What are the building blocks of a nucleotide? With regard to the $5^{\prime}$ and $3^{\prime}$ positions on a sugar molecule, how are nucleotides linked together to form a strand of DNA?

The type of model building used by Pauling and Watson and Crick involved the use of ball-and-stick units. Now we can do model building on a computer screen. Even though you may not be familiar with this approach, discuss the potential advantages of using computers in molecular model building.

If a nucleotide is replaced by a different nucleotide, this is called a(n) $\rule{1.5cm} {0.4pt}$ mutation.$\rule{1.5cm}{0.4pt}$ mutations occur if nucleotides are added in the middle of a gene.$\rule{1.5cm}{0.4pt}$ mutations occur if nucleotides are removed from the middle of a gene.

Species I is diploid ( $2 n=8)$ with chromosomes AABBCCDD; related species II is diploid ( $2 n=8$ ) with chromosomes MMNNOOPP. What types of chromosome mutations do individuals with the following sets of chromosomes have?
a. AAABBCCDD
b. MMNNOOOOPP
c. $A \mathrm{ABBCDD}$
d. AAABBBCCCDDD
e. AAABBCCDDD
f. $A A B B D D$
g. AABBCCDDMMNNOOPP
h. AABBCCDDMNOP

Which of the following is true of a species that has a chromosome number of 2n = 16?

A) The species is diploid with 32 chromosomes per cell.

B) Each diploid cell has eight homologous pairs of chromosomes.

C) The species has 16 sets of chromosomes per cell.

D) A gamete from this species has four chromosomes.

Which of the following is true of a species that has a chromosome number of 2n = 16?

A) The species is diploid with 32 chromosomes per cell.

B) The species has 16 sets of chromosomes per cell.

C) Each diploid cell has eight homologous pairs.

D) A gamete from this species has four chromosomes.

Species I is diploid (2n = 8) with chromosomes AABBCCDD; related species II is diploid (2n = 8) with chromosomes MMNNOOPP. Individuals with the following sets of chromosomes represent what types of chromosome mutations?

A) AAABBCCDD:

B) MMNNOOOOPP:

C) AABBCDD:

D) AAABBBCCCDDD:

E) AAABBCCDDD:

F) AABBDD:

G) AABBCCDDMMNNOOPP:

H) AABBCCDDMNOP:

Choose the best answer.

In tomatoes, red fruit $(R)$ is dominant over yellow fruit $(r)$, and tallness $(T)$ is dominant over shortness $(t)$. A plant that is RrTT is crossed with a plant that is rrTt. What are the chances of an offspring possessing both recessive traits?

a. None

b. $\frac{1}{2}$

c. $\frac{1}{4}$

d. $\frac{3}{4}$

In tomatoes, red fruit is dominant over yellow, two-loculed fruit is dominant over many-loculed fruit, and tall vine is dominant over dwarf. A breeder has two pure lines: (1) red, two-loculed, dwarf and (2) yellow, manyloculed, tall. From these two lines, he wants to produce a new pure line for trade that is yellow, two-loculed, and tall. How exactly should he go about doing so? Show not only which crosses to make, but also how many progeny should be sampled in each case.

In Tomatoes, the allele for red fruit is dominant over the allele for yellow fruit. If a plant that is homozygous for red fruit is crossed with a plant with yellow fruit:

a) what is/arethe genotype(s) and the phenotype(s) of the fruit produced in the F1 generation?

b) what is/are the genotype(s) and the phenotype(s)of the fruit produced in the F2 generation?

c) what is the phenotypic ratio of the F2 fruit?

In tomatoes, red fruit (R) is dominant over yellow fruit (r), and tallness (T) is dominant over shortness (t). A plant that is RrTT is crossed with a plant that is rrTt. What are the chances of an offspring possessing both recessive traits?

In tomatoes, red fruit (R) is dominant over yellow fruit (r). Red tomato plants were cross pollinated with yellow tomato plants. The next generation of plants produced no yellow fruit. Which of the following rows identifies the genotype and the phenotype of the parental red tomato plants respectively? Select one:

A. RR; red

B. red; Rr

C. red; RR

D. Rr; red

In the tomato, red fruit $(R)$ is dominant over yellow fruit $(r)$, and yellow flowers $(W f)$ are dominant over white flowers $(w f)$. A cross was made between true-breeding plants with red fruit and yellow flowers and plants with yellow fruit and white flowers. The $F_1$ generation plants were then crossed to plants with yellow fruit and white flowers. The following results were obtained:
333 red fruit, yellow flowers
64 red fruit, white flowers
58 yellow fruit, yellow flowers
350 yellow fruit, white flowers
Calculate the map distance between the two genes.

Twenty-five percent of the offspring of a certain pair of white sheep are black. If white is dominant to black, what was the genotype of the parents?