Problem Set 3.9: Meiosis Instructions: Read pages 367 to 373 in your text and answer the questions that follow.

1. List three ways in which sexual reproduction differs from asexual reproduction.

Sexual reproduction requires two parents, produces unique offspring, and requires the production of sex cells called gametes (meiosis). Asexual reproduction requires one parent, produces clones of the parent and requires only simple cell division (mitosis).

2. a) In what ways are the two chromosomes in a homologous pair similar to each other?

Two chromosomes in a homologous pair are similar in overall appearance and are made up of the same kind of genes. The two chromosomes in the pair contain genes to dictate a trait.

b) How many pairs of homologous chromosomes are there in a human body cell?

Humans have 23 homologous chromosome pairs (46 total)

3. a) What is the difference between a diploid cell and a haploid cell?

Diploid cells have pairs of homologous chromosomes

Haploid cells have only one chromosome of each type or form

b) Which type of cell results from mitosis and which type results from meiosis?

Mitosis produces regular complete cells while meiosis produces haploid cells (gametes or sex cells)

4. a) How many chromosomes does every human body cell contain?

Every body cell contains 46 chromosomes (except sex cells – which have 23)

b) Are these cells haploid or diploid?

Every body cell is diploid (except sex cells – which are haploid)

c) How many chromosomes does a human reproductive cell contain?

Gametes or sex cells have 23 chromosomes

d) Are these cells haploid or diploid?

Gametes are haploid – they possess one chromosome from each homologous

pair

5. Why is meiosis necessary for sexual reproduction?

Meiosis is necessary for sexual reproduction since human cells require 46 chromosomes. Since 46 will be needed in the offspring, human parents produce cells that contain 23 each (gametes) so that when ova and sperm combine in fertilization, the offspring will have the 46 needed chromosomes.

6. List the stages of meiosis and briefly describe what happens in each.

Prophase I – duplication of chromosomes, they coil

Metaphase I –homologous pairs of chromosomes line up at midline of cell

Anaphase I – one chromosomes from each homologous pairs goes to separate ends of cell

Telophase I – cell divides

Prophase II – they coil and new spindles form

Metaphase II –chromatids line up at midline of cell

Anaphase II –chromatids separate into opposite ends of cell

Telophase II – cells divide into gametes (haploid cells)

7. What is another name for the reproduction cells of a sexually reproducing organism?

Meiosis produces gametes (sperm and ova in humans)

8. What are the three basic steps in sexual reproduction? Write a sentence or two about the different ways each of these can occur (in different types of organisms)

Gamete production – sex cells are produced to halve the number of chromosomes

Fertilization – union of sex cells to produce a new individual with correct number of chromosomes

Embryo development – protection and nourishment of new individual until birth