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IMMS lectures > mitosis & meiosis > Flashcards

mitosis & meiosis Flashcards

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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
what happens in prometaphase
nuclear membrane breaks down microtubules invade nuclear space chromatids attach to microtubules spindle fibres attach to chromosomes at the kinetochore
26
what happens in metaphase
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
what happens in anaphase
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
what happens in telophase
cell has elongated and is nearly finished dividing nuclear membranes reform chromosomes unfold into chromatin cytokinesis begins
29
what happens in cytokinesis
cytoplasm divides to form 2 genetically identical daughter cells
30
how does mitosis affect tumours
helps to categorize them as benign or malignant lots of mitosis means they are more likely to be malignant
31
what are the clinical uses of mitosis (3)
detecting chromosome abnormalities categorising tumours as benign or malignant can grade malignant tumours - gives an idea about their biological behaviour
32
which anti cancer drugs attack the mitotic spindle
taxol vinca alkaloids - vinblastine,vincristine
33
which anti cancer drugs attack anaphase
colchicine like drugs
34
which anti cancer drug attacks spindle poles
ispinesib
35
can mitosis occur in all body cells
yes
36
can meiosis occur in all body cells
no
37
in what cells does meiosis occur
gametes only
38
what occurs in meiosis
the recombination of genetic material to generate diversity
39
how many cell divisions are there in meiosis
2 - meiosis I and II
40
what are the products of meiosis
4 haploid daughter cells
41
what are the stages of meiosis
interphase, prophase I, prometaphase I, metaphase I, anaphase I, telophase I, cytokinesis, interphase II, metaphase II, anaphase II, and telophase II
42
what happens in meiosis I
homologous chromosomes are separated and reduction from diploid to haploid cells occurs
43
what happens in prophase I
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
what happens in metaphase I
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
what happens in meiosis II
sister chromatids seperate haploid cells produced
46
define gametogenesis
the process by which gametes, or germ cells, are produced in an organism
47
what are primordial germ cells
the primary undifferentiated stem cell type that will differentiate towards gametes: spermatozoa or oocytes
48
what is the first stage of gametogenesis
the proliferation - (rapid increase in the amount of something) of primordial (undifferentiated) germ cells (developing gametes) by mitosis
49
describe gametogenesis in males
Primordial germ cells > lots of mitoses > spermatogonia (mature sperm)
50
when does gametogenesis start in males
at puberty and continues throughout life but some mitosis occurs in embryonic stages to produce primary spermatocytes present at birth
51
how long does sperm production take
60 - 65 days
52
how many sperm are produced
100 - 200 million
53
describe gametogenesis in females
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
how does the cytoplasm divide in males during sperm production
evenly
55
how does the cytoplasm divide in females during egg cell production
unevenly
56
when is meiosis I completed in egg cell production
at ovulation
57
when is meiosis II completed in egg cell production
it is only completed if fertilisation occurs
58
what is non-disjunction
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
what causes down sydnrome
non-disjunction at chromosome 21 resulting in trisomy 21 likelihood of this happening increases with the age of both men and females
60
what is gonadal mosaicism
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
what inheritance pattern is gonadal mosaicism most common in
autosomal dominant and X linked even though it can be observed with any
62
examples of diseases with gonadal mosaicism
oesteogenesis imperfecta duchenne muscular dystrophy

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