BI211 week 8-10

At what stage does the independent assortment of genes occur?

Meiosis I

What is the phenotypic ratio of dominant to recessive in a monohybrid cross?

3:1

How many phenotypes and degrees of freedom are there for a dihybrid cross?

4 phenotypes, 3 degrees of freedom

Given the parents AABb × Aabb, assume simple dominance for each trait and independent assortment. What proportion of the progeny will be expected to phenotypically resemble the first parent with genotype AABB?

50%

When crossing an organism that is homozygous recessive for a single trait with a heterozygote, what is the chance of producing an offspring with the homozygous recessive phenotype?

50%

In cats hair length determined by a gene with two alleles, long and short. The short allele is dominant to the long allele. If you were to cross a short-haired heterozygous cat with a long-haired cat, what is the expected phenotype ratio in their offspring?

50% long hair; 50% short hair

Why does independent assortment of different genes occur?

Because each pair of homologous chromosomes separate independently of the others.

Which of the following is true about alleles?

- Alleles have different DNA sequence - A haploid organism can only have one allele of a gene - A homologous chromosome pair may have different alleles

Select all the statements below that are TRUE about genetic sex.

- Males inherit their X chromosome from their mother - Females inherit an X chromosome from each parent. - Males inherit their Y chromosome from their father.

If a pure-breeding round corn plant is crossed with a pure-breeding wrinkled corn plant, which of the following is true of the F1 generation?

- The F1 will be heterozygous - The phenotype of the F1 will be the dominant phenotype

Which of the following are true of recombinant chromosomes? (Select all that apply.)

- They are created by crossing over events in meiosis I - They are more frequent when two genes are further apart

Which of the following values of the Chi-Square test statistic would be most likely to suggest that the null hypothesis were really true?

0.4251

What is the genotypic ratio in a monohybrid cross with alleles P and p?

1 PP : 2 Pp : 1 pp

For two unlinked genes, allele A is dominant to a, and allele B is dominant to b. In a dihybrid cross, AaBb x AaBb, what fraction of the offspring will be homozygous for both recessive traits?

1/16

Cinnabar eyes is a sex-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F1 males will have cinnabar eyes?

100%

In cats hair length determined by a gene with two alleles, long and short. The short allele is dominant to the long allele. If you were to cross a short-haired homozygous cat with a long-haired cat, what is the expected phenotype ratio in their offspring?

100% short hair

If the recombinant frequency (RF) is 12% how many cM (or map units) apart are the genes?

12 cM

You perform a test cross with a double heterozygous individual to a double homozygous recessive individual. You suspect the two genes are linked on the same chromosome with a recombinant frequency of 0.1. If you have 200 offspring how many total parental-type offspring do you expect to see?

180

For two unlinked genes, allele S is dominant to s, and allele Y is dominant to y. What is the expected phenotypic ratio of the progeny of a SsYy x ssyy test cross?

1:1:1:1

How many phenotypes and degrees of freedom are there for a monohybrid cross?

2 phenotypes, 1 degree of freedom (degrees of freedom is always 1 less than the number of categories/phenotypes)

The fur color gene (C - brown dominant to c - white) is linked to the fur texture gene (W - wavy dominant to w - straight). You cross a CcWw individual to a ccww individual (F1 cross). The F2 phenotypes are: 14 brown wavy, 12 white straight, 35 brown straight and 39 white wavy. How far apart are the color and texture genes?

26 cM

For a self cross between two CPSR/CYSW parents, what offspring phenotype ratio do you expect if the C and S genes are completely linked (no crossing over occurs between them) and CP purple is dominant to CY yellow and SR round is dominant to SW wrinkled.

3 purple round: 1 wrinkled yellow

The fur color gene (C - brown dominant to c - white) is linked to the fur texture gene (W - wavy dominant to w - straight). You cross a CcWw individual to a ccww individual (F1 cross) and get four phenotypes in the F2 offspring. Which of the following would be evidence that the P1 parents of the F1 CcWw individual came from a cross between pure-breeding brown wavy and white straight parents, instead of pure-breeding brown straight and white wavy parents?

Brown wavy and white straight offspring are more common than brown straight and white wavy offspring in the F2.

For cells with genotype CPSR/CYSW entering meiosis, what gamete genotypes are possible if the C and S genes are completely linked (no crossing over occurs between them). Select all that apply.

CPSR CYSW

For a self cross between two CPSR/CYSW parents, what offspring genotypes are possible if the C and S genes are completely linked (no crossing over occurs between them). Select all that apply.

CPSR/CYSW CPSR/CPSR CYSW/CYSW

Duchenne muscular dystrophy is a serious condition caused by a recessive allele of a gene on the human X chromosome. The patients have muscles that weaken over time because they have absent or decreased dystrophin, a muscle protein. They rarely live past their twenties. How likely is it for a woman to have this condition?

One-half of the daughters of an affected father and a carrier mother could have this condition.

For two unlinked genes, allele S is dominant to s, and allele Y is dominant to y. Which of the following are gamete genotypes produced by a plant of genotype SsYy?

SY, sY, Sy, sy

How does recombination frequency change with physical distance between genes on a chromosome?

The larger the distance between genes on the chromosome, the greater the chance that they will be separated by crossing over.

Which of Mendel's laws do linked gene violate?

The principle of independent assortment

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?

XNXn and XNY

Which of the following is true about a dominant allele?

You only need one dominant allele to produce the dominant phenotype.

Genes A and B are on the same chromosome. You perform a test cross AaBb x aabb and find the following numbers in the offspring. Aabb: 83 aaBb: 84 aabb: 17 AaBb: 16 Which of the following offspring genotypes are parental type? Select all that apply.

aaBb Aabb

If you have a heterozygous parent Ab/aB what genotype would you cross it to do perform a test cross and determine crossover frequency between A and B?

ab/ab

The fur color gene (C - brown dominant to c - white) is linked to the fur texture gene (W - wavy dominant to w - straight). You cross a CcWw individual to a ccww individual (F1 cross). The F2 phenotypes are: 14 brown wavy, 12 white straight, 35 brown straight and 39 white wavy. What were the phenotypes of the P1 cross that produced the CcWw individual if both P1 parents were purebreeding?

brown straight x white wavy

The shape and color gene are 17 map units apart on a chromosome. A third gene, kernel size, is 11 map units away from the shape gene and 28 map units away from the color gene. What is the order of these genes on the chromosome?

color, shape, size (Shape must be in the middle because it's 11 map units away from size and 17 maps units away from color (which are 28 map units away from each other, and 11+17=28))

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to ________.

disruption of mitotic spindle formation

A sexually reproducing animal has two genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism if the genes for head shape and tail length are unlinked? (Select all that apply.)

hT

Mendel's 1st Law, the Principle of Segregation, states that the pairs of alleles that control a character segregate (separate) as gametes are formed; half the gametes carry one allele, and the other half carry the other allele. At what stage of cell division are the two alleles separated?

meiosis I

You set up a monohybrid cross for flies with two alleles of a gene, "wild type" (normal) and "mutant". You count wild type and mutant flies in the F2 offspring and calculate a chi-square value of 0.012. Use the chi-square table above to report the p value and whether you accept or reject the hypothesis that the alleles segregate away from each other during gamete formation.

p value: 0.975>p>0.9 Conclusion: Accept hypothesis

You set up a dihybrid cross, where the F1 genotypes are AaBb x AaBb. A is dominant to a, and B is dominant to b. You count the numbers of individuals with each phenotype in the F2 and calculate a chi-square value of 0.62. Use the chi-square table above to report the p value and whether you accept or reject the hypothesis that the genes independently assort during gamete formation.

p value: 0.9>p>0.5 Conclusion: Accept hypothesis

Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this ratio suggest?

the parents were both heterozygous for the particular trait