Mendel and Meiosis Ch. 10
Terms in this set (33)
first stage of the cell cycle, during which a cell grows, matures, and replicates its DNA
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.
The second phase of meiosis I. During metaphase I the paired homologous chromsomes (tetrads) align at the center of the cell (the metaphase plate).
The third phase of meiosis I. the replicated homologous chromosomes are separated (the tetrad is split) and pulled to opposite sides of the cell.
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.
each cell is haploid with chromosomes in replicated form
sister chromatids align along the metaphase plate
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.
4 cell results....each cell is haploid with unreplicated chromosomes
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.
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.
A cell with two of each kind of chromosome is called _____________.
Sperm or egg cells are ______________.
A cell with one of each kind of chromosomes is called ___________.
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.
The reassortment of genetic information, which results in variation among organisms, is called ______ ________.
The _____ produced by each parent are shown along the sides of a Punnett square.
a. zygotes c. gametes
b. offspring d. hybrids
The passing on of traits from parents to offspring is called _____.
a. genetics c. inbreeding
b. heredity d. gene splicing
A cross involving two different traits
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
What are the possible gametes of this parent: GgWW
GW, GW, gW, gW
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.
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
law of independent assortment
Mendelian principle stating that genes for different traits are inherited independently of each other
both alleles are the same
both alleles are different
Both alleles are for the dominant trait.
Both alleles are for the recessive trait.
Purple flowers (P) are dominant to white flowers (p). Give the phenotype for each genotype listed below.
A dihybrid cross between two heterozygous parents produces a phenotypic ratio of __________.
A monohybrid cross between two heterozygous parents produces a phenotypic ratio of __________.
error in meiosis in which homologous chromosomes don't separate; gametes end up with wrong number of chromosomes
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