Chapter 7

Crossing over during Meiosis I is one of the processes that helps ensure genetic diversity in offspring. How does crossing over occur?

Homologous chromosomes exchange genetic material during Prophase I.

Law of Segregation

Mendel's law that states that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete

What hormones are secreted by the corpus luteum?

Progesterone and estrogen

Synapsis occurs during _____.

Prophase I

During _____ a spindle forms in a haploid cell.

Prophase II

What is the function of the scrotum?

Regulates the position of the testicles

When does DNA replication occur during meiosis?

S phase

The _______ is the lining of the uterine wall that changes in thickness during the menstrual cycle.

endometrium

Meiosis II typically produces _____ cells, each of which is _____.

four... haploid

In what organs does meiosis occur?

gonads

What stage in meiosis does random alignment occur?

metaphase 1

During _____ chromosomes align single file along the equator of a haploid cell.

metaphase 2

The phenomenon when homologous pairs of chromosomes fail to separate from each other during meiosis is called ______________?

nondisjunction

Which statement describes human sperm or egg cells? -They are produced by the process of mitosis. -They have one copy of each chromosome. -They have two copies of each chromosome. -They are genetically identical to all gametes made by a person.

they have one copy of each chromosome

Meiosis I produces _____ cells, each of which is _____.

two ... haploid

law of independent assortment

the law that states that genes separate independently of one another in meiosis

What are homologous chromosomes?

a pair of chromosomes with the same size, shape, and genes

After being expelled from the ovary, the first organ traveled by an egg is ______.

the oviduct

recombinant chromosomes

A chromosome created when crossing over combines the DNA from two parents into a single chromosome.

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

dihybrid cross

A cross between two individuals, concentrating on two definable traits

Homologous chromosomes migrate to opposite poles during _____.

anaphase 1

During what stage of meiosis do the sister chromosomes separate?

anaphase 2

When do sister chromatids separate from each other?

anaphase 2

During _____ sister chromatids separate.

anaphase II

A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____.

both parents are heterozygous for both genes

During which meiotic phase does crossing over occur?

prophase 1

Which processes lead to most genetic variation in sexually reproducing organisms?

random fertilization, independent orientation of chromosomes in meiosis, crossing over

Which characteristic traditionally determines how the 23 pairs of human chromosomes are numbered from 1 to 23?

size

At the end of _____ and cytokinesis, haploid cells contain chromosomes that each consist of two sister chromatids.

telophase 1

At the end of _____ and cytokinesis there are four haploid cells.

telophase 2