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Genetics > Cell division > Flashcards

Cell division Flashcards

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Biology 101 flashcards
1
Q

mitosis

A

somatic cell division, in which the nucleus also divides
produces 2 daughter cells with the same number of chromosomes (23 pairs)
separation of chromatids, one of which has been replicated from the other in the S phase

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2
Q

how long does mitosis last?

A

1-2 hours, continuous process

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3
Q

what are the phases in mitosis?

A

prophase

prometaphase

metaphase

anaphase

telophase

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4
Q

prophase

A

chromosomes condense and mitotic spindle begins to form. 2 centrioles form in each cell, from which microtubules radiate as they move towards opposite ends of the cell

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5
Q

prometaphase

A

nuclear membrane begins to disintegrate, allowing chromosomes to spread around the cell

each chromosome becomes attached at its centromere to a microtubule of the mitotic spindle

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6
Q

metaphase

A

chromosomes become aligned along the equatorial plane, each one attached to the centriole

maximally contracted and most easily visible

chromatids separate longitudinally but are attached at the centromere (not undergone division yet)

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7
Q

anaphase

A

centromere of each chromosome divides longitudinally and 2 daughter chromatids separate to opposite poles

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8
Q

telophase

A

chromatids are independent chromosomes consisting of a single double helix

two groups of daughter chromosomes become enveloped in a new nuclear membrane

cytokinesis - nuclear membrane separates

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9
Q

what does each daughter cell contain?

A

complete diploid chromosome complement

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10
Q

interphase

A

period between successive mitoses

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11
Q

how long does interphase last in rapidly dividing cells?

A

16-24 hours

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12
Q

components of interphase

A

G1, G2, S, G0

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13
Q

G1 phase

A

chromosomes become thin and extended

variation in length - responsible for variation in generation time between different cell populations

cells that have stopped dividing usually arrest in this phase and enter G0

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14
Q

S phase

A

when DNA replication occurs and chromatin of each chromosome is replicated
formation of 2 chromatids
DNA replication occurs at multiple points on a chromosome

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15
Q

sex chromatin

A

Barr body

one of the X chromosomes is always late in replicating - visualised during interphase in female somatic cells

cells from buccal mucosa - buccal smear

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16
Q

when does meiosis occur?

A

final stage of gamete formation

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17
Q

how does meiosis differ from mitosis?

A

mitosis results in each daughter cell having a diploid chromosome complement (46)
in meiosis the diploid count is halved so each mature gamete receives a haploid complement (23)

mitosis occurs in somatic cells and in early cell divisions in gamete formation. meiosis occurs only in final division of gamete maturation

mitosis is a 1 step process, meiosis has 2

18
Q

what is meiosis sometimes referred to?

A

reduction division - chromosome number is halved

19
Q

prophase 1

A

chromosomes enter phase already split longitudinally into 2 chromatids joined at the centromere

homologous chromosomes pair and exchange of homologous segments occurs between non-sister chromatids

20
Q

recombination

A

crossing over

exchange of homologous segments between chromatids occurs

21
Q

prophase 1 in the male

A

pairing occurs between homologous segments of the X and Y chromosomes at the tip of their short arms - this portion of each chromosome is the pseudoautosomal region

22
Q

five stages of prophase 1

A

leptotene

zygotene

pachytene

diplotene

diakinesis

23
Q

leptotene

A

chromosomes become visible as they start to condense

24
Q

zygotene

A

homologous chromosmes align directly opposite eachother (synapsis) and are held together at points along their length by filamentous structures (synaptonemal complexes)

25
Q

synapsis and synaptonemal complexes

A

homologous chromosomes aligning directly opposite eachother

filamentous structures holding chromosomes together

26
Q

pachytene

A

each pair of homologous chromosomes (bivalent) becomes tightly coiled. crossing over occurs

27
Q

bivalent

A

pair of homologous chromosomes

28
Q

diplotene

A

homologous recombinant chromosomes begin to separate but remain attached at points where crossing over has occurred (chiasmata)

29
Q

chiasmata

A

points on chromosomes where recombination has occured. small, medium and large chromosomes have 1, 2 adn 3 chiasmata respectively - approx. 40 recombination events per meiosis per gamete

30
Q

diakinesis

A

separation of homologous chromosome pairs proceeds as chromosomes become maximally condensed

31
Q

metaphase 1

A

nuclear membrane disappears and chromosomes align along equatorial plane, attached to the spindle

32
Q

anaphase 1

A

chromosomes separate to opposite poles of the cell as the spindle contracts

33
Q

telophase 1

A

each set of haploid chromosomes has separated completely to opposite ends of the cell, and cleaves into 2 new daughter gametes (secondary spermatocytes or oocytes)

34
Q

meiosis 2

A

each chromosome becomes aligned along the equatorial plane and splits longitudinally, forming 2 new daughter gametes - spermatids or ova

35
Q

consequences of meiosis

A

facilitates halving of the diploid number of chromosomes so each child receives half of its chromosome complement from each parent

potential for genetic diversity

36
Q

how does meiosis have potential to generate genetic diversity?

A

when the bivalents separate, they do so independently of each other - each gamete receives a selection of parental chromosomes
likelihood that 2 gametes contain same chromosomes is 1 in 8 million

chromatid contains portions of DNA derived from both parental homologous chromosomes

37
Q

what is gene shuffling?

A

dispersion of DNA into different gametes

38
Q

clinical relevance of mitosis

A

detecting chromosomal abnormalities
categorising tumours as benign or malignant
grading malignant tumors

39
Q

clinical relevance of the mitotic spindle

A

taxol

vinca alkaloids - vinblastine, vincristine

40
Q

clinical relevance of anaphase

A

colchicine like drugs

41
Q

clinical relevance of spindle poles

A

ispinesib

Genetics (7 decks)

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