Genetics Quiz 2

__________________ is a pattern of inheritance in which heterozygotes express phenotypes of both of the homozygotes.

Codominance

_______________ ____________ is a pattern of inheritance in which the heterozygous phenotype is intermediate between either of the homozygous phenotypes.

Incomplete dominance.

_______________ is a situation in which a single gene influences more than one phenotypic characteristic.

Pleiotropy

BEFORE

Tony Allison lived in the "high country" and visited the coast. His work was done ________ DNA structure and inheritance was understood.

A(n) __________________ is any chromosome other than a sex chromosome.

autosome

An organism that has two different alleles of a gene for a given character (for example, Yy) is said to be _____________ for that character.

heterozygous

An organism that has two identical alleles of a gene for a given character (for example, YY or yy) is said to be ______________ for that character.

homozygous.

In ______________ inheritance, the interactions of two or more functionally similar genes determine inheritance

polygenic

Crossing over results in ______________ -- the formation of new combinations of different alleles on a chromosome.

recombination

If a person has two normal copies of the hemoglobin allele, which statements are true? Select all that apply. 1) The person is protected against malaria. 2) The person is heterozygous at the hemoglobin locus. 3) The person is homozygous at the hemoglobin locus. 4) The person is susceptible to malaria.

3 and 4

________________ a recessive sex-linked disorder in which the blood fails to clot normally.

Hemophiliais

How did Dr. Allison test his hypothesis that sickle cell disease was connected to malaria? Select all that apply. 1) He expanded his study area beyond Kenya to the rest of East Africa to see if malaria and sickle disease were connected. 2) He evaluated blood samples for malaria parasites and the presence of sickle cells. 3) He looked for the underlying genetic mechanism causing sickle cell disease. 4) He studied the way that the malaria parasite interacts with sickle cells.

1 and 2

In what way does natural selection depend on the specific environment in which an organism lives? -natural selection is random, and the direction of the selective pressure cannot be predicted based on the environment. -natural selection produces traits that are always either helpful or harmful, regardless of the environment. -when an organism enters a new environment, it evolves all of the traits it needs to survive there -when the environment changes, traits that were beneficial to an organism may become harmful and vice versa.

when the environment changes, traits that were beneficial to an organism may become harmful and vice versa.

How does Dr. Allison's work provide an example of natural selection in humans? Select all that apply. 1) In areas with malaria, individuals with one sickle cell allele reproduced at higher rates than those with no sickle cell alleles. 2) Natural selection caused the sickle cell allele to appear in east African populations. 3) In areas without malaria, individuals with two sickle cell alleles reproduced at lower rates than those without sickle cell disease. 4) In areas with malaria, natural selection causes individuals to acquire the sickle cell allele as protection against malaria.

1 and 3

2, alleles

A human has _____ copies of each gene- one on each chromosome inherited from two parents. It is almost impossible for the gene sequences to be identical. These are _______, i.e. different versions of a gene sequence.

Individuals with one sickle cell allele are protected from malaria and do not have sickle cell disease, thus keeping the allele in the population. People with one sickle cell allele are protected from malaria, but do not have sickle cell disease. Protection from malaria comes at the cost of more sickle cell disease in the population

In the African American population the frequency is 1/500. Why is it so prevalent??

AA, SS, AS

In the case of Sickle Cell Anemia, ___ represents a homozygote with two alleles that make functional protein. _____ represents a homozygote with two mutated gene sequences that both make nonfunctional (or poorly functional) protein. _____ represents a heterozygote that makes some functional and some nonfunctional protein.

Which of the following statements accurately describes melanin's function? Everyone has the same type of melanin, but the amount varies from person to person. Melanin is a molecule that distinguishes humans from their primate relatives. Lighter skin has less of the dark-brown eumelanin that protects cells from UV damage. The more melanin an individual has in his or her skin cells, the more likely he or she is to get mutations in DNA.

Lighter skin has of the dark-brown eumelanin that protects cells from UV damage.

_____________ _____________ is a form of inheritance in which the interaction of multiple genes contributes to a single phenotype, such as skin color.

Polygenic inheritance

An organism's genetic makeup--its actual combination of alleles--is known as its _____________.

genotype.

Predict what will happen to the frequency of the sickle cell allele in areas where malaria has been eradicated. a) The sickle cell allele frequency will not be affected. b) The sickle cell allele will decrease in frequency. c) The sickle cell allele will increase in frequency.

b (The sickle cell will decrease in frequency.)

In 1949, Dr. Tony Allison observed a high frequency of Kenyans carrying the sickle cell allele in coastal areas and near Lake Victoria, but a lower frequency in the highlands. What did he hypothesize? a) He hypothesized that there was a connection between malaria and sickle cell disease. b) He hypothesized that malaria is a genetic disease. c) He hypothesized that sickle cell disease was an environmental, not a genetic disease. d) He hypothesized that malaria causes sickle cell disease.

c (He hypothesized that there was a connection between malaria and sickle cell disease.)

In some populations, 1 in 500 people have sickle cell disease. What reason does the film give for why a potentially deadly, inherited disease is found at such high frequencies? a) Individuals with two sickle cell alleles have an evolutionary advantage because they do not get sickle cell disease or get infected with malaria. b) Individuals with two normal hemoglobin alleles get both sickle cell disease and are susceptible to malaria, so these alleles are eliminated from the population. c) Sickle cell alleles are new mutations and not enough time has gone by for these alleles to be eliminated from the population by natural selection. d) Individuals with one sickle cell allele are protected from malaria and do not have sickle cell disease, thus keeping the allele in the population.

d (Individuals with one sickle cell allele are protected from malaria and do not have sickle cell disease, thus keeping the allele in the population.)

Compare sickle cell disease and malaria. a) Sickle cell disease and malaria are both inherited diseases. b) Sickle cell disease and malaria are both infectious diseases. c) Sickle cell disease and malaria are both genetic diseases. d) Sickle cell disease and malaria are both potentially lethal diseases.

d (Sickle cell disease and malaria are both potentially lethal diseases.)

Human populations in low-UV environments tend to have more lightly pigmented skin. One explanation is that the selective pressure for dark skin decreases as UV intensity decreases. At the same time there is selection for lighter skin to absorb more UV radiation, which is needed for vitamin D production. What evidence supports the vitamin D hypothesis for the evolution of lighter skin tones? -red hair and light skin are typical of people of northern European descent -lightly pigmented people tend to be at higher risk of vitamin D deficiency -lightly pigmented people cannot synthesize vitamin D in high-UV environments, such as equatorial Africa -indigenous peoples living at high latitudes have darker skin, but they eat foods rich in vitamin D

indigenous peoples living at high latitudes have darker skin, but they eat foods rich in vitamin D

When three or more alleles of the same gene exist in a population (as with human blood types), they are known as ______________ _________.

multiple alleles.

A(n) __________ is a diagram showing genetic relationships among a group of individuals, usually with respect to a specific genetic trait.

pedigree

An organism's traits--including its outward appearance, behavior, and other observable or measurable features--is known as its _______________.

phenotype.