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Genetics > L9-10: Mitosis, Meiosis and Sex > Flashcards

L9-10: Mitosis, Meiosis and Sex Flashcards

1
Q

Where does mitosis take place?

A

In somatic tissue

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2
Q

Why is mitosis necessary in humans?

A

Embryonic development
Replacement of skin cells
Wound healing
Production of reticulocytes

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3
Q

What are the phases of the cell cycle?

A

G1, S, G2 and mitosis

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4
Q

What are the key components of mitosis?

A

Kinetochore, spindle fibres, centriole, centrosome

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5
Q

What is the centriole made up of?

A

Composed of nine groups of microtubules that serve as foci for the generation of the mitotic spindle fibres

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6
Q

What happens in prophase?

A

Chromosomes condense
Centrioles divide and move apart

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7
Q

What happens in prometaphase?

A

Chromosomes are recognisable as double structures
Centrioles reach opposite poles
Spindle fibres form and attach to kinetochore

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8
Q

What happens in metaphase?

A

Centromeres align on the metaphase plate

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9
Q

What happens in anaphase?

A

Centromere split and the daughter chromosomes migrate to the opposite poles

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10
Q

What happens in telophase and cytokinesis?

A

Daughter chromosomes arrive at poles, chromosomes decondense and nuclear envelope reforms, cytokinesis cell division commences

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11
Q

How does genetic exchange occur?

A

Via crossing over as a chiasma forms

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12
Q

What are the phases of meiosis I & II?

A

I: Prophase
Metaphase
Anaphase
Telophase
II: Prophase
Metaphase
Anaphase
Telophase

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13
Q

What are the stages in prophase I called?

A

Leptonema
Zygonema
Pachynema
Diplonema
Diakinesis

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14
Q

What takes place in prophase I?

A

Duplicated chromosomes start to condense, synapsis begins, synapsis complete and crossing over takes place, synaptonemal complex disappearing and chiasma visible and bivalent ready for metaphase

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15
Q

What is the synaptonemal complex?

A

A nucleoprotein ‘zipper’ that forms between the paired homologous chromosomes

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16
Q

What takes place in meiosis I?

A

MI: Alignment of tetrads on metaphase plate
AI: One half of the tetrad migrates to one pole, other half to the opposite pole (disjunction)
TI: Nuclear membranes form around dyads and cells divide

17
Q

What happens in meiosis II?

A

PII: each dyad is composed of a pair of sister chromatids
MII: alignment of dyads on metaphase plate
AII: one half of dyad migrates to one pole the other half to the opposite pole
TII&C: four haploid daughter cells

18
Q

What is non-disjunction?

A

When the chromosomes do not separate which forms aneuploid gametes (not an exact multiple of the haploid number)

19
Q

What diseases/syndromes can be caused by human autosomal trisomies?

A

Warkany syndrome 2
Chronic Lymphocytic Leukemia
Patau Syndrome
Edwards Syndrome
Down Syndrome

20
Q

Why is sexual reproduction more advantageous than asexual reproduction?

A

Results in production of recombinant genotypes
Makes population better able to deal with changes in environment

21
Q

What is the difference of natural selection in sexual and asexual reproduction?

A

Sexual strains have a faster growth in harsh conditions in comparison to asexual strains

22
Q

What is heterogametic sex?

A

When males produce the unlike gametes (not always male)

23
Q

What is homogametic sex?

A

Females production of uniform gametes (not always female)

24
Q

What are Klinefelter and Turner syndromes?

A

Variation in the number of X chromosomes as a result of nondisjunction which results in aneuploidy

25
Q

What did the Klinefelter and Turner karyotypes determine?

A

That the Y chromosome determines male characteristics

26
Q

What are the features of the Y chromosome?

A

PARs (pseudoautosomal regions), MSY (male specific region of the Y) and SRY (sex determining region Y) - produces testis determining factor (TDF)

27
Q

What is dosage compensation?

A

The mechanism that keeps X-linked gene product doses similar between males and females

28
Q

What is a Barr body?

A

It is a method of darkly staining the nucleus of female cells

29
Q

What is the Lyon hypothesis?

A

Inactivation is random at an early point in development
Once inactivated all the progeny cells have the same X-chromosome inactivated

30
Q

What is an example of X- Mosaicism in humans?

A

Anhidrotic ectodermal dysplasia, males have no sweat glands and females have a mosaic of decors with and without sweat glands around the body

31
Q

How is the X chromosome inactivated?

A

At a site called XIC, key products are non-coding RNA transcripts (Xist and Tsix)
Xist coats X chromosome from spreading outwards so its densely packed into heterochromatin

Genetics (11 decks)

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