Question 1

Children born in areas where proper nutrition is not available to them do not always realize their full growth potential.These children have the genes for normal growth of bones.Which of the following statements can best explain this situation?

Accepted Answer

Proper nutrition is necessary for the expression of genes that promote normal growth of bones. Without the necessary nutrients, the genotype for normal growth is not able to be fully expressed, resulting in a phenotype that is smaller and less developed than expected. This is a clear example of an environmental effect on the phenotype.

Question 2

How many different types of gametes can be formed by plants with a genotype of PpYYrrTt?

Accepted Answer

The answer of How many different types of gametes can...

Question 3

If you crossed flies heterozygous for the Cy allele,what surviving genotypes would you find in the F₂ generation?

Accepted Answer

When crossing heterozygous flies for the Cy allele, there are two possible genotypes in the parent generation: Cy⁺/Cy⁺ and Cy/Cy⁺. When these parents are crossed, the possible genotypes in the F₂ generation are Cy⁺/Cy⁺, Cy⁺/Cy⁺ and Cy/Cy⁺. Cy/Cy can also be a possible genotype in the F₂ generation, but it was not given as an option. Therefore, the best choice is C.

Question 4

A diploid individual carrying two different alleles on its homologous chromosomes.

Accepted Answer

A "heterozygote" is an individual with two different alleles on their homologous chromosomes. This is contrasted with a "homozygote," who has two identical alleles on their homologous chromosomes. "Genotype" refers to the genetic makeup of an organism, and "phenotype" refers to the physical characteristics that result from that genotype.

Question 5

Based on the inheritance pattern,the secretor trait is

Accepted Answer

The secretor trait is autosomal dominant, meaning that only one copy of the dominant allele is needed for the trait to be expressed.

Question 6

Achondroplasia is a common form of dwarfism caused by autosomal dominant mutation in the fibroblast growth factor receptor gene 3.If a person with achondroplasia married and had children with a person of normal height,what is the probability that both their first child and second child would have achondroplasia?

Accepted Answer

Since achondroplasia is caused by an autosomal dominant mutation, there is a 50% chance that the offspring will inherit the mutation from the affected parent. Therefore, the probability of the first child having achondroplasia is 1/2. For the second child, the probability is still 1/2 as each birth is independent of the previous one. The probability of having two independent events occur together is calculated by multiplying the probabilities. Therefore, the probability that both the first and second child will have achondroplasia is (1/2)*(1/2) = 1/4 or 25%.

Question 7

A diploid individual whose two copies of a given gene are the same.

Accepted Answer

Homozygote refers to an individual with two identical alleles (copies) of a particular gene. In contrast, a heterozygote has two different alleles, and a genotype refers to the genetic makeup of an individual, which can include both homozygous and heterozygous alleles. Phenotype refers to an individual's observable physical or behavioral traits.

Question 8

In white tigers,the absence of fur pigmentation is caused by a recessive allele.This allele also causes the tigers to be cross-eyed.If two tigers heterozygous for this allele mate and produce offspring,what percentage can be expected to be white and/or cross-eyed?

Accepted Answer

The answer of In white tigers,the absence of fur pigmentation...

Question 9

You can use a Punnet square to do all of the following except

Accepted Answer

Punnett squares are not used to establish a pedigree, which is a chart that shows the occurrence of a particular trait or disease within a family over several generations.

Question 10

As a genetic counselor,you are constructing a human pedigree for a particular disease.You note that every generation shows the trait,suggesting that it is

Accepted Answer

If every generation shows the trait, it suggests that the trait is passed down from affected parents to their offspring in a dominant manner. This means that individuals with only one copy of the dominant allele will express the trait, whereas individuals with two copies of the recessive allele will not. This pattern is consistent with a dominant inheritance pattern. The fact that the trait is present in every generation suggests that it is not sex-linked, as sex-linked traits often skip generations depending on the sex of the affected parent.

Question 11

Based on the inheritance pattern of the secretor trait,a secretor can have a genotype of

Accepted Answer

The secretor trait follows an autosomal dominant pattern of inheritance, which means that individuals who are heterozygous (Se/se) will also express the dominant trait (being a secretor). Therefore, a secretor can have a genotype of either Se/Se or Se/se. The option B is incorrect because an individual with the genotype Se/ns would be a non-secretor, not a secretor. Option C is incorrect because it implies that all secretors have a homozygous dominant genotype when in reality, they can also be heterozygous. Option D is incorrect because individuals with a homozygous recessive genotype for the secretor gene (se/se) are non-secretors, not secretors.

Question 12

A person who has lost a large amount of blood but is still alive is found in a wrecked automobile under a highway bridge.Several people are helping the paramedics load the victim into the ambulance.After the ambulance has departed for the hospital,you overhear the following conversation from the persons who helped the paramedics."I am certain that when that guy gets to the hospital,they will transfuse him with any blood that they have in the blood bank since he has lost so much blood." The other person says,"Yeah,I bet you're right!" Having had a biology course,you know which blood could be safely given to anyone.Select it below.

Accepted Answer

Blood type O is known as the universal donor because its red blood cells do not have antigens A, B, or Rh on the surface. Therefore, it can be safely transfused to individuals with any blood type.

Question 13

The observable expression of the genes present.

Accepted Answer

The observable expression of the genes present is called the phenotype. The other options relate to the genetic makeup of an organism rather than the physical expression of those genes.

Question 14

As the new technician in a lab that studies coat color in rodents,you are assigned the task of counting and recording the coat color of the F₂ progeny of a dihybrid cross.Your results are: 18 agouti mice,6 black mice,8 albino mice.Based on this data,you conclude that coat color in rodents

Accepted Answer

The 9:3:3:1 ratio of agouti:black:albino:white mice indicates that coat color in rodents is determined by two genes, with one gene exhibiting incomplete dominance and the other gene exhibiting epistasis.

Question 15

Height and eye colors are two examples of continuous variation in humans.Whereas in pea plants the tall allele is dominant over the short allele,there are no intermediate heights in peas.Which of the following is the best explanation for the differences described above?

Accepted Answer

The presence of continuous variation in humans and multiple discrete variations in pea plants suggest that many genes, rather than one, control some traits in each species. This phenomenon is known as polygenic inheritance.

Question 16

Let R = red pigment and r = no pigment.In carnations,RR offspring make a lot of red pigment,rr offspring make no pigment and Rr offspring make a small amount of red pigment,thus appearing pink.Pink carnations are therefore an example of

Accepted Answer

Incomplete dominance is the inheritance pattern in which the heterozygote (Rr) exhibits an intermediate phenotype, distinct from either homozygote (RR or rr). This intermediate phenotype of pink color is observed in carnations, making incomplete dominance the best choice. Codominance would require both traits to be fully expressed in the heterozygote, which is not the case in the pink carnations. Epistatic interactions involve genes at different loci interacting to affect the expression of a trait, which is not applicable in this scenario. Blending was a classical theory of inheritance where the traits of the parents were thought to mix in the offspring, creating an intermediate phenotype. However, we now understand that inheritance is more complex and influenced by factors such as dominance and incomplete dominance.

Question 17

Let Y = yellow and y = green,and R = round and r = wrinkled.You cross YYRR peas with yyrr peas.All of the F₁ individuals are yellow and round with a genotype of YyRr.You then perform a F₂ cross and get the expected 9:3:3:1 phenotypic ratio.Which of the following is the correct genotypic ratio for yellow,round F₂ individuals?

Accepted Answer

First, let's identify the parental genotypes and the cross performed: YYRR (yellow and round) x yyrr (green and wrinkled) F1: YyRr (yellow and round) F1 x F1: YYRR YyRr YyRr yyrr YyRr YyRR YyRr yyRr YyRr YyRr YyRR yyRr yyrr yyRr yyRr yrrr Expected phenotypic ratio: 9(YR) : 3(Yr) : 3(yR) : 1(yr) Now we need to determine the genotypic ratio of the yellow and round individuals (Y- R-): From the Punnett square above, we can see that the following genotypes result in yellow and round seeds: YYRR (2/16), YyRR (2/16), YYRr (1/16), and YyRr (4/16) Therefore, the genotypic ratio for yellow and round F₂ individuals is: 1/16 YYRR, 2/16 YYRr, 2/16 YyRR, 4/16 YyRr (D)

Question 18

The totality of the alleles present in an organism.

Accepted Answer

The term that describes the totality of the alleles present in an organism is genotype. Heterozygote and homozygote refer to specific types of genotypes with respect to a particular gene or set of genes. Phenotype refers to the physical and observable characteristics of an organism, which result from its genotype and environmental factors.

Question 19

The genotypic ratio produced in the F₂ generation is

Accepted Answer

The F₂ generation results from a dihybrid cross between F_{_{and F}} individuals. The F1 generation of this cross is likely to be heterozygous for both traits (F), and when crossed with each other, will produce offspring with a 1:2:1 genotypic ratio. This ratio consists of one homozygous dominant for both traits (F_{_{), two heterozygous for both traits (F), and one homozygous recessive for both traits (F}}), which corresponds to choice B.

Question 20

If you crossed flies heterozygous for the Cy allele,what phenotypes would you find in the F₁ generation?

Accepted Answer

The Cy allele causes curly wings in flies. Heterozygous flies have one wild type allele and one Cy allele. When two heterozygous flies are crossed, their offspring can have different combinations of alleles. The Punnett square for this cross would be: | C | y | |-----|-----| | C | CC | Cy | | y | Cy | yy | So, in the F₁ generation, we would expect to see wild type flies with the genotype CC or Cy, and curly wing flies with the genotype Cy. Thus, the correct answer is A, wild type and curly wings.

Quiz 12: Patterns of Inheritance