Questions for Cell Cycle 1) Briefly describe all phases of the cell cycle and tell what happens in each.

2. Which phase is the shortest? Mphase.

3. What is G0 (Gap 0/Resting phase)? Is a period in the cells when they exist in quiescent state (Krogh, 2009)?

4. If a cell never entered the resting phase would it be a problem? Yes Why? All the damaged cells would survive.

5. Certain cells in the body stay in Gap 0 and rarely, if ever, divide. Name 2 cell types in the human body that do not divide. Muscle and nerve cell.

Other cell types in the body divide frequently (cycle fast). Name 1 tissue type in the body that divides often. Skin Why does this tissue type need to divide frequently? “The skin is the barrier of the body that protects it from injury and prevents the entry of dangerous substances and microorganisms. It is tough and constantly renewed.” ()

Mitosis

Questions for Mitosis

1. Explain the purpose of mitosis in the human body. Mitosis is used to repair and replace cells that wear out or die.

2. Briefly describe each phase of mitosis

 Prophase: nuclear envelope disintegrates, centrioles (microtubules) begin to form on both ends of the cell, and spindle fibers forming

Metaphase:  spindle fibers attach to centromere (centromere --> holds the sister chromatids together), chromosomes line up in the MIDDLE (connected to spindle fibers)

Anaphase: the spindle fibers pull the sister chromatids apart and AWAY from each other to opposite ends of the cell.

Telophase: nuclear envelope begins re-forming. Spindle fibers disappear, cell ready to separate into daughter cells (Krogh, 2009).

3. Describe and distinguish between replicated chromosomes and homologous chromosomes. Replicated have a matched pair of chromosomes. Homologous have an unmatched pair.

4. How many pairs of homologous chromosomes are found in the nucleus of a human somatic tissue cell? How many homologous pairs are found in a human gamete? 23 pairs in somatic tissue, and 23 only in the gamete (Krogh, 2009).

5.  Anaphase is unique in chromosome number. Explain. The cell becomes an N4 until it divides and becomes two N2s (Krogh, 2009).

6. Is a cell in anaphase diploid? Explain. It depends. If it starts out as haploid, then yes. If it started as diploid it would be N4. (Krogh, 2009).

Meiosis I                

Questions for Meiosis I

1. What is the purpose of meiosis in the human body? It is for reproduction using gamete cells.

2.  Briefly describe the phases of Meiosis I. Prophase is where DNA condenses and forms chromosomes. But the big difference is when chromosomes form chiasmata to trade bits of DNA so that what results is an individual, different than the parent cell. Metaphase Cells line the equator, the spindle forms and attaches to chromosomes. Anaphase: The spindle pulls apart the chromosomes where they migrate to the poles. Telophase: The cell splits, the nuclear envelope reappears and chromosomes unwind (Krogh, 2009).

3. Why is Meiosis I called reduction division? What is being reduced? The number of chromosomes, so that it will be able to unite with a gamete for sexual reproduction.

4. What is crossing over? During which phase of Meiosis I does crossing over occur? The trading of genetic material. It happens in prophase.

5. What is the significance of crossing over? Since crossing-over allows for the shuffling of genetic material between maternal and paternal homologous chromosomes, it results in genetic recombination. This shuffling ensures genetic variability in a population. That is why individuals look different (Krogh, 2009).
   

6. What is “Independent Assortment” of chromosomes? Who is associated with this theory? During what phase of Meiosis I does it occur? Random combining of chromosomes when two gametes join. Gregor Mendel. The metaphase. ( Module 3 Reading).

7. Both crossing over and “Independent Assortment” add genetic variation. How is genetic variation important to natural selection and adaptation? Because if there wasn’t independent assortment everyone would be the same!

Meiosis II

Questions for Meiosis II:

1. Briefly describe what happens in each phase of Meiosis II. Prophase: Strands of DNA form replicated chromosomes. They migrate to the poles while the nuclear envelope disappears. Metaphase Cell lines up along the equator and spindles appear and attach to the chromosomes. Anaphase Spindle fiber pulls the chromosomes apart and they migrate to the poles of the cell. Telophase: The cell divides and the chromosomes uncoil while the nuclear envelope reforms (Module 3 Reading).

2. In a female, the products of meiosis are referred to as ___eggs_________. In a male these cells are referred to as __sperm___________.

3. What is it called when chromosomes in meiosis fail to separate and travel together as the gametes are formed? Mutations that result in an abnormal number of chromosomes Nondisjunction occurs when chromosome fail to separate during meiosis. ( Krogh, 2009).

 Name 1 genetic condition caused by the failure of chromosomes to separate in Meiosis. Turner Syndrome

References

Do All Cells In The Human Body Divide?

Krogh, D. (2009). Biology - A guide to the natural world. San Francisco, CA: Pearson  

     Education Inc.

Module 3 Reading Bio 100. Retrieved January 21, 2011  

     

Module 3 Reading Bio 100L. Retrieved January 21, 2011