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
