Quick Review

1
Quick Review

1. What terms are used to describe cells containing
   the normal number of chromosomes?
2. What terms are used to describe cells containing
   half the number of chromosomes?
3. Mitosis produces ________ cells.
4. Meiosis produces ________ cells.
5. How many pairs of chromosomes do human body cells
   have? ___ pairs

Diploid
Haploid
diploid
haploid
23
2
Chromosome Numbers of Some Common Organisms
Organism Body Cell (2n) Gamete (n)
Human 46
Garden Pea 7
Fruit Fly 8
Tomato 12
Dog 78
Chimpanzee 24
Leopard Frog 26
Corn 10
Apple 17
Indian Fern 1260
23
14
4
24
39
48
13
20
34
630
3
Meiosis I

• During prophase I, the ____________ coil up and
  the ______ fibers form. Then each pair of
  homologous chromosomes come together to form a
  four-part structure called a _____ (tetra what
  number? __). A tetrad consists of two homologous
  chromosomes, each made up of two sister
  chromatids.
• These 4 chromatids in a ______ are held very
  close and tightly together. In fact, they are so
  close that the arms of non-sister chromatids can
  wind and twist around each other, and exchange
  genetic information. This is called ________
  ____. Crossing over results in new combinations
  of alleles.

chromosomes
spindle
tetrad
4
tetrad
crossing
over
4
The Phases of MEIOSIS

• Before meiosis begins Interphase
• Before meiosis begins, what must happen to the
  cells DNA/ chromosomes?__________________________
  __
• Meiosis occurs in sexual reproduction when 1
  diploid germ cell produces 4 haploid cells that
  can mature to become _______ (sperm or ova).

They must be copied/ duplicated
gametes
5
Prophase I
Like prophase of mitosis

1. The ______ ________ disappears.
2. ________ move to the opposite poles and the _____
   _____ form between the centrioles.
3. _________ condenses into sister _________

nuclear membrane
Centrioles
spindle fibers
Chromatin
chromatids
Unlike prophase of mitosis

1. Pairs of homologous chromosomes form ______
2. ______ _____ may occur.

tetrads
Crossing over
6
Metaphase I

1. Spindle fibers attach to the ____________________.
   
2. Tetrads line up at the _________ plate.

kinetochore or centromere
metaphase
Anaphase I

1. Tetrads, which consist of two _________
   __________, separate.

homologous chromosomes
7
Telophase I / Cytokinesis I
Nuclear envelope

1. ______ _______ reappears.
2. ______ ____ disappears.
3. __________, the division of the cytoplasm and the
   organelles begins and ends forming two cells.

Spindle fiber
Cytokinesis
8
Meiosis II

• The purpose of meiosis II is to separate _______
  ________ of each chromosome into separate cells.

sister chromatids
Prophase II

1. The _____ _________ disappears.
2. ______ ______ form.
3. ________ condenses into sister _________

nuclear membrane
Spindle fibers
Chromatin
chromatids
9
Metaphase II

1. Sister chromatids attach to the ______ ____
2. Sister chromatids line up at the _________ plate.

spindle fibers
metaphase
10
Anaphase II

1. Sister chromatids separate into ___________.
2. Chromosomes move to the opposite _____.

chromosomes
poles
11
Telophase II

1. ______ _______ reforms.
2. 4 _______ are formed.

Nuclear envelope
gametes