chap 12

One of the early ideas about heredity that was refuted by Mendel was: a)traits can be masked in some generations. b)traits are segregated among progeny. c)alleles do not influence each other. d)traits are transmitted directly. e)not all copies of a factor are identical.

traits are transmitted directly.

A method in which an individual of unknown genotype is crossed to a homozygous recessive individual is called a test cross. True False

true

Because of independent assortment, we can think of the dihybrid cross of consisting of two independent monohybrid crosses. True False

true

Dihybrid crosses demonstrated that alleles of one trait segregate independently of the alleles of other traits. True False

true

Many traits result from the additive expression of more than one gene. This is called polygenic inheritance. True False

true

Mendel's experiments with plants involved quantifying types of offspring and mathematically analyzing his observations.

true

The probability of either of two events occurring is the sum of their individual probabilities and is called the rule of addition. True False

true

The rule of addition is used when only one of several possibilities is sought while the rule of multiplication is used when more than one outcome is sought. Use the rule of addition when A OR B is required, use rule of multiplication when A AND B are required. True False

true

The rule of multiplication states that the probability of two independent events both occurring is the product of their individual probabilities. True False

true

Three alleles of the I gene exist and produce the different ABO blood types. The AB type represents an A gene on one chromosome and a B gene on the other. The type A must have an A allele on one chromosome but the other could be either an A or an i (allele for type O). True False

true

During meiosis, gene pairs, such as Mm and Pp will assort independent and a random combination of genes can end up in the gametes. When the big M and little m segregate during meiosis, each is just as likely to end up in the same gamete as the big P as the little p.

true Independent assortment occurs because there are different ways that the chromosomes can align in metaphase I of meiosis. Genes can be on different chromosomes or far apart on the same chromosome.

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)a single gene may affect more than one trait. B)a single trait may be affected by more than one gene. C)a single gene always affects only one trait, but traits may be affected by more than one gene. D)a single gene can affect more than one trait, and traits may be affected by more than one gene.

D)a single gene can affect more than one trait, and traits may be affected by more than one gene.

The F1 plants from the previous question are allowed to self-fertilize. The phenotypic ratio for the F2 should be a)all purple. b)1 purple:1 white. c)3 purple:1 white. d)3 white:1 purple.

c)3 purple:1 white.

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 traits to their offspring. c)If an allele is present it will be expressed. d)Traits do not blend.

c)If an allele is present it will be expressed.

The F1 generation of the monohybrid cross purple (PP) × white (pp) flower pea plants should a)all have white flowers. b_all have a light purple or blended appearance. c)all have purple flowers. d)have ¾ purple flowers, and ¼ white flowers.

c)all have purple flowers.

An organism's is/are determined by its . a)genotype; phenotype b)phenotype; genotype c)alleles; phenotype d)genes; alleles

c)alleles; phenotype

Blood types in human is an example of multiple alleles for one gene. In AB blood type, neither allele is dominant. This is also an example of: epitstasis. incomplete dominance. pleiotropy. polygenic inheritance. codominance.

codominance

The action of more than one gene can affect a single trait.

codominant

Height is an example of a: dominant trait. recessive trait. continuous trait. codominant trait.

continuous trait

Each allele has its own effect and some aspect of both alleles is seen in the heterozygote.

continuous variation

Pollen from a white-colored plant fertilizes a purple-colored plant; pollen from a purple-colored plant fertilizes a white-colored plant.

cross fertilization

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 ratio of F2 phenotypes? a) 3red 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

d) 3 red tall:6 pink tall:3 white tall:1 red short:2 pink short:1 white short

If the two genes in the previous question showed complete linkage, what would you predict for an F2 phenotypic ratio? a)1 red tall:2 pink short:1 white short b)1 red tall:2 red short:1 white short c)1 pink tall:2 red tall:1 white short d)1 red tall:2 pink tall:1 white short

d)1 red tall:2 pink tall:1 white short

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.

d)the action of multiple genes on a single phenotype.

What is the main reason to perform a testcross? determine the genotype of a plant determine the phenotype of a plant determine which allele is dominant make a mutation determine the age of a plant

determine the genotype of a plant

To follow the behavior of two different traits in a single cross.

dihybrid cross

If you cross a true-breeding dominant plant with a true-breeding recessive plant, what will be the phenotype of the resulting progeny? all dominant all recessive 50% dominant / 50% recessive 75% dominant / 25% recessive 25% dominant / 75% recessive

dominant

The form of each trait that is expressed in the F1 generation.

dominant

if one of the affected females in the third generation married an unaffected male, could she produce unaffected offsprings? if so, what are the chances of having unaffected offsprings?

each affected female had one unaffected parent 50 % of the offspring affected

A situation in which the expression of one gene can interfere with the phenotypic effects of a second gene.

epistasis

Prior to Mendel, concepts of inheritance formed a consistent model. The dominant view was of blending inheritance, in which traits of parents were carried by fluid and "blended" in offspring.

false

A testcross is performed by mating a homozygous dominant individual with an individual displaying the recessive trait. True False

false A testcross is performed by mating a homozygous recessive individual with an individual displaying the dominant trait.

To produce a hybrid plant you would cross-fertilize a heterozygous plant with a homozygous plant

false A true-breeding (homozygous) plant displaying one trait is cross-fertilized with a true-breeding (homozygous) plant displaying a different trait. The progeny will be hybrids.

Mendel demonstrated from monohybrid crosses that alleles do not segregate during reproduction.

false Monohybrid crosses demonstrated that alleles segregate during reproduction.

The first generation of offspring produced as a result of crossing two parental lines.

first filial generation (F1)

from the standpoint of genetic disease, why is it never advisable for close relatives to mate and have children?

genetic defects that remain hidden or dormant as heterozygotes in the recessive state are more likely to be revealed in homozygous state among closely related individuals

The total set of alleles that an individual contains, which provides the blueprint for an individual's traits.

genotype

The offspring produced when two haploid gametes containing different alleles fuse during fertilization.

heterozygous

The offspring produced when two haploid gametes containing the same allele fuse during fertilization

homozygous

An individual who has two of the same allele is said to be: homozygous. heteromologous. homologous. heterozygous. diplozygous.

homozygous.

An allele that has more than one effect on the phenotype of an individual.

incomplete dominance

When red snapdragons are crossed with white snapdragons, pink offspring result. This is an example of: codominance. incomplete dominance. pleiotropy. epistasis.

incomplete dominance

The predictable 9:3:3:1 phenotypic ratio that resulted from Mendel's dihybrid crosses illustrates the: law of probability. law of independent assortment. law of segregation. gene theory.

law of independent assortment.

which is more important in terms of explaining menders laws, meiosis 1 or 2?

meiosis 1 because during anaphase 1 homologous separate and are thus segregated and the alignment of different homologous pair at metaphase 1 is independent

To follow the behavior of two variations of a single trait in a cross

monohybrid cross

A graphical representation of matings and offspring over multiple generations for a particular trait.

pedigree

The appearance resulting from a given gene combination is referred to as the: genotype. phenotype. phototype. allelotype. stereotype.

phenotype

The physical appearance and other observable features that result from the expression of an allele.

phenotype

A gradation that results from a contribution of different combinations of alleles to a single trait.

pleiotropic

The heterozygote is intermediate in appearance between the two homozygotes.

polygenic inheritance

Many human traits are controlled by more than one gene; this is called: polygenic inheritance. pleiotropic inheritance. multiple alleles. codominance. incomplete dominance.

polygenic inheritance.

A simple diagram predicting the possible genotypes of a progeny based on the identity of the parental gametes.

pungent square

The form of each trait that is present but not expressed in the F1 generation.

recessive

Alternative forms of observed characters being distributed among the progeny of a mating.

reciprocal crosses

If two alternatives for a trait are red (R) and white (r) and red is dominant, the genotype of a homozygous recessive individual would be expressed as: RR. rr. Rr.

rr

Offspring obtained by allowing the F1 generation to self-fertilize.

second filial generation (f2)

Gametes produced by the male and female parts of two different flowers fuse to form viable offspring

segregation

what confounding problems could have been seen if mendel had chosen another plant with exposed male and female structures?

self fertilization or cross fertilization

The offspring produced from self-fertilization remain uniform from one generation to the next.

self-fertilization

From a dihybrid cross with epistasis one would expect to get a F2 progeny ratio of 9:3:3:1 expressed. True False

False Epistasis involves the inheritance of two or more enzymes that act sequentially. Any disruption of enzymes acting early in the sequence will prevent the action of those later in the sequence. Thus, a modified ratio of 9:7 results.

Which of the following represents a dihybrid? WWSs WwSS WwSs WWss WwSs

WwSs

Compared to the work of previous geneticists, the unique characteristic of Mendel's work was: a)keeping quantitative records of numbers of different progeny. b)choosing the garden pea for his experiment. producing hybrids. c)studying more than one generation. d)crossing true-breeding plants.

a

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

a) 1/16

how many different phenotypes appear in the F2 generation of a dihybrid cross? 1 2 3 4 5

4

A child having one heterozygous parent with a dominant genetic disorder has what chance of inheriting that disorder? 0% 25% 50% 75% 100%

50

If there is 25% chance that a child will inherit a recessive disease from it parents, what is the probability that one of a couple's first three children will have the disease? 10% 25% 50% 75% 100%

75

If an affected male with a recessive disorder married an unaffected female, what are their chances of having an unaffected offspring? 0% 25% 50% 75% 100%

100

In a monohybrid cross, what is the genotypic ratio of the F2 offspring? 4:1 3:1 2:1 1:2:1 1:3:1

1:2:1

If there is an equal chance that a child will be male or female, what is the probability that both of a couple's first two children will be female? 0% 10% 25% 50% 100%

25

Two carriers of albinism have three children. One child is affected but two children are not. What is the probability that their next child will be albino? 0% 25% 50% 75% 100%

25

Mendel chose the garden pea to use in his studies. Why? Check all that apply. 1)Many earlier investigators had produced hybrid peas by crossing different varieties, so Mendel knew that he could expect to observe segregation of traits among the offspring. 2)A large number of pure varieties of peas were available. 3)Pea plants are small and easy to grow, and they have a relatively short generation time. 4)Both the male and female sexual organs are enclosed within each pea flower allowing easy self-fertilization.

3 and 4

If you self-fertilize F1 progeny, what will be the dominant to recessive phenotypic ratio of the progeny? 4:1 3:1 2:1 1:2:1 1:3:1

3:1

Where two alternatives for a trait are 'B' and 'b', the phenotype of a homozygous dominant individual would be expressed as: BB. bb. Bb.

BB

You wish to breed guinea pigs but want all the offspring to have black coats. BB or Bb will show the pigmentation black and bb will show the pigmentation white. You cross an unknown genotype black coated male guinea pig with a recessive white coated female guinea pig. If your offspring show a phenotypic ratio of 3:1, what was the genotype of the male guinea pig? BB Bb bb

Bb

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 for these data? AHeight is determined by a single gene with incomplete dominance. BHeight is determined by a single gene with many alleles. CHeight is determined by the additive effects of many genes. DHeight is determined by epistatic genes.

C)Height is determined by the additive effects of many genes.

The second law of heredity that states that in a dihybrid cross, the alleles of each gene assort independently.

Principle of Independent Assortment

The first law of heredity states that two alleles for a gene segregate during gamete formation and rejoin randomly

Principle of Segregation

What property distinguished Mendel's investigation from previous studies? a)Mendel used true-breeding pea plants. b)Mendel quantified his results. c)Mendel examined many different traits. d)Mendel examined the segregation of traits.

b)Mendel quantified his results.

Where two alternatives for a trait are tall (S) and short (s) and tall is dominant, the genotype of a heterozygous individual would be expressed as: Ss. ss. SS.

Ss

Two phenotypically normal individuals have an affected child. What can we conclude about the parents? They both carry the affected allele. They could have only adopted the child. They are not affected. The disease is a dominant disease.

They both carry the affected allele.

Which gamete will be formed in an individual with genotype aaRR? AR Ar aR ar

aR

Each member of a gene pair or a particular form of a gene is a(n): genotype. progeny. allele. homologues. phenotype.

allele

The alternative forms of a single gene that exist in a population.

alleles

The principle of independent assortment predicts that: genes are malleable factors. a)genes are discrete factors. b)alleles segregate during meiosis. c)alleles of one gene assort independently of alleles of other genes. d)genes can be mutated.

alleles of one gene assort independently of alleles of other genes.

The darkness of the ears of Siamese cats is an example of: a mutation. a pleiotropic effect. a polygene. epistasis. an environmental effect.

an environmental effect.

What is the probability of obtaining an individual with the genotype bb from a cross between two individuals with the genotype Bb? a) ½ b) ¼ c) ⅛ d) 0

b) ¼

The recessive trait is not observed in the F1 (hybrid) progeny because its expression is masked by the dominant allele.

true One allele of the recessive trait is present in the F1 progeny but its expression is not observed because the expression of the dominant allele masks it.

Gametes produced by the male and female parts of the same flower fuse to form viable offspring.

true-breeding

Which cross of genotypes represents a testcross? Ww × WW ww × WW Ww × Ww WW × WW

ws x Ww