Genetics ch. 3

If there are 400 progeny total, what are the expected (theoretical) numbers of progeny in each phenotypic class?

200

If the first three F2 offspring grown from the cross described above are round, what is the probability that the next F2 offspring will be wrinkled?

25% The proportion of rr is ¼, so the next offspring has a 25% chance of being wrinkled.

If one is testing a goodness of fit to a 9:3:3:1 ratio, how many degrees of freedom would be associated with the Chi-square analysis?

3 degrees of freedom

Round (R) seed shape is dominant to wrinkled (r) seed shape in pea plants. If an RR plant is crossed with an rr plant, what is the frequency of phenotypes in the F2 generation?

3 round seeds, 1 wrinkled seed The F1 generation would have the genotype Rr, so crossing two heterozygotes would result in 3 plants with round seeds and 1 plant with wrinkled seeds.

What phenotypic ratio is expected in the progeny of such a cross? ___ Gray : ____ white

3:1

Albinism in humans is inherited as a simple recessive trait. For the following families, determine the most likely genotypes of the parents. Suppose that one of the normal children from Part B and one of the albino children from Part C become the parents of eight offspring. What would be the expected number of normal and albino offspring?

4 normal; 4 albino

Tightly curled or wooly hair is caused by a dominant gene in humans. If a heterozygous curly-haired person marries a person with straight hair, what percentage of their offspring would be expected to have straight hair?

50% straight

Given a total of 1024 offspring how many flies of each phenotype would you expect? _____ wildtype : _____ hairy : ____ vestigial : ___ vestigial hairy

576:192:192:64

A recessive allele in tigers causes the white tiger. If two normally pigmented tigers are mated and produce a white offspring, what percentage of their remaining offspring would be expected to have normal pigmentation?

75%

In peas, gray seed color (G) is dominant to white (g). For the purposes of this question, assume that Mendel crossed plants with gray seeds with each other and the following progeny were produced: 240 gray and 80 white. What are the most probable genotypes of the parents?

Both parents are Gg.

Two different matings were made between black members of the F2 generation with the following results. Cross Offspring Cross 1 All black Cross 2 ¾ black, ¼ white Label the genotypes of the parents and offspring in these two crosses. (Note that the offspring shown represent ratios of a large number of offspring, not just four individuals.)

Cross 1: WW x WW all WW Cross 2: Ww x Ww WW, Ww, ww

Name the single individual whose work in the mid-1800s contributed to our understanding of the particulate nature of inheritance as well as the basic genetic transmission patterns. With what organism did this person work?

Gregor Mendel; Pisum sativum

Which of the following would be true of a plant heterozygous for a single gene controlling flower color? (Assume complete dominance).

If crossed with another heterozygous plant, the majority of progeny will have the dominant flower color. There will be roughly three times as many plants with the dominant flower color as plants with the recessive flower color.

Of the methods listed below, which would be the best way to determine which of two alleles of a gene is dominant to the other?

Observe the relevant phenotype in the progeny that result from a cross between individuals from two different pure-breeding lines. All progeny will be heterozygous for the trait in question and will display the phenotype that corresponds with the dominant allele.

Assume that in a series of experiments, plants with round seeds (W) were crossed with plants with wrinkled seeds (w) and the following offspring were obtained: 220 round and 180 wrinkled. What is the most probable genotype of each parent?

One parent is ww, the other is Ww.

Label the genotypes of the parents (P1) and two offspring generations (F1 and F2). Labels can be used once, more than once, or not at all.

P1 = black (WW) x white (ww) F1 = black (Ww) F2 = black (W_; W_; W_) white (ww)

Which of the following phenomena is a consequence of Independent Assortment?

The phenotypic ratio among phenotypes produced from an F1 X F1 dihybrid cross is 9:3:3:1. The 9:3:3:1 ratio requires that the four gamete classes produced occur with equal frequency. This requires independent assortment.

In an individual that is heterozygous for a particular trait, the recessive allele is not expressed.

True Only the dominant allele is expressed in an individual that is heterozygous for a particular trait.

The 3:1 phenotypic ratio observed among progeny of an F1 X F1 cross requires random union of gametes.

True The 1:2:1 genotypic ratio represents relative probabilities of gamete combinations based on the assumption that gamete union is random.

Assume that a black guinea pig crossed with an albino guinea pig produced 5 black offspring. When the albino was crossed with a second black guinea pig, 4 black and 3 albino offspring were produced. What genetic explanation would apply to these data?

albino = recessive; black = dominant

What will be the phenotype of the offspring if two F2 white guinea pigs are mated?

all white

Which two genotypes in an individual would be expressed as the same phenotype in a diploid organism?

homozygous dominant and heterozygous Both of these genotypes would express the dominant phenotype. The homozygous dominant individual would have both copies of the dominant allele, and the heterozygous individual would have one copy of the dominant allele and one copy of the recessive allele, but only the dominant phenotype would be observed.

Albinism in humans is inherited as a simple recessive trait. For the following families, determine the most likely genotypes of the parents. A normal male and an albino female have six children, all normal. What are the most likely genotypes of the parents?

male: AA; female: aa

Albinism in humans is inherited as a simple recessive trait. For the following families, determine the most likely genotypes of the parents. A normal male and an albino female have six children, three normal and three albino. What are the most likely genotypes of the parents?

male: Aa; female: aa

Assuming no crossing over between the gene in question and the centromere, when do alleles segregate during meiosis?

meiosis I

Chi-square analysis can help us to decide whether __________.

our observations of an event differ from our expectations This is exactly the purpose of statistical tests.

The fundamental Mendelian process that involves the separation of contrasting genetic elements at the same locus would be called ________.

segregation

Mendel's unit factors in pairs are most accurately known to be _______.

two alleles on paternal and maternal homologs Mendel observed patterns of inheritance in offspring that stemmed from traits found in the parents. Mendel explained this phenomenon as the passage of "unit factors" that are transmitted from the parents to the offspring.

The phenotype of vestigial (short) wings (vg) in Drosophila melanogaster is caused by a recessive mutant gene that independently assorts with a recessive gene for hairy (h) body. Assume that a cross is made between a fly with normal wings and a hairy body and a fly with vestigial wings and normal body hair. The wild-type F1 flies were crossed among each other to produce 1024 offspring. Which phenotypes would you expect among the 1024 offspring?

vestigial hairy;wildtype;hairy;vestigial

Independent assortment explains _______.

why a collection of meiotic products that includes gametes of genotype Ab will also include gametes of genotype AB in roughly the same proportion Because alignment of the chromosomes is random, the alignment that produces Ab is just as likely as the alignment that produces AB. Therefore, the two genotypes should both occur with equal frequency.

Assuming independent assortment, what proportion of the offspring of the cross AaBbCcDd × AabbCCdd will have the aabbccdd genotype?

zero

What phenotypic ratio is expected? ___ round : ___ wrinkled

1:1

What genotypic ratio is expected in the progeny of such a cross? ____ GG : ___ Gg : ___ gg

1:2:1

A pea plant is heterozygous for two genes; one controlling height, one controlling color. The genotype is written PpTt. Based on the Law of Independent Assortment, approximately what proportion of the pollen produced by this plant should have the genotype PT?

1/4 There are four different possible genotypes. Independent Assortment assumes that all are equally likely. Therefore, each of the four should occur with roughly equal frequency (1/4).

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a). Two parents with normal pigmentation have an albino child. What is the probability that their next child will be albino? What is the probability that their next child will be an albino girl? What is the probability that their next three children will be albino?

1/4; 1/8; 1/64

What genotypic ratio is expected? ___ Ww : ___ ww

1:1

Which of the following statements is an example of independent assortment?

A tall pea plant will have the same ratio of yellow and green pods as a dwarf pea plant.

Which of the following genotypes represents a gamete produced by a failure to segregate during meiosis in a cell of genotype AaBbCC?

AaBC This gamete contains two copies of gene "A". Proper segregation would have separated A from a and allowed only one copy per gamete.

Albinism in humans is inherited as a simple recessive trait. For the following families, determine the most likely genotypes of the parents. Two normal parents have five children, four normal and one albino. What are the most likely genotypes of the parents?

Aa x Aa

The offspring of the P1 generation are known as the __________.

F1 generation The first filial, or F1, generation is the offspring of the P1, or parental generation.

A gene can have a maximum of two alleles.

False

The 9:3:3:1 ratio exhibited in the F2 generation of a dihybrid cross is a genotypic ratio.

False

The nonfunctional form of a gene is called a wild-type allele.

False

Independent assortment occurs only in cells that are heterozygous for two genes (AaBb) and not in cells that are completely homozygous (AABB or aabb).

False Even though there would be no genotypic differences in the products of such meioses, random alignment of chromosomes would still have occurred.