meiosis

Question 1

What is meiosis? describe the events that follow is/ the purpose of meiosis

Answer 1

-special type of cell div that occurs in the gametes and results in the formation of sex cells
-in humans it occurs in the ovaries and the testies
-involves stage two of cell division, both have similarites to the phases in mitosis
-the daughter cell is a haploid
- relates to sexual repo. as both parents provide half of the gentic information to the offspring. (23 chromosomes from sperm and egg respectively)
-the paired chromosomes are called homologus chromosomes
-during fertaliztion a haploud sperm unites with a haploid egg cell to produce a diploid
-the zygote then will begin diving by mitosis and become a multicell organism (the child)

Question 2

Meiosis stages

Answer 2

-meiosis have two stages of cellular divsion as opposed to the two in mitosis - meisosis I and II
- the two nuclear divisions results in four haploid cells as opposed to the two diploid cells produced in mitosis
- DNA REPLICATION ONLY OCCURS ONCE, right before meisosi I
- Meiosis I is called a reducion division beaucse the dipolid chromosome number is redu ed to a haploid.
- Meiosis II is marke by the seperation of the two sister chromatids

Question 3

Meiosis I includes which four stages?

Answer 3

Prophase 1
Metaphase 1
Anaphase 1
Telophase 1

Question 4

Meiosis 2 includes which four stages?

Answer 4

Prophases 2
Metaphase 2
Anaphase 2
Telophase 2

Question 5

Prophase 1

Answer 5

• Nuclear membrane begins to dissolve
• Centriole splits, parts move to opp. poles and spidle fiberes form
  -similar to mitosis prophase but during prophase 1 in meisosi crossing over often occurs

Question 6

Describe the events of crossing over in prophase I

Answer 6

-Chromosomes come in homologous pairs, this is called a tetrad as there are two sets of sister chromatids
-the homologous chromosomes come together, align with one non-sister chromatid across from another.
-then the non-sister chromatids intertwine
-when intertwined chromatids from different homologous chromosomes are able to break and exchange segments (why this process is called crossing over)
- this exchanges dna and promotes variation within the species

Question 7

Metaphase I

Answer 7

-Homologous chromosomes line up alone the equatorial plate
-unlike mitosis the chromosomes do not line up single file but rather across from each other
-this separates homologues chromosomes and results in HAPLOID daughter cells

Question 8

Anaphase I

Answer 8

-Homologous chromosomes move towards the poles, this is called SEGRIGATION
-Reduction division results in:
one member of each homologous pair will be found in each of the new cells
-note that sister chromatids will still be joined together

Question 9

telophase I

Answer 9

a nuclear membrane begins to form around each nucleus
- the chromosomes in the nuclei are not identical because each of the daughter nuclei contains one member of the homologous chromosome pair