Chapter 11 - Cont. (11.3 - 11.4)

Question 1

Contrast the cells produced by mitosis and meiosis.

Answer 1

Mitosis produces 2 diploid body cells. Meiosis produces 4 haploid gametes.

Question 2

What are the only kinds of cells that undergo meiosis?

Answer 2

Gametes are the only kinds of cells that undergo meiosis.

Question 3

Which one has more genetic info? A body cell or a gamete? Why?

Answer 3

The body cell would have more genetic info because it has 46 chromosomes.

Question 4

Why are the daughter cells produced by meiosis genetically different from each other whereas daughter cells produced by mitosis are not?

Answer 4

In meiosis, chromosomes cross over as well as going through cell division a second time. This results in new combinations of alleles on the chromosomes In mitosis, the pairs of homologous chromosomes in the parent cell form tetrads and then separate. As a result, each daughter cell receives only one chromosome from each homologous pair, and the particular chromosomes it receives are random. Thus, each daughter cell has a different combination of chromosomes.

Question 5

When are tetrads formed?

Answer 5

Tetrads are formed during Prophase I of Meiosis.

Question 6

What is crossing-over?

Answer 6

Crossing-over is the process of the chromatids of the homologous chromosomes crossing over one another. The crossed sections of the chromatids, which contain alleles, are exchanged. Crossing-over therefore produces new combinations of alleles in the cell.

Question 7

What is a gene map?

Answer 7

A gene map shows the relative locations of each gene.

Question 8

What are polygenic traits?

Answer 8

Traits controlled by two or more genes are said to be polygenic traits.

Question 9

What is incomplete dominance? What does it result in?

Answer 9

Incomplete dominance is a case of neither allele being dominant. The heterozygous phenotype lies between the 2 homozygous phenotype. For example, the F1 generation produced by parents RR (red) and WW (white) would consist of RW (pink).

Question 10

What is codominance and what does it result in?

Answer 10

Codominance is when phenotypes produced by both alleles are clearly expressed. For example, if a black feathers alleles was codominant with a white feathers allele, then the chicken would be both black and white.

Question 11

What are genes with more than two alleles said to have?

Answer 11

A gene with more than two alleles is said to have multiple alleles.

Question 12

What is the difference between haploid and diploid?

Answer 12

A cell that contains both sets of homologous chromosomes is diploid (“two sets”). The diploid number of chromosomes is represented by the symbol 2N. Some cells contain only a single set of chromosomes and therefore a single set of genes. These cells are haploid (“one set”). The gametes of sexually reproducing organisms are haploid.

Question 13

If a fruit fly’s diploid number is 8 (2N = 8), what would their haploid number be?

Answer 13

Their haploid number would be 4. (N = 4)

Question 14

If a body cell in a butterfly contains 24 chromosomes, how many would a butterfly egg contain?

Answer 14

The butterfly egg would contain 12 chromosomes.

Question 15

How many chromosomes does a human zygote contain?

Answer 15

A human zygote should have 46 chromosomes.

Question 16

What are some differences between mitosis and meiosis?

Answer 16

Mitosis is a form of asexual reproduction, while meiosis is a form of sexual reproduction. Mitosis produces two genetically identical diploid cells, whereas meiosis produces four genetically different haploid cells. Mitosis does not normally change the chromosome number of the original cell. Meiosis reduces the chromosome number by half.

Question 17

What does homologous mean?

Answer 17

Homologous means that each of the four chromosomes from the male parent has a corresponding chromosome from the female parent. The chromosomes that pair up during meiosis, are called homologous chromosomes.

Question 18

What are tetrads?

Answer 18

Tetrads are structures that contain four chromatids and are the result of each replicated chromosome pairing with its corresponding homologous chromosome during Prophase I of meiosis.

Question 19

What is fertilization?

Answer 19

Fertilization is the fusion of male and female gametes. It generates new combinations of alleles in a zygote, the name given to a fertilized egg.

Question 20

What will happen when two genes are located close to each other?

Answer 20

When two genes are located close to each other, they will rarely assort independently.

Question 21

When referring to the diploid or haploid number of an organism, what does N represent?

Answer 21

N represents the number of chromosomes in a sperm or egg cell (gamete).

Question 22

What is a key difference between Prophase I and Prophase II?

Answer 22

Crossing-over doesn’t occur in Prophase II.