Mendel’s Genetics

By: Janeth Serratos, William Jo, Shane Berchtold, Simon Kuang

Review

MeiosisMeiosis is a process of reduction division in which the number of chromosomes per each cell is cut in half.

Meiosis

Stages of Meiosis1. 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 Meiosis5. 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.Hybridsb.Dominant Factorsc.Allelesd.Recessive Factors

Answer 1

Different forms of genes are called:a.Hybridsb.Dominant Factorsc.Allelesd.Recessive Factors

Question 2

Organisms that have two identical alleles for a particular trait are said to bea.Hybridb.Heterozygousc.Homozygousd.Dominant

Answer 2

Organisms that have two identical alleles for a particular trait are said to bea.Hybridb.Heterozygousc.Homozygousd.Dominant

Question 3

The physical characteristics of an organism are itsa.Geneticsb.Hereditaryc.Phenotyped.Genotype

Answer 3

The physical characteristics of an organism are itsa.Geneticsb.Hereditaryc.Phenotyped.Genotype

Question 4

A situation in which a gene has more than two alleles is known asa.Complete Dominanceb.Co-dominancec.Polygenic Dominanced.Multiple Alleles

Answer 4

A situation in which a gene has more than two alleles is known asa.Complete Dominanceb.Co-dominancec.Polygenic Dominanced.Multiple Alleles

Question 5

Unlike mitosis, meiosis in male mammals results in the formation ofa.One haploid cellb.Three diploid polar bodiesc.Four diploid gamete cellsd.Four haploid gamete cells

Answer 5

Unlike mitosis, meiosis in male mammals results in the formation ofa.One haploid cellb.Three diploid polar bodiesc.Four diploid gamete cellsd.Four haploid gamete cells

Question 6

A gene map showsa.The number of possible alleles for a geneb.The relative location of genes on the chromosomec.Where chromosomes are in the celld.How crossing over occurs

Answer 6

A gene map showsa.The number of possible alleles for a geneb.The relative location of genes on the chromosomec.Where chromosomes are in the celld.How crossing over occurs

Question 7

To maintain the chromosome number of an organism, the gametes musta.Become a diploidb.Become recessivec.Be produced by mitosisd.Be produced by meiosis

Answer 7

To maintain the chromosome number of an organism, the gametes musta.Become a diploidb.Become recessivec.Be produced by mitosisd.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.