BIOL 1005 Lecture Notes - Lecture 33: Sister Chromatids, Homologous Chromosome, Spindle Apparatus

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9 Mar 2016

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Produces four new cells each of which is haploid. Pairs of chromosomes of each type of n different types are split apart. This results in one set of n (half as many) chromosomes in each daughter cell. Recombination provides the raw materials for evolution (different genetic combinations of dna, and genes) Meiosis ii- separation of double stranded (sister) chromosomes which were distributed to the cells as a result of meiosis i. Stages of meiosis: prophase i- same as prophase in mitosis (disappearance of nuclear membrane and the nucleoli; condensation of chromatin. ) However new events also occur: homologous chromosomes-- a pair of chromosomes which have the same linear sequence of genes, but may not contain the same genetic information within the genes. These paired homologous double stranded chromosomes are called a tetrad ( also called four chromatids): chiasma- (cross) intimate association between two non-sister chromosomes in a tetrad.

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Title: Meiosis Lab

Part 1: Modeling Meiosis Without Crossing Over (reformat as needed)

Take photos of the following stages of your meiosis bead simulation. Insert and label the following images:

Meiosis 1: Prophase I and Metaphase I

Meiosis 2: Metaphase II and Telophase II

Part 2: Modeling Meiosis With Crossing Over (reformat as needed)

Take photos of the following stages of your meiosis bead simulation. Insert and label the following images:

Meiosis with Crossing Over: Metaphase I and Telophase II

Questions â use the lab Introduction, your textbook and other sources to answer the following.

What is the state of DNA at the end of meiosis I? Are the chromosomes replicated or unreplicated? Diploid or haploid?

Why are chromosomes important?

How are Meiosis I and Meiosis II different?

Name two ways meiosis contribute to genetic recombination or genetic variety.

Why do you use non-sister chromatids to demonstrate crossing over? What would happen if you crossed over sister chromatids?

How many chromosomes were present in your simulation when meiosis I started?

Why is it necessary to reduce the chromosome number in gametes, but not in other cells of an organism?

If humans have 46 chromosomes in each of their body cells, determine how many chromosomes you would expect to find in the following:

Sperm	Egg	Daughter cell after mitosis	Daughter cell after meiosis

Investigate a disease that is caused by a chromosomal mutation due to nondisjunction. When does the mutation occur? What chromosome is affected? What are the consequences?

10. Make a simplified diagrammeiosis starting with a cell containing3 pairs ofchromosomes.

Include and Label: Each stageof meiosis I & II and indicate if a cell is haploid (n) ordiploid (2n); plasma membrane, nuclear envelope, sisterchromatids,separation of sister chromatids, spindle fibers/microtubules,tetrad, homologous chromosomes, separation of homologouschromosomes, cleavage furrow.

What happens to the DNA during the interphase inpreparation for meiosis?

What happens to the DNA during the interphase betweenmeiosis I and II?

How do the daughter cells compare genetically to theparent cell after....

a) meiosis I?

b) meiosis II?

What is the diploid number for the species diagrammedabove? 2n =

What is the haploid number? n=

crimsonhamster738

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.

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BIOL 1005 Lecture Notes - Lecture 33: Sister Chromatids, Homologous Chromosome, Spindle Apparatus

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