BMS 150 Lecture Notes - Lecture 8: Dihybrid Cross, Homologous Chromosome, Zygosity

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9 Feb 2017

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Document Summary

Gene: a section of dna on a chromosome which codes for a specific protein. Autosomal dominant: only one copy of that particular allele is required for the trait to be expressed completely. Autosomal recessive: two copies of the same allele are required for the trait to be expressed completely. X-linked recessive: females must have two copies of the same allele for the trait to be expressed, while males only require one copy (only have one x chromosome) Homozygous: having both copies of the gene be the same allele (ie, two alleles for brown eyes or two alleles for blue eyes) Heterozygous: having two different alleles for the same gene, in which case the dominant allele is expressed, or a mixture of the two alleles is expressed (codominant or incomplete dominance) Genotype: the trait for which the allele codes for (ie, tallness) Phenotype: the physical appearance depends on the environment (tall/short) Worked on pea plants in a monastery.

Related Questions

When a parent who is heterozgyous for a trait is crossed with a parent who is heterozygous for a trait, the offspring will:

(remember homozygous means two of the same alleles and heterozygous means two different alleles)

Select one:

a. have 3 out of 4 the dominant phenotype and 1 out of 4 the recessive phenotype

b. have 2 out of 4 the dominant phenotype and 2 out of 4 the recessive phenotype

c. all have the dominant phenotype

d. have 1 out of 4 the dominant phenotype

When a parent who is heterozgyous for a trait is crossed with a parent who is homozygous dominant for a trait, the offspring will:

(remember homozygous means two of the same alleles and heterozygous means two different alleles)

Select one:

a. all have the recessive phenotype

b. all will have the dominant allele

c. all be homozygous dominant genotype

When a parent who is heterozgyous for a trait is crossed with a parent who is heterozygous for a trait, the offspring will:

(remember homozygous means two of the same alleles and heterozygous means two different alleles)

Select one:

a. have 3 dominant phenotypes, 2 heterozygous genotypes, and 1 homozygous recessive genotype

b. have 1 dominant phenotype, 2 heterozygous genotypes, and 1 homozygous recessive phenotype

c. have all dominant phenotypes, 2 heterozygous genotypes, and 1 homozygous recessive genotype

When doing Punnett squares for fur, the letter f represents ______ and the letter F represents _____.

Select one:

a. the recessive allele, the dominant allele

b. the dominant allele, the recessive allele

c. the dominant gene, the recessive gene

d. the recessive gene, the dominant gene

10.

When a parent who is heterozgyous for a trait is crossed with a parent who is homozygous recessive for a trait, the offspring will:

(remember homozygous means two of the same alleles and heterozygous means two different alleles)

Select one:

a. be half heterozygous and half homozygous recessive

b. be all heterozygous

c. be all homozygous recessive

d. be all homozygous dominant

QUESTION 1

Jim is blood type A, his brother John is type O and his sister Jane is type AB. What are the genotypes of their parents?

Which of the following is true for alleles that show incomplete dominance?

Heterozygotes have a genotype like the dominant allele.

Homozygotes have a genotype like the recessive allele.

Heterozygotes have a phenotype intermediate between the dominant and recessive alleles.

Homozygotes have the same phenotype as the heterozygotes.

QUESTION 3

Which principle of inheritance concluded that when games are formed in meiosis, the two alleles of each gene separate from one another, and each gamete receives only one allele?

independent assortment

Which term best describes a condition in which alleles at one locus can alter the expression of alleles at another locus?

polygenic inheritance

A single unit of genetic information located on a chromosome defines:

The physical expression (appearance or function) of an organism's genes defines:

genotype

a single characteristic

Palomino horses (golden color with a blond mane) are an incompletely dominant trait produced by the combination of the chestnut color allele and the cream color allele. If you wanted to produce as many palominos as possible, which mating strategy below would be the best choice?

Which term best describes the effect of a single gene on multiple aspects of the phenotype?

polygenic inheritance

QUESTION 9

Which term best describes the separate expression of both alleles for a single trait in the same cell?

polygenic inheritance

QUESTION 10

One form of a gene found on a single chromosome defines:

A chocolate lab (whose mother was a yellow lab) is mated with a black lab whose genotype is BbEe. What fraction of the offspring would be expected to be yellow labs?

What type of allele is always expressed regardless of whether the individual is homozygous or heterozygous for it?

Both the dominant and recessive alleles

Given the parents AABBGgHhrr Ã AabbGgHhRr, assume simple dominance and independent assortment. What proportion of the progeny will be expected to have the genotype AaBbggHHrr?

___________________ is defined as having two of the same type of allele for a particular trait.

The physical position of an allele on a single chromosome defines:

Which term best describes two or more genes affecting the phenotype in an additive fashion?

codominance

polygenic inheritance

We have discussed how recessive phenotypes are more likely to be expressed in males if the corresponding gene is found on the X-chromosome. For example, one-type of colorblindness is caused by a recessive X linked allele, and this trait is much more common inmales than females. But we have also discussed how, in placental mammals, one copy of each X chromosome is randomly silenced in female cells (X inactivation). This raisessomewhat of a paradox. Why donât half of heterozygous females exhibit colorblindness just like hemizygous males that carry the recessive allele?

Based on your under standing of Xinactivation in placental mammals, provide an explanation for why heterozygous females generally do not exhibit colorblindness despite the random silencing of one X chromosome.

b.How would your answer change if we were talking about a marsupial mammal (inwhich the paternally inherited copy of the X chromosome is inactivated in every cell)? Would you expect half of heterozygous females in a marsupial species toexhibit color blindness? Why or why not?

BMS 150 Lecture Notes - Lecture 8: Dihybrid Cross, Homologous Chromosome, Zygosity

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