Chapter 8: Cell Reproduction Mitosis and Meiosis. Where is all the genetic information found in a cell?. On the genes on the Chromosomes Chromosomes are actually DNA and proteins If cells were the size of a basketball, your DNA would stretch 64km (40 miles). A Tale of Tall DNA.
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Chapter 8:Cell Reproduction Mitosis and Meiosis
If you unraveled all your chromosomes from all of your cells and laid out the DNA end to end, the strands would stretch from the Earth to the Moon about 6,000 times.
Human – 46 Fruit fly - 8
Chimpanzee – 48 Mosquito - 6
Gorilla – 48 King Crab - 208
Horse – 64Potato - 48
Donkey - 62 Bat - 44
1 set came from each of your parents – 23 pairs for the 2 sets
2 identical chromosomes are called homologous chromosomes
Found in gametes – 23 in us
1N sperm + 1N egg = 2N Zygote
Males have 44 autosomes and 1 unmatched set of sex chromosomes – XY
Females have all 23 pairs matching – XX sex chromosomes
Involved with body cells
The Cell Cycle
Prophase- Longest phase in Mitosis
Made of kinetochore fibers - connect kinetochores to spindle polar fibers
Polar fibers – extend from centriole to centriole Kinetochore (disk-shaped proteins) on centromeres.
Dividing up of cellular contents. Occurs simultaneously with Telophase
Mitosis and Cytokinesis
23 + 23 = 46
46 + 46 = 92
92 + 92 = 184
1N sperm + 1N egg = 2N zygote
23 + 23 = 46 (zygote)
& unlinks genes that are located
on the same chromosome.
Anaphase I& Telophase I
Chromosomes separate independently of each other. This is known as Independent assortment.
Results in random separation of chromosomes & genetic recombination.
Results in 2 - 1N cells
Results in 4-1N cells
At the end of Meiosis II, there are four 1N cells.
Makes 4 haploid spermatids (sperm) from 1 2N primary sperm cell. Looks like normal Meiosis
Produces ovum (eggs) from 1 diploid primary egg cell. Difference occurs during cytokinesis during meiosis I and meiosis II.
Unequal distribution of the cytoplasm resulting in 1 large ovum and 3 small polar bodies.
Polar bodies serve no function in animals but are needed in to plant embryos.
1st Meiotic Division
2nd Meiotic Division