Chapter 23-Heredity: The Continuity of Life

Question 1

What is the transmission of characteristics from parent to offspring by means of genes?

Answer 1

Heredity

Question 2

Heredity is the transmission of characteristics from parent to offspring by means of ______________, units of genetic information, in the chromosomes of the cells.

Answer 2

Genes

Question 3

As the number of cells increase in the human body, certain cells are called out to become specialized components of tissues and organs in a process called:

Answer 3

Differentiation

Question 4

What kind of cell in humans (also called a body cell) has 46 chromosomes?

Answer 4

Somatic cell

Question 5

What term refers to the egg and sperm of the human parents which each contain only 23 chromosomes?

Answer 5

Gametes

Question 6

In what specially designed type of cell division do the egg and sperm originate in which occurs in the ovaries of females and the testes of males?

Answer 6

Meiosis

Question 7

When an egg and a sperm unite in the process of fertilization, the result is a single fertilized egg cell known as a:

Answer 7

Zygote

Question 8

A sperm cell contains half the usual number of chromosomes; what is this set known as?

Answer 8

Haploid set

Question 9

Since the sperm cell contains half the usual number of chromosomes and the egg cell contains half, the zygote contains the complete number of chromosomes, known as what kind of set?

Answer 9

Diploid

Question 10

Because the number of chromosomes is reduced by one half in meiosis, it is often called:

Answer 10

Reduction division

Question 11

What are the two successive stages that meiosis occurs in?

Answer 11

First and second meiotic division

Question 12

In the first meiotic division of meiosis, homologous chromosomes pair up in a process called _________________, in which an exchange of genetic information takes place between paired homologous chromosomes.

Answer 12

Synapsis

Question 13

Little was known about heredity until the mid-19th century when an Austrian monk named ________________ began working with pea plants in his small monastery garden in what is now the Czech Republic, and is called the father of genetics.

Answer 13

Gregor Mendel

Question 14

What is the scientific study of heredity?

Answer 14

Genetics

Question 15

In modern genetics, different forms of a gene for a particular trait, such as various seed colors, are called:

Answer 15

Alleles

Question 16

If an organism has two identical alleles for the same trait, it is said to be:

Answer 16

Homozygous

Question 17

If an organism has one allele different from the other, it is said to be:

Answer 17

Heterozygous

Question 18

What shows up in the offspring even if an allele for a different trait is also present?

Answer 18

Dominant traits

Question 19

Dominant traits show up in the offspring even if an allele for a different trait is also present. This fact is known as the:

Answer 19

Law of dominance

Question 20

The trait which does not show up when the dominant allele is present is known as the:

Answer 20

Recessive trait

Question 21

We can use what to represent the dominant allele for round seeds?

Answer 21

R

Question 22

We can use what to represent the recessive allele for wrinkled seeds?

Answer 22

r

Question 23

The letters used to refer to different plants (Rr, rr, RR) describe the _______________ of an individual, which is the actual combination of alleles inherited for a particular trait.

Answer 23

Genotype

Question 24

What is the outcome or expression of the genes in the physical appearance of the individual?

Answer 24

Phenotype

Question 25

Mendel used the term ___________ to describe an organism with two different alleles for a particular trait.

Answer 25

Hybrid

Question 26

What law states that alleles for each trait segregate or separate randomly during the formation of gametes?

Answer 26

Law of segregation

Question 27

What was the mixing or blending of traits in these plants called?

Answer 27

Codominance

Question 28

What is an organism that is heterozygous for two traits called?

Answer 28

Dihybrid

Question 29

Scientists now know that many traits of an organism, such as the seed color and the seed shape in peas, are inherited independently of each other according to what law? In other words, the segregation of one gene does not influence the segregation of another.

Answer 29

Law of independent assortment

Question 30

If two genes are located close to each other, both traits may be inherited together and not be sorted independently. This is known as _________________, and the genes are said to be linked.

Answer 30

Linkage

Question 31

When several genes are linked together, they are known collectively as a:

Answer 31

Linkage group

Question 32

What are the chromosomes which determine an organism’s sex?

Answer 32

Sex chromosomes

Question 33

Thomas Hunt Morgan demonstrated that not only were white eyes recessive to red eyes, but that the trait was ________________ because it was located in the X chromosome.

Answer 33

Sex-linked

Question 34

What is the extent which a certain gene exists in a population?

Answer 34

Gene frequency

Question 35

What is one of the most common hereditary diseases among children in the United States, and is caused by a recessive gene?

Answer 35

Cystic fibrosis

Question 36

Receiving a CF gene from only one parent makes the child a:

Answer 36

Carrier

Question 37

What happens when both alleles for a trait are equally expressed in a heterozygous individual?

Answer 37

Codominance

Question 38

A person suffering from what disease is H^2H^2 and makes only abnormal hemoglobin molecules; the abnormal hemoglobin causes the red blood cells to become sickle-shaped under certain conditions?

Answer 38

Sickle-cell anemia

Question 39

If a normal person marries a person with sickle-cell anemia, their children must be heterozygous. Because neither gene is dominant, both express themselves. This is called:

Answer 39

Sickle-cell trait

Question 40

What occurs when there are more than two different alleles of a gene for a particular trait?

Answer 40

Multiple allele inheritance

Question 41

Recent advances in genetics have demonstrated that most genes influence not just one trait but several seemingly unrelated traits. This is known as:

Answer 41

Pleiotropy

Question 42

What involves traits controlled by many different pairs of genes? Thus, instead of one pair of genes controlling an expression, many pairs are involved.

Answer 42

Polygenic inheritance

Question 43

Some people have advocated the practice of ___________________, an attempt to improve the human race through the control of hereditary factors.

Answer 43

Eugenics