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102 Theme 3 > Lecture 4: DNA and Chromosomes > Flashcards

Lecture 4: DNA and Chromosomes Flashcards

1
Q

what are the stages of DNA replication

A 
interphase
- G1 (cell growth)
- S (DNA replication)
- G2 (DNA checking)
mitosis
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
cytokinesis
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2
Q

what are telomeres for

A

protect end of chromosome from fraying

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3
Q

what do the spindle fibres attach to

A

kinetochore which forms around the centromere

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4
Q

what happens during prophase

A
  • chromosomes condense
  • mitotic spindles form
  • intact nuclear envelope
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5
Q

what happens during prometaphase

A
  • nuclear membrane disintegrates

- spindle microtubules attach to kinetochores

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6
Q

what happens during metaphase

A

chromosomes align at equator

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7
Q

what happens during anaphase

A

sister chromatids separate and are pulled towards opposite spindle poles

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8
Q

what happens during telophase

A
  • chromosomes arrive at poles
  • nuclear envelopes reform
  • contractile ring starts to form in the middle
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9
Q

what happens during cytokinesis

A
  • nuclear envelopes completed
  • contractile ring creates cleavage furrow
  • cytoplasm divides, creating two daughter cells
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10
Q

what is the rate of mitosis controlled by

A

the phosphorylation of cyclin-dependent kinases (CDKs)

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11
Q

which regulator checks for damaged DNA in the G1 phase

A

p53, muttion in this causes 50% of cancers

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12
Q

in which direction is DNA synthesised during replication

A

5’ to 3’

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13
Q

what are the effects of DNA being replicated in multiple locations

A
  • a leading strand with continuous synthesis
  • lagging strand is read in the opposite direction, so has discontinuous synthesis
  • lagging strand forms Okazaki fragments
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14
Q

outline the steps of DNA replication

A
  • DNA primase adds RNA primer onto lagging strand, allowing DNA polymerase to bind
  • binding proteins hold single stranded DNA straight
  • ligase joins together small gaps
  • nuclease cuts DNA, and exonuclease removes RNA primer
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15
Q

what is Werner’s Syndrome

A
  • caused by mutation in DNA helicase, which causes errors in DNA replication and repair
  • premature aging disorder
  • increases risk of cataracts, atherosclerosis, osteoporosis and cancer
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16
Q

what is Xeroderma Pigmentosum

A
  • mutation to UV repair system
  • UV light causes formation of thymine dimers, and XP sufferers can’t remove these
  • causes acute sun sensitivity
  • hypo and hyper pigmentation
  • multiple cancers at young age
  • intellectual disability
  • progressive degeneration
17
Q

which mechanismss prevent accumulation of mutations

A
  • DNA checking done by DNA polymerase during replication

- excission repair systems throughout cell life repair DNA damage

18
Q

what are single nucleotide polymorphisms

A
  • single base change in DNA sequence
  • results in normal genetic variation of population
  • synonymous causes no change in amino acid sequece
  • non-synonymous causes a change in amino acid sequence
19
Q

what is sickle cell anaemia caused by

A

single base substitution in HBB gene on chromosome 11

20
Q

is sickle cell anaemia a loss or gain of function

A

loss

21
Q

what does sickle cell anaemia cause

A
  • haemoglobin beta chain gets sticky ad forms rigid rods
  • red cells become a sickle shape
  • clogs up capillaries and red blood cells get stuck
  • patients susceptible to strokes and heart attacks
22
Q

what is cystic fibrosis caused by

A

deletion of 8 base pairs in CTFR gene

23
Q

is cystic fibrosis a loss or gain of function

A

loss

24
Q

what does cystic fibrosis cause

A
  • misfolding of protein involved in chloride transport, so it can’t be transported to the cell surface
  • loss of chloride transport leads to mucus build up on lungs
25
Q

what is Huntington’s disease caused by

A

insertion of CAG trinucleotide repeats in HTT gene

  • normal range is 6-35
  • can be a carrier between 36-29
  • sufferers have 40-120
26
Q

is Huntington’s a loss or gain of function

A

gain

27
Q

what does Huntington’s disease cause

A
  • CAG repeats code for glutamine, and polyglutamines stick together which is toxic and causes neuronal cell death
  • causes uncontrollable muscle movements
  • loss of memory and depression
  • difficulties in speech and swallowing

102 Theme 3 (10 decks)

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