Mendel and Meiosis Ch. 10

Telophase II

4 cell results....each cell is haploid with unreplicated chromosomes

What are the possible gametes of this parent: AABB

AB, AB, AB, AB

What are the possible gametes of this parent: AaBb

AB, Ab, aB, ab

Homozygous dominant

Both alleles are for the dominant trait. AA

Homozygous recessive

Both alleles are for the recessive trait. aa

During which phase(s) does crossing over occur? Why is crossing over important?

Crossing over occurs during prophase I. This is important because it increases genetic variation.

What are the possible gametes of this parent: GgWW

GW, GW, gW, gW

Why is it important that meiosis produces gametes that have only half the number of chromosomes of the parent cell?

Gametes need half the number of chromosomes as a body cell because they will fuse together to form the zygote. The zygote will then have the correct number of chromosomes.

Explain how crossing over in meiosis results in genetic variation.

In crossing over, genetic information is exchanged between homologous chromosomes. This exchange creates new combinations of genes, leading to increased genetic variation in the offspring.

How can you tell the difference between meiosis I and meiosis II by looking at the cells?

Meiosis I has only one cell. Meiosis II has 2 and then 4 cells.

law of independent assortment

Mendelian principle stating that genes for different traits are inherited independently of each other

Prophase I

The first phase of meiosis I. During prophase I the replicated chromosomes condense, homologous chromsomes pair up, crossing over occurs between homologous chromosomes, the spindle is formed, and the nuclear envelope breaks apart into vesicles. Prophase I is the longest phase of meiosis.

Telophase I

The fourth of meiosis I. the number of chromosoms is now reduced by half. After this phase the cell is considered to be haploid. Note however, that the chromosomes are still replicated, and the sister chromatids must still be separated during meiosis II.

Metaphase I

The second phase of meiosis I. During metaphase I the paired homologous chromsomes (tetrads) align at the center of the cell (the metaphase plate).

Anaphase I

The third phase of meiosis I. the replicated homologous chromosomes are separated (the tetrad is split) and pulled to opposite sides of the cell.

Anaphase II

The third phase of meiosis II. During anaphase II the sister chromatids are finally spearated at their centromeres and puled to opposite sides of teh cell. Note that anaphase II is identical to mitotic anaphase, excep the number of chromosmes was reduced by half during meiosis I.

A monohybrid cross between two heterozygous parents produces a phenotypic ratio of __________. a. 3:1 b. 1:2:1 c. 9:3:3:1

a. 3:1

Purple flowers (P) are dominant to white flowers (p). Give the phenotype for each genotype listed below. a. PP b. Pp c. pp

a. purple b. purple c. white

The passing on of traits from parents to offspring is called _____. a. genetics c. inbreeding b. heredity d. gene splicing

b. heredity

Heterozygous

both alleles are different Aa

Homozygous

both alleles are the same AA, aa

A dihybrid cross between two heterozygous parents produces a phenotypic ratio of __________. a. 3:1 b. 1:2:1 c. 9:3:3:1

c. 9:3:3:1

The _____ produced by each parent are shown along the sides of a Punnett square. a. zygotes c. gametes b. offspring d. hybrids

c. gametes

A cross involving two different traits

dihybrid

A cell with two of each kind of chromosome is called _____________.

diploid

Prophase II

each cell is haploid with chromosomes in replicated form

nondisjunction

error in meiosis in which homologous chromosomes don't separate; gametes end up with wrong number of chromosomes

Interphase

first stage of the cell cycle, during which a cell grows, matures, and replicates its DNA

Sperm or egg cells are ______________.

gametes

The reassortment of genetic information, which results in variation among organisms, is called ______ ________.

genetic recombination

A cell with one of each kind of chromosomes is called ___________.

haploid

Law of segregation

members of a pair of homologous chromosomes separate during the formation of gametes and are distributed to different gametes so that every gamete receives only one member of the pair

Metaphase II

sister chromatids align along the metaphase plate