Meiosis

Question 1

Meiosis

Answer 1

Takes place in the ovaries and testes only. And has 2 outcomes:

• Reduction Division: produces 4 daughter cells with half the number of chromosomes
• Recombination: products of meiosis have different combinations of genes.

Question 2

Meiosis I

Answer 2

Reduction division (2n -> n) 
-separating homologous chromosomes (tetrads)

Question 3

Meiosis II

Answer 3

Similar to Mitosis (n -> n)

-separating sister chromatids (splitting double-stranded chromosomes)

Question 4

Synapsis

Answer 4

Homologous chromosomes find each other and pair up side by side so corresponding genes are aligned.
-occurs in Prophase I

Question 5

Tetrad

Answer 5

2 chromosomes (4 chromatids) in homologous pair come together to form a tetrad.

Question 6

Crossing Over

Answer 6

Chromatids intertwine during synapsis, sometimes intertwined chromatids from adjacent homologous chromosomes exchange segments of DNA.
= more genetic variation

Question 7

Random Independent Assortment

Answer 7

Homologous chromosomes line up on equatorial plate with one chromosome from each pair positioned on either side of equatorial plate randomly.
-occurs in Metaphase I

Question 8

Segregation

Answer 8

Homologous pairs separate and each homologue moves toward opposite poles of the cell.
=reduction division (2n ->n)
-occurs in Anaphase I

Question 9

Gametogenesis in Females

Answer 9

Called “oogenesis”

• cytoplasm does not divide equally after each nuclear division
• 1 of 4 daughter cells, called the “ootid” receives most of the cytoplasm, other 3 are “polar bodies” with die and are absorbed by the body
• takes 28 days to produce

Question 10

Gametogenesis in Males

Answer 10

Called “spermatogenesis”

• formation of sperm
• spermatocyte differentiate into spermatids
• equal division of cytoplasm
• 4 sperm cells are produced

Question 11

Karyotypes

Answer 11

Organized profile of a person’s chromosomes

• arranged/numbered by size, largest to smallest
• helps scientists quickly identify chromosomal alterations that result in genetic disorder
• chromosomes stained to show banding

Question 12

Nondisjunction

Answer 12

Chromosomes don’t separate properly

• one daughter cell will be LACKING genetic info and one will have TOO MUCH
• much more devastating in a gamete
• offspring with abnormal chromosome number are called aneuploidy

Question 13

Trisomy 21

Answer 13

Down’s Syndrome (extra chromosome at chromosome #21)
-characteristic facial features, short stature, heart defects, respiratory infections, mental delays, sexually underdeveloped and sterile

Question 14

Trisomy 13

Answer 14

Patau Syndrome (extra chromosome at chromosome #13)
-serious eye, brain, and circulatory defects, as well as cleft plate

Question 15

Trisomy 18

Answer 15

Edward’s Syndrome (extra chromosome at chromosome #18)

-almost every organ system affected

Question 16

XXY

Answer 16

Klinefelter’s Syndrome (extra X chromosome in male)

• have male sex organs but abnormally small testes and man is sterile
• breast enlargement and other feminine body characteristics

Question 17

XYY

Answer 17

Super Male

• no real syndrome
• taller than normal
• can be more violent

Question 18

XXX

Answer 18

Trisomy X

• females
• healthy

Question 19

Monosomy

Answer 19

Chromosome is present as only one, instead of 2, in the fertilized egg

Question 20

XO

Answer 20

Turner’s Syndrome

• appears female but sex organs do not mature at adolescence, secondary sex characteristics fail to develop
• sterile and short in stature