1. Reproduction Valentine’s Day
Perfect time to introduce the next subject in class

2. Biology, 9th ed,Sylvia Mader
Chapter 09
Asexual Reproduction
One parent
The prokaryotic chromosome is a ring of DNA
Binary fission
Cell splits in two
Produces two genetically identical daughter cells, exactly like the original– asexual reproduction
The Cell Cycle

3. Binary Fission The Cell Cycle Biology, 9th ed,Sylvia Mader Chapter 09
Slide #3
Binary Fission
The Cell Cycle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
chromosome
1. Attachment of chromosome to
a special plasma membrane
site indicates that this
bacterium is about to divide.
cell wall
plasma
membrane
cytoplasm
2. The cell is preparing for binary
fission by enlarging its cell wall,
plasma membrane, and overall
volume.
3. DNA replication has produced
two identical chromosomes.
Cell wall and plasma membrane begin to grow inward.
4. As the cell elongates, the
chromosomes are pulled apart.
Cytoplasm is being distributed
evenly.
5. New cell wall and plasma
membrane has divided the
daughter cells.
© Dennis Kunkel Microscopy, Inc./Visuals Unlimited
SEM
2,345X

4. Sexual Reproduction Two parents Sexual Reproduction
Cell splits twice
Produces four daughter cells, genetically different from the parent and each other –meiosis
Increases genetic variation

5. Haploid vs. Diploid HAPLOID 1n One copy of each chromosome DIPLOID 2n
Two copies of each chromosome
Homologous chromosomes

6. Chromosome Structure

7. Homologous Chromosomes
Biology, 9th ed,Sylvia Mader
Chapter 10
Homologous Chromosomes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a.
Sister chromatids
nonsister
chromatids
duplication
duplication
kinetochore
centromere
chromosome
homologous pair
chromosome
paternal chromosome
maternal chromosome b.
a: © L. Willatt/Photo Researchers, Inc.
Meiosis & Sexual Reproduction

8. Biology, 9th ed,Sylvia Mader
Overview of Meiosis
Chapter 10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Diploid parent cell
2n = 4
Meiosis & Sexual Reproduction

9. Meiosis & Sexual Reproduction synapse and then separate.
Biology, 9th ed,Sylvia Mader
Overview of Meiosis
Chapter 10
Slide #9
Meiosis & Sexual Reproduction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
centrioles
nucleolus
centromere
chromosome
duplication
2n = 4
2n = 4
MEIOSISI
Homologous pairs
synapse and then separate. 9

10. Overview of Meiosis Meiosis & Sexual Reproduction 10
Biology, 9th ed,Sylvia Mader
Overview of Meiosis
Chapter 10
Slide #10
Meiosis & Sexual Reproduction
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
First division
Second division
Four haploid
daughter cells
centrioles
nucleolus
sister chromatids
centromere
synapsis
chromosome
duplication
2n = 4
2n = 4
n = 2
n = 2
MEIOSISI
Homologous pairs
synapse and then separate.
MEIOSISII
Sister chromatids separate,
becoming daughter chromosomes. 10

11. Genetic Variation For humans - 23 pairs of chromosomes:
Independent Assortment
Crossing Over
Random Fertilization
(8 million)(8 million) = 64 trillion possible offspring

12. Independent Assortment
Biology, 9th ed,Sylvia Mader
Chapter 10
Independent Assortment
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Combination 7
Combination 3
Combination 5
Combination 1
Combination 2
Combination 4
Combination 6
Combination 8
There is a 50/50 chance that gamete gets maternal/ paternal homologous chromosome
# of possible gametes = 223 >8 million possible gamete combinations
Meiosis & Sexual Reproduction

13. Crossing Over Occurs During Meiosis I
Biology, 9th ed,Sylvia Mader
Chapter 10
Crossing Over Occurs During Meiosis I
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
sister chromatids
of a chromosome
sister chromatids
of its homologue
Homologous chromosomes swap genes during prophase I
Crossing over increases genetic variation even more A A a a A a B B b b B b
chiasmata of
nonsister
chromatids
1 and 3 c C C c C c D D d d D d 1 2 3 4 1 2 3 4 1 2 3 4
Bivalent
forms
Crossing-over
has occurred
Daughter
chromosomes a. b. c. d.
Meiosis & Sexual Reproduction