Question 1

What genetic disorder is associated with the lack of an enzyme necessary for the normal metabolism of the amino acid phenylalanine?

Accepted Answer

Phenylketonuria (PKU) is caused by a deficiency of phenylalanine hydroxylase, the enzyme necessary for the normal metabolism of the amino acid phenylalanine. Without this enzyme, phenylalanine and its byproducts can accumulate in the body, causing intellectual disability, seizures, and other serious health problems.

Question 2

Which allele combination represents a recessive monohybrid trait?

Accepted Answer

For a recessive monohybrid trait, both alleles must be lowercase. In this case, "a" represents the recessive allele. Therefore, only option A (aa) represents a recessive monohybrid trait.

Question 3

The skin pigment melanin is expressed differently according to exposure to sunlight,with a greater production of the molecule with greater exposure.However,the degree of production can never exceed the inherited genetic level.What evolutionary advantage would be gained from having this phenotypic range for skin pigmentation?

Accepted Answer

The ability to produce more melanin only when necessary allows for protection against harmful UV radiation without wasting resources on producing excess melanin. This would provide an evolutionary advantage by allowing individuals to efficiently regulate their skin pigmentation to match their level of sun exposure, reducing their risk of skin cancer and other UV-related health issues.

Question 4

Which of the following is an autosomal dominant disorder?

Accepted Answer

Marfan syndrome is an autosomal dominant disorder, meaning that if one parent has the gene mutation, there is a 50% chance of their offspring inheriting the disease. Tay-Sachs, sickle cell disease, cystic fibrosis, and phenylketonuria are all inherited in an autosomal recessive pattern.

Question 5

All but one of the following experiments would allow a scientist to discover if the phenotype of an organism would be affected by environmental changes.Choose the experiment that would NOT show environmental effects.

Accepted Answer

This experiment involves feeding mice identical diets, which means there is no variation in environmental conditions to observe any phenotypic changes.

Question 6

To try and discover if the environment has an effect on a particular characteristic,scientists often examine

Accepted Answer

Identical human twins that were separated at birth have the same genetic material, so any differences in their characteristics must be due to environmental factors. This allows scientists to study the effects of the environment on a particular characteristic while controlling for genetic differences.

Question 7

Indicate the genotypic and phenotypic ratios that you could expect if an individual who is heterozygous for Huntington disease has children with a normal individual.

Accepted Answer

The answer of Indicate the genotypic and phenotypic ratios that...

Question 8

Huntington disease is an autosomal dominant disorder that leads to progressive degeneration of brain cells.There is no effective treatment for the disorder and individuals usually die in their 40s or 50s,10 to 15 years after the onset of symptoms.Which of these statements about Huntington disease is true?

Accepted Answer

Huntington disease usually appears during middle age, around 30 to 50 years old. Option A is incorrect because as an autosomal dominant disorder, only one copy of the mutated gene is required to develop the disease, regardless of whether one or both parents are carriers. Option B is incorrect because there is no evidence that Huntington disease skips a generation. Option C is incorrect because carriers of the Huntington disease gene may not display symptoms, but can still pass on the gene to their children. Option E is incorrect because Huntington disease is caused by a mutation in the huntingtin gene, which codes for a protein that plays a role in brain cell function.

Question 9

Indicate the phenotypic and genotypic ratios expected for the offspring from a straight-haired man and a wavy-haired woman.

Accepted Answer

The answer of Indicate the phenotypic and genotypic ratios expected...

Question 10

How many alleles are required to express a monohybrid trait?

Accepted Answer

Monohybrid traits involve the inheritance of a single gene and two alleles, one from each parent. Therefore, two alleles are required to express a monohybrid trait.

Question 11

The leaves of a maple tree vary in size depending on the location of the leaves on the tree.Those growing at the outer region of the tree tend to be smaller than those growing closer to the trunk of the tree.This allows leaves that are growing in the shade to have a larger surface area.This show that genes have the ability to

Accepted Answer

The fact that the size of maple leaves varies depending on their location on the tree shows that genes can respond to environmental factors, in this case, the amount of sunlight available.

Question 12

You have two true-breeding rose bushes,one with red flowers and one with white flowers.A cross between these two roses yields a bush with pink flowers.What condition does this demonstrate?

Accepted Answer

The fact that the cross between the red and white rose bushes produces a pink flower shows incomplete dominance, where neither allele is completely dominant over the other and results in an intermediate phenotype.

Question 13

Which genetic disorder is associated with an irregular shape of the red blood cells?

Accepted Answer

Sickle cell disease is associated with an irregular shape of the red blood cells, which can cause them to get stuck and block blood flow. This can lead to pain, organ damage, and increased risk of infections.

Question 14

You have two true-breeding rose bushes,one with red flowers and one with white flowers.A cross between these two roses yields a bush with white flowers that have red splotches.What condition does this demonstrate?

Accepted Answer

This condition demonstrates codominance, where both alleles are expressed equally in the phenotype, resulting in flowers with both red and white colors.

Question 15

In the human population,short fingers are dominant over long fingers.Indicate the genotypic and phenotypic ratios if a heterozygous short-fingered female reproduces with a long-fingered male.

Accepted Answer

The answer of In the human population,short fingers are dominant...

Question 16

Hydrangeas are a flowering plant with large showy blooms.When a plant is grown in aluminum-rich soil it has blue flowers.If the same plant is transplanted into soil that is lacking aluminum,the flowers produced will be pink.This is an example of

Accepted Answer

The color of hydrangea flowers is not solely determined by genetics, but rather is heavily influenced by environmental factors such as soil acidity and the presence of aluminum ions. Therefore, this is an example of environmental effects.

Question 17

Which genetic disorder is associated with a defect in the elastic connective tissue protein called fibrillin?

Accepted Answer

Marfan syndrome is a genetic disorder that affects the body's connective tissue, most notably the protein fibrillin. A defect in fibrillin leads to weakened elastic fibers in connective tissues, causing a range of symptoms including long limbs, joints that can bend beyond the normal range of motion, and weakened blood vessels.

Quiz 23: Patterns of Gene Inheritance