Gamete Formation & Nondijunction

Question 1

What is gametogenesis?

Answer 1

Gamete (sex cell formation)

• formed from germ cells
• specializes into either sperm or eggs

Question 2

Spermatogenesis

Answer 2

Sperm formation

Question 3

Oogensis

Answer 3

Egg formation (ovum formatjon)

Question 4

What are the names for various steps in soermatogensis?

Answer 4

1. Diploid spermatogonia (og germ/parent cell)
2. Primary spermatocyte (halfway through meiosis)
3. 4 spermatoids (end result. They are undifferentiated sperm cells)

Question 5

How do you calculate the number of possible pairings during independent assortment, according to the number of chromosomes?

Answer 5

2^n

Question 6

What are the names of the steps during oogenesis?

Answer 6

1. Diploid oogonia (og germ/parent cell)
2. Primary oocyte (halfway through meiosis)
3. 1 ova , 3 polar bodies

Question 7

What type of cell undergoes meiosis

Answer 7

Germ cell

Question 8

What is the name for an egg

Answer 8

Ova. Ovum plrl

Question 9

What are polar bodies? What happens to them?

Answer 9

3 polar bodies are made during meiosis. They have nothing but a nucleus, because all the organelles went to the egg - they quickly get recycled.

Question 10

When does meiosis end/ when does an undifferentiated egg cell become an egg?

Answer 10

Right before it becomes a zygote.

Question 11

What is nondisjunction?

Answer 11

Mistake that occurs during meiosis. Chromosomes don’t properly split, resulting in an abnormal number of chromosomes (aneuploidy - happens in autosomes or sex cells)

Question 12

Aneuploidy

Answer 12

Abnormal number of chromosomes

Either 45 or 47

Question 13

Trisonomy

Answer 13

Extra chromosome that occurs due to nondisjunction (chromosome doesnt split properly)

Question 14

Monosomy

Answer 14

Lack of a chromosome in an unfertilized cell, due to non disjunction. Very fatal due to the lack of genetic information

Question 15

What are the two categories for nondisjunction?

Answer 15

1. Failure to split homologous chromosomes, occurs during meiosis 1
   - the result is that all of the gametes are irregular
2. Failure to split sister chromatids, occurs in meiosis 2
   - results in half the gametes being irregular (often occurs in females over 35)

Question 16

Result of nondisjunction disorder

Answer 16

Results in a lot of human genetic disorders, cells arnt able to function properly.
Changes physical appearance as well as mental challenges.
(Cases of monosomy are usually fatal)

Ex. Down syndrom- extra chromosome 21 (3 instead of 2)

Question 17

Amniocentesis

Answer 17

Diagnosing fetus by pushing a needle into the moms stomach to get a sample of DNA. Could cause a miscarriage

Question 18

Chorionic villus

Answer 18

Tests fetuses DNA through the vagina. Could cause a miscarriage

Question 19

Why are women over 35 more at risk to have children with genetic complications

Answer 19

Girls start meiosis when they’re in the womb, so they create a limited amount of cells that will turn to eggs (stops at pro phase 1)
Meiosis then continues after puberty, but there still remains a set number of eggs.
As the women ages, so does the organelles, allowing for more complications.

Question 20

Deletion (abnormal chromosome disorder)

Answer 20

Lose an allele/section of the chromosome when crossing. Could be very fatal.

ABCDEFG - ABDEFG

Question 21

Duplication (abnormal chromosome structure)

Answer 21

Sequence reattached to an already complete chromosome

Question 22

Inversion (abnormal chromosome structure)

Answer 22

Segment rematches in the wrong order during cross over

ABCDEFG - ABCGFED

Question 23

Translation (abnormal chromosome structure)

Answer 23

Crossing over happens between pairs of chromosome that arnt homologous