lecture 9- meiosis

Question 1

why is sexual reproduction important for survival

Answer 1

the varied genes give better chances to individuals for survival

Question 2

where does meiosis happen

Answer 2

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

Question 3

meiosis results in cells that

Answer 3

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

Question 4

why is the number of chromosomes halved

Answer 4

to prevent mutations
to keep number of chromosomes constant between all generations

Question 5

what are homologous pairs

Answer 5

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

Question 6

what are alleles

Answer 6

alternative versions of a gene

Question 7

what is the goal of meiosis

Answer 7

to convert diploid parent cells to haploid sex cells

Question 8

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

Answer 8

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

Question 9

what is the process of meiosis

Answer 9

meiosis one (two daughter cells): prophase l metaphase l anaphase l telophase l cytokinesis
meiosis (4 daughter cells): prophase ll metaphase ll anaphase ll telophase ll cytokinesis

Question 10

what is meiosis preceded by

Answer 10

interphase (same as mitosis)

Question 11

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

Answer 11

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

Question 12

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

Answer 12

tetrads

Question 13

what is synapsis

Answer 13

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

Question 14

what holds the pairs together during synapsis

Answer 14

proteins

Question 15

what is crossing over

Answer 15

exchange of genetic information between nonsister chromatids

Question 16

when does crossing over happen

Answer 16

prophase l

Question 17

how is metaphase l difference than the mitotic metaphase

Answer 17

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

Question 18

during anaphase l what happens

Answer 18

the homologous chromosomes pairs get separated (one X per side of cell)

Question 19

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

Answer 19

yes

Question 20

are the chromosomes replicated again between meiosis l and ll

Answer 20

no

Question 21

how does meiosis ll compared to mitosis

Answer 21

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

Question 22

how many cells are resulted from a parent oocyte

Answer 22

one ovum and three polar bodies

Question 23

what are polar bodies

Answer 23

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

Question 24

why is the one ovum the biggest one

Answer 24

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

Question 25

how does oogenisis and the ovarian cycle work

Answer 25

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

Question 26

what are the three ways of increasing genetic variation

Answer 26

crossing over
independent assortment of chromosomes
random fertilization

Question 27

what is the independent assortment of chromosomes

Answer 27

homologous chromosome pairs being arranged in different order

Question 28

what is random fertilization

Answer 28

any sperm can fuse with any ovum

Question 29

how does evolution play into meiosis

Answer 29

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

Question 30

how are alleles connected to mutations

Answer 30

a mutation is the original source of different alleles