Genetics - Chapter 4

A child with one parent who is heterozygous for an autosomal dominant trait and the other parent who is homozygous recessive for that trait (unaffected), has a(n) ______ chance of being affected.

50%

A blood test cannot determine if a person is a carrier of Tay-Sachs disease because the mutant allele is undetectable.

False

A pedigree is always able to provide enough information to rule out all but one possible pattern of inheritance.

False

All males are homozygous for Y-linked traits.

False

An X-linked dominant trait is passed to half the children of a heterozygous affected mother, but sons and daughters are not equally affected.

False

For two parents who are heterozygous for an autosomal recessive trait, the risk of having an unaffected child is 25% and the risk of having an affected child is 75%.

False

Human traits are controlled only by the genetic material found in the 46 chromosomes.

False

Huntington disease is an autosomal dominant condition; therefore, it is impossible for affected individuals to have unaffected offspring.

False

Males always pass an X chromosome to their sons and a Y chromosome to their daughters, while females pass an X chromosome to all of their offspring.

False

Males who are color-blind, a condition carried on the X chromosome, are always homozygous for this trait.

False

Mitochondrial genes are passed from the father to all of his children.

False

Most of those affected with an autosomal dominant genetic disorder are homozygous for that trait.

False

Only one parent needs to transmit a recessive mutant allele for a child to be affected.

False

Penetrance and expressivity refer to genotypic variations in expression of inherited traits.

False

A pedigree analysis is constructed for many reasons, including determining the risk of passing a certain genetic trait onto one's offspring.

True

Abraham Lincoln's son, Robert, showed no signs of Marfan syndrome.

True

Because affected females may be either heterozygous or homozygous for an X-linked dominant trait, twice as many females are typically affected as males.

True

Duchenne muscular dystrophy and Becker's muscular dystrophy are caused by different mutations in the same X-linked gene.

True

For autosomal dominant traits, heterozygous affected males can pass the trait to both daughters and sons.

True

If a pedigree analysis suggests that an autosomal or X-linked inheritance pattern is equally likely, then additional genetic testing is needed to identify the pattern of inheritance.

True

In individuals affected by cystic fibrosis, a genetic mutation leads to an absent or nonfunctional protein.

True

In non-Mendelian inheritance, affected females pass mitochondrial genes to all of their offspring.

True

Inheritance of common recessive alleles can sometimes resemble dominant inheritance patterns in pedigree analyses.

True

It is possible to perform genetic testing on a deceased individual as long as DNA is available.

True

Males affected with a maternal mitochondrial genetic disorder cannot transmit the mutation to any of their children.

True

Males never give an X chromosome to any of their sons.

True

Males transmit X-linked traits to all of their daughters but none of their sons.

True

Mitochondria convert food energy into ATP.

True

Mitochondria evolved from free-living prokaryotes adapted to life inside primitive eukaryotes.

True

Most affected individuals with rare traits have phenotypically normal but heterozygous parents.

True

OMIM, an online catalog of human genetic traits, is accessible to everyone.

True

Phenotypic variation can occur in traits controlled by the same allele.

True

Recessive traits are only expressed in homozygous individuals.

True

The frequency of heterozygotes for cystic fibrosis shows ethnic variations.

True

There is an online catalog with information about genes, genetic traits, chromosome location, DNA sequence and protein sequence that is available to the public online.

True

When two parents, each of whom is affected by an autosomal recessive condition, have children, each of the offspring will be similarly affected.

True

Y-linked traits are only expressed in males.

True

X-linked

X-linked

Every individual affected with an autosomal dominant condition has at least one affected parent, unless:

a mutation is invlolved

Suppose a pedigree analysis reveals that a child has inherited the genetic condition thalassemia from her parents, both of whom are unaffected. This information suggests ________. a. a recessive pattern of inheritance b. the parents must be homozygous for thalassemia c. the parents must be consanguineous d. the parents had a 100% chance of having a child with this condition e. a dominant pattern of inheritance

a. a recessive pattern of inheritance

Suppose a pedigree analysis reveals that a genetic condition is present in males and females equally. This information suggests a(n) ________ pattern of inheritance. a. autosomal b. X-linked c. Y-linked d. sex-linked e. dominant

a. autosomal

A male who is affected by red-green color blindness must ________. a. be hemizyous for the color blindness trait b. have defects in the rod light receptor cells of his retina c. have parents who are both affected by color blindness d. pass this trait onto his sons e. be homozygous for the color blindness trait

a. be hemizyous for the color blindness trait

A pedigree analysis ________. a. is useful for predicting the risk of passing a genetic condition onto one's offspring b. cannot be use for predicting the risk of adults developing symptoms of a genetic condition c. can reveal autosomal but not sex-linked traits d. is useful for genetic studies due to the large sizes of typical families e. always reveals the inheritance pattern of a genetic trait

a. is useful for predicting the risk of passing a genetic condition onto one's offspring

penetrance

an aspect of phenotypic variation - this is the probability that a disease phenotype will be present when the disease genotype is present

expressivity

an aspect of phenotypic variation - this refers to the range of phenotypes resulting from a given genotype

HD

an autosomal dominant disorder associated with progressive neural degeneration and dementia

camptodactyly

an autosomal dominant disorder causing an immobile digit

sickle cell anemia

an often fatal, recessive genetic disorder associated with abnormal hemoglobin, misshapen blood cells and the blockage of blood vessels

cystic fibrosis

an often fatal, recessive genetic disorder associated with abnormal secretions of the exocrine glands

The gene associated with Marfan Syndrome has a high mutation rate, meaning that affected individuals can _______

appear in families with no previous history of the trait

If DNA testing reveals that Abraham Lincoln carried the gene for Marfan syndrome, ________. a. it would explain why he did not survive the assassination b. his descendants who inherited the gene will either have, or be carriers of, Marfan syndrome c. it would explain why only one of his children lived until adulthood d. it would explain his short stature e. we will understand why he made certain decisions as U.S. President

b. his descendants who inherited the gene will either have, or be carriers of, Marfan syndrome

Mutations in mitochondrial genes affect primarily muscles and nervous tissue because ________. a. these tissues require the least energy b. these tissues require the most energy c. only these tissues require energy d. only cells in these tissues have mitochondria e. mitochondria are only present in females

b. these tissues require the most energy

A male affected by hemophilia, an X-linked recessive disorder, has a ________ chance of passing the trait onto his sons, and a ________ chance of passing the trait onto his daughters. a. 50%; 50% b. 0%; 0% c. 0%; 100% d. 25%; 75% e. 100%; 0%

c. 0%; 100%

Suppose a woman with the mitochondrial disorder progressive external ophthalmoplegia has children with a man who does not have the condition. What are the chances that their children will have progressive external ophthalmoplegia? a. All of the girls but none of the boys will have progressive external ophthalmoplegia. b. All of the boys but none of the girls will have progressive external ophthalmoplegia. c. All of their children will have progressive external ophthalmoplegia. d. None of the children will have progressive external ophthalmoplegia. e. Fifty percent of the boys and fifty percent of the girls will have progressive external ophthalmoplegia.

c. All of their children will have progressive external ophthalmoplegia.

Mitochondria evolved from ________. a. the transfer of genes from prokarytoes to eukaryotes b. free-living plants c. free-living prokaryotes d. the transfer of genes from eukaryotes to prokaryotes e. free-living eukaryotes

c. free-living prokaryotes

Testis determining factor (TDF) is ________. a. responsible for female sexual development b. never expressed in males c. passed from father to son d. an X-linked gene e. only expressed in the homozygous condition

c. passed from father to son

Erythropoietic protoporphyria is an autosomal recessive condition, in which affected individuals have excessive cutaneous photosensitivity. This condition, however, sometimes exhibits a pseudodominant inheritance pattern, meaning that ________. a. the allele is X-linked b. the allele is Y-linked c. the recessive allele is common d. the allele switches from recessive to dominant e. this condition cannot be cured

c. the recessive allele is common

What information is available via the OMIM and Entrez databases? a. Information on autosomal, but not sex-linked, genes b. Information on sex-linked, but not autosomal, genes c. Data on the evolution of mitochondria and eukaryotes d. Data on genes, chromosomal location, and DNA and protein sequence e. Genetics program requirements at Johns Hopkins University

d. Data on genes, chromosomal location, and DNA and protein sequence

Polydactyly is an autosomal dominant trait in which affected individuals have more than five fingers and/or toes. If a pedigree analysis indicates that an individual affected by polydactyly has two unaffected parents, then this suggests that polydactyly exhibits ________. a. increased expressivity b. autosomal recessive inheritance c. reduced expressivity d. reduced penetrance e. increased penetrance

d. reduced penetrance

Because Marfan syndrome is an autosomal dominant disorder ________. a. both parents must have Marfan syndrome in order to have a child with the condition b. affected individuals are typically short in stature and have unusually strong connective tissue c. affected individuals must inherit recessive alleles from both parents to express the condition d. all affected individuals must be homozygous dominant e. at least one parent must have Marfan syndrome in order to have a child with the condition

e. at least one parent must have Marfan syndrome in order to have a child with the condition

Cystic fibrosis is characterized by ________. a. normal lung function, but abnormal pancreatic function b. insufficient mucus production c. autosomal dominant inheritance d. abnormal lung function, but normal pancreatic function e. excess mucus production

e. excess mucus production

autosomal

genetic traits found on chromosomes 1-22

heterozygous

organisms carrying non-identical alleles for a single gene

homozygous

organisms carrying two identical alleles of a gene

consanguinity

parents who are related to each other (typically first cousins)

hemizygous

refers to X-linked genes in males who have only one X chromosome and therefore only one member of a chromosome pair

For autosomal dominant traits, the numbers of affected females and males are ______

roughly equal

y-linked

the pattern of inheritance resulting from genes on the male sex chromosome

Because most individuals affected with autosomal dominant disorders are heterozygotes, two affected individuals can have_______

unaffected children