genetics

Meiosis produces… 

Mature sperm and eggs

G1 phase: 

Cell growth, chromosomes are not duplicating or dividing

S phase:

Duplication of chromosomes into sister chromatids

G2 phase:

Cell growth, synthesis of proteins required for mitosis

During meiosis I homologous pairs are…

Pulled apart

During meiosis I, sister chromatids…

Stay together

During meiosis I daughter cells contain ____ the number of chromosomes as parent cells

Half

Meiosis I phases:

Prophase I, Metaphase I, Anaphase I, Telophase I and cytokinesis

Prophase I:

Homologous chromosomes pair up to form tetrads and exchange genetic information

Metaphase I:

Paired homologous chromosomes align along the center of the cell

Anaphase I:

Homologous chromosomes separate and are pulled to opposite poles of the cell by spindle fibers

Chiasmata:

Site of crossing over

Shugoshin:

Cohesion proteins stay around centromeres so that they don’t get dissolved

Metaphase II:

Two sister chromatids align single-file along the center of the two haploid daughter cells

Anaphase II:

Centromere cohesion cleaved and then the centromeres split and sister chromatids separate, making two individual chromosomes

You’ve isolated a mutant that fails to undergo synapsis, resulting in unpaired homologous chromosomes in meiosis I. What do you predict the wild-type version of this mutated gene encodes?

A protein that is part of the synaptonemal complex

Meiosis I can assort two ways: RR, rr, TT, tt

Meiosis I can assort two ways: RR, rr, TT, tt

Mitosis, meiosis, or both: reduces the chromosomal content of a cell from diploid to haploid (2n to n)

Meiosis

Mitosis, meiosis, or both: occurs in somatic cells

Mitosis

Mitosis, meiosis, or both: occurs in somatic cells

Meiosis

Mitosis, meiosis, or both: results in two diploid cells

Mitosis

Mitosis, meiosis, or both: DNA replication occurs before the process

Both, during S phase

Mitosis, meiosis, or both: results in four haploid cells

Meiosis

Mitosis, meiosis, or both: involves independent assortment of non-homologous chromosomes

Meiosis

Pseudoautosomal regions (PARs)

Enable sex chromosomes to pair during meiosis I

The X and Y chromosomes align during metaphase I of meiosis due to a…

Pseudoautosomal region that is similar between the X and Y chromosomes

Hemizygous:

Having half the number of alleles as females with two X chromosomes

Reciprocal crosses:

For x-linked traits yield different outcomes depending on which parent carries the trait

• Generational skipping

• Unaffected parents having affected children

• Horizontal pattern

Autosomal recessive

• Vertical pattern 

• Trait isn’t skipping generations

• Every affected individual has an affected parent

Autosomal dominant

• Sex bias

• Crisscross inheritance

X-linked recessive

• Sex bias

• Vertical pattern

X-linked dominant

DNA replication occurs…

Before mitosis and meiosis

Original diploid genotype is Aa Bb:

This cell has alleles AA aa BB bb

Mitosis and meiosis I

Original diploid genotype is Aa Bb:

This cell has alleles AA aa BB

None of them

Original diploid genotype is Aa Bb:

This cell has alleles A and B

Gamete

In genotype AaFf, the A and a indicate

Alleles on homologous chromsomes

Austin and Kajai both have an X-linked dominant disease. Kajai’s mother does not have the disease but her father does. Austin and Kajai have a son. What is the probability that this son will have the disorder?

50%

A man has ichthyosis, an X-linked recessive trait that causes him to have dry scaly skin all over his body. His wife does not display the trait. This couples’ daughter has patches of dry scaly skin and they have a son. Which of the following statements describes the son’s phenotype?

50% chance the son has dry scaly skin all over his body