USF Genetics Exam 2

Place the steps in QTL mapping in order, wth the first step at the top

1-Two inbred strains that differ in a quantitative trait are crossed together 2-F1 offspring are backcrossed to the parental strains 3-F2 offspring are assessed for their phenotype and molecular markers 4-Markers that are significantly associated with the quantitative trait are determined using computer programs and statistical analysis

In bread wheat, hull color is determined by two genes. For the first gene, the R1 allele produces red color, and the r1 allele produces white color. Similarly, the R2 allele results in red pigment, and the r2 allele does not. The effects of the red alleles are additive. In a self-cross of a strain with genotype R1r1R2r2, what phenotypic ratio is expected in the offspring?

1:4:6:4:1

How many genes control hull color in bread wheat?

2

Polygenic inheritance is the transmission of a trait that is determined by

2+ different genes

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?

3

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

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

Achondraplasia

A common form of dwarfism associated with a defect in the growth of long bones (Autosomal dominant fashion)

What is a normal distribution?

A frequency distribution that varies in a symmetrical way around an average value

Select the human disorders that are inherited in an autosomal recessive fashion.

Albinism Cystic Fibrosis Phenylketonuria PKU Sickle Cell Disease Tay-Sachs Disease

The following are types of Mendelian inheritance patterns involving two genes. Match each pattern to its correct definition. Epistasis:

Alleles of one gene mask the phenotypic effects of the alleles of a different gene

Aniridia

An absence of the iris of the eye, leasing to visual impairment and sometimes blindness (Autosomal dominant fashion)

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

The following are types of Mendelian inheritance patterns involving two genes. Match each pattern to its correct definition. Gene modified effects:

An allele of one gene modifies the phenotypic outcome of the alleles of a different gene

Sickle Cell Anemia

Anemia blockages in blood circulation (Autosomal Recessive)

Select human disorders inherited in autosomal dominant fashion.

Aniridia Achondroplasia Marfan Syndrome Familial Hypercholesterolemia Huntington Disease

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

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

In a QTL mapping experiment, the two strains that are selected for breeding must:

Differ with respect to a quantitative trait Be highly inbred

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.

Preimplantation genetic diagnosis is a method of testing for genetic diseases in ______.

Embryos produced by in vitro fertilization

True or False. A disease with a genetic origin in a mouse is unlikely to be an inherited disease in humans.

False

True or False. Dizygotic twins share a genetic disease more frequently than monozygotic twins.

False

Familial Hypercholesterolemia

Familial Hypercholesterolemia: Very high serum levels of low-density lipoprotein (LDL), a predisposing factor in heart disease (Autosomal dominant fashion)

Phenylketonuria (PKU)

Foul-smelling urine, neurological abnormalities, mental impairment; may be remedied by diet modification starting at birth (Autosomal Recessive)

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 graphs show the relationship between seed weight and genotype for a single gene that influences seed weight. Which statement describes the difference between the two graphs?

Graph A shows a low environmental effect on seed weight, whereas Graph B shows a high environmental effect

In the accompanying pedigree, a filled symbol indicates an individual with Huntington's disease while a clear symbol shows an unaffected individual. Considering the symbol for individual II-5, you conclude that her father, I-1 is ______ allele for Huntington's disease.

Heterozygous for the autosomal dominant

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

For which of the following genotypes would the effects of codominance be observed in the individual's phenotype?

IAIB

Albinism

Inability to synthesize melanin, resulting in white skin, hair, etc (Autosomal Recessive)

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

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

The following are types of Mendelian inheritance patterns involving two genes. Match each pattern to its correct definition. Gene Redundancy:

Loss of function in a single gene has no phenotypic effect, but loss of function of two genes has an effect

In QTL mapping, researchers try to identify the association between ___

Molecular markers and the phenotypes of quantitative traits

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

Huntington Disease

Neurodegeneration that occurs relatively late in life, usually in middle age (Autosomal dominant fashion)

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

Which of the following are examples of quantitative traits

Number of bristles in Drosophila Speed of flight in birds Blood pressure in humans

What tool do scientists use to follow a human pattern of inheritance from generation to generation?

Pedigree analysis

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

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

Tay-Sachs Disease TSD

Progressive neurodegeneration (Autosomal Recessive)

Monozygotic twins ______.

Share 100% of the same alleles

Development of male characteristics requires the action of the ______ gene on the mammalian ______.

Sry; Y chromosome

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 (Autosomal dominant fashion)

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

Identify observations that are consistent with a disease having a genetic basis.

The sleep disorder called narcolepsy has been related to an allele for a faulty neural receptor in dogs. Some humans also suffer from narcolepsy. A cancerous growth of immature nerve cells called neuroblastoma is associated with a deletion in a specific region of chromosome 11. Tay-Sachs disease can occur in 1/2500 births in a specific eastern European population while the frequency is 1/250,000 across Europe.

In the accompanying pedigree, a filled symbol indicates an individual with Huntington's disease while a clear symbol shows an unaffected individual. Which of the following characteristics of inheritance can be observed for this affected family?

The trait occurs in both males and females. An affected individual has at least one affected parent.

True or False. Genetic diseases often show a specific age of onset

True

True or False. 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

The following are types of Mendelian inheritance patterns involving two genes. Match each pattern to its correct definition. Complementation:

Two parents that express the same or similar recessive phenotypes produce offspring with a wild-type phenotype

Consider the children of II-6 and II-7 in the accompanying pedigree for a family affected by Tay-Sachs disease. What is one genotype that could have been produced by these two parents but was not observed?

Unaffected homozygote

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 Blank______.

Variable expressivity

Cystic Fibrosis

Water imbalance in tissues of the pancreas, intestine, sweat glands, and lungs due to impaired ion transport; leads to lung disease (Autosomal Recessive)

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

Consider the accompanying partial pedigree showing inheritance of hemophilia in the family of Queen Victoria and Prince Albert. If Xh is the allele for hemophilia and XH is the allele for normal blood clotting, which genotypes are MISSING among the children of Alice of Hesse and her husband, in the middle of the figure?

X^HX^H X^HY

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

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

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

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

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

Quantitative traits are ______.

controlled by multiple genes

A continuous trait is a trait that

does not fall into discrete categories

Brittle bone disease is caused by a mutation in a gene that codes for collagen fibers. The product of the mutant allele binds to normal collagen and disrupts proper fiber formation. The mutation can be described as a ______ mutation.

dominant-negative

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

The ability to prevent the symptoms of phenylketonuria by restricting the diets of patients who inherit the disease is an example of ___ effects on a phenotype.

environmental

The effect of phenylketonuria, an autosomal recessive disorder in which individuals are unable to metabolize phenylalanine, can be altered by a restricted diet with limited amounts of phenylalanine. This is an example of ______.

environmental effects on gene expression

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 situation where one functional copy of an allele is not sufficient to produce a normal phenotype

haploinsufficiency

The purpose of QTL mapping is to ______.

identify the chromosomal locations of genes that influence a quantitative trait

The chromosomal location of one or more genes that influence a quantitative trait is called a quantitative trait ___

locus

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

A frequency distribution is a graph that shows the

number of individuals in various phenotypic categories

Amniocentesis is a procedure for ___

obtaining fetal cells in a sample from the fluid surrounding the fetus

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

Quantitative traits tend to show a continuum of variation because they are usually ___ , meaning that they are controlled by multiple genes.

polygenic

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

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

When a human disease is caused by a mutation in a single gene, the pattern of inheritance is called ___ Mendelian inheritance.

simple

In QTL mapping, after two inbred strains are crossed with one another, the F1 offspring are backcrossed to both parental strains. Researchers next analyze the association ______.

the phenotype being studied and molecular markers on the chromosomes

Approximately how many human diseases have a genetic basis?

thousands

A trait that is influenced by many genes and is inherited quantitatively is defined as a(n) ___ trait

threshold

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