Chapter 12 Patterns of Inheritance
universal blood receiver
AB
assuming independent assortment, which of the following are examples of gametes produced by an AaBb individual?
AB, ab
universal blood donor
O
punnett square
a diagrammatic way of showing the possible genotypes and phenotypes of genetic crosses
An organism's ____ is/are determined by its ______.
alleles; phenotype
phenylthiocarbamide (PTC) sensitivity
dominant; ability to taste PTC as bitter
mendel used the garden pea plant to study inheritance because the pea plants a) existed in one variety b) produced few offspring c) were edible d) have short generation times
have short generation times
heterozygous
having two different alleles of the same gene; the term is usually applied to the one or more specific loci, as in "heterozygous with respect to the W locus" (Ww)
if the offspring from a testcross contain homozygous and heterozygous, the genotype of the unknown parent must be ____
heterozygous
the potential outcomes of the offspring of a testcross include which of the following? a) heterozygous b) homozygous dominant c) homozygous recessive
heterozygous and homozygous recessive
If the offspring from a testcross contain only heterozygotes, the genotype of the unknown parent must be _____
homozygous
Which of the following is NOT a part of Mendel's five-element model? a) traits have alternative forms (what we now call alleles) b) parents transmit discrete to their offspring c) if an allele is present it will be expressed d) traits do not blend
if an allele is present it will be expressed
dominance is not always complete
in complete dominance the heterozygote is intermediate & in codominance no single allele is dominant, and the heterozygote shows some aspect of both homozygotes example: japanese four o'clocks, human blood groups
a 9:3:3:1 ratio represents the 16 potential combinations between gametes in an _____ assorting dihybrid cross
independently
alleles
one of two or more alternative states of a gene
cross-fertilization involves placing ____ from one plant onto the stigma of a flower on a different plant
pollen
reciprocal fertilization
pollen collected from anthers of a white flower placed onto the stigma of a purple flower with anthers removed
cross fertilization
pollen from a white-flowered plant is used to fertilize a purple-flowered plant, while pollen from a purple-flowered plants is used to fertilize a white-plant
human height is an example of a trait that has a continuous distribution of phenotypes. human height is therefore an example of _____ inheritance
polygenic
a trait that has multiple genes contributing to its expression is know as a
polygenic trait
cystic fibrosis
recessive; abnormal gland secretion, leading to liver degeneration and lung failure
sickle cell anemia
recessive; defective hemoglobin that causes red blood cells to curve and stick together
hemophilia
recessive; inability of blood to clot properly, some clots form but the process is delayed
red-green color blindness
recessive; inability to distinguish red or green wavelengths of lights
alkaptonuria
recessive; inability to metabolize homogentisic acid
albinism
recessive; lack of melanin pigmentation
duchenne muscular dystrophy
recessive; wasting away of muscles during childhood
true-breeding
said of a breed of variety of organism in which offspring are uniform and consistent from one generation to the next. this is due to the genotypes that determine relevant traits being homozygous
an individual with a dominant phenotype, may have a genotype of:
homozygous dominant and heterozygous
Which of the following are inherited as dominant traits? huntington disease brachydactyly albinism hemophilia
huntington disease, brachydactyly
the classical assumptions of heredity would eventually lead to all members within a species having
the same appearance
self-fertilization
the union of egg and sperm produced by a single hermaphroditic organism
in a heterozygous individual, the probability of a recessive allele being present in a gamete is
.5
in a homozygous recessive individual the probability of the dominant allele being present is:
0
how many potential phenotypes can results from a dihybrid cross when the traits assort independently from one another?
4
reciprocal crosses
a genetic cross involving a single trait in which the sex of the parents is reversed; for example, if pollen from a white-flowered plant is used to fertilize a purple-flowered plant, the reciprocal cross would be pollen from a purple-flowered plant used to fertilize a white-flowered plant
a mismatched blood transfusion may lead to ____ in the blood due to the reaction between blood cells antigens and antibodies
agglutination
homozygous
being a homozygote, having two identical alleles of the same gene; the term is usually applied to one or more specific loci, as in "homozygous with respect to the W locus" (WW or ww)
the concept of inheritance which suggested that parents make equal contributions to their offspring and that their genetic material blends together is called
blending inheritance
an individual with two identical alleles of a gene of a particular trait has a(n) ______ genotype with respect to that gene
homozygous
codominant
describes a case in which two or more alleles of a gene are each dominant to other alleles but not to each other. the phenotype of a heterozygote for codominant alleles exhibit characteristics of each of the homozygous forms. for example, in human blood types, a cross between an AA individual and a BB individual yields AB individuals
the result of a testcross indicate that all of the offspring have a dominant phenotype. the genotype of the parent in question must be: a) homozygous recessive b) heterozygous c) homozygous dominant
homozygous dominant
incomplete dominance
describes a case in which two or more alleles of a gene do not display clear dominance. the phenotype of a heterozygote is intermediate between the homozygous forms. for example, crossing red-flowered with white-flowered four o'clocks yields pink heterozygous
what type of cross follows the simultaneously inheritance of two different traits?
dihybrid cross
which of the following genotypes are true-breeding? a) tt b) Tt c) TT d) tT
tt, TT
In a cross of Aa Bb cc x Aa Bb Cc, what is the probability of obtaining an individual with the genotype AA Bb Cc? a) 1/16 b) 3/16 c) 1/64 d) 3/64
1/16
What is the probability of obtaining an individual with the genotype bb from a cross between two individuals with the genotype Bb?
1/4
match these percentages based on the 3:1 ratio in the F2 generation of a monohybrid cross: 1/2 1/4 1/4 & not true-breeding true-breeding dominant true-breeding recessive
1/4 = true-breeding dominant 1/4 = not true-breeding 1/2 = true-breeding recessive
how many possible allele combinations (consider all possible combinations even those that are identical) are produced in the offspring of heterozygous parents in a dihybrid cross?
16
a 3:1 phenotypic ratio in the F2 generation of a monohybrid cross represents this genotypic ration:
1:2:1
in incomplete dominance, the genotypic ratio in the F2 generation is which of the following? a) 1:2:1 b) 9:3:3:1 c) 3:1
1:2:1
if a particular gene in a population has multiple alleles, how many alleles can an individual inherit?
2
a punnett square for a single trait should be set up as a _____ square
2x2
The F1 plants from the previous question (monohybrid cross purple (PP) x white (pp) flower pea plants) are allowed to self-fertilize. The phenotypic ration for the F2 should be: a) all purple b) 1 purple: 1 white c) 3 purple: 1 white d) 3 white: 1 purple
3 purple: 1 white
Japanese four o'clocks that are red and tall are crossed to white short ones, producing an F1 that is pink and tall. If these genes assort independently, and the F1 is self-crossed, what would you predict for the ration of F2 phenotypes? a) 3 red tall: 1 white short b) 1 red tall: 2 pink short: 1 white short c) 3 pink tall: 6 red tall: 3 white tall: 1 pink short: 2 red short: 1 white short d) 3 red tall: 6 pink tall: 3 white tall: 1 red short: 2 pink short: 1 white short
3 red tall: 6 pink tall: 3 white tall: 1 red short: 2 pink short: 1 white short
in a dihybrid testcross, a homozygous recessive individual would be crossed with which of the following potential individuals: a) aabb b) AaBB c) AaBb d) Aabb e) AABB
AaBB, AaBb, AABB
which of the following is an example of a testcross? a) AaBb x AABB b) AaBb x aabb c) aabb x aabb d) AaBb x AaBb
AaBb x aabb (in a testcross, one of the individuals has be to homozygous recessive)
in a dihybrid testcross, a homozygous recessive individuals would be crossed with which of the following potential individuals: AaBb AaBB aabb Aabb AABB
AaBb, AaBB, AABB
this generation is produced when the F1 monohybrids self fertilize
F2
When you cross true-breeding tall and short tobacco plants you get an F1 that is intermediate in height. When this F1 is self-crossed, it yields an F2 with a continuous distribution of heights. What is the best explanation of these data?
Height is determined by the additive effect of many genes
What property distinguished Mendel's investigation from previous studies? a) Medel used true-breeding pea plants b) Mendel quantified his results c) Mendel examined many different traits d) Mendel examined the segregation of traits
Mendel quantified his results
in terms of probabilities, the cross of a tall yellow seeded pea plants (TTYy) with a tall green seeded pea plant (Ttyy) is equivalent to which two monohybrid crosses? a) TT x Tt and Yy x yy b) TT x Yy and Tt x yy c) TT x yy and Tt x Yy
TT x yy and Tt x Yy
an individual with genotype Aa can produce which gamete(s)?
Two: A and a
pedigree
a consistent graphic representation of matings and offspring over multiple generations for a particular genetic trait, such as albinism or hemophilia
pea plants are self-fertilizing which means that a female gamete is fertilized by which of the following?
a male gamete from the same plant
testcross
a mating between a phenotypically dominant individual of unknown genotype and a homozygous "tester", done to determine whether the phenotypically dominant individual is homozygous or heterozygous for the relevant gene
ABO blood groups
a set of four phenotypes produced by different combinations of three alleles at a single locus; blood types are A, B, AB, and O, depending on which alleles are expressed as antigens on the red blood cell surface
pleiotropic
a single gene can affect more than one trait example: a pleiotropic allele dominant for yellow fur in mice is recessive for a lethal developmental defect; cystic fibrosis; sickle cell anemia
Mendel's model assumes that each trait is determined by a single factor with alternate forms. We now know that this is too simplistic and that
a single gene can affect more than one trait, and traits may be affected by more than one gene
quantitative traits
a trait that is determined by the effects of more than one gene; such a trait usually exhibits continuous variation rather than discrete either-or values
in a cross between two individuals who are both heterozygous Tt, if you want to determine the probability that the offspring will have either the genotype TT or the genotype Tt, you would need to use the ____ rule
addition
a nonfunctional allele for tyrosinase is characteristic of the genetic condition called _____
albinism
The F1 generation of the monohybrid cross purple (PP) x white (pp) flower pea plants should: a) all have white flowers b) all have purple flowers c) all have a light purple or blended appearance d) have 3/4 purple flowers and 1/4 white flowers
all have purple flowers
dominant
an allele that is expressed when present in either the heterozygous or the homozygous condition
recessive
an allele that is only expressed when present in the homozygous condition, but being "hidden" by the expression of a dominant allele in the heterozygous condition
dihybrid cross
an individual heterozygous cross involving two different traits, such as flower color and plant height
the law of independent assortment is related to which of the following activities in meiosis?
chromosome alignment
huntington disease
dominant; degeneration of nervous system, starting in middle age
hypercholesterolemia
dominant; elated levels of blood cholesterol and risk of heart attack
polydactyly
dominant; extra fingers and toes
camptodactylly
dominant; inability to straighten little finger
middigital hair
dominant; presence of hair on middle segment of fingers
brachydactyly
dominant; short fingers
the law of independent assortment states that alleles of different genes assort independently of each other during ____ formation
gamete
in his studies, mendel referred to unit factors that are passed intact from one generation to the next. we now know that these factors are actually ____
genes
environmental factors
genes may be affected by the environment example: siamese cats
multiple alleles for one gene
genes may have more than two alleles example: ABO blood type in humans
the results of a testcross indicate that all of the offspring have a dominant phenotype. the genotype of the parent in question must be
homozygous dominant
a true-breeding line can be which of the following? a) homologous b) homozygous dominant c) homozygous recessive d) heterozygous
homozygous dominant and homozygous recessive
epistasis
interaction between two nonallelic genes in which one of them modifies the phenotypic expression of the other
the physical basis for allele segregation is the behavior of chromosomes during the process of ______
meiosis
Mendel's Principle of Segregation
mendel's first law of heredity, stating that alternative alleles for the same gene segregate from each other in production of gametes
principle of independent assortment
mendel's second law of heredity, stating that genes located on nonhomologous chromosomes assort independently of one assortment
mendel observed a 3:1 ratio in _____ crosses between dominant and recessive in the F2 offspring
monohybrid
the inheritance pattern of many traits (more or less) complex than simple Mendelian patterns
more
polygenic inheritance
more than one gene can affect a single trait example: four genes are involved in determining eye color; human height
the rule of addition is applied to events with _________ outcomes
mutually exclusive
juvenile glaucoma is a hereditary disease that causes blindness due to the degeneration of nerves in which of the following? optic nerve cornea retina blind spot
optic nerve
in snapdragons, alleles resulting in red pigment and white pigment exhibit incomplete dominance. if red snapdragons are crossed with pure white snapdragons the offspring of the F1 generation will be: a) red b) white c) purple d) pink
pink
sickle cell anemia is caused by a ____ allele because this mutation has more than on effect on the phenotype
pleiotropic
this allele is one that has more than one effect on a phenotype
pleiotropic
gene interaction
products of genes can interact to alter genetic ratios example: the production of a purple pigment in corn, coat color in mammals
a ____ trait is one that that is not expressed in a heterozygous individual
recessive
those who are homozygous ______ will exhibit the symptoms of cystic fibrosis, including abnormalities of the pancreas, intestine, sweat glands, and lungs
recessive
an example of a _____ cross is using pollen from a green-seeded pea plant to fertilize a yellow-seeded pea plant and then using pollen from a yellow-seeded pea plant to fertilize a green-seeded pea plant
reciprocal
this rule is applied to events with mutually exclusive outcomes:
sum
self fertilization
takes place within an individual flower if it is not disturbed
the cross of an individual who has a dominant phenotype with an individual who is homozygous recessive for that gene is known as a ______
testcross
Phenotypes like height in humans, which show a continuous distribution, are usually the result of: a) an alteration of dominance for multiple alleles of a single gene b) the presence of multiple alleles for a single gene c) the action of one gene on multiple phenotypes d) the action of multiple genes on a single phenotype
the action of multiple genes on a single phenotype
Mendelian ratio
the characteristic dominant-to-recessive phenotypic ratios that Mendel observed in his genetics experiments. For example, the F2 generation in a monohybrid cross shows a ratio of 3:1, the F2 generation in a dihybrid cross shows a ratio 9:3:3:1
genotype
the genetic constitution underlying a single trait or set of traits
hybridization
the mating of unlike parents
Mendel's work involved quantitative experiments are careful analysis of the offspring carrying specific traits. he paid the most attention to which of the following? a) the total number of offspring, regardless of what type they were b) the numbers of every different type of offspring c) the numbers of the offspring that were of a specific gender
the numbers of every different type of offspring
first filial generation
the offspring resulting from a cross between a parental generation ( P ); in experimental crosses, these parents usually have different phenotypes
second filial generation
the offspring resulting from a cross between members of the F1 generation
segregation
the process by which alternative forms of traits are expressed in offspring rather than blending each trait of the parents in the offspring
phenotype
the realized expression of the genotype; the physical appearance or functional expression of a trait
rule of multiplication
the rule stating that for two independent events, the probability of both events occurring is the product of the individual probabilities
rule of addition
the rule stating that for two independent events, the probability of either event occurring is the the sum of the individual probabilities
prior 20th century, the two main ideas that provided the basis for most thinking about hereditary were: a) traits are transmitted directly from parents to offspring b) traits in offspring are different from parents c) heredity occurs within species
traits are transmitted directly from parents to offspring and heredity occurs within species
true or false: crossing pure breed white flowered pea plants with pure breed purple flowered pea plants produced hybrid pea plants with purple flowers
true
an individual can acquire only ____ allele(s) per trait, even if multiple alleles are present in the population
two
the probability of genotypes in an independently assorted dihybrid cross is based on a probabilities of: a) the parent's genotypes b) two monohybrid crosses c) mutually exclusive events
two monohybrid crosses
a temperature-sensitive enzyme, ______, is responsible for the pattern of fur color in Siamese cats
tyrosinase
continuous variation
variation in a trait that occurs along a continuum, such as the trait of height of human beings; often occurs when a trait is determined by more than one gene
a punnett square has rows and columns which represent gametes made by males and females. at the intersection of each row and column we combine the corresponding gametes to produce the genotype of a potential ____
zygote