Chapter 3 Study Guide

Question 1

Who cross-pollinated plants to observe different characteristics in his genetics experiments?

Answer 1

Gregor Mendel

Question 2

What does the notation TT mean?

Answer 2

homozygous alleles

Question 3

What does a pun net square do?

Answer 3

Shows all the possible outcomes of a genetic cross

Question 4

An purebred animal with white feathers is crossed with a purebred animal with black feathers. Both of their offspring have black and white feathers. Why?

Answer 4

The alleles for feather color are codominant

Question 5

The chromosome theory of inheritance states that what is carried from parents to offspring on chromosomes?

Answer 5

Genes

Question 6

Traits refer to specific what?

Answer 6

Characteristics

Question 7

An organism’s what is it’s genetic makeup?

Answer 7

genotype

Question 8

Factors that control traits are called what?

Answer 8

Genes

Question 9

The notation Tt means what?

Answer 9

Heterozygenous alleles

Question 10

What is probability?

Answer 10

How likely it is for an event to occur

Question 11

If a homozygous black guinea pig (BB) is crossed with a homozygous white guinea pig (bb) what is the probability that an offspring will be black?

Answer 11

100%, because black is a dominant color

Question 12

An organisms physical appearance is what?

Answer 12

It’s phenotype

Question 13

Who discovered that the sex cells of grasshoppers have half the number of chromosomes found in body cells?

Answer 13

Walter Sutton

Question 14

When sex cells combine to produce offspring, each sex cell will contribute how many number of chromosomes found in body cells?

Answer 14

Half

Question 15

The different forms of a gene are called what?

Answer 15

Alleles

Question 16

In a flower, color is inherited by genes that show incomplete dominance. In such flowers, a cross between a homozygous red flower and a homozygous white flower will always result in pink flowers. A cross made between two pink flowers. What is the for each phenotype?

Answer 16

1 red, 2 pink, and 1 white

Question 17

What kind of organism is the offspring of many generations of organisms that have had the same trait?

Answer 17

Purebred

Question 18

If this allele is present, its trait will appear in the organism. What kind of trait?

Answer 18

Dominant

Question 19

The process by which the number of chromosomes is reduced by half and sex cells form is called what?

Answer 19

Meiosis

Question 20

If D represents the dominant allele of a gene, the d represents what?

Answer 20

The recessive allele

Question 21

In a cross between two hybrid Tt pea plants, 50 percent of the offspring will be what?

Answer 21

Tt

Question 22

An organism that has two dominant or two recessive alleles is said to be what?

Answer 22

Homozygous

Question 23

Genes are carried from parents to their offspring through what?

Answer 23

Chromosomes

Question 24

A woman gives birth to her son. Two years later, she gives birth to another son. What is the probability that her third child will be a girl?

Answer 24

The probability is 1 in 2, or 50 %. The two possible results are equally likely with each birth, because each birth is an in dependent event. The probability that one result will occur does not depend on previous births.

Question 25

Explain why Mendel’s cross of purebred tall and short pea plants resulted in only tall plants.

Answer 25

Each of the offspring had one allele for height from each parent. Each offspring had one allele for tall stems, and one for short stems. The allele for tall stems is dominant. Since each offspring inherited a dominant allele for tall stems, each plant had tall stems.