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IMMS lectures > mitosis & meiosis > Flashcards

mitosis & meiosis Flashcards

1
Q

where is DNA found in the cell

A

nucleus and mitochondria

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2
Q

what are the DNA complementary base pairs

A

A and T
C and G

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3
Q

how many hydrogen bonds are there between A & T

A

2

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4
Q

how many hydrogen bonds are there between C & G

A

3

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5
Q

how does DNA coil

A

it coils around nucleosomes, then again into supercoils and then again into chromosomes

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6
Q

how many chromosomes in human genome

A

46 (22 pairs + sex chromosomes)

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7
Q

how many genes on each chromosome

A

several hundred

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8
Q

how long is the continuous DNA duplex on each chromosome

A

around 10 to power of 7 bp

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9
Q

what do you call the long arm of a chromosome

A

q

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10
Q

what do you call the short arm of a chromosome

A

p

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11
Q

what separates the two arms of a chromosome

A

centromere

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12
Q

what stains can be used to identify chromosomes

A

giemsa (G banding) & Quinacrine (Q banding)

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13
Q

how many chromosome bands does G banding give

A

around 400 - 500

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14
Q

what is the telomere

A

section of DNA at the end of a chromosome

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15
Q

what does the telomere do

A

stops chromosomes from unravelling

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16
Q

why do we need mitosis (2 reasons)

A

1) growth
2) to replace dead cells

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17
Q

what are the stages of the cell cycle

A

G1, S, G2, Mitosis

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18
Q

what is interphase

A

G1, S, G2

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19
Q

what is the G0 phase

A

contains cells that are mitotically inactive and not in the cell cycle

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20
Q

what happens in G1

A

cell grows and replicates content

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21
Q

what happens in S

A

chromosomes replicate

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22
Q

what happens in G2

A

cell prepares for mitosis and checks for errors

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23
Q

what are the stages of mitosis

A

prophase, prometaphase, metaphase, anaphase, telophase

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24
Q

what happens in prophase

A

chromatin condenses into chromosomes
mitotic spindles begin to form
centrosomes nucleate microtubules and move to opposite poles of nucleus

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25
Q

what happens in prometaphase

A

nuclear membrane breaks down

microtubules invade nuclear space

chromatids attach to microtubules
spindle fibres attach to chromosomes at the kinetochore

26
Q

what happens in metaphase

A

chromosomes line up along the equatorial plane/ metaphase plate(middle of the cell)

helps to ensure sister chromatids are split evenly between the two daughter cells

27
Q

what happens in anaphase

A

spindle fibres contract

sister chromatids separate and are pulled to opposite poles of the cell because the centromere is broken

spindle fibres not attached to chromatids will elongate the cell to prepare it for division

28
Q

what happens in telophase

A

cell has elongated and is nearly finished dividing

nuclear membranes reform

chromosomes unfold into chromatin

cytokinesis begins

29
Q

what happens in cytokinesis

A

cytoplasm divides to form 2 genetically identical daughter cells

30
Q

how does mitosis affect tumours

A

helps to categorize them as benign or malignant

lots of mitosis means they are more likely to be malignant

31
Q

what are the clinical uses of mitosis (3)

A

detecting chromosome abnormalities
categorising tumours as benign or malignant
can grade malignant tumours - gives an idea about their biological behaviour

32
Q

which anti cancer drugs attack the mitotic spindle

A

taxol
vinca alkaloids - vinblastine,vincristine

33
Q

which anti cancer drugs attack anaphase

A

colchicine like drugs

34
Q

which anti cancer drug attacks spindle poles

A

ispinesib

35
Q

can mitosis occur in all body cells

A

yes

36
Q

can meiosis occur in all body cells

A

no

37
Q

in what cells does meiosis occur

A

gametes only

38
Q

what occurs in meiosis

A

the recombination of genetic material to generate diversity

39
Q

how many cell divisions are there in meiosis

A

2 - meiosis I and II

40
Q

what are the products of meiosis

A

4 haploid daughter cells

41
Q

what are the stages of meiosis

A

interphase, prophase I, prometaphase I, metaphase I, anaphase I, telophase I, cytokinesis, interphase II, metaphase II, anaphase II, and telophase II

42
Q

what happens in meiosis I

A

homologous chromosomes are separated and reduction from diploid to haploid cells occurs

43
Q

what happens in prophase I

A

nuclear membrane breaks down

chromosomes condense

spindle fibres appear

crossing over occurs between non-sister chromatids at chiasmata resulting in genetic diversity

[genes sort independently thus if 1 gene switches over, doesn’t mean another one will],

44
Q

what happens in metaphase I

A

maternal and paternal versions of the same chromosome (homologous chromosomes) align along the equator of the cell.

random/independent assortment occurs on the metaphase plate - also resulting in genetic diversity

45
Q

what happens in meiosis II

A

sister chromatids seperate
haploid cells produced

46
Q

define gametogenesis

A

the process by which gametes, or germ cells, are produced in an organism

47
Q

what are primordial germ cells

A

the primary undifferentiated stem cell type that will differentiate towards gametes: spermatozoa or oocytes

48
Q

what is the first stage of gametogenesis

A

the proliferation - (rapid increase in the amount of something) of primordial (undifferentiated) germ cells (developing gametes) by mitosis

49
Q

describe gametogenesis in males

A

Primordial germ cells > lots of mitoses > spermatogonia (mature sperm)

50
Q

when does gametogenesis start in males

A

at puberty
and continues throughout life
but
some mitosis occurs in embryonic stages to produce primary spermatocytes present at birth

51
Q

how long does sperm production take

A

60 - 65 days

52
Q

how many sperm are produced

A

100 - 200 million

53
Q

describe gametogenesis in females

A

Primordial germ cell > 30 mitoses > oogonia

Oogonia enter prophase 1 of meiosis 1 by 8th month of intrauterine life (in-utero)
then the Process is suspended
Cells enter ovulation 10-50 years later
Cytoplasm divides unequally - 1 egg & 3 polar bodies

54
Q

how does the cytoplasm divide in males during sperm production

A

evenly

55
Q

how does the cytoplasm divide in females during egg cell production

A

unevenly

56
Q

when is meiosis I completed in egg cell production

A

at ovulation

57
Q

when is meiosis II completed in egg cell production

A

it is only completed if fertilisation occurs

58
Q

what is non-disjunction

A

Failure of chromosome pairs to separate in Meiosis 1 or sister chromatids to separate properly in meiosis 2.
can occur in prophase I or II
can result In down syndrome or monosomy (loss of a chromosome)

59
Q

what causes down sydnrome

A

non-disjunction at chromosome 21 resulting in trisomy 21
likelihood of this happening increases with the age of both men and females

60
Q

what is gonadal mosaicism

A

Occurs when precursor germline cells to ova or spermatozoa are a mixture of two or more genetically different cell lines (due to errors in mitosis)
* One cell line is normal, the other is mutated
* Incidence increases with advancing paternal age
* Parent is healthy ( since genetic change is only in the germline so all the other cells are unaffected - have usual genetic components), but the foetus may have genetic diseases

61
Q

what inheritance pattern is gonadal mosaicism most common in

A

autosomal dominant and X linked

even though it can be observed with any

62
Q

examples of diseases with gonadal mosaicism

A

oesteogenesis imperfecta
duchenne muscular dystrophy

IMMS lectures (22 decks)

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