Mendel’s Genetics
By: Janeth Serratos, William Jo,
Shane Berchtold, Simon Kuang
Review
Meiosis
Meiosis is a process of reduction division in
which the number of chromosomes per each
cell is cut in half.
Meiosis
Stages of Meiosis
1. Interphase:
• Cells undergo a round of DNA replication, forming duplicate chromosomes.
2. Prophase 1:
• Each chromosome pairs with its corresponding homologous chromosome to form a
tetrad.
3. Metaphase 1:
•
Spindle fibers attach to the chromosomes.
4. Anaphase 1:
• The fibers pull the homologous chromosomes toward opposite ends of the cell.
5. Telophase 1 and Cytokinesis:
• Nuclear membranes form. The cell separates into two cells.
Stages of Meiosis
5. Prophase 2:
• Meiosis 1 results in two haploid (N) daughter cells, each with half the number of
chromosomes as the original cell.
6. Metaphase 2:
• The chromosomes line up in a similar way to the metaphase stage of mitosis.
7. Anaphase 2:
• The sister chromatids separate and move toward opposite ends of the cell.
8. Telophase 2 and Cytokinesis:
• Meiosis 2 results in four haploid (N) daughter cells.
Gamete Formation
• In many female animals, the cell divisions at the end of meiosis 1 and 2 are uneven,
so that a single cell, which becomes an egg, receives most of the cytoplasm. The
other three cells produced in the female during meiosis are known as polar bodies
and usually do not participate in reproduction.
Gamete Formation
•In male animals, the haploid gametes produced by meiosis are called sperm. In
female animals, generally only one of the cells produced by meiosis is involved in
reproduction. This female gamete is called an egg in animals and an egg cell in some
plants.
Gamete Formation
Comparing Mitosis and Meiosis
•Mitosis results in the production of two genetically identical
diploid cells. A diploid cell that divides by mitosis gives rise to
two diploid (2N) daughter cells. The daughter cells have sets of
chromosomes and alleles that are identical to each other and to
the original parent cell.
Comparing Mitosis and Meiosis
•Meiosis produces four genetically different haploid cells. Begins
with a diploid cell but produces four haploid (N) cells. These cells
are genetically different from the diploid cell and from one
another. Meiosis is how sexually reproductive organisms produce
gametes.
Vocabulary
• Homologous:
• Term used to refer to chromosomes that each have a
corresponding chromosome from the opposite-sex parent
• Diploid
• Term used to refer to a cell that contains both sets of
homologous chromosomes
• Haploid:
• Term used to refer to a cell that contains only a single set
of chromosome and therefore only a single set of genes.
Vocabulary
• Meiosis
• Process by which the number of chromosomes in cut in
half through the separation of homologous chromosomes
in a diploid cell
• Tetrad
• Structure containing 4 chromatids that forms during
meiosis
• Crossing-over
• Process which homologous chromosomes exchange
portions of their chromatids during meiosis
Quiz
Question 1
Different forms of genes are called:
a.Hybrids
b.Dominant Factors
c.Alleles
d.Recessive Factors
Answer 1
Different forms of genes are called:
a.Hybrids
b.Dominant Factors
c.Alleles
d.Recessive Factors
Question 2
Organisms that have two identical alleles for a
particular trait are said to be
a.Hybrid
b.Heterozygous
c.Homozygous
d.Dominant
Answer 2
Organisms that have two identical alleles for a
particular trait are said to be
a.Hybrid
b.Heterozygous
c.Homozygous
d.Dominant
Question 3
The physical characteristics of an organism are
its
a.Genetics
b.Hereditary
c.Phenotype
d.Genotype
Answer 3
The physical characteristics of an organism are
its
a.Genetics
b.Hereditary
c.Phenotype
d.Genotype
Question 4
A situation in which a gene has more than two
alleles is known as
a.Complete Dominance
b.Co-dominance
c.Polygenic Dominance
d.Multiple Alleles
Answer 4
A situation in which a gene has more than two
alleles is known as
a.Complete Dominance
b.Co-dominance
c.Polygenic Dominance
d.Multiple Alleles
Question 5
Unlike mitosis, meiosis in male mammals results
in the formation of
a.One haploid cell
b.Three diploid polar bodies
c.Four diploid gamete cells
d.Four haploid gamete cells
Answer 5
Unlike mitosis, meiosis in male mammals results
in the formation of
a.One haploid cell
b.Three diploid polar bodies
c.Four diploid gamete cells
d.Four haploid gamete cells
Question 6
A gene map shows
a.The number of possible alleles for a gene
b.The relative location of genes on the
chromosome
c.Where chromosomes are in the cell
d.How crossing over occurs
Answer 6
A gene map shows
a.The number of possible alleles for a gene
b.The relative location of genes on the
chromosome
c.Where chromosomes are in the cell
d.How crossing over occurs
Question 7
To maintain the chromosome number of an
organism, the gametes must
a.Become a diploid
b.Become recessive
c.Be produced by mitosis
d.Be produced by meiosis
Answer 7
To maintain the chromosome number of an
organism, the gametes must
a.Become a diploid
b.Become recessive
c.Be produced by mitosis
d.Be produced by meiosis
Question 8
Which is only correct of a true-breeding plant?
a.If allowed to pollinate itself, it will produce
offspring identical to itself.
b.It cannot reproduce if it pollinates itself.
c.It produces a new cell when pollinated.
d.If allowed to pollinate itself, its offspring will
not breed with others of a different species.
Answer 8
Which is only correct of a true-breeding plant?
a.If allowed to pollinate itself, it will produce
offspring identical to itself.
b.It cannot reproduce if it pollinates itself.
c.It produces a new cell when pollinated.
d.If allowed to pollinate itself, its offspring will
not breed with others of a different species.
Question 9
What happens in crossing over?
a.Exchange of chromosomes in portion I.
b.Formation of six haploid cells in telophase II.
c.Exchange of portions of chromatids in
prophase I.
d.Exchange of portions of chromatids in
prophase II.
Answer 9
What happens in crossing over?
a.Exchange of chromosomes in portion I.
b.Formation of six haploid cells in telophase II.
c.Exchange of portions of chromatids in
prophase I.
d.Exchange of portions of chromatids in
prophase II.
Question 10
What is the result of mitosis?
a.Four genetically different haploid cells.
b.Two genetically identical haploid cells.
c.Four genetically identical diploid cells.
d.Two genetically identical diploid cells.
Answer 10
What is the result of mitosis?
a.Four genetically different haploid cells.
b.Two genetically identical haploid cells.
c.Four genetically identical diploid cells.
d.Two genetically identical diploid cells.