Chromosomes and Cell Division Flashcards

1
Q

What is the end replication problem?

A

through multiple generations, strands will get shorter

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2
Q

What is the solution to the end replication problem?

A

telomerase

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3
Q

What are centromeres?

A
  • Protein complexes that bind to microtubules and are required during cell division
  • They are the constricted region joining sister chromatids
  • site of kinetochores
  • repetitive SNA sequences- satellite DNA
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4
Q

Hererochromatin vs Euchromatin

A
  • Heterochromatins has a condensed structure and silenced genes
  • Euchromatin has an open structure and active genes
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5
Q

Describe the structure of chromatin.

A
  • formed of DNA packaged histones
  • histones have a positive charge, DNA negative
  • 146 bp DNA wrapped around core of 8 histones= nucleosome
  • further wrapping of nucleosomes
  • form solenoid structure
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6
Q

By what factor is DNA condensed by at metaphase?

A

10,000

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7
Q

What is the purpose of packaging DNA?

A
  • negatively charged DNA neutralised by positive charged histone proteins
  • DNA takes up less space
  • Inactive DNA can be folded into inaccessible locations until required
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8
Q

What is colchine?

A
  • a microtubule inhibitor

- it enriches the population of cells that are visible

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9
Q

Metacentric

A

p length= q length

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10
Q

Submetacentric

A

p length< q length

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11
Q

acrocentric

A

p length «< q length

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12
Q

What does FISH stand for?

A

Fluorescent in situ hybridisation

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13
Q

What types of FISH probes are there?

A
  • unique sequence probes
  • centromeric probes (useful for determining chromosome number)
  • telomeric probes (detecting subtelomeric rearrangements, often present in children wit unexplained mental retardation)
  • whole chromosome probes (cocktail of probes, used with different dyes, spectral karyotype, detecting translocation and rearrangements)
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14
Q

What is meiosis?

A
  • cell division in germ cells
  • diploid cells (in ovaries and testes) divide to form haploid cells)
  • chromosomes are passed on as re-arranged (recombinant) copies which creates genetic diversity
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15
Q

What is a defining event in sexual reproduction?

A

recombination between homologues

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16
Q

What are the 2 forms of gametogenesis?

A
  • oogenesis= process of egg formation

- spermatogenesis= process of sperm formation

17
Q

Why is there a greater chance of mutation in sperm than in eggs?

A

they go through more cell divisions

18
Q

How many sperm and eggs are produced in each cycle of gametogenesis?

A
  • 4 sperm

- 1 egg + 3 polar bodies

19
Q

Describe fertilisation.

A
  • two haploid cells form 1 diploid cell which develops into an embryo
  • whether sperm contains an X or Y chromosome determines if the embryo is female or male
  • embryo contains an assortment of genes from each original parent- more genetic diversity
20
Q

What is maternal inheritance?

A

mitochondria (and their DNA) come only from the mother via the egg

21
Q

When does X inactivation occur?

A
  • In the zygote both X chromosomes are active

- In the early embryo random inactivation of one X occurs

22
Q

What are 2 tandemly repeated DNA extragenic sequences?

A
  • satellite DNA

- microsatellite DNA

23
Q

What are 2 highly repeated interspersed DNA extragenic sequences?

A

-SINEs (short interspersed nuclear elements)

LINEs (long interspersed nuclear elements)