BIO152H5 Chapter Notes - Chapter 12: Karyotype, Allosome, Cytokinesis

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31 Jan 2013

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Meiosis is a type of nuclear division. It results in cells that have half as many chromosomes as the parent cell, and in animals it occurs prior to the formation of eggs and sperm. When an egg and a sperm cell combine to form an offspring, the original number of chromosomes is restored. Each cell produced by meiosis receives a different combination of chromosomes. Because genes are located on chromosomes, each cell produced by meiosis receives a different complement of genes. Meiosis leads to offspring that are genetically distinct from each other and from their parents. The leading hypothesis to explain meiosis is that genetically variable offspring are more likely to thrive in changing environments. If mistakes occur during meiosis, the resulting egg and sperm cells may contain the wrong number of chromosomes. Offspring with an incorrect number of chromosomes usually do not develop normally.

Related Questions

Which statements pertaining to genetic variability are correct? Check all that apply (note that wrong answers will be deducted from right answers)!

Crossing over is defined by the exchange of chromosome pieces during metaphase one of meiosis.

If a germ cell (i.e. parent cell before meiosis) had only two pairs of homologous chromosomes (i.e. 4 chromosomes total) there are 2 possible combinations of maternal and paternal chromosomes in gametes.

Siblings produced by sexual reproduction are different because sperms are different from one another and eggs are different from one another, and the combination of an egg and sperm is basically unique.

Random fertilization means that all possible combinations of eggs and sperm are equally likely, i.e. it is pure chance which sperm fuses with which egg.

Individual chromosomes contain thousands of genes. This means that during each crossing over event, more than one gene is exchanged between paternal and maternal chromosomes.

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-Complete the following sentences: metaphase of mitosis, prophase II of meiosis, crossing over, anaphase I of meiosis, variable, random fertilization, identical, random orientation, metaphase I of meiosis, prophase I of meiosis, metaphase II of meiosis, reduction division

Two processes that occur during meiosis produce genetically ____________ cells.

In a process called ____________ , paired homologous chromosomes align randomly at the cell equator. This occurs during this stage of cell division: ____________ .

In a process called ____________ , genetic material is exchanged between homologous chromosomes. This occurs during this stage of cell division: ____________ .

-Complete the following paragraph to describe nondisjunction and the resulting effects on chromosome number.

words: euploidy, primary nondisjunction, nomal, nondisjunction, secondary nondisjunction, homologous chromosomes, abnormal, trisomy, monosomy, sister chromatids, aneuploid

1.During meiosis I, ____________ separate and move towards opposite ends of the poles.

2.During meiosis II, ____________ separate and move towards opposite ends of the poles.

3.During meiosis I, if both members of a homologous pair go into the same daughter cell, ____________ is said to occur and no normal gametes are produced.

4.During meiosis II, if the sister chromatids fail to separate and both daughter chromosomes go into the same gamete, ____________ is said to occur. Half the gametes are aneuploid while the other half are euploid.

5.If an egg that contains 24 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

6.If an egg that contains 22 chromosomes instead of 23 chromosomes is fertilized by a normal sperm, ____________ is said to have occurred.

What type of daughter cells are produced during meiosis?

A. genetically distinct due to crossing over

B. genetically identical to the mother cell

C. genetically identical to each other

D. genetically aneuploids

What is NOT a benefit of asexual reproduction compared to sexual reproduction?

A. The offspring will be as successful in the habitat as the parent.

B. all members of the population can reproduce themselves

C. The only source of variation in the next generation is mutation.

D. They do not require another organism of the opposite sex.

In what phase of meiosis does Independent assortment of homologous chromosomes occur?

A. meiosis I

B. interphase

C. cytokinesis

D. meiosis II

In what phase of meiosis does Independent assortment of homologous chromosomes occur?

A. meiosis I

B. interphase

C. cytokinesis

D. meiosis II

BIO152H5 Chapter Notes - Chapter 12: Karyotype, Allosome, Cytokinesis

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