1. Which of the following is an accurate statement concerning the differences between DNA and RNA?

a. RNA is usually double-stranded, but DNA is usually single-stranded.
b. RNA has the sugar deoxyribose, but DNA has the sugar ribose.
c. RNA contains three different nucleotides, but DNA contains four different nucleotides.
d. RNA lacks the base thymine (which is found in DNA) and has uracil instead.

2. The DNA sequence of a codon in a gene was changed from AAT to AAC. This type of mutation is called a(n) __________.
a. point mutation
b. insertion mutation
c. deletion mutation

3. The cells in your skin have a different shape and different function from the cells in your liver because the two types of cells have different __________.

a. DNA
b. proteins
c. lipids
d. carbohydrates

4. Genetic recombination (crossing over) produces __________.

a. new chromosomes
b. mutations
c. new combinations of alleles
d. longer chromosomes

5. Which one of the following statements is true?
a. An allele is either dominant or recessive, not in between.
b. A particular gene can have only two alleles.
c. A single trait can be affected by many different genes.
d. The environment is irrelevant to gene expression.

6. What is the root cause of sickle-cell anemia?

a. mutations in the gene that directs the synthesis of the hemoglobin protein
b. an amino acid substitution in the hemoglobin protein
c. malaria
d. abnormally shaped red blood cells

7. What are restriction enzymes?

a. enzymes that are limited (i.e., restricted) in how big they can become
b. vitamins such as vitamin A
c. plasmids
d. enzymes that cleave through a DNA helix wherever they encounter a specific sequence of nucleotides