chapter 13

meiosis I

(reductional division) homologous chromosomes pair up and separate resulting in two haploid daughter cells with replicated chromosomes

prophase I

chromosomes form tetrads, homologous chromosomes align by genes, crossing over occurs

Which of the following statements correctly describes a karyotype?

It is an organized image of a cell's chromosomes.

meiosis

cell division for gametes

mutations

changes in an organisms DNA

haploid cell (n)

has one set of chromosomes

Somatic cells of roundworms have four individual chromosomes per cell. How many chromosomes would you expect to find in an ovum from a roundworm?

two

genes

unit of heredity

sex chromosomes

X and Y chromosomes.

chiastema

x-shaped regions where crossing over occurs

meosis II

(equational division) sister chromatids separate resulting in four haploid daughter cells with unreplicated chromosomes

diploid number in humans

23

how many pairs of chromosomes do humans have

23 pairs of chromosomes (diploid cells)

Which of the following processes occurs when homologous chromosomes cross over in meiosis I?

Corresponding segments of non-sister chromatids are exchanged.

How are sister chromatids and homologous chromosomes different from each other?

Homologous chromosomes contain the same gene loci but may have different alleles of a particular gene. Sister chromatids are identical copies of each other produced during DNA replication.

sister chromatids

Identical copies of a chromosome; full sets of these are created during the S subphase of interphase.

Which of the following statements is correct in comparing sexual and asexual reproduction?

In sexual reproduction, individuals transmit half of their nuclear genes to each of their offspring.

telophase II and cytokinesis

Nuclei form, the chromosomes begin to decondense

phases of meiosis I

Prophase I, Metaphase I, Anaphase I, Telophase I

Which of the following statements describes the chromosomal makeup of each daughter cell after telophase of meiosis I?

The cells are haploid, and the chromosomes are each composed of two chromatids.

Which of the following statements is correct regarding the human sex chromosomes?

They determine an individual's biological sex

female sex chromosomes

XX

male sex chromosomes

XY

asexual reproduction

a single individual passes genes to its offspring without the fustion of gametes

tetrad

structure containing 4 chromatids that forms during meiosis

During which of the following phases of meiosis do homologous chromosomes separate?

anaphase I

During which of the following phases of meiosis do centromeres split and sister chromatids migrate to opposite poles of the cell?

anaphase II

crossing over

begins in early prophase, portions of nonsiter chromatids trade places

Many organisms spend most of their life cycle in the diploid state. If meiosis produces haploid cells, how is the diploid number restored for these types of organisms?

by fertilization

Which of the following occurs during meiosis but not during mitosis?

crossing over occurs.

three mechanisms that contribute to genetic variation

crossing over, independent assortment of chromosomes and random fertilization

telophase I and cytokinesis

each half of the cell has a haploid set of chromosomes, each chromosomes still consists of two sister chromatids

what is the product of meiosis?

four genetically distinct daughter cells with a haploid set of unreplicated chromosomes

Meiosis II is similar to mitosis in that

ister chromatids separate during anaphase.

human gametes are produced by _____.

meiosis

The two homologs of a pair move toward opposite poles of a dividing cell during

meiosis I.

During which of the following processes do homologous pairs of chromosomes align adjacent to one another at the metaphase plate of a cell?

metaphase I of meiosis

autosomes

non-sex chromosomes (22 pairs)

corssing over

nonsister chromatids exchange DNA segmetns between nonsister chromatids

karyotype

ordered display of the pairs of chromosomes from a cell

anaphase I

pairs on homologous chromosomes separate, sister chromatids remain attached at the centromere

Crossing over occurs during _____.

prophase I

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

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

what are genes made up of

segments of DNA

metaphase II

sister chromatids arranged at metaphase plate, sister chromatids are no longer identical

anaphase II

sister chromatids separate moving toward oppostie poles

random fertilization

source of genetic variation caused by the unlimited number of possible sperm and egg combinations

metaphase I

tetrads line up at metaphase plate, microtubules from one pole are attached to the kinetochore of one chromosome on each tetrad

prophase II

the duplicated chromosomes and spindle fibers reappear in each new cell, two haploid cells

life cycle

the generation to generation sequence of stages in the reproductive history of an organism

synapsis

the pairing of homologous chromosomes during meiosis

independent assortment of chromosomes

the random distribution of maternal and paternal chromosomes into gametes during metaphase I

Independent assortment of chromosomes is a result of which of the following processes?

the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I

chromosomes in homologous pair are...

the same length and shape and carry genes controlling the same inherited characters

homologous chromosomes

the two chromosomes in each pair

In diploid cells: mitosis results in the formation of how many cells; meiosis results in the formation of how many cells?

two diploid cells ... four haploid cells

sexual reproduction

two patents give rise to an offspring that have unique combination of geness inherited from the two parents

diploid cell (2n)

two sets of chromosomes