meiosis

Question 1

what is meiosis

Answer 1

the division of one cell into four cells each of which has half the chromosome number as the parent cell , each of the four cells is genetically different from each other

Question 2

when does meiosis occur

Answer 2

during gametogenesis a process during which gametes are formed

Question 3

where does meiosis occur in plants

Answer 3

in the anther to produce pollen grains and in the ovary to produce the ovule

Question 4

where does meiosis occur in humans

Answer 4

in the testes to produce sperms and in the ovary to produce an ovum

Question 5

where does meiosis occur in some lower organisms

Answer 5

immediately after fertilization

Question 6

halving effect

Answer 6

meiosis allows for diploid cells in the sex organ to form haploid gametes

Question 7

doubling effect

Answer 7

when two haploid gametes fuse , they form a diploid zygote

Question 8

how is the number of chromosomes kept constant from one generation to the next

Answer 8

the halving effect of meiosis overcomes the doubling effect of fusion

Question 9

when does meiosis take place

Answer 9

in most plants and animals including humans meiosis take place when gametes are formed (before fertilization )

Question 10

what doe these gametes therefore have

Answer 10

half the chromosome number or one set of chromosomes ( haploid number or n ) compared to adults

Question 11

what does the fusion of the gametes result in

Answer 11

the diploid chromosome number being restored in the zygote which undergoes mitosis to produce a multicellular adult

Question 12

what results in diploid zygotes

Answer 12

the adults are haploid giving rise to haploid gametes which on fertilization results in diploid zygotes

Question 13

what is the function of meiosis occurring in the zygote or zygospore ( after fertilization)

Answer 13

th alve the chromosome number so that the new offspring also have the haploid number of chromosomes

Question 14

meiosis in moss and ferns

what do mosses and ferns show

Answer 14

they show an alternation generations whereby a haploid gametophyte ( gamete producing) generation alternates with a diploid sporophyte ( spore producing ) generation

Question 15

what does haploid gametophytes produce

Answer 15

haploid gametes by mitosis

Question 16

what does the diploid sporophyte produce

Answer 16

haploid spores by meiosis

Question 17

what allows for such alternation of generations

Answer 17

the halving effect

Question 18

what is meiosis

Answer 18

the division od one cell into four cells each of which only has half the chromosome number as the parent cell and each of the four cells is genetically different from each other and the parent cell

Question 19

how many divisions does the nucleus undergo

Answer 19

two divisions
1) meiosis I
2) meiosis II

Question 20

even though meiosis is a continuous process what various events in this process is it divided into

Answer 20

prophase , metaphase , anaphase ,telophase

Question 21

what begins before meiosis

Answer 21

dna replication takes place before meiosis begins during a stage called interphase

Question 22

interphase

dna replicates in the preparation for what

Answer 22

nuclear division

Question 23

interphase

why does dna replicate

Answer 23

so that the genetic material is doubled in the chromatin network

Question 24

interphase

what happens to the single stranded chromosome’s

Answer 24

they become double stranded

Question 25

prophase I what happens to the nuclear membrane

Answer 25

begins to disappear

Question 26

prophase I what does the chromatin network unwind to form

Answer 26

to form distinct chromosomes

Question 27

prophase I what is each chromosomes made up of

Answer 27

two identical chromatids (because of dna replication in interphase

Question 28

prophase I what do the chromosomes come together in

Answer 28

together in homologous pairs i.e. two identical chromosomes , one of paternal origin and one of maternal origin

Question 29

prophase I where does crossing over take place

Answer 29

between chromatids of homologous chromosomes leading to the exchange of genetic material

Question 30

prophase I what does the centrosome split into

Answer 30

into two centrioles which start moving in opposite directions

Question 31

metaphase I what forms between the centrioles

Answer 31

spindle threads

Question 32

metaphase I where does the chromosomes become arranged

Answer 32

along the equator in homologous pairs , attached to spindle threads

Question 33

metaphase I what happens to the spindle threads

Answer 33

they contract

Question 34

anaphase I what happens to the two chromosomes of each homologous pair ( each with two chromatids )

Answer 34

they are pulled to the opposite poles

Question 35

telophase I what appear forming a nucleus at each pole

Answer 35

two groups of chromosomes

Question 36

telophase I what happens the cytoplasm

Answer 36

divides to form two new cells

Question 37

telophase I thus what do we have resulting from the division of cytoplasm

Answer 37

we have a nucleus in each cell within which there is half the number of chromosomes as the original

Question 38

telophase I why are the two new cells genetically different

Answer 38

because of crossing over