 7 (cystic fibrosis transmembrane conductance regulator)