L14- Mitosis and meiosis review Flashcards

1
Q

missegregation in meiosis (non-disjunction)

A

• A third of all identified miscarriages • Infertility • Leading cause of learning disabilities

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2
Q

in a metaphase spread

A

chromosomes are stained when they are actively dividing - can then be grouped according to size and shape (A-G)

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3
Q

karyotyping

A

A way of organising/ numbering chromosomes in order of size and pattern

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4
Q
  • How are karyotypes described (separated by commas, no space)
A

o Chromosome number o Sex complement o Structural changes  E.g. 46,XY, Normal male karyotype

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5
Q

describe a male with trisomy 21

A

47, XY, +21

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6
Q

during proper disjunction of chromosomes

A

one chromatid goes to either pole

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7
Q

mosaicism

A

Presence of two or more cell lines in an individual

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8
Q

mosaicism can be

A

Throughout the body or tissue limited

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9
Q

in non disjunction

A

both chromatids go to one pole-causes aneuploidy

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10
Q

if mitotic nondisjunction occurs at the first post zygotic division

A

leads to non-mosaic karyotype - monosomy line usually lost unless involves X chromosome

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11
Q

if mitotic nondisjunction occurs in later cell divisions

A

leads to mosaic karyotype

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12
Q

degree of mosaicism

A

depends on when the nondisjunction occurs (i.e. during the first post-zygotic division or in later mitotic divisions)

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13
Q

mitotic nondisjunction can occur in both

A

meiosis I and II

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14
Q

the later the non-disjunction occurs in meiosis

A

the more likely you will have more normal cells

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15
Q

nondisjunction in the sex chromosomes - X chromosomes

A

• Living with one X is still viable i.e. in women one X chromosome is always silenced through imprinting • Living with 3 X is viable (2 silenced)

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16
Q

nondisjunction in the sex chromosomes- Y

A

XYY- though male may have more masculine traits e.g. over production of testosterone (criminal thing)

17
Q

what stage is G0

A
  • Separate stage outside the cell cycle directly after M - Quiescent stage  Can be destination for the cell- e.g. nerve or cardiac cell which doesn’t need to divide anymore.  Could enter cell cycle (temporary rest) again if correct signal are there
18
Q

is random assortment or crossing over more important in eugenic variation

A

both equally important

19
Q

how many chromosomes does every human somatic cells contain in G2, just before mitosis

A

47 chromosomes (92 chromatics)

20
Q

during which phase of mitotic are the homologues chromosomes of each pair lined up

A

ever in mitosis- homologous pairs do not line up in mitosis (only in meiosis when maternal and paternal chromosomes line up)

21
Q
  1. During mitosis the nucleolus disappears during prophase. - What is the nucleolus?
A

 Region of 5 diff chromosomes where ribosomal RNA genes are expressed  Heavily stained area in the nucleus

22
Q

Why is it that the nucleolus is present in the nucleus during interphase, but absent during most of mitosis?

A

 Nucleolus is absent during mitosis:  Chromosomes condense in prophase  Genes on chromosome will not be transcribed anymore  Join other chromosomes to be separated in mitosis

23
Q

How do the sex chromosomes ‘find each other’?

A

 X and X have very similar sequences  X and Y (different sequences) find each other due to having a small region of identical sequence

24
Q
  1. Consider the consequences of a two crossing over events happening, one chiasma in PAR1 and one chiasma in AMELX/AMELY.
A
  • Swap over between the 2 cross over events- any material between cross over will swap from non-sister chromatid to another
25
Q

describe anaphase lag

A

Anaphase lag- chromosome either stays behind or is too slow and will stay behind and become degraded- diff to nondisjunction- unequal distribution