[11] Mastering Biology Flashcards
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one D allele have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in the figure above, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. Which of the boxes marked 1−4 correspond(s) to plants with dark leaves?
1, 2, and 3
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one D allele have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in the figure above, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. Which of the boxes correspond(s) to plants with a heterozygous genotype?
2 and 3
In a particular plant, leaf color is controlled by gene locus D. Plants with at least one D allele have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F1 offspring is allowed to self-pollinate. The predicted outcome of the F2 is diagrammed in the Punnett square shown in the figure above, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. Which of the plants will be true-breeding?
1 and 4
What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
Traits are inherited in discrete units and are not the results of the “blending” of traits.
Which of the following statements correctly describes a monohybrid cross?
a) A monohybrid cross involves organisms that are heterozygous for one character.
b) A monohybrid cross produces a single offspring.
c) A monohybrid cross involves a single parent.
d) A monohybrid cross is performed for one generation.
a) A monohybrid cross involves organisms that are heterozygous for one character.
How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?
8
Which of the following statements correctly describes one difference between the law of independent assortment and the law of segregation?
a) The law of segregation requires having two or more generations to describe.
b) The law of independent assortment explains the segregation of two or more genes relative to one another.
c) The law of segregation is accounted for by anaphase of mitosis.
d) The law of segregation explains the segregation of two or more genes relative to one another.
b) The law of independent assortment explains the segregation of two or more genes relative to one another.
Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. What does this suggest about the trait?
that the parents were both heterozygous for a single trait
A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
HT
When crossing an organism that is homozygous recessive for a single trait with one that is heterozygous for the same trait, what is the chance of producing an offspring with the homozygous recessive phenotype?
50%
What was Mendel’s explanation for his observation that traits that had disappeared in the F1 generation reappeared in the F2 generation of the pea plants he used in his experiments?
Traits can be dominant or recessive, and the recessive traits were “hidden” by the dominant ones in the F1.
Why did the F1 offspring of Mendel’s classic pea cross always look like one of the two parental varieties?
One allele was dominant.
Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of crosses BbTt × BBtt will be expected to have black fur and long tails?
1/2
In certain plants, the tall trait is dominant to the short trait. If a heterozygous plant is crossed with a homozygous tall plant, what is the probability that the offspring will be short?
0
Two true-breeding stocks of pea plants are crossed. One parent has red axial flowers, and the other has white terminal flowers; all F1 individuals have red axial flowers. The genes for flower color and location assort independently. If 1,000 F2 offspring resulted from the cross, approximately how many of them would you expect to have red terminal flowers?
190
Two true-breeding stocks of pea plants are crossed. One parent has red axial flowers, and the other has white terminal flowers; all F1 individuals have red axial flowers. The genes for flower color and location assort independently. Among the F2 offspring, what is the probability of plants with white axial flowers?
3/16
What is the difference between heterozygous and homozygous individuals?
All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.
When constructing a Punnett square, the symbols on the outside of the boxes represent _______, while those inside the boxes represent _______.
gametes, progeny
True or false? The same phenotype can be produced by more than one genotype.
True
True or false? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.
False
If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?
None
Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?
25%
A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the “1” in the 9:3:3:1 ratio)?
ttpp
Which of the following statements apply to the variation in human skin color?
a) Variability in human skin color can be explained by the activity of a single gene.
b) The color of human skin and the skin of our closest primate relative exhibits a similar range in variability.
c) Human skin color variation likely evolved in response to differences in the intensity of sunlight around the world.
d) Human skin color variation is primarily determined by the type and amount of melanin pigment in the skin.
e) Human skin color variation evolved recently in hominid evolution, once some populations of our human ancestors migrated out of Africa.
c) Human skin color variation likely evolved in response to differences in the intensity of sunlight around the world.
d) Human skin color variation is primarily determined by the type and amount of melanin pigment in the skin.
e) 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 accurately describes melanin’s function?
a) Everyone has the same type of melanin, but the amount varies from person to person.
b) Melanin is a molecule that distinguishes humans from their primate relatives.
c) The more melanin an individual has in his or her skin cells, the more likely he or she is to get mutations in DNA.
d) Lighter skin has less of the dark-brown eumelanin that protects cells from UV damage.
d) Lighter skin has less of the dark-brown eumelanin that protects cells from UV damage.
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?
the melanin in darkly pigmented skin protects circulating folate from being destroyed by UV radiation, and folate is important in human reproduction
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?
indigenous peoples living at high latitudes have darker skin, but they eat foods rich in vitamin D
Based on the risk factors discussed in the video, which of the following groups would be most likely to develop the bone disease rickets?
children born to parents with dark skin living far from the equator
In what way does natural selection depend on the specific environment in which an organism lives?
when the environment changes, traits that were beneficial to an organism may become harmful and vice versa.
In humans, wavy hair occurs in heterozygotes (HSHC) offspring of people with straight hair (HSHS) and curly hair (HCHC). Which of the following crosses would produce offspring with the ratio of 1 straight:2 wavy:1 curly?
wavy x wavy
Which of the following describes the ability of a single gene to have multiple phenotypic effects?
pleiotropy
Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this expression of phenotypes?
pleiotropy
Skin color in humans has a wide variety of phenotypes. The expression of this trait is caused by more than two genes. What type of inheritance pattern is responsible for this expression?
polygenic inheritance
Characters in humans such as a person’s red and white blood cell counts vary quite a bit depending on such factors as altitude and physical activity. Traits like this are referred to as
multifactorial
Which of the following statements correctly describes an example of epistasis?
a) Recessive genotypes for each of two genes (aabb) result in an albino corn snake.
b) In cacti, there are several genes for the type of spines.
c) In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.
d) In Drosophila (fruit flies), white eyes can be due to a combination of multiple genes.
c) In rabbits and many other mammals, one genotype (ee) prevents any fur color from developing.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies. These results indicate which of the following about the inheritance pattern of fur color in Labrador retrievers?
a) Yellow is dominant to black.
b) Brown is dominant to black.
c) Black is dominant to brown and to yellow.
d) Epistasis is involved.
Epistasis is involved.
Labrador retrievers are black, brown, or yellow. In a cross of a black female with a brown male, results can be all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies. How many genes must be responsible for these coat colors in Labrador retrievers?
2
Labrador retrievers have black, brown, or yellow fur. Fur color is controlled by two genes, one of which exhibits epistasis. Black (B) is dominant over brown (b) in one gene, and (E) is dominant over (e) in the other gene. The (E) gene is epistatic to the (B) gene. In a cross of a black female with a brown male, results can be all black puppies, 1/2 black to 1/2 brown puppies, or 3/4 black to 1/4 yellow puppies. In one cross of black × black, the results were as follows: 9/16 black, 4/16 yellow, 3/16 brown.
The genotype eebb must result in which of the following?
yellow
Radish flowers may be red, purple, or white. A cross between a red-flowered plant and a white-flowered plant yields all-purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. True-breeding red-flowered long radishes are crossed with true-breeding white-flowered radishes. All of the F1 offspring are purple-flowered and long radishes. The flower color trait in radishes is an example of which of the following types of inheritance?
incomplete dominance
Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. The relationship between genes S and N is an example of
epistasis
The figure above shows a pedigree chart for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle.
What is the genotype of individual II-5?
ww
The figure above shows a pedigree chart for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle.
What is the likelihood that the offspring of IV-3 and IV-4 will have the trait?
50%
The figure above shows a pedigree chart for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle.
What is the probability that individual III-1 is Ww?
1
