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Biology > Meiosis > Flashcards

Meiosis Flashcards

1
Q

why is sexual reproduction important for survival

A

the varied genes give better chances to individuals for survival

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2
Q

where does meiosis happen

A

-in cells that will become gametes (not egg or sperm itself)
-spermatocytes and primary oocytes (both produced by mitosis)

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3
Q

how are sperm produced

A

from spermatocytes via meiosis

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4
Q

how are eggs (secondary oocytes) produced

A

from primary oocytes via meiosis

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5
Q

meiosis produces cells that

A

-have half the # of chromosomes found in the original parent cell
-are genetically different from the parent cell and each other

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6
Q

why is the number of chromosomes halved

A

-to prevent mutations
-to keep number of chromosomes constant between all generations
-or else chromosomes double each generation

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7
Q

what are homologous pairs

A

-chromosome pair that have the same genes (chromosome one of mom with chromosome one of dad)
-not identical (because of alleles) but similar

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8
Q

what are alleles

A

alternative versions of a gene

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9
Q

what do alleles control

A

they control the same character but do not necessarily contain the same genetic info

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10
Q

what is the goal of meiosis

A

to convert diploid parent cells to haploid sex cells

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11
Q

how does the duration of mitosis compared to the duration of meiosis

A

mitosis takes around 12-24 hours
meiosis takes over 48 days depending on the species and cell type

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12
Q

what is the process of meiosis

A

-meiosis I (two daughter cells): prophase l metaphase l anaphase l telophase l cytokinesis
-meiosis II (4 daughter cells): prophase ll metaphase ll anaphase ll telophase ll cytokinesis

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13
Q

what is meiosis preceded by

A

interphase (same as mitosis)
-46 chromosomes but 92 chromatids

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14
Q

what’s the difference between mitotic prophase and meiosis prophase l

A

in mitosis the sister chromatids stay together
in meiosis l homologous pairs attach with another homologous pair (2Xs next to each other)

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15
Q

what are two pairs of homologous chromosomes next to each other called

A

tetrads

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16
Q

what is synapsis

A

two homologous chromosomes pair (2Xs) are held together tightly and crossing over happens

17
Q

what holds the pairs together during synapsis

A

proteins

18
Q

what is crossing over

A

exchange of genetic information between nonsister chromatids

19
Q

when does crossing over happen

A

prophase I

20
Q

what is the end result of crossing over

A

chromosomes will have the same number of genes but the sister chromatids are no longer identical

21
Q

when can crossing over occur

A

can occur anytime on a chromosome during propahse I as agreat way to introduce variation

22
Q

how is metaphase l difference than the mitotic metaphase

A

-in mitosis the sister chromatids line up single file
-in meiosis l chromosomes line up as homologous pairs (tetrads)

23
Q

what happens in anaphase I

A

the homologous chromosomes pairs get separated (one X per side of cell)
- diploid into haploid

24
Q

are telophase l and cytokinesis the same for meiosis l as for mitosis

A

yes

25
Q

are the chromosomes replicated again between meiosis l and ll

A

no

26
Q

how does meiosis ll compared to mitosis

A

almost the same except the sister chromatids are not identical because of the crossing over

27
Q

where does cytokinesis occur

A

occurs in each cell produced by meiosis

28
Q

how many cells are resulted from a parent oocyte

A

one ovum and three polar bodies

29
Q

what are polar bodies

A

non functioning cells that aren’t big enough to continue the meiosis process

30
Q

why is the one ovum the biggest one

A

because it has better chances of surviving past fertilization
has more nutrients to cell divide (to make zygote), can meet its metabolic needs

31
Q

how does oogenisis and the ovarian cycle work

A

all eggs are made before birth, not fully developed which starts at puberty (paused until then)

32
Q

what are the three ways of increasing genetic variation

A

-crossing over
-independent assortment of chromosomes (M1)
-random fertilization (conception)

33
Q

what is the independent assortment of chromosomes

A

each pair of chromosomes sorts maternal and paternal homologues into daughter cells independently of the other pairs in meiosis I

34
Q

what is random fertilization

A

any sperm can fuse with any ovum

35
Q

what is the evolutionary significance

A

-natural selection results in the accumulation of genetic variations favoured by environment
-certain combinations of alleles may work better

36
Q

how are alleles connected to mutations

A

a mutation is the original source of different alleles

Biology (12 decks)

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