Meiosis

FACULTY OF APPLIED SCIENCES

BIO 150 METABOLISM AND CELL DIVISION (SEM NOVEMBER 2014-APRIL 2015) LABORATORY REPORT EXPERIMENT 7:CELL REPRODUCTION II Date of Experiment:11!""!1# Date of $%&mi''ion:1"!""!1#

INTRODUCTON

Meiosis is the singularly important biological event that not only maintains a constant chromosomes number for most species of plant or animals, but also provides a means of genetic variable because of crossing over and the subseuent e!change of genetic material" In meiosis, immature or primordinal germ cells undergo a #reduction$ in the diploid number of chromosomes characteristic for the species and become mature ga metes" In this study, meiosis %ill be studied as it occurs in the development o nature pollen grains the flo%ering plants" This pollen grains give rise to male gametes, %hich fuse %ithin an egg produce a &ygote"

O'()CTI*)+

" To observe and identify the stages of meiosis in -ily$s anther" ." To observe and identify the stages of meiosis from a given slide"

/00/R/TU+

• • • • • • •

Microscope +lide of lilium root tip mitosis +lide of lilium anther early prophase +lide of lilium root tip mitosis +lide of lilium root tip +lide of lilum anther first divisions +lide of lilium anther late prophase

0ROC)DUR)

"  cm of apical %as cut of from the lilium ." The lilium %as placed on the %atch glass containing acetic orcein stain and 1C- in the appro!imately proportions of the ten parts of stain to one parts of acid" 2" The %atch glass %as %armed, but not boiled, for five minutes on the spirit lamp" The acid helps the tissue to macerated so that the stain can be easily absorbed" 3" 2 mm of the lilium %as cut and the part %as discarded furthest from the ape!" 4" T%o or three drops of acetic orcein added to the lilium" 5" The lilium %as bro6e %ith a needle so as to spread it out as thinly as posibles %ithout interfering too much %ith arrangement of the ce lls" 7" The cover slips %as put on, covered %ith filter paper and suashed gently" 8" The slide %as %armed on the spirit lamp for about ten secinds to intensify the staining" The slide should be %armed but not to hot to touched" 9" The stages in meiosis %as e!amained" :" / labeled diagram for each stage %as provided" " There %as a simplified notes on the changes that occur in every stages in meiosis besides the labeled diagram"

O'+R*/TION+

DI/;R/M 0rophase II

NOT)+ Ne% spindle apparatus is formed on each of   the t%o cells from telophase I" the still< duplicated chromosomes stretch out and then

recondense" +pindle microtubules from each  pole attach to the 6inetochores of each of the sister chromatids" Metaphase II The duplicated chromosomes are aligned along the euator by the spindle comple! in each of the t%o cells"

/naphase II Centromeres of sister chromatids are separated from

each

other

and

the

no%

single

chromosomes are pulled to the poles of the t%o cells"

Telophase II )ach ne% nucleus formed has half the number  of the original chromosomes and eacg nucleus has

one

of

each

type

of

homologous

chromosome" Cyto6inesis results in a total of  four ne% cells, the haploid products" =U)+TION+

" >here else you can find this process in -ily? /nther"

." 1o% do you identify the meiotic division that occurs in the lilium anther? The meiotic divisions is half the number of chromosomes as the parent" @our haploid microscope %ill produce in each germ cell in the male organs or anther %hich undergoes

meiosis in the lily" +i! ro%s of ovules in the lily ovulary, can produre egg cells by meiosis" Meiosis I and Meiosis II are the t%o consecutive divisions in meiosis" The t%o members of each pair of chromosomes separated in first meiotic divisions, the identical chromatids of each chromosomes are separated in the second meiotic divisions" 2" ;ive the significance of meiotic process in organisms" The ovule and ovary are given in variation in genetic" 3" ;ive the difference bet%een the meiotic and mitotic process that occur in -ily" Meiotic 0rocess There are t%o cell division, the first and the

Mitotic 0rocess The cell divide only once"

second meiotic divisions" Chromatids of t%o homologous chromosomes

The t%o

chromosome

do not

e!change

e!change segments during crossing over" segments during prophase" There is no centromeric division uring Divisions of the centromers ta6e place during anaphase I" Centromers divide only during anaphase" anaphase II Occurs in germ cells +pindle fiber do not reappear at telophase I"

Occurs in the somatic cells of the body +pindle fibers disappear completely telophase"

in