Meiosis

Question 1

Purpose of meiosis

Answer 1

• To create sex cells (gametes) of the correct number of chromosomes. Takes a diploid cell and works to halve it
• To increase the genetic variation during sexual reproduction

Question 2

Somatic

Answer 2

Body cells, diploids (2n)

Question 3

Gametes

Answer 3

Sex cells, haploids (n)

Question 4

What is “n” for humans

Answer 4

n = 23

Question 5

Chromosome 23

Answer 5

Chromosome 23 determines the gender of the offspring.

• Females have two homologous X chromosomes (XX).
• Males have one X chromosome and one Y chromosome (XY), which are not homologous.

Question 6

Diploid are made …

Answer 6

23 chromosome from the father and 23 from the mother, homologous chromosomes join together from 23 pairs and 46 total

Question 7

What is the only non homologous chromosomes except

Answer 7

Male chromosome are the only exception when it comes to homologous pairs. Because in order to make a male it requires both an X and Y chromosome

Question 8

Prophase 1

Answer 8

• Chromatins condense to form chromosomes, which contains 2 sister chromatids
• Sister chromatids are held together by a centromere in
• Homologous chromosome (4 chromatids), which consist of two sister chromatids join together where they exchange genetic information through cross over

Question 9

Cross over

Answer 9

Homologous chromosomes join up with each other, where they exchange genetic information (segments) to increase the genetic variation

Question 10

Metaphase 1

Answer 10

• Homologous chromosome pairs line up randomly along the middle
• Spindle fibers attach the the centromere of each chromosome and mover them

Question 11

Anaphase 1

Answer 11

• Spindle fibers shorten pulling the homologous chromosomes away from each other and to opposite poles

Question 12

Telophase/cytokinesis 1

Answer 12

*The nucleus and nuclear membrane begin to reform
* The cell begins pinching inward, as the cleavage furrow forms, making two new cells
* Begin to un condense slightly

Question 13

Prophase 2

Answer 13

• each daughter will undergo prophase two,
  *they are now haploids (23 chromosomes)
• New centrioles in spindle fibres will form
• homologous chromosomes are no longer present only chromosomes which contain two sister chromatids,
  *Chromosome will condense again
• nucleus and nuclear membrane will disappear

Question 14

Metaphase 2

Answer 14

Spindle fibers will attach to the centromere between the sister chromatids (chromosome) and line them up along the metaphase plate (middle) of the the cell

Question 15

Anaphase 2

Answer 15

Spindle fibers shorten and separate the sister chromatids, pulling them away from each other to opposite poles
Chromosomes now consist of one sister chromatid

Question 16

Telophase/ cytokinesis 2

Answer 16

The nucleus and nuclear membrane reform

Cell pinches inward as the cleavage furrow forms

The chromosome un condensed

Forms 4 new cell

Question 17

Goal of meiosis 1

Answer 17

Separate homologous pairs, reducing the chromosomes number by half. and rise to two daughter cells with 23 chromosomes each which consist of 2 sister chromatids

Question 18

Goal it meiosis 2

Answer 18

The goal is to separate sister chromatids and give rise to two more cells

Question 19

Independent assortment and cross over genetic variation

Answer 19

Independent assortment is the random lining up of the homologous chromosomes during metaphase 1 and their separation during anaphase 1. Along with cross over that happens during prophase 1, which randomly exchanges genetic information with homologous chromosomes, they increase the genetic variation and uniqueness between each gamete

Question 20

gametogenesis

Answer 20

Is the process in which a diploid cell is formed into a haploid cell by..
1) meiosis
2) cellular differentiation (spermatogenesis, oogenesis)

Question 21

spermatogenesis

Answer 21

• Occurs in males testicles
• A spermatogonium undergoes mitosis. One of the daughter cell will stay a spermatogonium while the other will become a spermatocyte
• A spermatocyte will undergo meiosis and give rise to four genetically unique sperm cells
• About 1 billion sperm is produce in a day

Question 22

Oogenesis

Answer 22

*Occurs in the female ovaries
* oogonium undergoes mitosis, producing a oogonium and a oocyte.
*Oocyte undergoes meiosis which gives rise to the ovum and the polar bodies
*the ovum receives most of the cytoplasm and will become the egg
*the polar bodies receive less cytoplasm and will eventually die and be absorbed
* Only one ovum is produced

Question 23

Similarly between mitosis and meiosis

Answer 23

• Both undergo DNA replication during interphase stage S
• Both give rise to daughter cells
• Both undergo similar stages ( P M A T)

Question 24

Differences between mitosis and meiosis

Answer 24

*Meiosis gives rise to 4 genetically unique daughter cells, while mitosis gives rise to two genetically identical daughter cells

*Meiosis is for genetic variation and sexually reproduction, while mitosis is for growth repair and and asexually reproduction

• meiosis gives rise to haploids (23 chromosomes), while mitosis gives rise to diploids (46 chromosomes)