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Chapter 13 Study Guide Meiosis-ANSWERS

13.1 Chromosomes are inherited_____________________________________________

1. Chromosomes are made of segments of DNA called __GENES_____, which are found at specific places along the chromosome called a___LOCUS________.

2. Compare and contrast asexual and sexual reproduction.

Asexual- parent produces identical cell by mitosis = offspring a clone of parent

Sexual- egg or sperm produced by meiosis = offspring are not clones of parents because they have a set of chromosomes from each parent.

13.2 Meiosis and Fertilization alternate in sexual life cycles________________________

3. What cells undergo Meiosis? Where are these cells located in the human body?

Certain Diploid cells located in the male or female gonad ONLY. These cells undergo meiosis to produce gametes or sex cells, egg or sperm. NO OTHER CELLS IN YOUR BODY UNDERGO THIS PROCESS!

4. A human has 46 chromosomes. How many of these chromosomes were inherited from Mom? 23

5. What is a karyotype and at what stage in the cell cycle can one be constructed?

Ordered representation of homologous chromosomes usually constructed from a prophase cell. Chromosomes are ordered from largest to smallest. The sex chromosomes (XX or XY) are placed last, at the bottom right of the karyotype.

6. What are Homologous chromosomes? What is each homologue composed of during mitotic phases of the cell cycle?

-2 chromosomes with same length, centromere position and order of genes (although the type of gene may be different). One homologue was inherited from mom, the other homologue was inherited from dad.

-Each homologue is composed of 2 sister chromatids (when the cell is preparing to divide) until anaphase of mitosis or anaphase 2 of meiosis.

7. What is the difference between autosomes and sex chromosomes?

Autosome- any homologue that is not an X or Y chromosome. All autosomes have a homologue.

Sex chromosomes- X or Y chromosome that determines gender of organism. If you are a female XX, you have a homologous chromosome. If you are a male XY, you do not have a homologus chromosome for this chromosome. The X chromosome is very large and contains many more genes compared to the Y chromosome. We will discuss this further in chapter 15.

8. An organism has a diploid number of chromosomes 2n = 48. What is the haploid chromosome number? 24

13.3 Meiosis reduces chromosome number_____________________________________

9. Describe the major event(s) that occur in each stage of Meiosis:

Interphase- cell grows, organelles produced, copy DNA

Prophase I- chromosomes condense, homologous chromosomes come together to form tetrads, non-sister chromatids crossover (exchange genetic material) places where these crossing over events occur are called chiasmata

Metaphase I- Homologous chromosomes line up together (in tetrads) on the metaphase plate.

Anaphase I- Homologous chromosomes move to opposite poles of the cell

Telophase I and cytokinesis- 2 haploid daughter nuclei form followed by division of cytoplasm (cytokinesis)

Prophase II- in each daughter cell, spindle forms,

Metaphase II- sister chromatids line up on metaphase plate

Anaphase II- sister chromatids move to opposite poles of the cell

Telophase II and cytokinesis- 4 haploid nuclei form followed by cytokinesis to form 4 haploid cells

10. How many cell division events take place during meiosis? 2

11A. How is metaphase of Meiosis I different from metaphase in mitosis?

Metaphase Meiosis = homologous chromosomes line up together on metaphase plate.

Metaphase Mitosis = homologous chromosomes do not line up together on metaphase plate.

11B. Identify and describe at least 2 more events that distinguish meiosis from mitosis.

1. Homologous chromosomes line up together on metaphase plate during meiosis I

2. Non-sister chromatids of homologous chromosome pairs cross over during prophase of meiosis I

3. During anaphase I of meiosis homologues separate, during anaphase I of Mitosis sister chromatids separate

13.4 Genetic Variation_____________________________________________________

12. The genetic variation observed in offspring produced by sexual reproduction can be accounted for by what three main behaviors of chromosomes during meiosis

1. Crossing over between non-sister chromatids of homologous chromosome pairs during Prophase I of meiosis.

2. Independent assortment of homologous pairs on the metaphase plate of metaphase I and II of meiosis

3. Random fertilization