Chapter 9 Study Guide

What is a tetrad? When do tetrads form?

Tetrads are paired chromosomes and they form in Prophase 1.

How are meiosis and mitosis similar? Differ?

The are similar because they are both cell division but they differ because meiosis has genetic variation and mitosis is genetically identical.

Describe the production of sperm in males. What is the process called? How many sperm is produced from each testis cell?

It undergoes meiosis and interphase. The process is called Spermatogenesis. It produces 4 sperm.

What does it mean for a cell to be diploid and give examples.

A cell is diploid when it contains two homologous sets of chromosomes. An example is the human cell.

What does it mean for a cell to be haploid and give examples.

A cell is haploid when it has a single set of chromosomes and this is the sex organs.

What is a gamete? What is a female gamete? What is a male gamete?

A gamete is a sex organ. A female gamete is the ovary and the male gamete is the testes.

What is a homologous chromosome? Where did each homologous chromosome come from?

A homologous chromosome is two chromosomes of each matching pair. One comes from your mom and one comes from your dad.

What is a zygote? How is a zygote formed?

A zygote is a fertilized egg. It is formed when the fusion of nuclei along with the cytoplasm from the gametes.

Explain asexual reproduction and give examples.

Asexual reproduction is done with only one parent and is genetically identical to the parent. Some examples of asexual reproduction is fungi and plants.

How does crossing over during Prophase 1 contribute to genetic variation? How does random alignment of tetrads during Metaphase 1 contribute to genetic variation?

Crossing over can produce a single chromosome that contains a new combination of genetic information. How the chromosomes in each homologous pair line up and separate is a matter of chance.

Humans have 46 chromosomes. How many chromosomes do you have in each cell after mitosis is complete? If an organism has 20 chromosomes, how many chromosomes would be present in each cell after mitosis?

If you have 46 chromosomes, after mitosis each cell with have 23 chromosomes. If you have 20 chromosomes, after mitosis each cell will have 10 chromosomes.

Explain how cytokinesis differs in plant and animal cells

In plant cells, cytokinesis builds a cell plate to form the two different cells. In animal cells, cytokinesis pinches in to form two different cells.

What happens before meiosis begins?

Interphase

Describe the production of eggs in females. What is the process called? What is a polar body? How many eggs are produced in each ovary cell?

It goes through meiosis and interphase. It is called Oogenesis. A polar body is a small haploid cell that is formed concomitantly as an egg cell during oogenesis, but which generally does not have the ability to be fertilized. 1 eggs is produced.

How many cell divisions are involved in meiosis? Mitosis?

Mitosis has one division and meiosis has two.

What is nondisjunction?

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division.

What are the advantages and disadvantages of sexual reproduction?

The advantages to sexual reproduction are lots of genetic variation. The disadvantages to sexual reproduction is that there is two parents and that it takes more energy.

Describe what is occurring to the chromosomes and the cell during each phase of the cell cycle. (Interphase, Mitosis)

The cell cycle includes G1, Synthesis, G2, Prophase, Metaphase, Anaphase, and Telophase. In G1, the cells grow, make protein, RNA, and other molecules. In Synthesis, the cells DNA duplicates. In G2, the cells produce substances to trigger cell division. G1, Synthesis, and G2 are considered to be in the "Interphase" stage. In Prophase, the chromatin fibers can be seen with a light microscope, each chromosome now consists of a pair of sister chromatids joined at the centromere, the nuclear envelope breaks down, spindles form and start tugging sister chromatids towards the center. In Metaphase, the chromosomes all gather in a plane across the middle of the cell and all of the chromosomes are attached to the spindle fibers. In Anaphase, the chromatids separate and the microtubules are bringing the chromosomes to opposite poles. In Telophase, the cell divides in two, the nuclear envelope forms, and the chromosomes uncoil.

What are the phases of meiosis? Describe what happens in each phase.

The phases of meiosis are G1, Synthesis, G2, Prophase 1, Metaphase 1, Anaphase 1, Telophase 1, Prophase 2, Metaphase 2, Anaphase 2, Telophase 2. In G1, the cells grow, make protein, RNA, and other molecules. In synthesis, the cells DNA duplicates. In G2, the cells produce substances to trigger cell division. In Prophase 1, homologous chromosomes actually stick together, the paired chromosomes are referred to as tetrads, the tetrads attach to spindles, the tetrads "crossover." In Metaphase 1, the tetrads move to the middle of the cell and line up across the spindle. In Anaphase 1, homologous chromosomes are separated, sister chromatids remain attached. In Telophase 1, the cell divides and the nuclear envelope form. In Prophase 2, in each haploid daughter cell a spindle forms, attaches to the centromeres, and moves the individual chromosomes to the middle of the cell. In Metaphase 2, the chromosomes line up in the middle of the cell with spindle microtubules attached to each sister chromatid. In Anaphase 2, the sister chromatids separate and move to opposite poles. In Telophase 2, the the cells split one more time producing four haploid cells.

How do egg and sperm cells become haploid?

They become haploid when meiosis occurs.

What is trisomy? Give an example of a genetic disorder caused by trisomy.

Trisomy is a genetic disorder in which a person has three copies of a chromosome instead of two. If you have trisomy 21 you have Down's Syndrome.

As a starfish developed from a zygote to a larva what type of cell division occurred? What happened to the size of the cells as the cells divided?

When the starfish developed from a zygote to a larva mitosis occurred. As the cell divided more and more the cell got smaller.