Chapter 13
Ignoring crossover, how many kinds of gametes can be produced by an organism with a diploid number of 8?
16
The egg (ovum) of a rabbit contains 22 chromosomes. How many chromosomes are in the somatic (body) cells of a rabbit?
44
__________ are a group of genetically identical individuals produced by a process called __________.
Clones; asexual reproduction
What is the result when a diploid cell undergoes meiosis?
Four haploid cells
Which of the following occurs in meiosis, but not mitosis?
Homologous chromosomes separate. A number of key differences between meiosis and mitosis exist. Basically, meiosis reduces the number of chromosome sets from two (diploid) to one (haploid), whereas mitosis conserves the number of chromosome sets. Therefore, meiosis produces cells that differ genetically from their parent cell and from each other, whereas mitosis produces daughter cells that are genetically identical to their parent cell and to each other. In addition, homologous chromosomes separate during anaphase I. This event follows synapsis, an event unique to prophase I.
Which life cycle stage is found in plants but not animals?
Multicellular haploid
Which of the following is a function of mitosis in humans?
Multiplication of body cells
Unless the chromosomes were stained to show band patterns, a karyotype would be least likely to show which of the following?
Part of a chromosome turned around. An inversion, where part of a chromosome is turned around, affects neither the number of chromosomes nor the length of a chromosome, and is generally difficult to detect without staining to show chromosomal bands. An extra or missing chromosome can be detected by counting the number of chromosomes displayed.
How many genes are present in the human genome?
Tens of thousands
What is a locus?
The precise location of a gene on a chromosome.
The life cycle called __________ in plants has two multicellular stages: the __________ and the __________.
alternation of generations; haploid gametophyte; diploid sporophyte
Sister chromatids differ from nonsister chromatids in that sister chromatids __________.
are products of the S phase of the cell cycle and are two copies of one chromosome
A clone is the product of __________.
asexual reproduction and mitosis
Somatic cells in humans differs from gametes in that human somatic cells __________.
contain two sets of each of the 23 chromosome types
Regardless of whether an organism is an animal, a plant, a fungus, or an algal cell, all zygotes are __________ and are formed during the __________ of two __________ gametes.
diploid; fertilization; haploid
Darwin realized the importance of heritable variation to evolution __________.
even though he never read any of Gregor Mendel's work
A life cycle in which the only multicellular form is haploid is most typical of __________.
fungi
Allelic variation is an important source of __________ in a population.
genetic diversity
A pair of genetic structures carrying genes that control the same inherited characters are called __________.
homologous chromosomes The two chromosomes of a pair have the same length, centromere position, and staining pattern: These are called homologous chromosomes, or homologs. Both chromosomes of each pair carry genes controlling the same inherited characters. For example, if a gene for eye color is situated at a particular locus on a certain chromosome, then the homolog of that chromosome will also have a version of the same gene specifying eye color at the equivalent locus.
The process called __________ reduces the chromosome number by __________.
meiosis; two consecutive cell divisions
In meiosis, __________ of __________ cross over and form __________.
nonsister chromatids; homologous pairs; chiasmata
The zipper-like complex that forms in meiosis occurs during __________ and is called the __________.
prophase I; synaptonemal complex Prophase I of meiosis is a very busy time. The prophase I cell shown in the figure below is at a point fairly late in prophase I, when homologous pairing, crossing over, and chromosome condensation have already taken place.
At the end of mitosis, __________ daughter cells that are genetically __________ are formed, while at the end of meiosis, __________ daughter cells that are genetically __________ are formed.
two; identical; four; distinct
Regarding the role of cohesin protein in maintaining cohesion between sister chromatids, which of the following statements is false? During meiosis I, cohesion holds sister chromatids together along their lengths as chiasmata form between homologs. During meiosis I, cohesion holds sister chromatids together along their lengths as chiasmata form between homologs and cleavage of cohesins between sister chromatid arms at anaphase I allows homologs to separate. During meiosis I, cohesion holds sister chromatids together along their lengths as chiasmata form between homologs and during meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms During meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms. Cleavage of cohesins between sister chromatid arms at anaphase I allows homologs to separate.
During meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms.
Which of the following statements about homologous chromosomes is correct?
They have genes for the same traits at the same loci.
Somatic cells in animals differ from gametes in that somatic cells __________.
are all of the cells of the body except for the gametes and their precursors
Characteristic of the bdelloid rotifer is that it __________.
is an example of an animal that has not reproduced sexually in 40 million years
The major contribution of sex to evolution is that __________.
it provides a method to increase genetic variation
Genetic diversity requires __________.
sexual reproduction, independent assortment, crossing over between nonsister chromatids of homologous chromosomes, and random fertilization
