Chapter 7: Heredity

Question 1

Gregor Mendel

Answer 1

Studied inheritance using garden peas.

Question 2

Particulate Inheritance

Answer 2

Inheriting characteristics through genes.

Question 3

Multiplication Rule

Answer 3

The rule of probability used when there are two independent events.

Question 4

Addition Rule

Answer 4

The rule of probability used when there are related events.

Question 5

Law of Dominance

Answer 5

If you cross a homozygous dominant organism with a homozygous recessive organism, you will get a hybrid, but it will have the dominant phenotype.

Question 6

Law of Segregation

Answer 6

During the formation of gametes, the traits of the parents separate.

Question 7

Monohybrid Cross

Answer 7

Cross between two hybrids.

Question 8

Testcross

Answer 8

A cross used to determine the genotype of an organism, because an organism that has a dominant phenotype is either TT or Tt.

Question 9

Law of Independent Assortment (Dihybrid Cross)

Answer 9

When a cross is carried out between tow individuals hybrid for two or more traits on different chromosome.

If genes are linked (if the gene for yellow seed color was linked to gene for tall), they will not assort independently.

Question 10

Incomplete Dominance

Answer 10

Also known as blending. For example, a red (RR) Japanese 4 o’clock flower crossed with a white (WW) 4 o’clock flower will create pink (RW) offspring.

Question 11

Codominance

Answer 11

Where both traits are present. A good example is the MN blood group, where its surface molecules are those of MM and NN.

Question 12

Multiple Alleles

Answer 12

When there are more than two allelic forms of the same gene, such as the four blood types: A, B, AB, and O.

Question 13

Pleiotropy

Answer 13

The ability of a gene to have multiple affects on the organism. An example is cystic fibrosis, where the thickening of mucus on cells causes poor absorption of nutrients and chronic bronchitis.

Question 14

Epistasis

Answer 14

When a trait is controlled by two genes, but one gene masks the other one. For example, in agouti mice, the mouse can only come in three colors: agouti, black, and white. However, the gene for B is epistatic to A, so when B is gone, the mouse will be white.

Question 15

Polygenic

Answer 15

Where the phenotype of the genes can vary along a spectrum. For example, skin color and tallness are examples, because the tallness and color skin varies between all people.

Question 16

Multifactorial Disease

Answer 16

When an underlying genetic component has a substantial environmental influence. For example, risk for heart disease can increase with bad genetics, but also can be caused through unhealthy foods and meat.

Question 17

Penetrance

Answer 17

The percentage of organisms with a genotype that actually exhibits the expected phenotype.

For example, many people with the genotype for breast cancer do exhibit it sometime in their life, but some never develop breast cancer.

Question 18

Linked Genes

Answer 18

Genes on the same chromosome.

Question 19

Sex-Linked Traits

Answer 19

Traits carried on the X chromosome (Few are carried on the Y chromosome).

Question 20

Recessive Sex-Linked Traits

Answer 20

A female will express the phenotype only if she carries two mutated genes. Examples include color blindness, hemophilia, and Duchenne muscular dystrophy.

Question 21

Dominant Sex-Linked Traits

Answer 21

A female will express the phenotype if she inherits only one mutated gene. Males inherit only one X linked gene, so if he inherits a mutated one, he will express it.

Question 22

Chiasma

Answer 22

A physical bridge made at the place where crossing over occurs.

Question 23

Recombination

Answer 23

The result of a cross-over.

Question 24

Recombination Frequency

Answer 24

The likelihood that the cross-over will occur.

Question 25

Barr Body

Answer 25

The dark spot of condensed chromosome that an inactive X becomes.

Question 26

Mutations

Answer 26

Changes in the genome that can occur in gametes or somatic cells, and often by random chance.

Question 27

PKU

Answer 27

Autosomal recessive disease that causes an inability to break down phenylalanine.

Question 28

Cystic Fibrosis

Answer 28

Autosomal recessive. Characterized by buildup of extracellular flu in the lungs, digestive tract, etc.

Question 29

Tay-Sachs Disease

Answer 29

Autosomal recessive. Caused by the lack of enzyme to break down lipids for brain function.

Question 30

Huntington’s Disease

Answer 30

Autosomal dominant. A degenerative disease of the nervous system.

Question 31

Hemophilia

Answer 31

Sex-linked recessive. Caused by the absence of normal proteins used for blood clotting.

Question 32

Color blindness

Answer 32

Sex-linked recessive.

Question 33

Duchenne muscular dystrophe

Answer 33

Sex-linked recessive. Progressive weakening of the muscles and loss of control.

Question 34

Sickle-cell disease

Answer 34

Autosomal recessive. Mutation that results in deformed blood cells, but carriers are resistant to malaria.

Question 35

Down Syndrome

Answer 35

47 chromosomes due to trisomy 21. Mental retardation, characteristic facial features, prone to leukemia.

Question 36

Karyotype

Answer 36

Procedure that shows the size, number, and shape of chromosomes to alert abnormalities.

Question 37

Chromosomal Mutation Types

Answer 37

1. Deletion: a fragment of the chromosome is lost during cell division.
2. Inversion: when a chromosomal fragment detaches and reattaches in the opposite orientation.
3. Translocation: when a fragment of a chromosome reattaches to a wrong chromosome.
4. Polyploidy: when a cell or organism has an extra set of chromosomes.

Question 38

Nondisjunction

Answer 38

When chromosomes fail to separate as they should, often in meiosis.

Question 39

Aneuploidy

Answer 39

Any abnormal number of chromosomes.

Question 40

Trisomy

Answer 40

When a chromosome is present in a triplicate.

Question 41

Triploid

Answer 41

An organism that has an extra set of chromosomes.

Question 42

Genomic imprinting

Answer 42

A variation in phenotype depending on whether the trait is inherited from the mother or the father. Occurs during gamete formation.

Question 43

Extranuclear Genes

Answer 43

Genes located in the mitochondria or chloroplasts. Linked to several very rare and severe inherited diseases in humans.