BI226 Study Guide - Nondisjunction, Single Transverse Palmar Crease, Homologous Chromosome

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salmondeer718

11 Apr 2013

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Chapter 6 chromosomal mutations: an organism or cell is euploid when it has one complete set of chromosomes, or exact multiples of complete sets. Nondisjunction in meiosis i will produce four gametes, two with a chromosome duplicated, and two that are missing a chromosome. Fusion of a normal gamete with one containing a chromosomal duplication will produce a zygote with three copies of that chromosome, and two of all the others. Fusion of abnormal gametes with normal ones will produce the genotypes discussed previously. Normal gametes are also produced and when fertilized will produce normal zygotes: more complex gametic chromosome composition can result when: Nondisjunction occurs in mitosis (result is somatic cells with unusual chromosome complements). Aneuploidy: autosomal aneuploidy is not well tolerated in animals, and in mammals is detected mainly after spontaneous abortion. Monosomy involves loss of a single chromosome (2n-1) Nullisomy involves loss of one homologous chromosome pair (cell is 2n-2)

Related Questions

Match the terms to the definitions provided.

Question 1 options:

	gamete
	somatic cells
	zygote
	sexual reproduction

1.	Reproductive life cycle that involves an alternation between haploid and diploid cells
2.	A single cell with a diploid number of chromosomes resulting from the fusion of an egg and a sperm.
3.	Cells (egg or sperm) resulting from a meiotic division of germ-line cells
4.	The non-reproductive cells found in embryos and mature individuals

Question 2 (5 points)

Match the terms to the definitions provided.

Question 2 options:

	syngamy
	haploid
	meiosis
	diploid
	germ-line cells

1.	The cells that will eventually undergo meiosis to produce gametes.
2.	The number of chromosomes found in gametes (eggs or sperm).
3.	The process by which two haploid gametes fuse to form a new diploid cell.
4.	A specialized reduction division that produces cells with half the normal number of chromosomes.
5.	Two sets of chromosomes present in the somatic cells of adult individuals.

-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.

Imagine that a human primary oocyte undergoes the first meiotic division but experiences a nondisjunction event such that both copies of chromosome 7 are transmitted to the first polar body and neither are inherited by the secondary oocyte. Oogenesis is then completed and the resulting egg is fertilized by a healthy sperm with normal chromosomal content.

a. How many chromosomes will be present in the resulting zygote?

b. Would you describe this zygote as haploid, diploid, polyploid, or aneuploid?

c. Would you expect this nondisjunction event to result in substantial phenotypic effects on the resulting offspring or would the outcome be more or less the same as if the nondisjunction event had not occurred?

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BI226 Study Guide - Nondisjunction, Single Transverse Palmar Crease, Homologous Chromosome

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