Chp 4 Homework; Extensions of Mendelian Inheritance
Among the children of two parents with the HbA HbS genotype, what fraction is expected to be unaffected by sickle cell anemia and resistant to malaria?
1/2
In four-o'clock plants, red flower color is dominant to white flower color. However, heterozygous plants have a pink color. If a pink-flowered plant is crossed with a white-flowered plant, what will be the phenotypic ratios of their offspring?
1/2 pink, 1/2 white
Achondroplasia is a type of dwarfism caused by the presence of a dominant allele (A). However, the presence of two dominant alleles is lethal. What is the probability that two individuals with achondroplasia have a non-dwarf child?
1/3
For dog coat color, the dominant S+ allele results in full pigmentation while the recessive si allele leads to white patches on the legs and belly called Irish spotting. Two fully-pigmented dogs have puppies with Irish spotting. What is the approximate fraction of offspring with Irish spotting expected from this cross?
1/4
Instead of the Mendelian ratio of 3:1, the ratio of phenotypes for offspring from a cross between two individuals who are heterozygous for sickle cell disease is ________ __________ ___________-
1:2:1
Huntington disease is a lethal condition for which symptoms begin to appear in middle age. The age at which a person begins to show disease symptoms is called the ______of ________
Age of Onset
One form of hereditary deafness is inherited with an X-linked recessive allele. What can be expected for the offspring of a deaf mother and a father with normal hearing?
All of the sons will be deaf and all of the daughters will have normal hearing.
The interaction of two genes to produce a phenotype was first described by __________.
Bateson and Punnett
Suppose a mother with the IAi genotype and a father with the IBi genotype have one child with type A blood and one child with type AB blood. Which is the best description of the observed genetic patterns?
Codominance is observed for the child with type AB blood while complete dominance is observed for the child with type A blood.
Suppose a mother with the IAi genotype and a father with the IBi genotype have two children, one with a codominant genotype and one with a genotype demonstrating complete dominance. Which genotypes can the children have?
Codominant = IAIB; Complete dominance= IBi
Which of the surface antigens related to blood type would be found on the red blood cells of an individual with the IAIB genotype?
Each red blood cell would carry both surface antigen A and surface antigen B.
Which choice does NOT represent an explanation for pleiotropy?
Expression of two genes that affect cell function in more than one way
When more than one wild-type allele occurs in a population, the phenomenon is called
Genetic polymorphism
Colorblindness is inherited with an X-linked recessive allele. Which term describes the genotype for a colorblind male?
Hemizygous
Hemophilia is inherited with an X-linked recessive allele. Which term describes the genotype for a male who has this blood-clotting disorder?
Hemizygous
For which of the following genotypes would the effects of codominance be observed in the individual's phenotype?
IaIb
What type of inheritance accounts for the data shown for pea seeds?
Incomplete dominance
Which pattern is shown by a heterozygous individual that has a phenotype that is intermediate between the phenotypes of the dominant and recessive homozygotes?
Incomplete dominance
Select the two fundamental laws of inheritance discovered by Mendel.
Law of segregation Law of independent assortment
What phenomenon is observed in a population when three or more alleles can be found for a single gene?
Multiple alleles
If a geneticist describes a trait as being 70% penetrant, what would they mean?
Only 70% of the individuals who carry the allele(s) for a trait express the trait.
For each description on the left, choose the appropriate pattern of inheritance on the right.
Overdominance Heterozygote has a phenotype that is more beneficial than the phenotypes of either homozygote Incomplete dominance Heterozygote has a phenotype that is intermediate between the phenotypes of the homozygotes Codominance Heterozygote expresses both alleles without showing an intermediate phenotype Simple Mendelian Inheritance Alleles for the trait show a strict dominant/recessive relationship
For dog coat color, the dominant S+ allele results in full pigmentation while the recessive si allele leads to white patches on the legs and belly called Irish spotting. Suppose that a cross between a fully-pigmented female and an Irish-spotted male yields some puppies with the mother's phenotype and others with the father's phenotype. What is the genotype of the fully-pigmented female parent in this cross?
S+si
Which is the pattern of inheritance for holandric genes?
Transmitted only from father to son
A trait that a son can inherit only from his mother must be due to an allele found on ______.
X-chromosome
A cell with at least one copy of a wild-type allele will typically produce ______.
a functional version of the protein specified by this allele
A paralog ____________.
can explain the lack of phenotype for a gene knockout
The production of wild-type offspring from a cross between parents that both display the same recessive phenotype illustrates the genetic phenomenon of _______.
complementation
The following pathway is proposed to explain the inheritance of purple flower color in pea plants: Colorless Precursor→Colorless Intermediate→Purple Pigment. A dominant allele for Gene C provides an enzyme that converts Colorless Precursor→Colorless Intermediate. A dominant allele for Gene Pprovides an enzyme that converts Colorless Intermediate→Purple Pigment. An explanation of why plants with CCpp and ccPP genotypes have white petals while plants with the CcPp genotype have purple flowers is
complementation occurs in the CcPp plant, showing that the mutations preventing color in the white plants are in different genes.
A temperature-sensitive allele that causes the death of an organism only with exposure to a specific range of temperatures is a(n) ______ allele,
conditional lethal
An allele that leads to the death of the organism only under specific environmental influences is called a(n) ______ allele,
conditional lethal
Parents can unknowingly pass on a dominant lethal allele for Huntington disease to their offspring because the ______.
disease symptoms often do not appear until after the parent has had children
When Blue-Eyed Mary plants inherit at least one dominant allele for a gene for flower color, their petals are blue to match their name. If plants are homozygous recessive for a second gene, however, they develop white petals. The effect of the second gene on the first flower color gene is called
epistasis
A gene that codes for a product that is necessary for the survival of an organism is called a(n) ______ gene.
essential
Pleiotropy can be caused by ______.
expression of one gene at different stages of development expression of one gene that affects cell function in more than one way expression of one gene in different cell types
Corn kernels can have a purple color due to the dominant allele of one gene. When the alleles of a second gene are present in the homozygous recessive genotype, the kernel color is changed to red. This is an example of ______.
gene interaction
If a combination of two or more genes is required to produce a specific trait, it is called a(n) _______.
gene interaction
The pattern where allelic variants of two different genes affect a single trait is called ___________ ________
gene interaction
A population that contains more than one wild-type allele demonstrates ______.
genetic polymorphism
Hemophilia is an X-linked recessive trait. In order for a female child to have hemophilia ________
her father must have hemophilia and her mother may have hemophilia or be a carrier
One form of hereditary deafness is inherited with an X-linked recessive allele. A woman with normal hearing has a son with hereditary deafness. The woman's genotype at this gene locus is ______.
heterozygous
Humans homozygous for the sickle cell allele have sickle cell anemia. A human that is heterozygous for the sickle cell allele is an example of _____________.
heterozygous advantage
In overdominance, the _______ genotype is beneficial over the _______ genotypes.
heterozygous, homozygous
Genes located only on the Y chromosome are called ______ genes.
holandric
Suppose a genetic test shows that a woman has inherited the dominant BRCA1 allele that causes breast cancer. If she does not develop breast cancer in her lifetime, the phenomenon is called
incomplete penetrance
Dark pigmentation of fur in dogs depends on the production of ______ by cells called ______.
melanin; melanocytes
A dog's fur will have white patches if cells called do not produce the pigment melanin.
melanocytes
A single gene for white coloring on the coats of dogs has four alleles with a hierarchy of dominance. Various combinations of these alleles can lead to solid coat, Irish-spotting, piebald-spotting and white coats. This inheritance pattern for white coloring is due to the existence of ______ for the gene for coat coloring.
multiple alleles
Less frequent alleles that have genetic changes making them defective in protein production are called ______ alleles.
mutant
When a preexisting allele is changed to a new version that no longer codes for a functional protein, the new allele is called a _______ allele.
mutant allele
The melanocytes responsible for fur pigmentation in dogs originate as precursor cells called melanoblasts found in which area of the embryo?
neural crest
A gene that produces a beneficial product that is not absolutely required for survival of the organism is called a(n) ______ gene.
nonessential
Genes that are not required for survival, but are likely to be beneficial to the organism, are called _________.
nonessential genes
Heavy metals, such as copper, are required for proper development. However, if too much copper is present it can lead to developmental defects. A scientist was interested in studying the developmental defects that could occur at various concentrations of copper. Genetically identical organisms were grown in 6 different concentrations of copper. This experiment evaluates a/an _____________.
norm of reaction
The situation where a heterozygote has a characteristic that makes it more likely than either homozygous individual to reproduce in a given environment is called
overdominance
When an allele causes a disease in the homozygous recessive genotype but confers resistance to a different disease in heterozygotes, the phenomenon is calle
overdominance
While causing sickle-cell anemia in homozygous individuals, the product of the HbS allele provides resistance to malaria in individuals with the HbA HbS genotype. This advantage to heterozygotes demonstrates ______.
overdominance
The allele for sickle cell anemia leads to multiple changes in the individual's phenotype, including the type of hemoglobin produced, the shape of red blood cells, the onset of anemia and reduced susceptibility to malaria. The name for these multiple effects on phenotype is ______
pleiotropy
The multiple effects of a single gene on the phenotype of an organism is called _______.
pleiotropy
The pattern where one gene affects many traits is called
pleiotropy
To produce dark fur coloration in dogs, precursor cells called melanoblasts must ___
proliferate and differentiate into pigment-producing melanocytes migrate to various areas of the body, including the ventral region arise within the neural crest in the dorsal region of the embryo
The pedigree below traces a trait through a family. Filled in circles and square show affected individuals. The inheritance of this trait by individual III-3 exemplifies ______.
pseudoautosomal inheritance
A lethal allele usually shows a(n) ______ inheritance pattern.
recessive
For X-linked genes, ______ crosses give different outcomes.
reciprocal
The cross on the right in panel "b" is an example of a ________ cross.
reciprocal
In cattle, the presence or absence of scurs follows a sex-influenced pattern of inheritance. A heterozygous male has _______ and a heterozygous female has ______
scurs, no scurs
An allele that causes death in some, but not all individuals in a population is a(n) _____ allele.
semilethal
In humans, a gene found on the Y chromosome but not on the X chromosome is a _______ - linked gene.
sex
Chromosomes that differ between males and females are called ______ ________
sex chromosome
Chromosomes that differ in size and composition between males and females are called ______.
sex chromosomes
When a daughter can inherit a sex-linked allele from either her mother or father, it must be located on ______.
the X chromosome
Pink four o'clock flowers have one copy of the allele for red petals and one copy of the allele for white petals. The best explanation for the pink petal color is ______.
the single allele for red petals causes the production of about 50% of the normal enzyme so petal color is lighter
Individuals with an HbS HbS genotype suffer from sickle cell anemia because ______.
they produce hemoglobin S, a variant that causes their red blood cells to form a crescent shape when oxygen concentration is low
Colorblindness is due to an X-linked recessive allele. To be colorblind, females must inherit ______ copy(ies) of this allele and males must inherit ______ copy(ies).
two; one
A person with type A blood can safely donate blood to people with ______ blood.
type A and type AB
Epistasis is _______________.
when one gene can mask the expression of a second gene
A ______ allele is the most prevalent allele in a population and usually encodes a protein that is made in the proper amount and functions normally.
wild type
The most commonly-occurring allele in a population is called the - allele.
wild type
A person with type O blood can donate to people
with all blood types.
Suppose that there are two male mice who are homozygous for the same allele. They are raised under the same environmental conditions: receiving the same types of foods in cages exposed to the same ranges of temperature. Despite this attention to animal care, one mouse dies and the other survives. Which type of allele is likely to be responsible for this death?
Semilethal allele
Which is the inheritance pattern where an allele is dominant in one sex and recessive in the opposite sex?
Sex-influenced inheritance
Which inheritance pattern is shown for a trait occurring in one sex but not in the opposite sex?
Sex-limited inheritance
Which description on the left matches each pattern of inheritance on the right?
Simple Mendelian inheritance Follows a strict dominant/recessive relationship X-linked Traits for which males inherit only one allele while females inherit two alleles Lethal alleles Alleles that have the potential to cause death Codominance Pattern in which both alleles are expressed in the heterozygote without blending Incomplete dominance Pattern producing an intermediate phenotype in the heterozygote
The holandric gene on the mammalian Y chromosome that is essential for the development of male characteristics is called the _________ gene.
Sry
Development of male characteristics requires the action of the ______ gene on the mammalian ______.
Sry; Y chromosome
A patient with sickle cell disease may experience a painful episode leading to tissue and organ damage because cells carrying hemoglobin S ______.
form abnormal crescent shapes that block capillaries, depriving nearby cells of oxygen
The type of mutation that leads to increased expression of an altered protein in a cell which does not normally express the protein is called __________ a --___________ __________ mutation.
gain of function
The Antennapedia mutation causes fruit flies to develop legs in the places on their heads where antenna would normally be found. Expression of the Antennapedia gene product in a location where it is not usually active is due to a ______ mutation for a ______ mutant allele.
gain-of-function; dominant loss-of-function; recessive
An allele that can lead to the death of an individual is a(n) ______ allele.
lethal
The allele that causes Huntington disease in humans is an example of a(n) _______ that exerts its effects later in life
lethal allele
For ______ inheritance, a given allele is dominant in one sex and recessive in the opposite sex.
sex-influenced
A trait that is expressed in only one sex and not seen in the opposite sex shows ______ inheritance.
sex-limited
In humans, a gene found in the X chromosome but not the Y chromosome is called a(n) ______ gene
sex-linked
Himalayan coloring in rabbits is due to a dominant allele that codes for a tyrosinase enzyme which participates in the production of the dark pigment melanin. In cold temperatures, dark coloring is only found in the ears, nose and feet of the animal. White coloration develops on body areas where blood flow keeps the animal warm. The tyrosinase enzyme is most likely due to a ______.
temperature-sensitive allele
In fruit flies, the para mutation causes a change in a sodium channel necessary for conducting nerve signals. Mutant flies have normal movement at 22oC but become immediately paralyzed at 29oC. The paralysis is reversed when the temperature returns to 22oC. The para mutation is most likely due to a ______
temperature-sensitive allele