Exam 2 McGraw Hill Questions 24, 4, 28
Manx cats have shortened tails due to the autosomal dominant allele M that affects spine formation. This allele is lethal in homozygotes. The autosomal recessive allele m leads to normal tail development. If two Manx cats are mated to each other, what is the fraction of offspring expected to have normal tail lengths?
1/3
Suppose that the covering on corn kernels can have a purple color due to the dominant allele P of gene 1. The genotype pp leads to a colorless covering. Alleles of gene 2 can modify the purple color, with the dominant allele R having no effect but genotype rr changing the purple color to red. Alleles of gene 2 have no effect on plants with genotype pp for gene 1. For the cross PpRr x PpRr, what fraction of the plants are expected to have red covering on their corn kernels?
3/16
When Blue-Eyed Mary plants inherit at least one dominant allele B of gene 1 their petals are blue to match their name. Plants with bb genotype will have white petals. Alleles of gene 2 can modify the blue color, with the dominant allele M having no effect but the genotype mm changing the blue color to magenta. Alleles of gene 2 have no effect on plants with genotype bb for gene 1. For the cross BbMm X BbMm, what fraction of the offspring are expected to have magenta petals?
3/16
Suppose that the covering on corn kernels can have a purple color due to the dominant allele P of gene 1. The genotype pp leads to a colorless covering. Alleles of gene 2 can mask the purple color, with the dominant allele C having no effect but genotype cc changing the purple color to colorless. Alleles of gene 2 have no effect on plants with genotype pp for gene 1. For the cross PpCc x PpCc, what fraction of the plants are expected to have colorless covering on their corn kernels?
7/16
In cats, gene 1 specifies coat color; allele B leads to black coat while allele b leads to chocolate coat color. Gene 2 can inhibit coat color: genotype cc leads to an albino cat while at least one copy of allele C allows the full color from gene 1 to be expressed. What is the phenotypic ratio produced for the following cross: BbCc x BbCc?
9 black: 3 chocolate: 4 albino
In fruit flies, dominant alleles for two different genes are required for red eye color. Suppose Gene 1 has alleles R and r and Gene 2 has alleles E and e. Only flies with at least one R allele and at least one E allele will have red eyes; all other genotypes lead to white eyes. For the cross RrEe x RrEe, what fraction of the offspring are expected to have red eyes?
9/16
What is a normal distribution?
A frequency distribution that varies in a symmetrical way around an average value
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; onset
Select the human disorders that are inherited in an autosomal recessive fashion.
Albinism: Inability to synthesize melanin, resulting in white skin, hair, etc Cystic fibrosis: Water imbalance in tissues of the pancreas, intestine, sweat glands, and lungs due to impaired ion transport; leads to lung disease Phenylketonuria (PKU): Foul-smelling urine, neurological abnormalities, mental impairment; may be remedied by diet modification starting at birth Sickle cell disease: Anemia, blockages in blood circulation Tay-Sachs disease (TSD): Progressive neurodegeneration
Epistasis
Alleles of one gene mask the phenotypic effects of the alleles of a different gene
Which of the following characteristics of inheritance can be observed in the accompanying pedigree of a family affected by Tay-Sachs disease?
An affected offspring can have two unaffected parents The trait occurs in both males and females Affected individuals are offspring of heterozygous parents
Gene modifier effects
An allele of one gene modifies the phenotypic outcome of the alleles of a different gene
Select human disorders inherited in autosomal dominant fashion.
Aniridia: An absence of the iris of the eye, leasing to visual impairment and sometimes blindness Achondroplasia: A common form of dwarfism associated with a defect in the growth of long bones Marfan syndrome: Tall and thin individuals with abnormalities in the skeletal, ocular, and cardiovascular systems due to a weakening in the elasticity of certain body tissues Familial Hypercholesterolemia: Very high serum levels of low-density lipoprotein (LDL), a predisposing factor in heart disease Huntington Disease: Neurodegeneration that occurs relatively late in life, usually in middle age
What is the inheritance pattern for a trait that occurs with equal frequency in both sexes and will be inherited, on average, by 50% of the offspring of an affected individual who had only one affected parent?
Autosomal dominant
What is the inheritance pattern when the trait occurs with the same frequency in both sexes and two unaffected heterozygotes have, on average, 25% affected children?
Autosomal recessive
A meristic trait is a trait that
Can be counted and expressed in whole numbers
A quantitative trait is defined as a trait that
Can be described numerically
Suppose a disease-causing allele shows autosomal recessive inheritance. How could a carrier of this disease-causing allele be identified?
Carriers often show reduced activity for the enzyme encoded by the allele.
A method for obtaining fetal cells in a sample of the fluid surrounding the fetus is called ______.
Chorionic villus sampling
Characteristics that are determined by several genes and are also influenced by environmental factors are called ___ traits
Complex
A trait that does not fall into discrete categories is referred to as a(n) ___ trait
Continuous
Select features that are consistent with a disease having a genetic basis.
Different populations tend to have different disease frequencies. The disease has a characteristic age of onset. A human disorder may resemble a disorder known to have a genetic basis in animals. Identical twins share the disease more often than non-identical twins. The disease doesn't spread to individuals sharing similar environmental situations. There is a correlation between a human disease and a mutant gene or chromosomal alteration. A person with a disease is more likely to have genetic relatives with the disease than are people in the general population.
A continuous trait is a trait that
Does not fall into discrete categories
Preimplantation genetic diagnosis is a method of testing for genetic diseases in ______.
Embryos produced by in vitro fertilization
The pattern observed when individuals with the same genotype show slight differences in the resulting phenotype is called variable
Expressivity
A disease with a genetic origin in a mouse is unlikely to be an inherited disease in humans.
False
Dizygotic twins share a genetic disease more frequently than monozygotic twins.
False
A graph that presents phenotypic categories on the x-axis and the number of individuals that fall into a category on the y-axis is called a(n) ___ distribution.
Frequency
A dominant genetic disorder can be caused by a ______ mutation, where the product of an altered gene gains a new or abnormal function.
Gain-of-function
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(n) ___ - ___ - ___ mutation
Gain-of-function
When one gene can compensate for the loss of function of another gene, the phenomenon is called ___ - ___
Gene; redundancy
A population that contains more than one wild-type allele demonstrates______.
Genetic polymorphism
Tay-Sachs disease is inherited with an autosomal recessive allele that leads to a defect in the enzyme hexosaminidase A. When cells are collected from patients, cells with different genotypes exhibit different amounts of enzymatic activity. Rank the amount of enzymatic activity that would be detected in a biochemical assay on cells from patients of these genotypes, with the genotype producing the LEAST amount of enzymatic activity on top.
Homozygous recessive Heterozygous Homozygous dominant
Genetic testing is used to determine whether a(n) ______ has a disease-causing gene, while genetic screening is used to determine how frequently the gene is found in a(n)______.
Individual; population
Select the two fundamental laws of inheritance discovered by Mendel.
Law of independent assortment Law of segregation
A situation where a disease may be caused by mutations in two or more different genes is called ___
Locus heterogeneity
The disease hemophilia is caused by a deficiency in any one of three blood clotting factors. Two of these factors are encoded by genes on the X chromosome and the other clotting factor gene is located on an autosome. Since mutations in more than one gene can cause hemophilia, this represents ______.
Locus heterogeneity
Gene Redundancy
Loss of function in a single gene has no phenotypic effect, but loss of function of two genes has an effect
Manx cats have shortened tails due to the autosomal dominant allele M that affects spine formation. This allele is lethal in homozygotes. The autosomal recessive allele m leads to normal tail development. What is the genotype for a Manx cat?
Mm
Twins that are genetically identical to each other are called ___ twins.
Monozygotic
Which of the following characteristics of inheritance for hemophilia can be observed in the accompanying partial pedigree for the family of Queen Victoria and Prince Albert?
Mothers of affected males often have brothers with the disease Males are more likely to be affected than females
Simple Mendelian inheritance is a pattern observed when a human disorder is caused by ___
Mutation in a single gene
The growth of scurs, small horn-like growths on the faces of cattle, is inherited with the sex-influenced alleles Sc and sc. The trait is dominant in males and recessive in females. Suppose a male with no scurs is mated to a female with scurs. What is the pattern expected for their offspring?
None of the female offspring will have scurs but all of the male offspring will have scurs.
Fruit flies reared at various temperatures have different numbers of facets in their compound eyes. From high to low temperatures, the range is from 750 to greater than 1000 facets. This range of phenotypes is called the ______.
Norm of reaction
Which of the following are examples of quantitative traits
Number of bristles in Drosophila Speed of flight in birds Blood pressure in humans
One gene can compensate for the loss of function of another gene in cases where a duplicate gene or ___ has arisen over evolutionary time or when the function of another ____ can be increased to compensate for the missing protein product of the non-functional gene.
Paralog; protein
Codominance:
Pattern in which both alleles are expressed in the heterozygote without blanding
Incomplete dominance:
Pattern producing an intermediate phenotype in the heterozygote
The use of information about a patient's genotype in order to select a medication or therapy that is specifically suited to the patient is called
Personalized medicine
Quantitative traits tend to show a continuum of variation because they are usually ___ , meaning that they are controlled by multiple genes.
Polygenic
Embryos produced by in vitro fertilization can undergo genetic testing by ______.
Preimplantation genetic diagnosis
Personalized medicine can be used to select a ___
Preventative measure Therapy Medication
A disease causing agent made only of protein is called a ___
Prion
A trait that can be described numerically, such as height or weight, is defined as a(n) __ trait
Quantitative
The field of genetics that studies the inheritance of complex traits is called __ genetics
Quantitative
The length of an ear of corn is an example of a(n) ___ trait
Quantitative
Which field of genetics studies the inheritance of complex traits?
Quantitative genetics
The holandric gene on the mammalian Y chromosome that is essential for the development of male characteristics is called the ___ gene.
SRY
A complex trait is a trait that is influenced by
Several genes and the environment
For ______ inheritance, a given allele is dominant in one sex and recessive in the opposite sex.
Sex-influenced
Which is the inheritance pattern where an allele is dominant in one sex and recessive in the opposite sex?
Sex-influenced inheritance
Monozygotic twins ______.
Share 100% of the same alleles
Which of these is a common example of widespread genetic screening of newborns to identify certain disorders?
Test for excess phenylalanine indicating phenylketonuria (PKU)
The graph shows a hypothetical situation in which seed weight is controlled by three genes, each with light (w) and heavy (W) alleles, and a low environmental effect. If the environmental effect were high, ______.
The overlaps between genotypes increases
Approximately how many human diseases have a genetic basis?
Thousands
For summer squash, the dominant allele Y for gene 1 leads to yellow color while the recessive allele y leads to green color. Alleles of gene 2 can prevent color formation, with the dominant allele W leading to white squash while the recessive allele w does not interfere with color development. How many phenotypes would be observed among the offspring of the following cross: YyWw x YyWw?
Three
A trait that is influenced by many genes and is inherited quantitatively is defined as a(n) ___ trait
Threshold
X-linked:
Traits for which males inherit only one allele while females inherit two alleles
Genetic diseases often show a specific age of onset
True
Identical twins share a genetic disease more often than fraternal twins
True
In bread wheat, the color of the hull can be dark red, white, or various intermediate shades of red. Genetic analysis of this trait has demonstrated that it is controlled by
Two loci with additive effects on hull color
Polygenic inheritance is the transmission of a trait that is determined by
Two or more different genes
Complementation
Two parents that express the same or similar recessive phenotypes produce offspring with a wild-type phenotype
Greig cephalopolysyndactyly, a developmental disorder determined by a dominant allele, can affect the hands, feet, head and/or face. In one family, the mother had fused fingers on both hands while her daughter not only had fused fingers but also developed malformations in her toes and skull. This outcome is explained by______.
Variable expressivity
What is the inheritance pattern for a trait that is more likely to occur in females when it is lethal to males?
X-linked dominant
What is the inheritance pattern for a trait that more commonly affects males than females and which will occur in about 50% of the sons born to the unaffected daughter of an affected male?
X-linked recessive
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
Gene redundancy can be demonstrated by ______.
a gene duplication event where a paralog can carry out the function of a missing gene increase in function of one protein to compensate for the loss of function of a similar one
Lethal alleles:
alleles that have the potential to cause death
The abnormal form of a prion protein causes a neurodegenerative disease by ______.
catalyzing the conversion of the normal protein form to the abnormal form
A small portion of the fetal part of the placenta is removed to prepare a karyotype in the process called ______.
chorionic villus sampling
Parents can unknowingly pass on a dominant lethal allele for Huntington's disease to their offspring because the ______.
disease symptoms often do not appear until after the parent has had children
For a heterozygote, production of sufficient quantities of the functional protein by the ___ allele compensates for the production of a non-functional protein by the ___ allele.
dominant; recessive
Simple Mendelian inheritance:
follows a strict dominant/recessive relationship
A dominant genetic disorder can be caused by ___, a situation where one functional copy of an allele is not sufficient to produce a normal phenotype
haploinsufficiency
The growth of scurs, small horn-like growths on the faces of cattle, is inherited with the sex-influenced alleles Sc and sc. The trait is dominant in males and recessive in females. If an animal is heterozygous for these alleles, it will ______.
have scurs if it is male but have no scurs if it is female
When a preexisting allele is changed to a new version that no longer codes for a functional protein, the new allele is called a(n) ___ allele.
mutant
Amniocentesis is a procedure for ___
obtaining fetal cells in a sample from the fluid surrounding the fetus
In a certain type of plant, the stem is always at least 20 centimeters long. Two genes (A and B) with additive alleles influence the stem length. For these two genes, each dominant allele adds an additional 2 cm to the length of the stem; the recessive alleles do not change the length of the stem. If a plant with the genotype AaBb is allowed to self-cross, what proportion of the offspring will be 22 cm tall?
4/16
In cats, gene 1 specifies coat color; allele B leads to black coat while allele b leads to chocolate coat color. Gene 2 can inhibit coat color: genotype cc leads to an albino cat while at least one copy of allele C allows the full color from gene 1 to be expressed. From the cross bbCc x BbCc, what fraction of the offspring are expected to be albino?
4/16
For harebell plants, dominant alleles for two separate genes are needed to produce blue petal color. Suppose Gene 1 has alleles P and p and Gene 2 has alleles B and b. Only plants with at least one P allele and at least one B allele will have blue petals; all other genotypes lead to white petals. For the cross PpBb x PpBb, what fraction of the offspring are expected to have white petals?
7/16
A frequency distribution in which a trait varies in a symmetrical way around an average value is called an ___ distribution and produces an __ -shaped curve
Normal; bell
A frequency distribution is a graph that shows the
Number of individuals in various phenotypic categories
What tool do scientists use to follow a human pattern of inheritance from generation to generation?
Pedigree analysis
A trait that is expressed in only one sex and not seen in the opposite sex shows ______ inheritance.
Sex-limited
Males and females can inherit the same alleles, but the influence of hormones in the pathway to gender development leads to expression of these alleles in only one gender for ___ - ___ inheritance.
Sex-limited
When a human disease is caused by a mutation in a single gene, the pattern of inheritance is called ___ Mendelian inheritance.
Simple
Development of male characteristics requires the action of the ______ gene on the mammalian ______.
Sry; Y chromosome
When a human disease is caused by a mutation in a single gene, scientists follow the pattern of inheritance by analyzing charts called human ___
pedigree
Over 10 million Americans are heterozygous for the allele for Cystic Fibrosis, while about 30,000 people with homozygous recessive genotypes have the disease. Cystic Fibrosis results from a deficiency of a chloride-ion channel protein usually found in the membranes of cells lining the airway passages. Carriers produce sufficient amounts of the channel protein to avoid disease symptoms. The allele that prevents the disease in carriers is a(n) ___ allele and the one that causes the disease is a(n) ______ allele.
wild-type; mutant