Chapter 10

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10.1 Q/A

1) Compare and Contrast Mitosis with Meiosis.

Mitosis creates an exact replica of the cell. 2 cells are the by-product, original, and clone.

Meiosis is a sexual process that creates 4 unique haploid cells called gametes by swapping genetic information.

2) Compare and Contrast Sexual and Asexual Reproduction. In which Domains and Kingdoms (chapter 1) do you see sexual reproduction?

Sexual reproduction- Eukaryotes. Animal, Plants, some fungi, and some Protista

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10.2

1) Explain meiosis and fertilization in terms of diploid and haploid chromosome numbers

Meiosis starts with a diploid cell, undergoes a special type of cell division 2 times, becoming a haploid gamete.

2) Human somatic cells usually have how many chromosomes in their nucleus?

There are 46 chromosomes in somatic human cells.

3) How many chromosomes are present in healthy, human gametes?

There are 23 chromosomes are present in healthy human gametes

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10.3 Q/A

1) List and Explain the events of the phases of meiosis including prophase1, prophase 2, metaphase 1, metaphase 2, anaphase 1, anaphase 2, telophase 1, telophase 2, cytokinesis 1, cytokinesis 2. (note: put the phases in ORDER!)

prophase 1: The homologous chromosomes lie next to each other, forming a tetrad. This is when crossing over happens(unique to prophase 1). Normal events such as mitotic spindle formation happen along with the breakdown of the nucleolus.

metaphase 1: Tetrads align at the equator. Sister kinetochores of each homologue are attached to spindle fibers attached to only one of the poles.

anaphase 1: Homologous chromosomes separate and move to the poles where each pole receives a mixture of maternal and paternal chromosomes.

telophase 1: Sister chromatids de-condense a little and the nuclear membrane may partially reform and cytokinesis usually occurs.

cytokinesis 1: The two nuclear membranes and their organelles split forming two daughter cells.

prophase 2: re-condensation of the chromosomes and events similar to prophase in mitosis NO CROSSING OVER.

metaphase 2: Sister chromatids line up at the equator.

anaphase 2: Sister chromatids separate into chromosomes.

telophase 2: One copy of each homologous chromosome at each pole. Nuclear membrane reforms.

cytokinesis 2: Cells split and 4 gametes are the final product with 23 single chromosomes in each.

2) Define: Tetrad, synaptonemal complex, crossing over/ genetic recombination, sister chromatids. What function(s) do these things have during prophase 1 of meiosis?

Tetrad: 2 homologous chromosomes stuck together. (4 chromatids total). there are as many tetrads as there are haploids in the organism. This allows for crossing over.

Synaptonemal Complex: This makes sure that the Tetrad sticks together while crossing over.

Crossing over/genetic recombination: Parts of chromosomes are swapped. Used to increase genetic diversity during prophase 1.

sister chromatids: The chromatids involved, forming duplicate chromosomes and crossing over.

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Q/A 10.4

1) Explain why evolutionary forces would select for such a complex and involved process such as meiosis?

Meiosis came around probably shortly after the appearance of eukaryotic cells, in order to allow for greater diversity in social cells/organisms. Evolution is like a race, and the faster a species evolves to the next stage, or in response to stimuli, the more successful it is, thus meiosis is the preferable reproduction way.

2) What are the benefits and drawbacks of sexual reproduction?

Some advantages of sexual reproduction are that it allows for more diversity and thus quicker evolution through greater genetic diversity.

Some drawbacks of Sexual reproduction are that you need a member of the opposite sex in order to reproduce and that growth speed is limited because males do not produce offspring themselves.