DNA and chromosomes Flashcards

1
Q

State the 4 parts of the cell cycle

A
  • G1 phase
  • S phase
  • G2 phase
  • M phase
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2
Q

What happens during the M phase

A
  • mitosis (nuclear division)
  • cytokinesis (cytoplasmic divison)
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3
Q

Which phases does mitosis include?

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

What happens during the S phase of the cell cycle?

A

DNA replication

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5
Q

What happens during prophase?

A
  • chromosomes condense
  • mitotic spindles form
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6
Q

What happens during prometaphase?

A
  • nuclear membrane disintegrates
  • spindles attach to kinetochores
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7
Q

What happens during metaphase?

A

chromosomes align at equator

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8
Q

What happens during anaphase?

A
  • sister chromatids seperate
  • pulled towards spindle poles
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9
Q

What happens during telophase?

A
  • chromosomes arrive at poles
  • nuclear envelopes reform
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10
Q

What happens during cytokinesis?

A

cytoplasm divides resulting in two genetically identical cells

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11
Q

What do chemotherapy drugs target?

A

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

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12
Q

Which direction is DNA synthesised in?

A

5’ to 3’ end

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13
Q

How is he accumulation of mutations prevented ?

A
  • proof reading capacity of DNA polymerase during DNA replication
  • excision repair systems act throughout cell life repairing DNA damage
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14
Q

How do you characterise mutations?

A
  • impact on individual or offspring (somatic or germ line)
  • scale of mutation
    (chromosome or SNP)
  • effect on normal function
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15
Q

Describe what an SNP is?

A
  • single nucleotide polymorphism
  • single base chnage in DNA sequence
  • no change in amino acid sequence
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16
Q

What are monogenic genetic diseases?

A
  • single gene disorders
17
Q

Give the 3 kind of monogenic genetic diseases and examples

A
  • substitution (sickle cell anaemia)
  • deletion (cystic fibrosis)
  • insertion (huntington’s disease)
18
Q

Describe sickle cell anaemia

A
  • single nucleotide substitution in HBB gene (beta chain of haemoglobin)
  • misshapen blood cells do not survive as long and clog capillaries
19
Q

Describe cystic fibrosis

A
  • abnormal mucus un lungs
  • results in lung infections, difficulty breathing, digesting food
  • impaired chloride transport (loss of function)
20
Q

Describe Huntington’s disease

A
  • neurodegenrative disease
  • uncontrollable muscle movements
  • loss of memory and depression
  • difficulties with speech and swallowing
  • damage of nerve cells in areas on the brain
21
Q

What is the cause of Huntington’s disease ?

A
  • 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
22
Q

What is the cause of cystic fibrosis?

A

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

23
Q

What controls the cell cycle checkpoints and how?

A
  • cyclins
  • protein kinases (cdks)
  • phosphorylation of cdk/cyclin complexes
24
Q

List the steps of DNA replication for the leading strand

A
  1. DNA helicase
  2. DNA primase
  3. DNA polymerase
25
List the steps of DNA replication for the lagging strand
1. DNA primase 2. DNA polymerase 3. DNA nuclease 4. DNA polymerase 5. DNA ligase
26
Describe Werners syndrome
- premature aging disorder - mutation in DNA helicase - increased risk of cataracts, atherosclerosis, osteoporosis and cancer
27
What is xeroderma pigmentosum?
- autosomal recessive disorder - mutation in UV repair - unable to remove thymine dimers
28
What are some symptoms of xeroderma pigmentosum?
- acute sun sensitivity - hypo/hyper pigmentation - multiple cancers at a young age - intellectual disability - progressive degradation
29
Is cystic fibrosis a loss or gain of function?
loss of function
30
Is sickle cell anaemia a loss or gain of function?
loss of function
31
Is Huntington's disease a loss or gain of function?
gain of function