BIOL 242 Lecture Notes - Lecture 19: Synapsis, Meiosis, Dna Replication

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azuremole431

2 May 2019

School

University of San Diego

Department

Biology Courses

Course

BIOL 242

Professor

Paul Bradley

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Document Summary

Crossing over combines dna inherited from each parent. Contributes to genetic variation by combining dna from 2 parents into a single chromosome. In humans, an average of 1-3 crossover events occurs per chromosome. 3 events are unique to meiosis, and all 3 occurs in meiosis i. Synapsis and crossing over in prophase i. Homologous chromosomes physically connect and exchange genetic information. Meiosis (can only occur in diploid cells) Occurs during interphase before meiosis i but not meiosis ii. 2, each including prophase, metaphase, anaphase, and telophase. Occurs during prophase i along with crossing over between nonsister chromatids; resulting chiasmata hold pairs together due to sister chromatid cohesion. 4, each haploid (n); genetically different from the parent cell and from each other. Produces gametes (in animals) or spores (in fungi and in plant sporophytes) Reduces number of chromosome sets by half and introduces genetic variability among the gametes or spores. Mitosis (occurs in both diploid and haploid cells)

Related Questions

3)During Metaphase I of meiosis, microtubules called spindle fibers attach to the

	homologous pairs of each chromosome
	non-homologous pairs of each chromosome
	non-sister chromatids of each chromosome
	chiasmata of each chromosome
	centrosome of each chromosome

4)Which meiotic process generates genetic diversity?

	Independent assortment
	Transcription
	Mitosis
	Translation

5)Crossing over:

	Occurs between two homologous chromosomes in Meiosis
	Occurs only in Mitosis
	Can occur in Mitosis and Meiosis
	Involves the exchange of DNA between two chromosomes
	Involvs the exchange of centromeres between two chromosomes

Consider each of the following statements.

In meiosis, the chromosomal material doubles during the lastpremeiotic interphase.

The greater the number of chromosome pairs, the greater is theeffect of meiosis in producing genetically distinct gametes.

The diploid number of chromosomes is half the haploidnumber.

A cell that will not divide again remains in the GÂ2 stage ofinterphase.

The correct sequence of events during meiosis is: synapsis ?dyad formation ? chiasma formation

In an organism with n = 3, there is a 1 in 8 probability of agamete with all maternally derived chromosomes contributing to theproduction of a zygote.

An organism with n = 3 can produce 8 different kinds of gametesin relation to combinations of maternal and paternalchromosomes.

Separation of sister chromatids occurs during anaphase I ofmeiosis and is the physical basis for the law of independentassortment.

A single diploid cell that undergoes meiosis in the male testiswill produce 4 genetically different gametes if crossing-over isignored.

The independent alignment of different tetrads at metaphase I ofmeiosis is the physical basis of the law of independentassortment.

If a diploid cell has 20 pairs of chromosomes, there will be 10tetrads during prophase I of meiosis.

If a diploid cell has 20 pairs of chromosomes, there will be 20bivalents during prophase I of meiosis.

If a diploid cell has 20 pairs of chromosomes, there will be 80chromatids present during metaphase of mitosis.

If a diploid cell has 20 pairs of chromosmes, the organism canmake 20² types of gametes if crossing-over isignored.

Segregation of sister chromatids occurs during anaphase I ofmeiosis and is the physical basis of the law of segregation.

For an individual with a diploid number of 30 chromosomes, therewill be 60 chromatids at metaphase I of meiosis.

For an individual with a diploid number of 30 chromosomes, therewill be 15 tetrads at metaphase II of meiosis.

yellowpig507

-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.

BIOL 242 Lecture Notes - Lecture 19: Synapsis, Meiosis, Dna Replication

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