Bio K101 chapter 13

a chromosome created when crossing over combines DNA from 2 parents into a single chromosome

recombinant chromosomes

homologous chromatids

same location but one paternal and one maternal

a zipper like structure composed of proteins which connects a chromosome to its homolog tightly along their lengths during part of prophase 1 of meiosis

synaptonemal complex

If meiosis did not occur in sexually reproducing organisms, then

chromosome number would double in each generation (Each sex cell would end up having 46, resulting in a baby with 92 chromosomes, heck no, that's bad!)

a cell containing two chromosomes (2n) one set inherited from each parent

diploid cell

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

Somatic cells in humans contain __________ set(s) of chromosomes and are therefore termed __________.

two; diploid

The zipper-like complex that forms in meiosis occurs during __________ and is called the __________.

prophase I; synaptonemal complex

Genetic diversity requires __________.

sexual reproduction, independent assortment, crossing over between nonsister chromatids of homologous chromosomes, and random fertilization

During prophase I of meiosis, homologous chromosomes lie side by side. This phenomenon is known as

tetrad formation

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

chromosomes of the same length and such, one from mother, one from father

homologous chromosomes

Homologous chromosomes synapse or pair during:

prophase I

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

Which of the following events does not occur in prophase II? a) formation of the spindle b) condensation of chromatin into chromosomes c) formation of chiasmata d) removal of the nuclear membrane e) None of the above, since all the events occur in prophase II

c) formation of chiasmata (This is in prophase I)

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

a specific place along the length of a chromosome where a certain gene is located

locus

when homologous pairs seperate

meiosis 1

when sister chromatids seperate

meiosis 2

The process called __________ reduces the chromosome number by __________.

meiosis; two consecutive cell divisions

Which life cycle stage is found in plants but not animals?

multicellular haploid

In meiosis, __________ of __________ cross over and form __________.

nonsister chromatids; homologous pairs; chiasmata

How many genes are present in the human genome

Tens of thousands

Which of the following occurs in meiosis, but not mitosis?

Homologous chromosomes separate.

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.

asexual reproduction produces

a clone

A zygote contains the ________________ complement of chromosomes.

diploid

During which phase does crossing-over occur?

prophase 1

Ignoring crossover, how many kinds of gametes can be produced by an organism with a diploid number of 8?

16

An animal with a diploid number of 36 chromosomes will have ________ chromosomes in its gametes and _________ chromosomes in its somatic cells.

18; 36 (remember, gamete is a sex cell that has "ha"lf or is a "ha"ploid. Somatic cells are all other normal body cells where in this case 2n=36, so having 2n think of "di"ploid.)

In a human cell at prophase I, there are ____________ tetrads.

23 (a tetrad is 2 pairs of homologous chromosomes, so 4 individual chromosomes total!)

The egg (ovum) of a rabbit contains 22 chromosomes. How many chromosomes are in the somatic (body) cells of a rabbit?

44

human diploid number

46

During which of the following stages of meiosis do the sister centromeres separate?

anaphase II

Regarding the role of cohesin protein in maintaining cohesion between sister chromatids, which of the following statements is false?

During meiosis II, cohesion holds sister chromatids together along their lengths as the second meiotic spindle forms.

The sources of genetic variation during meiosis are:

crossing-over and the random assortment of maternal and paternal chromosomes

Which of the following events does not occur during meiosis I? a) DNA exchange b) pairing of homologous chromosomes c) separation of sister chromatids d) separation of homologous chromosomes e) crossing-over between homologous chromosomes

c) separation of sister chromatids (meiosis I is separation of homologous pairs!)

Somatic cells in humans differs from gametes in that human somatic cells __________.

contain two sets of each of the 23 chromosome types

Which of the following statements about homologous chromosomes is correct?

They have genes for the same traits at the same loci.

During prophase I, each chiasma represents:

a site of crossing-over (The joining bridge between the homologues is chiasmata, or synaptic complex)

A maternal homologue and a paternal homologue synapse to form:

a tetrad

The life cycle called __________ in plants has two multicellular stages: the __________ and the __________.

alternation of generations; haploid gametophyte; diploid sporophyte