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Chapter 11: Meiosis and Sexual Reproduction
Section 1: Reproduction
Gamete: haploid reproductive cell that unites with another haploid
reproductive cell to form a zygote
Zygote:
Diploid:
Haploid:
Homologous Chromosome: chromosomes that have the same
sequence of genes, that have the same structure and that pair during
reproduction
Reproduction:
I. Asexual reproduction
A.
B. Individual is _________________________________ to parent
C. _______________________________ – asexual reproduction
of prokaryotic cells
D. ____________________________ – reproduction in which body
breaks into several pieces, the pieces regrow missing parts
E. ________________ – a new individual splits off from existing one
F. Parthenogenesis – process in which female makes viable egg that
grows into an adult without being fertilized by a male
II. Sexual Reproduction
A.
1. Each parent produces a reproductive cell called a
2. Gametes join to form a zygote in a process called
3. Offspring has traits of both parents because both give gamete
B. Germ (Sex) Cells and Somatic Cells
1. Germ (Sex) cells –
2. Somatic cells –
C. Advantages of Sexual Reproduction
1. Asexual reproduction is easier and faster way to reproduce
2. Sexual reproduction provides variation (differences) in genes
3. Diverse populations more able to survive environmental change
4.
III. Chromosome Number
A. Genes are located on Chromosomes
1. Each chromosome has thousands of genes that play a role in
determining how an organism develops and functions
2.
3. If an organism has too few or too many it won’t develop and
function properly
4. Human somatic cells have
5. Human sex cells have
B. Haploid and Diploid Cells
1. Diploid cells =
2. Haploid cells =
C. Homologous Chromosomes
1.
2. One of each pair of chromosomes comes from one parent
3. Carry different forms of genes
a. Example – mom may give gene for rolling tongue; dad may
give gene for not rolling tongue
D. Autosomes and Sex Chromosomes
1. autosomes –
2. Sex chromosome –
a. XX =
b. XY =
Section 2: Meiosis
Meoisis:
Crossing Over: a process in which genetic material is exchanged
between homologous chromosomes
Independent Assortment: the random distribution of the pairs of
genes on different chromosome to the gametes
Cytokinesis:
I. Stages of Meiosis
A. A diploid cell goes through 2 divisions to form four haploid cells
1. Meiosis I –
2. Meiosis II –
B. Meiosis I
1. Begins with a diploid cell that has copied its chromosomes
2.
a.
b.
c.
d.
chromosomes condense
nuclear envelope breaks down
homologous chromosomes pair
crossing over occurs (exchange of genetic material)
3.
a. spindle moves pairs of homologous chromosomes to equator
of cell
4.
a. homologous chromosomes separate
b. spindle fibers pull chromosomes to opposite poles
c. cytokinesis begins
5.
a. cytokinesis continues
C. Meiosis II
1. Begins with 2 daughter cells formed from Meiosis I –
2.
a. new spindles form
3.
a. chromosomes line up along the equator
b. chromosomes attach at their centromeres to spindle fibers
4.
a. centromeres divide
b. chromosomes move to opposite sides of the cell
c. cytokinesis begins
5.
a. nuclear envelope forms around each set of chromosomes
b. spindle breaks down
c. cells continue cytokinesis
6.
D. Comparing Mitosis & Meiosis
Mitosis
Types of Cell Made
Genetically
Stages
E. Genetic Variation
1.
2. Made possible by sexual reproduction
3. 3 Key Contributions
a.
b.
c.
Meiosis
4. Crossing Over
a. happens when one arm of a chromosome crosses over the
arm of another
b. each chromosome breaks at the point of the crossover and
then re-forms it full length with a piece from the other
chromosome
c.
5. Independent Assortment
a.
b. can line up in either of 2 equally probable ways
c. 4 haploid cells have a different assortment in each
probability
6. Random Fertilization
a.
b. number of possible outcomes is squared
c. in humans 223 x 223 =
Section 3: Multicellular Life Cycles
Life Cycle: all of the events in the growth and development of an
organism until the organism reaches sexual maturity
Sperm:
Ovum:
I. Diploid Life Cycle
A.
B. Meiosis and Gamete Formation
1.
II. Haploid Life Cycle
A.
1. Meiosis in a diploid zygote results in the formation of the first
cell of a multicellular haploid individual
III. Alternation of Generations
A. Plants and most multicellular protists have a life cycle that
alternates between a haploid phase and a diploid phase
1. Sporophyte –
2. Gametophyte –