Meiosis and Reproduction

Question 1

alleles

Answer 1

different versions of genes

Question 2

prophase 1

Answer 2

• Chromosomes condense
• Spindle is forming
• Nuclear membrane is disintegrating

Question 3

Prometaphase I

Answer 3

• Nuclear membrane disintegrates completely

* Bivalents attach to spindle

Question 4

Metaphase I

Answer 4

• Bivalent lines up at the middle of the cell

o Aka homologous pairs

Question 5

Anaphase I

Answer 5

• Bivalents separate and move to poles

* Sister chromatids remain attached

Question 6

Telophase I and Cytokinesis

Answer 6

• Chromosomes arrive at the poles
• Nuclear membrane begins to reform
• Cell pinches together and separates
• Two haploid daughter cells
• Chromosomes de-condense
• 23 pairs=haploid
• 46 chromosomes= diploid (2n)

Question 7

Prophase II

Answer 7

• Chromosomes condense
• Spindle forms
• Nuclear envelope starts to disintegrate

Question 8

Telophase II

Answer 8

• Cells pinch off
• 4 haploid daughter cells
• chromosomes de-condense

Question 9

Nondisjunction

Answer 9

chromosomes don’t separate correctly

can result in:
o A fertilized egg missing 1 copy of a chromosome
o A fertilized egg with 3 copies of a chromosome (trisomy)

usually lethal

Question 10

trisomy1

Answer 10

fertilized egg never implants in the uterus

Question 11

common trisomies

Answer 11

21, 18,13, X and Y

Question 12

genetic abnormalities

Answer 12

increased with advanced maternal age

Question 13

genetic variation

Answer 13

• Meiosis=basis for evolution
• Darwin realized that genetic variation was necessary for evolution
• Couldn’t explain how it happened, or why offspring resembled but were not identical to their parents
• Gregor Mendel developed theories to answer these questions