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WorksheetsQuiz Lecture 10
Total questions: 26
Worksheet time: 13mins
All of the following combinations are possible in the gametes of an organism that is AaBb EXCEPT:
Ab.
aa.
aB.
AB.
ab.
Gregor Mendel concluded that each pea has two units for each trait, and each gamete contains one unit. Mendel's "units" are now called
transcription factors.
characters.
genes.
chromosomes.
A pea plant with red flowers is test crossed; half of the resulting progeny have red flowers, whereas the other half have white flowers. The genotype of the test-crossed parent was
rr.
RR.
Rr.
either RR or Rr.
Which of the following statements regarding genotypes and phenotypes is false?
The expressed physical traits of an organism are called its phenotype.
The genetic makeup of an organism constitutes its genotype.
An organism with two different alleles for a single trait is said to be homozygous for that trait.
Alleles are alternate forms of a gene.
A recessive allele is one
that appears only in a heterozygote.
that is not expressed as strongly as a dominant allele.
that must be lethal in the homozygous condition.
whose effect is masked by a dominant allele.
that produces no effect when present in the homozygous condition.
Dr. Smith's parents have normal hearing. However, Dr. Smith has an inherited form of deafness. Deafness is a recessive trait that is associated with the abnormal allele d. The normal allele at this locus, associated with normal hearing, is D. Dr. Smith's parents could have which of the following genotypes?
Dd and Dd
DD and dd
dd and dd
Dd and DD
Which of the following statements about genotypes and phenotypes is true?
Individuals with the same genotype might have different phenotypes.
Matings between individuals with recessive phenotypes produce offspring with dominant phenotypes.
Individuals with the same phenotype might have different genotypes.
Matings between individuals with dominant phenotypes cannot produce offspring with recessive phenotypes.
Which of the following terms refers to a situation where a single phenotypic character is determined by the additive effects of two or more genes?
polygenic inheritance
incomplete dominance
pleiotropy
codominance
Genes located close together on the same chromosomes are referred to as ________ genes and generally ________.
linked; sort independently during meiosis
linked; do not sort independently during meiosis
codependent; do not sort independently during meiosis
homologous; are inherited together
Codominance occurs when
a heterozygote expresses an intermediate phenotype.
both of the alleles in a heterozygote are expressed phenotypically in an individual.
offspring exhibit several different phenotypic expressions of a single trait.
expression of two different alleles alternates from one generation to the next.
Which of the following statements best explains why dominant alleles that cause lethal disorders are less common than recessive alleles that cause lethal disorders?
Lethal disorders caused by dominant alleles are usually more severe than lethal disorders caused by recessive alleles.
Unlike lethal disorders caused by recessive alleles, lethal disorders caused by dominant alleles usually cause the death of the embryo.
The presence of a lethal dominant allele causes sterility.
Most individuals carrying a lethal dominant allele have the disorder and die before they reproduce, whereas individuals carrying a lethal recessive allele are more likely to be healthy and reproduce.
Imagine that a newly discovered species of fish normally has three eyes (E), but the rare mutation (e) causes "diopthalmic" fish with two eyes to be born. In addition, eye color in these fish is inherited similarly to humans, with black eyes (B) being dominant to blue (b). Assuming these two genes are carried on separate chromosomes, what must the genotypes of two black-eyed, three-eyed parents be if they have a blue-eyed, diopthalmic son?
EEBB and eebb
eeBB and EEbb
Both eebb
Both EeBb
You conduct a dihybrid cross. A ________ ratio would make you suspect that the genes are linked.
12:1:1:4
3:1
9:3:3:1
1:1:1:1
The mechanism that "breaks" the linkage between linked genes is
pleiotropy
crossing over.
codominance
independent assortment.
When the expression of a trait is influenced by the action of many genes, the pattern of inheritance is called
complete dominance.
polygenic inheritance.
incomplete dominance.
discontinuous variation.
multiple alleles.
Justin has type A blood and his wife Brittany has type B blood. Justin's parents both have type AB blood, and Brittany's parents also both have type AB blood. What are the chances that Justin and Brittany's son Theodore has type A blood?
25%
0%
100%
75%
Suppose you cross a pea plant with yellow, smooth seeds with one that has wrinkled, green seeds. You examine the seeds of 967 offspring and find that some have yellow, smooth seeds and some have yellow, wrinkled seeds, but no green seeds of either type show up. What is the genotype of the yellow-seeded parent? (Y = yellow, y = green; S = smooth, s = wrinkled)
YySS
YYSs
YYSS
YYss
YySs
Although the law of independent assortment is generally applicable, when two loci are on the same chromosome, the phenotypes of the offspring sometimes do not fit the phenotypes predicted. This is due to
inversions.
chromatid abnormalities.
chromosome exchange.
translation.
linkage
All the offspring of a cross between a red-flowered plant and a white-flowered plant have pink flowers. This means that the allele for red flowers is ________ to the allele for white flowers.
codominant
recessive
incompletely dominant
dominant
Varieties of plants in which self-fertilization produces offspring that are identical to the parents are referred to as
hybrids
monohybrid crosses.
the F2 generation.
true-breeding.
All the offspring of a cross between a black-eyed Mendelian and an orange-eyed Mendelian have black eyes. What is the expected phenotypic ratio of a cross between two orange-eyed Mendelians?
0 black-eyed:1 orange-eyed
1 black-eyed:3 orange-eyed
1 black-eyed:0 orange-eyed
3 black-eyed:1 orange-eyed
If A is dominant to a and B is dominant to b, what is the expected phenotypic ratio of the cross AaBb × AaBb?
9:3:3:1
16:0:0:0
1:1:1:1
8:4:2:2
A testcross is
a mating between an individual of unknown genotype and an individual heterozygous for the trait of interest.
a mating between two individuals of unknown genotype.
a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest.
a mating between two individuals heterozygous for the trait of interest.
Sex-linked conditions are more common in men than in women because
most genes associated with the sex-linked conditions are linked to the Y chromosome, which determines maleness.
the sex chromosomes are more active in men than in women.
men need to inherit only one copy of the recessive allele for the condition to be fully expressed.
men acquire two copies of the defective gene during fertilization.
The expression of both alleles for a trait in a heterozygous individual illustrates
pleiotropy
polygenic inheritance.
codominance.
Imagine that smurfs live in widely separated groups and rarely interbreed, so geneticists know very little about them. On one occasion, two smurfs from different groups did mate. A big-footed, white smurf mated with a small-footed, blue smurf. Three offspring resulted: one big-footed and blue and two small-footed and blue. Which statement about the inheritance of color in smurfs is most likely to be correct?
Blue is dominant to white.
White is dominant to blue.
White is dominant to blue.
