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BIOL 100: Ch. 9

Terms in this set (82)

In some parts of Africa, the frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?
Darwin's explanation of the natural selection
The traits of an individual controlled by his or her genotype are his or her ________.
phenotype
Hypophosphatemia (vitamin D-resistant rickets) is inherited as a sex-linked dominant trait. The relevant gene is found on the X chromosome. What is the expected outcome of a cross between a homozygous recessive woman and a man with hypophosphatemia?
1. Fifty percent of their daughters and fifty percent of their sons exhibit hypophosphatemia (wrong)

2. All of their sons and none of their daughters exhibit hypophosphatemia (wrong)

3.
Which of the following individuals will inherit an X-linked allele from a man who carries it?
All of his daughters
Which stage(s) of meiosis or mitosis is the basis of Mendel's laws of segregation and independent assortment?
The behavior of chromosomes during metaphase I and anaphase I of meiosis
How many alleles exist for a given gene in a population?
1. always one allele per gene (wrong)

2. only two
A mating between a purebred purple-flowered pea plant and a purebred white-flowered pea plant would be called a ________.
1. dihybrid cross (wrong)

2. monohybrid cross
Scientists have long been interested in differences between dogs and wolves in their social behavior toward humans. Dogs and wolves share a common ancestor. In trying to understand the differences, a researcher analyzed data collected from 18 domesticated dogs and 10 wolves that had been raised by humans.

Which data would be most useful to this study?
The extent to which the dogs and the wolves sought assistance from humans when presented with a challenge.
The first-born child of generation I is a _________.
1. Male (wrong)

2. Female
In humans, the presence or absence of dimples is a trait controlled by a single gene. What is the genotype of an individual who is heterozygous for dimples?
Dd
Widow's peak, a pointed hairline on the forehead, is a genetic trait caused by a dominant allele. It can be traced back through a family's history using pedigree analysis.The pedigree shown here is of three generations of a family. Notice that some individuals (shown in gray) have a widow's peak ( W = dominant allele and w = recessive allele).

This pedigree supports the fact that widow's peak is due to a dominant allele, because if it were due to a recessive allele and both parents show the recessive phenotype, then ________.
all of the offspring would have a widow's peak
Which technique is used to collect fetal cells during pregnancy for genetic testing?
1. testcross (wrong)

2. amniocentesis
Mendel's laws are based on the behavior of chromosomes during ________.
metaphase I and anaphase I of meiosis
In the case of the ABO blood group, both alleles A (IA) and B ( IB) may be expressed as the phenotype. This demonstrates __________.
codominance
An individual with (naturally) curly hair and an individual with (naturally) straight hair mate; all of their offspring have (naturally) wavy hair. What is the relationship between the alleles for hair texture?
incomplete dominance
This pedigree indicates a pattern of inheritance that is _________.
1. carried on the Y chromosome (wrong)

2. autosomal recessive
The ________ is most commonly found in nature.
1. parental type (wrong)

2. Dominant trait
Linked genes are usually ________.
located close together on a chromosome
_________ genes violate Mendel's law of independent assortment.
Linked
An individual who is homozygous ________.
carries two copies of the same allele for a gene
Which of the following is an inherited trait influenced by multiple alleles?
ABO blood group
A mating between a purebred purple-flowered pea plant and a purebred white-flowered pea plant would produce a(n) ________.
1. F 2 generation (wrong)

2. Hybrid
The best definition of a purebred plant is one that ________.
passes on the next generation only those traits identical to the parent
A ________ allele will always be expressed regardless of the identity of the other allele.
Dominant
Scientists have long been interested in differences between dogs and wolves in their social behavior toward humans. Dogs and wolves share a common ancestor. In trying to understand the differences, a researcher analyzed data collected from 18 domesticated dogs and 10 wolves that had been raised by humans.

Which data would be most useful to understand the genetic basis of this behavior?
1. The pedigree for the dogs and the geographic location from which the wolves came. (wrong)

2. Examination of DNA from the ancient ancestor of dogs and wolves. (wrong)

3.
In _________, an inherited trait is controlled by two or more genes.
polygenic inheritance
Duchenne muscular dystrophy is a sex-linked recessive trait in humans. Patients experience progressive and irreversible muscle weakness over time, and they rarely live past their 20s. How likely is it for a woman to have this condition?
One-half of the daughters of an affected father and a carrier mother could have this condition.
If a woman with type AB blood marries a man with type O blood, which of the following blood types could their children possibly have?
A and B
Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?
1. XNXN and XnY (wrong)

2. XNXn and XNY
The most likely pattern of inheritance for the trait in the pedigree is ___________.
1. Sex linked (wrong)

2.
Which of these crosses will produce only heterozygous offspring?
AA × aa
Scientists have long been interested in differences between dogs and wolves in their social behavior toward humans. Dogs and wolves share a common ancestor. In trying to understand the differences, a researcher analyzed data collected from 18 domesticated dogs and 10 wolves that had been raised by humans.

If she discovered that the degree of social relationship a dog exhibited toward humans was positively correlated with a chemical modification of a part of a chromosome rather than what alleles a dog had, this would be an example of ________.
epigenetics
Albinism is a recessive trait. An albino man and a homozygous normal pigmented woman marry and have four children. What is the phenotype of the children?
100% normal skin pigment
A couple has two female children. What is the probability that their next child will be male?
50%
Humans have been applying the principles of genetics for many years without actually knowing about genes. Evidence for this is that humans ________.
choose to save seeds from plants with the best yield to plant for the next generation
Which trait is polygenic in humans?
height
To determine the genotype of an individual who expresses a dominant trait, you would cross that individual with an individual who ________.
is homozygous recessive for that trait
The ABO blood group in humans is based on the presence of three alleles in the population: IA, IB and i. The four blood types, A, B, AB, and O, result from different combinations of the three alleles. A child has blood type B. The father is blood type A. The diploid genotype of the mother is _______.
1. IBi, IBIB, or IAIB (wrong)

2. IAIB (wrong)

3.
Mendel's law of segregation indicates that
gametes have one allele copy for each gene.
Two alleles expressing exactly the same information for a trait are designated as ________.
homozygous
An individual who is heterozygous for cystic fibrosis ________.
A carrier
Which could help identify a trait that is determined by the effects of two or more genes (polygenic inheritance)?
1. A mating between a homozygous and a heterozygous individual produces more than the expected number of offspring expressing the dominant trait. (wrong)

2.
Recessive genetic disorders are more common than dominant genetic disorders because ________.
carriers are not eliminated by the disease before passing the defective alleles on to their offspring
Which of the following describes the ability of a single gene to have multiple phenotypic effects?
pleiotropy
If an individual carries two different alleles for the same trait, the individual is ________ for the trait.
heterozygous
Round seeds ( R) are dominant to wrinkled seeds ( r), and yellow seeds ( Y) are dominant to green seeds ( y). What is the expected phenotypic ratio of a cross between an RrYy and an rryy individual?
1. 9:3:3:1 (wrong)

2.
Which of the following statements about independent assortment or segregation is correct?
The law of independent assortment describes the behavior of two or more genes relative to one another.
In humans, free earlobes ( E) are dominant to attached earlobes ( e) and the presence of freckles ( F) is dominant to the absence of freckles ( f). If an individual heterozygous for both of these traits were to mate with an individual with attached earlobes and no freckles, what is the probability of having a child with attached earlobes and freckles?
25%
A man has extra digits (six fingers on each hand and six toes on each foot). His wife and their daughter have the normal number of digits (five fingers on each hand and five toes on each foot.) Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next (third) child will have extra digits?
1/2
What is the key to the recognition of incomplete dominance?
The phenotype of the heterozygote falls between the phenotypes of the homozygotes.
Predict the possibility of an offspring with a widow's peak, a dominant inherited trait affecting the hairline, when both parents are heterozygous for the trait.
75% of the offspring will have a widow's peak.
Widow's peak, a pointed hairline on the forehead, is a genetic trait caused by a dominant allele. This pedigree shows the inheritance of this trait through three generations of a family. The individuals shown in gray have a widow's peak (W = dominant allele and w = recessive allele). What is Mary's genotype?
Ww
The parents of a child with unusual disease symptoms take the child to a doctor for help. The doctor suspects that the condition might have a genetic basis. She recommends that the child be taken to a specialty clinic where physicians and staff members are trained to diagnose genetic diseases and counsel parents. Ultimately, the child is diagnosed with a rare recessively inherited disease. The parents are tested for the gene, and both are found to be heterozygous. The parents are expecting another child and ask about a test to determine if this child may carry the disease. All but one of these tests may detect genetic disorders in the unborn child. Choose the EXCEPTION.
1. blood tests to measure levels of alpha-fetoprotein (wrong)

2.
To determine the phenotype of an individual who expresses a dominant trait, you would cross that individual with an individual who is homozygous recessive for that trait. This technique is referred to as a(n) ________.
Test cross
Attached earlobes are recessive to free earlobes. What genotypic ratio is expected when an individual with attached earlobes mates with an individual heterozygous for free earlobes?
1:1
What is the difference between a monohybrid cross and a dihybrid cross?
A dihybrid cross involves organisms that are heterozygous for two characters, whereas a monohybrid cross involves organisms that are heterozygous for single character
An individual with the blood group genotype LMLN has the phenotype MN. What is the relationship between the LM and LN alleles?
codominance
A woman has blond hair and brown eyes. This statement is best described as indicating ________.
phenotype
Which of the following statements correctly explains the fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment?
All of the genes controlling the traits behaved as if they were on different chromosomes.
The most likely pattern of inheritance for the trait in the pedigree is _________.
1. Autosomal recessive (wrong)

2.
Mendel's law of segregation has its basis in which phase of gamete meiosis?
anaphase I of meiosis
In order for a male to inherit a sex-linked (X-linked) disorder, he must receive the allele from _______.
his mother only.
An individual with the genotype AaBb produces four different gametes in equal proportions. This is a demonstration of ________.
Mendel's law of independent assortment
Assume that having three nostrils is inherited as a sex-linked trait on the Y chromosome. A man with three nostrils has a daughter who has a son with a man who has only two nostrils. What is the probability that the three-nostril man's grandson has three nostrils?
0%
In pea plants, the tall phenotype is dominant to the dwarf phenotype. If a heterozygous pea plant is crossed with a homozygous tall pea plant, what is the probability that the offspring will be dwarf in size?
0
The parents of a child with unusual disease symptoms take the child to a doctor for help. The doctor suspects that the condition might have a genetic basis. She recommends that the child be taken to a specialty clinic where physicians and staff members are trained to diagnose genetic diseases and counsel parents. Ultimately, the child is diagnosed with a rare recessively inherited disease. The parents are tested for the gene, and both are found to be heterozygous. The parents want to have another child but are afraid this child will also be affected.

What would genetic counselors say is the probability that the second child will have the disease?
1/4
Mendel continued some of his experiments into the F2 or F3 generation in order to ________.
observe whether or not a recessive trait would reappear
An individual with (naturally) curly hair and an individual with (naturally) straight hair mate; all of their offspring have (naturally) wavy hair. If an individual with wavy hair mates with an individual with straight hair, what is the probability that their child will have curly hair?
1. 75% (wrong)

2.
Mendel's law of independent assortment has its basis in which of the following events of meiosis I?
1. synapsis of homologous chromosomes (wrong)

2.
The ABO blood group in humans is based on the presence of three alleles in the population: IA, IB and i. The four blood types, A, B, AB, and O, result from different combinations of the three alleles. An individual with blood type AB reflects what type of interaction between these alleles?
1. complete dominance (wrong)

2.
What would you examine to determine whether a trait is sex linked?
pedigree
A purebred plant that produces yellow seeds is crossed with a purebred plant that produces green seeds. The F 1 plants have yellow seeds. What is the expected phenotypic ratio of seed color of the offspring of an F 1 × F 1 cross?
3:1
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?
1. T (wrong)

2. HT
Which of the following phenotypes is an example of polygenic inheritance?
skin pigmentation in humans
Genetic tests available to pregnant mothers include _________, in which a sample of fluid surrounding the fetus is removed and the fetal cells in the fluid are analyzed.
amniocentesis
This hypothetical pedigree for a disease in humans illustrates inheritance that is ________.
1. sex-linked dominant (wrong)

2.
What is the specific location of a gene on a chromosome?
1. Allele (wrong)

2. Locus
A child is diagnosed with a recessively inherited disease. The parents are tested for the gene, and both are found to be heterozygous. The parents want to have another child. What is the probability that the second child will have the disease?
1/4
A woman who is heterozygous for blood type A mates with a man who is homozygous for blood type O. What blood type(s) could their children have?
50% type A, 50% type O
Attached earlobes are recessive to free earlobes. What is the probability of having a child with attached earlobes when an individual with attached earlobes mates with an individual heterozygous for free earlobes?
50%
Marfan syndrome is the result of inheriting a single allele. Individuals with Marfan syndrome are tall and long-limbed, and have both cardiovascular and eye defects. Marfan syndrome is an example of ________.
pleiotropy
What is the key to the recognition of codominance?
The heterozygote expresses the phenotype of both homozygotes.
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