Question 1

A purebred plant that produces yellow seeds is crossed with a purebred plant that produces green seeds.The seeds of all of the offspring are yellow.Why?

Accepted Answer

If the offspring all have yellow seeds, that means they all received at least one copy of the dominant yellow allele from one of their parents. Since the yellow allele is dominant, it masks the presence of the green allele, leading to the expression of yellow seeds. Therefore, the only possible genotype of the offspring is heterozygous (Yy), since a homozygous dominant parent would only produce yellow offspring and a homozygous recessive parent would only produce green offspring.

Question 2

Which of these crosses will produce only heterozygous offspring?

Accepted Answer

A

Question 3

The best definition of a purebred plant is one that ________.

Accepted Answer

A purebred plant is a plant that is genetically uniform and breeds true for particular traits. This means that when self-fertilized, it will produce offspring that are identical to the parent plant. Cross-fertilization with another purebred plant will also result in offspring that exhibit the same traits as the parents. Therefore, option B, which states that a purebred plant self-fertilizes to produce offspring identical to the parent, is the best definition.

Question 4

Round seeds (R)are dominant to wrinkled seeds (r),and yellow seeds (Y)are dominant to green seeds (y).What is the expected phenotypic ratio of a cross between an RrYy and an rryy individual?

Accepted Answer

The answer of Round seeds (R)are dominant to wrinkled seeds...

Question 5

A mating between a purebred purple-flowered pea plant and a purebred white-flowered pea plant would produce a(n)________.

Accepted Answer

A mating between a purebred purple-flowered pea plant and a purebred white-flowered pea plant would produce a hybrid, as it involves crossing two purebreds with different traits to produce offspring with a combination of the two traits. A purebred variety refers to a population of individuals with identical traits resulting from multiple generations of self-fertilization or inbreeding. P generation refers to the parental generation used in a cross, while F₂ generation refers to the second filial generation resulting from a cross between two F₁ hybrids.

Question 6

In humans,free earlobes (E)are dominant to attached earlobes (e)and the presence of freckles (F)is dominant to the absence of freckles (f).If an individual heterozygous for both of these traits were to mate with an individual with attached earlobes and no freckles,what is the probability of having a child with attached earlobes and freckles?

Accepted Answer

The answer of In humans,free earlobes (E)are dominant to attached...

Question 7

According to Mendel's law of segregation,________.

Accepted Answer

Mendel's law of segregation states that during the formation of gametes, the two alleles for a gene separate, so each gamete receives only one allele for each gene.

Question 8

The ________ is most commonly found in nature.

Accepted Answer

The wild-type trait is the most common phenotype found in nature. This is because it is often the original or ancestral form of a trait and has been conserved over time due to its functional advantages. Recessive traits may be common in certain populations if they have a higher frequency of consanguinity or if there is a selective advantage for heterozygotes. Parental type refers to the original combination of traits found in a parental organism, and dominant traits may be less common if they are detrimental to the organism's survival or reproduction.

Question 9

A purebred plant that produces yellow seeds is crossed with a purebred plant that produces green seeds.The F₁ plants have yellow seeds.What is the expected phenotypic ratio of seed color of the offspring of an F₁ × F₁ cross?

Accepted Answer

The F1 generation is heterozygous for seed color, with both Yy genotype. When these F1 plants undergo self-fertilization, the possible genotypes of offspring are YY, Yy, and yy in a 1:2:1 ratio. The phenotypic ratio is determined by the genotype: YY and Yy both produce yellow seeds, while yy produces green seeds. Therefore, the expected phenotypic ratio of yellow to green seeds in the offspring of an F1 x F1 cross is 3:1.

Question 10

What name is given to the specific location of a gene on a chromosome?

Accepted Answer

The specific location of a gene on a chromosome is called a locus.

Question 11

To determine the phenotype of an individual who expresses a dominant trait,you would cross that individual with an individual who ________.

Accepted Answer

To determine the phenotype of an individual who expresses a dominant trait, you need to know whether the individual is homozygous dominant or heterozygous. By crossing the individual with an individual who is homozygous recessive for that trait, you can determine whether the individual is homozygous dominant or heterozygous. If the offspring of the cross all show the dominant phenotype, the individual is homozygous dominant. If some of the offspring show the recessive phenotype, the individual is heterozygous. Crossing with an individual expressing the dominant trait or homozygous dominant would not provide any information about the genotype of the individual being tested.

Question 12

Alleles are described as ________.

Accepted Answer

Alleles are alternate versions of a gene that can code for different traits or characteristics. Homologous chromosomes refer to pairs of chromosomes with similar genes, while environmental factors can affect gene expression but are not themselves alleles. Alternate phenotypes may be the result of different combinations of alleles, but the term "allele" specifically refers to the specific versions of a gene.

Question 13

A couple has two female children.What is the probability that their next child will be male?

Accepted Answer

The probability of having a male child is always 50%, regardless of the gender of the previous children or any other factors. The gender of a child is determined by the X and Y chromosomes from the parents, and each pregnancy is an independent event with a 50/50 chance of producing a male or female child. Therefore, the fact that the couple already has two female children has no impact on the probability of having a male child in the future.

Question 14

An individual who is homozygous ________.

Accepted Answer

Homozygous individuals have two copies of the same allele for a gene, meaning they express the trait associated with that allele. This could be either the dominant or recessive trait depending on the specific alleles involved. Therefore, options A and D are not necessarily true. Option B is incorrect since homozygous individuals by definition have two copies of the same allele, not two different alleles.

Question 15

An individual with the genotype AaBb produces four different gametes in equal proportions.This is a demonstration of ________.

Accepted Answer

This scenario is an example of Mendel's Law of Independent Assortment, which states that during gamete formation, different pairs of alleles segregate independently of each other. This means that the inheritance of one trait does not affect the inheritance of another trait, which is why the individual with the genotype AaBb can produce four different gametes in equal proportions.

Question 16

Attached earlobes are recessive to free earlobes.What genotypic ratio is expected when an individual with attached earlobes mates with an individual heterozygous for free earlobes?

Accepted Answer

The answer of Attached earlobes are recessive to free earlobes.What...

Question 17

Attached earlobes are recessive to free earlobes.What is the probability of having a child with attached earlobes when an individual with attached earlobes mates with an individual heterozygous for free earlobes?

Accepted Answer

The answer of Attached earlobes are recessive to free earlobes.What...

Question 18

What data or test would you seek to determine whether or not a trait is sex linked?

Accepted Answer

A pedigree would be the best choice to determine whether or not a trait is sex linked. Sex-linked traits are inherited differently between males and females, and a pedigree can show the pattern of inheritance and help to determine if the trait is linked to the X or Y chromosome. Karyotype and DNA sequence tests can provide information about the individual's genetic makeup but may not necessarily reveal whether a trait is sex-linked. A blood test would also not be specific enough for determining whether a trait is sex-linked.

Question 19

Mendel crossed purebred purple-flowered plants with purebred white-flowered plants,and all of the resulting offspring produced purple flowers.The offspring are all ________,and the allele for purple flowers is ________.

Accepted Answer

Since all the resulting offspring produced purple flowers, they must have inherited at least one allele for purple flowers from their parents. The fact that one parent was purebred for purple flowers suggests that it had two dominant alleles for purple flowers (PP). The fact that the other parent was purebred for white flowers suggests that it had two recessive alleles for white flowers (pp). When these two parents are crossed, their offspring inherit one allele from each parent. If the offspring all produced purple flowers, their genotype must be Pp, meaning they inherited one dominant allele from the purple-flowered parent and one recessive allele from the white-flowered parent. In this case, the allele for purple flowers is dominant, and the heterozygous offspring are able to express it even though they also have a recessive allele for white flowers.

Question 20

In humans,the presence or absence of dimples is a trait controlled by a single gene.What is the genotype of an individual who is heterozygous for dimples?

Accepted Answer

Since the presence of dimples is controlled by a single gene, we can use the letter "D" to represent the dominant allele for dimples and the letter "d" to represent the recessive allele for no dimples. A heterozygous individual has one copy of each allele, so their genotype would be "Dd".

Quiz 9: Patterns of Inheritance