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2. Foundations of Medicine PoD > Chromosomes > Flashcards

Chromosomes Flashcards

1
Q

Structure of (eukaryotic) chromosome

A

Linear Chromosome:
* Telomere
* Centromere
* Heterochromatin (gene-poor DNA)
* Euchromatin (“active” DNA)

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2
Q

breifly describe telomeres

structure and function

A
  • Repeats (of 5’-TTAGGG-3’)
  • Hundreds of copies at the ends of chromosomes
  • Some lost at mitosis - end replication problem
  • Telomerase

Function: protect DNA ends (shorten as age)

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3
Q

End-replication problem

A

The ends of linear DNA cannot be replicated completely during lagging strand DNA synthesis

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4
Q

name the 5 phases of mitosis

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
    +Cytokenisis

PMAT

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5
Q

Prophase

A
  • chromosomes condense
  • nuclear membrane disappears
  • spindle fibres form from the centriole
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6
Q

Metaphase

A
  • chromosomes aligne at the equator of the cell
  • attached by fibre to each centriole (by spindle fibres)
  • Mex condensation of chromosome
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7
Q

Anaphase

A
  • sister chromatids seperate at centromere
  • Seperate longitudinally
  • Move to opposire ends of cell
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8
Q

Telophase

A
  • New nuclear membranes form
  • Each cell contains 46 chromosomes (diploid)
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9
Q

Cytokinesis

A
  • cytoplasm seperates
  • Two new daughter cells
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10
Q

briefly explain centromeres

A
  • Region joining sister chromatids
  • Site of kinetochore attachement
  • Required for chromosome seperation during cell division
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11
Q

what is chromatin

A

a mixture of DNA and proteins that form the chromosomes

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12
Q

what happens during interphase

weird question/answer ik - from PP

A

Genes are transcribes and DNA replication occurs (S phase)

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13
Q

Heterochramatin

what is it and structure

A

Inactive DNA with “silenced” genes - condensed structure

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14
Q

Euchromatin

what is it and structure

A

Active genes and open structure

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15
Q

Proportion of DNA that is protein coding

A

Not much: ~2%

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16
Q

what are extragenic sequences

A

DNA space between two genes of a genome

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17
Q

What can extragenic sequences include

A
  • Tandemly repeated DNA sequences
    satellite DNA
    Minisatellite DNA
  • highly repeated interspersed DNA sequences - not sure what they are… no biological function
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18
Q

functions of non-coding DNA

A
  • regulation of gene expression
    as such, regulation of protein synthesis
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19
Q

What is the structure of chromatin

A

DNA packed with histone proteins to form chromatin
Packaged into units called nucleosomes

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20
Q

nucleosomes

A

segments of DNA wrapped around histone proteins - “beads on a string”

21
Q

how does DNA bind to histones

A

charge (DNA -ve and histone +ve)

22
Q

what does further wrapping of nucleosomes form

A

solenoid structure

23
Q

packaging of DNA order

A

DNA-histone-nucleosomes-solanoid scaffold loop chromatids-chromosome

24
Q

What is the purpose of packaging DNA

A
  • -ve DNA neutralised by +ve histone proteins
  • DNA takes up less space
25
Q

what can we do to inactive dna

A

fold it into inaccessible locations until required

26
Q

what is inactive chromatin characterised by

don’t need to know?

A

specific histone covalent modification

27
Q

p arm

A

shortest arm on chromosome based on distance from centromere

Think: p = petite

28
Q

q arm

A

longer arm on chromosome based on distance from centromere

29
Q

karayotype

A

an individual’s complete set of chromosomes

30
Q

number of chromosomes humans have

A

46 (23 pairs)

31
Q

fluorescent in situ hybridisation - FISH

A

fluorescent DNA probes to target specific chromosomal locations within the nucleus, resulting in colored signals that can be detected using a fluorescent microscope

32
Q

4 types of FISH probes and describe a bit about each/some of them

FISH = fluorescent in situ hybridisation

A
  • Unique sequence probes
  • Centrometic probes - determine chromo number
  • Telomeric probes - detect subtelomeric rearrangements
  • Whole chromosome probes - spectral karyotype, detect translocations and rearrangements
33
Q

what is a germ cell

A

cells in the body that develop into sperm and eggs

34
Q

Summarise meosis (start and end points not whole process)

A
  • Cell division in germ cells
  • Diploid cells (in ovaries and testes) divide to form haploid cells
  • Chromosomes are passed on as re-arranged (recombined) copies - creates genetic diversity
35
Q

what happens in chromosome numbers duuring meiosis and recombination

A

Diploid (2n) becomes two haploid (n) cells
46—> 2x23

36
Q

summarise meiosis and recombination

A

single round of DNA replication but 2 rounds of cell division:
PMAT and then 2nd miotic division where attachment between sister chromatids is broken and they seperate

37
Q

gametogenesis

A

production of gametes from haploid precursor cells

38
Q

oogenesis

A

process of egg formation

39
Q

spermatogenesis

A

process of sperm formation

40
Q

difference between oogenesis and spermatogeneis in males and females

(both=gametogenesis)

A
  • sperm go through more cells divisions - more chance on mutation
  • Duration: sperm 60-65 days, eggs 10-50 years
  • Commences: puberty in males and early embrionic life in females
  • Gamete production per mitosis: 4 spermatids and 1ovum + 3 polar bodies
  • Gamete production: 100-200 million per ejaculate compared to 1 ovum per menstrual cycle
  • No. mitoses in gamete formation: 30-500 in males and 20-30 in females

see sheet

41
Q

XX

A

female

42
Q

XY

A

male

43
Q

what determines gender of embryo

A

whether sperm contains X or Y chromosome

44
Q

Fertilisation

A

Two haploid cells (egg, sperm) form 1 diploid cell (Zygote)

45
Q

where does the embryo get its genetic material

A

assortment of genes from each original parent - inc genetic diversity

46
Q

Where can the mitochondria and its DNA only come from

A

Mother via the egg - maternal inheritance

47
Q

why does X-inactivation occur in females

A

females have a double does of gene product on X-chromosome

48
Q

what does X-inactivation in females occur

A

random inactivation of one X chromosome - can result in funny things if mutation on one chromo and not the other

49
Q

types of structural chromosome abnormalities

A

Four main types of structural chromosomal aberrations are deletion, duplication, inversion, and translocation

2. Foundations of Medicine PoD (28 decks)

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