Genetics Chapter 2 Study Guide

Front 1

Refers to an allele whose presence in a heterozygous genotype results in a phenotype characteristic of the allele.

Back 1

dominant trait

Front 2

The mechanism of inheritance in which the statistical relations between the distribution of traits in successive generations result from (1) particulate hereditary determinants (genes), (2) random union of gametes, and (3) segregation of unchanged hereditary determinants in the reproductive cells.

Back 2

mendelian genetics

Front 3

The phenomenon in which two recessive mutations with similar phenotypes result in a wildtype phenotype when both are heterozygous in the same genotype; complementation means that the mutations are in different genes.

Back 3

complementation

Front 4

The cross of an F1 heterozygote with a partner that has the same genotype as one of its parents.

Back 4

backcross

Front 5

A diagram representing the familial relationships among relatives.

Back 5

pedigree

Front 6

An organism produced by the mating of genetically unlike parents; also, a duplex nucleic acid molecule produced of strands derived from different sources.

Back 6

hybrid

Front 7

The principle that the probability that any one of a set of mutually exclusive events is realized equals the sum of the probabilities of the separate events.

Back 7

addition rule

Front 8

The observable properties of a cell or an organism, which result from the interaction of the genotype and the environment.

Back 8

phenotype

Front 9

The presence, in a population, of more than two alleles of a gene.

Back 9

multiple alleles

Front 10

Separation of the members of a pair of alleles into different gametes in meiosis.

Back 10

segregation

Front 11

The most common phenotype or genotype in a natural population; also, a phenotype or genotype arbitrarily designated as a standard for comparison.

Back 11

wildtype

Front 12

Differences in the severity of expression of a particular genotype.

Back 12

variable expressivity

Front 13

A genetic test to determine whether two mutations are alleles (are present in the same functional gene).

Back 13

complementation test

Front 14

The hereditary unit defined experimentally by the complementation test. At the molecular level, a region of DNA containing genetic information, usually transcribed into an RNA molecule that is processed and either functions directly or is translated into a polypeptide chain; a gene can mutate to various forms called alleles.

Back 14

gene

Front 15

Refers to an allele, or the corresponding phenotypic trait, expressed only in homozygotes.

Back 15

recessive trait

Front 16

Absence of melanin pigment in the iris, skin, and hair of an animal; absence of chlorophyll in plants.

Back 16

albinism

Front 17

The principle that the probability that all of a set of independent events are realized simultaneously equals the product of the probabilities of the separate events.

Back 17

multiplication rule

Front 18

The process by which genes are passed from one generation to the next.

Back 18

transmission genetics

Front 19

A substance able to stimulate the production of antibodies.

Back 19

antigen

Front 20

Dominantly inherited degeneration of the neuromuscular system, with onset in middle age.

Back 20

huntington disease

Front 21

A heterozygote for a recessive allele.

Back 21

carrier

Front 22

Random distribution of unlinked genes into gametes, as with genes in different (nonhomologous) chromosomes or genes that are so far apart on a single chromosome that the recombination frequency between them is 1/2.

Back 22

independent assortment

Front 23

A term referring to an interaction between nonallelic genes in their effects on a trait. Generally, epistasis means any type of interaction in which the genotype at one locus affects the phenotypic expression of the genotype at another locus. In a more restricted sense, it refers to a situation in which the genotype at one locus determines the phenotype in such a way as to mask the genotype present at a second locus.

Back 23

epistasis

Front 24

The proportion of organisms having a particular genotype that actually express the corresponding phenotype. If the phenotype is always expressed, penetrance is complete; otherwise it is incomplete.

Back 24

penetrance

Front 25

A genotype that is heterozygous for one pair of alleles; the offspring of a cross between genotypes that are homozygous for different alleles of a gene.

Back 25

monohybrid

Front 26

The second generation of descent, produced by intercrossing or self-fertilizing F1 organisms.

Back 26

F2 generation

Front 27

A cross in which the sexes of the parents are the reverse of those in another cross.

Back 27

reciprocal cross

Front 28

A technique used to separate molecules on the basis of their different rates of movement in response to an applied electric field, typically through a gel.

Back 28

electrophoresis

Front 29

Condition in which the phenotype of a heterozygous genotype is intermediate between the phenotypes of the homozygous genotypes.

Back 29

incomplete dominance

Front 30

Having the same allele of a gene in homologous chromosomes.

Back 30

homozygous

Front 31

A group of mutations that fail to complement one another.

Back 31

complementation group

Front 32

The product of the fusion of a female and a male gamete in sexual reproduction; a fertilized egg.

Back 32

zygote

Front 33

A mature reproductive cell, such as sperm or egg in animals.

Back 33

gamete

Front 34

Carrying dissimilar alleles of one or more genes; not homozygous.

Back 34

heterozygous

Front 35

A type of genetic experiment in which the geneticist seeks to isolate multiple new mutations that affect a particular trait.

Back 35

mutant screen

Front 36

Refers to phenotypes in which the presence of both alleles in heterozygous genotypes can be detected.

Back 36

codominant

Front 37

Any of the alternative forms of a given gene.

Back 37

allele

Front 38

The first generation of descent from a given mating.

Back 38

f1 generation

Front 39

The parents used in a cross, or the original parents in a series of generations; also called the P generation if there is no chance of confusion with the grandparents or more remote ancestors.

Back 39

p1 generation

Front 40

A technique used to separate molecules on the basis of their different rates of movement though a gel in response to an applied electric field.

Back 40

gel electrophoresis

Front 41

A cross-multiplication square used ifor determining the expected genetic outcome of a mating.

Back 41

punnett square

Front 42

A brother or sister, each having the same parents.

Back 42

sibling

Front 43

Heterozygous at each of two loci; progeny of a cross between true-breeding, or homozygous, strains that differ genetically at two loci.

Back 43

dihybrid

Front 44

Refers to a strain, breed, or variety of organism that yields progeny like itself; homozygous.

Back 44

true- breeding

Front 45

A group of brothers and sisters.

Back 45

sibship

Front 46

The genetic constitution of an organism or virus, typically with respect to one or a few genes of interest, as distinguished from its appearance, or phenotype.

Back 46

genotype

Front 47

A blood protein produced in response to a specific antigen and capable of binding with the antigen.

Back 47

antibody

Front 48

Mating of two organisms produces a 3:1 ratio of phenotypes in the progeny. The parental genotypes are ___

Back 48

Aa x Aa

Front 49

Mating a heterozygous individual with a recessive homozygote is called a ___

Back 49

testcross

Front 50

In families where one parent is homozygous for a recessive trait and the other is heterozygous, what is the probability of their having a child with the homozygous recessive genotype?

Back 50

0.5

Front 51

Assuming independent assortment, how many different gametes can be formed by an organism that is homozygous for 5 and heterozygous for 2 genes?

Back 51

4

Front 52

In a complementation test, if the combination of two recessive mutations results in a wildtype phenotype, then the mutations are regarded as ___

Back 52

alleles of different genes

Front 53

Two parents with blood types A and B have a child who has 0 blood type. What is the chance that their next child will be B?

Back 53

0.25

Front 54

Among sibships consisting of two children, and assuming a sex ratio of 1:1, what is the proportion with no girls?

Back 54

0.5

Front 55

Probabilities are calculated using the multiplication rule when they ___

Back 55

are idependent

Front 56

In the cross AABB x aabb, F2 progeny is produced in a phenotypic ratio of 13:3. What does this deviation from the expected 9:3:3:1 indicate?

Back 56

epistasis

Front 57

In a testcross of Aa Bb Cc DD Ee, where the genes show independent assortment, what is the expected frequency of aa bb cc Dd ee progeny?

Back 57

0.25

Front 58

F2 generation of a monohybrid cross, observed traits are___

Back 58

3:1

Front 59

F2 genertion of a dihybrid cross, observed traits are___

Back 59

9:3:3:1

Front 60

modification of the 9:3:3:1 ratio is___

Back 60

epistasis

Front 61

mutations are in different genes

Back 61

Complementation

Front 62

proportion of organisms whose phenotype matches their genotype for a given trait

Back 62

penetrance

Front 63

____is the phenomenon in which two recessive mutations with similar phenotypes result in a wildtype phenotype when both are heterozygous in the same genotype.

Back 63

complementation

Front 64

Codominance means that the phenotype of the heterozygous genotype is an intermediate between those of the homozygous genotypes. true or false?

Back 64

false

Front 65

Dominance is a property of a pair of alleles in relation to a particular attribute of phenotype. true or false?

Back 65

true

Front 66

The probability of two independent possibilities being realized simultaneously is given by the product of their separate probabilities.

Back 66

Multiplication Rule

Front 67

The probability of the realization of one or the other of two mutually exclusive possibilities is the some of their separate probabilities.

Back 67

addition rule

Front 68

Segregation of the members of any pair of alleles is independent of the segregation of other pairs in the formation of reproductive cells.

Back 68

The Principle of Independent Assortment