Unit A Section 3.3

Question 1

Before genes were discovered, how did people avoid getting unwanted animal offspring?

Answer 1

only animals with the most desirable

characteristics, or traits, were allowed to reproduce

Question 2

Were the experiments with breeding successfully?

Answer 2

-Mating champion males with champion females did not always produce champion dogs, horses, cattle, or cats.

Question 3

What is a purebred?

Answer 3

• an animal whose ancestors have produced only an offspring with a specific trait such as white fur
• for several generations
• The term “true-breeding” is applied to such a lineage

Question 4

What is a hybrid?

Answer 4

An individual produced by crossing two purebred parents that differ in a trait such as coat colour is known as a hybrid

Question 5

What is a dominant trait/allele?

Answer 5

A trait or allele that is expressed when present.

Question 6

What is a recessive allele?

Answer 6

A recessive allele or trait is an allele that is not expressed when present.

Question 7

How is there a chance for a recessive allele to be expressed?

Answer 7

• A recessive trait appears in the offspring only if two recessive alleles are inherited.
• In contrast, even one dominant allele will cause the dominant trait to appear.

Question 8

How are chromosomes inherited?

Answer 8

-In sexual reproduction, chromosomes are inherited
in pairs: one from each parent
-In an offspring, the combination of alleles carried on the chromosomes determines what the offspring is like

Question 9

What is Incomplete Dominance?

Answer 9

the dominant allele does not dominate the recessive allele entirely; rather, an intermediate trait appears in the offspring.

Question 10

What if the baby does not have the eye color or any other feature that matches any of the two parents?

Answer 10

• eye color was determined by just one pair of alleles at a single gene location
• a baby’s different eye color was caused by two recessive alleles: one from each parent.

Question 11

What is “codominance.”

Answer 11

Another pattern of inheritance is called “codominance.”