Chapter 14: Genes

Question 1

Character

Answer 1

A heritable feature that varies among individuals in a population such as hair color

Question 2

Trait

Answer 2

A variant for a character such as the actual color of hair a person has

Question 3

P generation

Answer 3

A true beeding parental generation such as purple color flowers

Question 4

F1 generation

Answer 4

Hybrid offspring of a parental generation

Question 5

F₂ generation

Answer 5

Generation of offspring that result from the F₁ generation

Question 6

Alleles

Answer 6

Alternate versions of a gene such as purple and white petal colors in pea plants

Question 7

Law of segregation

Answer 7

Two alleles for a heritable chracter segregate during gamete formation and end up in different gametes

An egg or sperm gets only one of the two alleles that are present in the diploid cells of the organism making the gamete

Question 8

Phenotype vs. genotype

Answer 8

A phenotype describes an organism’s appearance or observable traits

A genotype is an organism’s genetic makeup

Question 9

Testcross

Answer 9

The breeding of an organism with an unknown genotype with a recessive homozygote to reveal the gentype of the unknown organism

Question 10

Monohybrids

Answer 10

The F₁ progeny of crosses of true-breeding parents that are all heterozygous for one particular character that is being followed in the cross

Question 11

Monohybrid cross

Answer 11

A cross between F₁ monohybrid heterozygotes

Question 12

Dihybrids

Answer 12

The F₁ hybrids of individuals heterozygous for two characters being followed in a cross

Question 13

Dihybrid cross

Answer 13

A cross between F₁ dihybrid heterozygotes

Question 14

Law of independent assortment

Answer 14

Two or more genes will assort independently during gamete formation; each pair of alleles segregates independently of any other pair of alleles

Only applies to genes located on different chromosomes or that are very far apart on the same chromosome

Question 15

Multiplication rule

Answer 15

The probability that one event and another event will occur such as two coins landing on heads

Probability of one event is multiplied by the probability of the other event

Question 16

Addition rule

Answer 16

The probability that one event or another mutually exclusice event will occur such as rolling a 1 or a 2 on a six-sided dice

Probability of one event is added to the probability of the other event

Question 17

Incomplete dominance

Answer 17

When neither allele is completely dominant and F₁ hybrids have an intermediate phenotype

Question 18

Codominance

Answer 18

The two alleles each affect the pheotype in seperate, distinguishable ways

AB blood pheotypes are not all one or the other but express both antigens

Question 19

Tay-Sachs disease

Answer 19

An inherited disorder in humans where brain cells cannot metabolize certain lipids due to a deficiency in a crucial enzyme

An individual who is heterozygous for the disease will have impaired enzyme function but does not exhibit any significant deficits

Question 20

Pleiotropy

Answer 20

A property of genes in which they exert phenotypic effects on multiple characters rather than only influencing one

Question 21

Epistasis

Answer 21

The phenotypic expression of a gene at one locus alters that of a gene at a second locus

Question 22

Polygenic inheritance

Answer 22

An additive effect of two or more genes on a single pheotypic character such as height or skin color

Usually the result of quantitative characters- characters that do not exist as two discrete varieties but instead present as gradiations along a continuum in a population

Question 23

Pedigree

Answer 23

A family tree describing the a trait across generations from information in an individuals family tree

Question 24

Recessively inherited disorders

Answer 24

Albinism

Tay-Sachs disease- highest incidence among Ashkenazic Jews

Sickle-cell disease- most common recessively inherited disorder

Cystic fibrosis- chloride ion transport channels in the plasma membrane are absent or defective which leads to elevated intracellular chloride levels which causes excessive water uptake

Question 25

Consanguineous matings

Answer 25

Consanguineous matings (i.e., matings between close relatives) increase the chance of mating between two carriers of the same rare allele

Question 26

Dominantly inherited disorders

Answer 26

Achondroplasia- a form of dwarfism

Huntington’s disease- fatal neurodegenerative disease that doesn’t cause phenotypic effects until an individual is 35-45 years old

Question 27

Fetal testing

Answer 27

Amniocentesis

Chorionic villus sampling (CVS)- a sample of the placenta is removed and tested