CHAPTER 11

A? x aa

Which of these is a testcross?

Design a test for identifying heterozygous carriers of the allele

A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Which of the following statements describes the best use of this discovery?

children born to parents with dark skin living far from the equator

Based on the risk factors discussed in the video, which of the following groups would be most likely to develop the bone disease rickets?

the melanin in darkly pigmented skin protects circulating folate from being destroyed by UV radiation, and folate is important in human reproduction

Darker skin is more prevalent in high-UV areas. Dr. Nina Jablonski proposed a hypothesis to explain the selective pressure for darker skin in these environments. On what evidence did she base this hypothesis?

meiosis I, anaphase

During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur?

50% on average; 100%

Fraternal twins share _____ of the same genes, while identical twins share _____ of the same genes.

Cross the green-pod plant with a yellow-pod plant.

How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?

1

How many variables should there be in a well-designed experiment?

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

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?

0 homozygous black (BB): 1 heterozygote (black) (Bb): 1 homozygous orange (bb)

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the genotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

1 black : 1 orange

If B represents the allele for black eyes (dominant) and b represents the allele for orange eyes (recessive), what would be the phenotypic ratio of a cross between a heterozygous black-eyed MendAlien and an orange-eyed MendAlien?

at age 3 or 4, when children are dressed in gender-specific clothing

In the essay, the point is made that perhaps the environment of the children has already guided their preferences in toys BEFORE the experiment was conducted. Given the choices below, what is the earliest age at which environment could potentially shape the preferences of a child?

the average lifespan

In the essay, the point is made that the right questions must be asked when designing an experiment that measures how genetics and environment "shape who we are." Which of the following measurements is probably the least valuable in such an experiment?

In what way does natural selection depend on the specific environment in which an organism lives?

In what way does natural selection depend on the specific environment in which an organism lives?

law of segregation

Suppose that the botanist carried out the test cross described in Parts A and B and determined that the original green-pod plant was heterozygous (Gg). Which of Mendel's findings does her test cross illustrate?

menders law of segregation only

That each gamete contains a single allele of the eye color gene is an illustration of _____.

are all Rr

The result of the following cross indicates that genotypically the offspring _____.

RR

The result of the following cross indicates that the genotype of the female parent is _____.

rr

The result of the following cross indicates that the genotype of the male parent is _____.

recessive to

The result of the following cross indicates the orange eyes are _____ black eyes.

III only

Use the following pedigree (the figure) for a family in which dark-shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual's age at the time of diagnosis. A slash through the symbol indicates that the individual is deceased. The affected woman in generation IV is thinking about her future and asks her oncologist (cancer specialist) whether she can know whether any or all of her children will have a high risk of the same cancer. The doctor would be expected to advise which of the following: (I) genetic counseling; (II) prenatal diagnosis when/if she becomes pregnant; (III) testing to see whether she has the allele; (IV) testing to see whether her future spouse or partner has the allele?

There were too few subjects. In other words, the sample size was too small.

What was an important limitation in the experiments shown in the video?

comparing identical twins raised in the same environment with identical twins raised in different environments

Which of the following experiments would provide the best data for determining the effect of environment?

comparing identical twins raised in the same environment with fraternal twins raised in the same environment

Which of the following experiments would provide the best data for determining the effect of genetics?

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

Which of the following statements accurately describes melanin's function?

1.Human skin color variation is primarily determined by the type and amount of melanin pigment in the skin. 2.Human skin color variation likely evolved in response to differences in the intensity of sunlight around the world. 3.Human skin color variation evolved recently in hominid evolution, once some populations of our human ancestors migrated out of Africa.

Which of the following statements apply to the variation in human skin color?