Deck 5: Beyond Mendels Law

Question 1

The alleles that control which blood group antigens appear on the surfaces of red blood cells are

A) incompletely dominant.
B) variably expressed.
C) codominant.
D) semidominant.
E) phenocopies.

Answer 1

C

Question 2

Mendel's results and conclusions were accurate,but are seen differently today,because we now realize that

A) pea color is actually more complex than the human visual system can perceive.
B) pea inheritance is different from human inheritance.
C) single-gene traits are usually influenced by the environmental and other genes.
D) he didn't count enough peas to draw conclusions.
E) he didn't repeat his experiments enough times.

Answer 2

C

Question 3

Marbles is a Manx cat whose tail is so short that she appears not to have one.The genotype for short tail in Manx cats is heterozygous (Mm).Cats that are genotype mm have normal length tails,but cats that are genotype MM die before birth due to very abnormal brains and spinal cords.Marbles has one copy of a recessive _____ allele.

A) pleiotropic
B) penetrant
C) lethal
D) polymorphic
E) silent

Answer 3

C

Question 4

Epistasis and multiple alleles differ in that

A) epistasis is an interaction between two different chromosomes, and multiple alleles affect a single gene.
B) epistasis is an interaction between two genes, and multiple alleles are variants of the same gene.
C) epistasis affects males and multiple alleles occur in females.
D) epistasis only occurs in genes that have multiple alleles.
E) in epistasis one gene masks another, but one allele cannot mask the effect of another.

Question 5

Multiple alleles are common because

A) RNA is an informational molecule, and many sequences are possible for a particular gene.
B) proteins are informational molecules, and many amino acid sequences are possible.
C) a gene sequence can vary in different ways and still encode a functional protein.
D) there are many humans on the planet.
E) people have many children.

Question 6

Several members of the Fitzsimmons family have polydactyly,and they differ in their numbers of extra fingers and toes.Yet certain relatives who should have extra digits don't,such as Megan Fitzsimmons.She has two children,a son with two extra fingers and a daughter with an extra toe,and her father has an extra digit on each hand and foot.Polydactyly is

A) variably expressive and incompletely penetrant.
B) invariably expressive and completely penetrant.
C) pleiotropic and a phenocopy.
D) dominant and recessive.
E) incompletely dominant and completely recessive.

Question 7

Familial hypercholesterolemia illustrates incomplete dominance in humans because

A) heterozygotes have an intermediate number of LDL receptors on their liver cells.
B) homozygous wild type individuals have an intermediate number of LDL receptors on their liver cells.
C) homozygous mutant individuals have an intermediate number of LDL receptors on their liver cells.
D) heterozygotes have an intermediate number of LDL receptors on their kidney cells.
E) heterozygotes have the minimal number of HDL receptors on their liver cells.

Question 8

Some combinations of recessive alleles cause problems so severe that the fetus ceases to develop.Such lethal allele combinations appear to alter Mendelian ratios because

A) the allele is masked in heterozygotes.
B) carriers do not constitute a progeny class.
C) they do not show a 1:2:1 genotypic ratio.
D) homozygotes for the lethal allele do not appear as a progeny class.
E) homozygotes for the lethal allele pass it on to half their offspring.

Question 9

If allele T (long tongue)exhibits incomplete dominance over the recessive allele t (short tongue),a heterozygote for this gene would most likely have

A) a long tongue.
B) a short tongue.
C) a tongue that changes length.
D) a tongue of intermediate length.
E) a forked tongue.

Question 10

Zuzu is a white cat.She is genotype Ww for the "white masking gene" that reduces the number of melanocytes (pigment-containing cells).As a result,her body makes pigment,but it cannot get into the cells where it would color the fur.Zuzu's white masking gene is ______ to the melanin pigment gene because it prevents full expression of the pigment.

A) epigastric
B) episomic
C) epidermic
D) epistatic
E) epidural

Question 11

Hairlessness in dogs is inherited from a single dominant allele.Inheriting two dominant alleles is lethal for the embryo.Ralph and Penelope are both hairless dogs.What is the probability that Penelope will give birth to a hairy puppy?

A) 3/4
B) 1/3
C) 2/3
D) 1/4
E) 1/2

Question 12

Hairlessness in dogs is inherited from a single dominant allele.Inheriting two dominant alleles is lethal for the embryo.Penelope,a hairless dog,is wildly attracted to a hairy dog,Arnold.They mate.The probability that Arnold's sperm fertilizing Penelope's oocyte conceives a pup that would be hairless like Penelope is

A) 3/4.
B) 1/3.
C) 2/3.
D) 1/4.
E) 1/2.

Question 13

When the cystic fibrosis gene was discovered in 1989,only one mutation was described,and a diagnostic test developed to detect it.Over the years,as more mutations were discovered,they were added to the test panel.Today,most pregnant women are offered a CF test that detects 100 or so alleles,although more than 1600 mutations have been discovered.These facts illustrate

A) multiple alleles.
B) pleiotropy.
C) phenocopy.
D) independent assortment.
E) lethal alleles.

Question 14

The Addams family has an autosomal dominant condition in which webbing attaches the second toe to the third toe and the second toe is longer than the big toe.Only some of the Addams' who inherit the mutant allele have a second toe longer than the big toe.In addition,the extent of webbing varies.This phenotype is

A) both inherited and non-inherited.
B) dominant and recessive.
C) variably expressive and incompletely penetrant.
D) invariably expressive and completely penetrant.
E) genetically heterogeneic and a phenocopy.

Question 15

Can a woman with blood type A have a child with blood type O with a man who is AB?

A) Yes, because of codominance between the I^A and I^B alleles.
B) No, because a man with type AB blood could not contribute an i allele.
C) Yes, because of epistasis between the I and the H genes.
D) No, because the child's genotype must be ii.
E) Cannot tell from the phenotypes.

Question 16

Morris is a big,healthy bull.One spring,he fathers ten calves,but five of them are stillborn,their muscles very rigid in a phenotype called "contracture." Three of the dams (mothers of the stillborns)are also Morris' daughters,and the fourth is his half-sister.Farm animals have little chance for romance and so often mate with their close relatives.The large number of stillborns is most likely due to

A) recessive lethal alleles that occur as new mutations in the doomed offspring.
B) dominant lethal alleles that Morris shares with his mates.
C) multiple lethal alleles that Morris shares with his mates.
D) co-dominance between two lethal alleles.
E) allergy to the feed.

Question 17

An example of an "outside the gene" influence is

A) chemical groups that block or activate expression of certain genes.
B) the relationship of the sugars and phosphates of the DNA molecule to each other.
C) the genotype of one's partner.
D) age.
E) the number of vesicles in the cell.

Question 18

Brittany and Jarod have been trying to have a second child for 10 years.They have one healthy child,but Brittany has had four early spontaneous abortions.One explanation for the many pregnancy losses is that Brittany and Jarod

A) are not having sex frequently enough.
B) are each heterozygous for lethal alleles of the same gene.
C) are each homozygous for lethal alleles of the same gene.
D) have different alleles for all of their vital genes.
E) are having sex too often.

Question 19

A gene may have many alleles,but a person has only two alleles for a gene,because

A) having more than two alleles is always lethal.
B) a gene can be altered in many ways, but a person has only two copies of any gene.
C) a person is haploid because of meiosis.
D) having more than two alleles unbalances the chromosomes.
E) humans are not normally triploid.

Question 20

Different alleles that are both expressed in a heterozygote are

A) dominant.
B) codominant.
C) incompletely dominant.
D) homozygous dominant.
E) automatically dominant.

Question 21

Marfan syndrome can be caused by mutations in either of two genes,but mutations in one of the genes blocks activity of the other.This means that Marfan syndrome demonstrates

A) variable expressivity and complete penetrance.
B) an acquired phenotype.
C) late onset and early onset.
D) genetic heterogeneity and epistasis.
E) none of the above.

Question 22

LOD (logarithm of the odds)scores are used to indicate linkage between genes.A LOD score of __ or greater is a strong indicator of linkage.

A) 0.5
B) 1
C) 2
D) 3
E) 3.2 billion

Question 23

Pat Wright,whose story is told at the beginning of Chapter 5,has alkaptonuria.Her symptoms include back spasms,dark urine,arthritis,hearing loss,gallstones,heart valve damage,and darkened ear tips.This condition is therefore

A) genetically heterogenic.
B) pleiotropic.
C) dominant.
D) completely penetrant.
E) epistatic.

Question 24

Mitochondrial DNA differs from nuclear DNA in that it

A) crosses over within the same strand.
B) is inherited from the father only.
C) is present only in cells of the nervous and muscular systems.
D) it is poorer at DNA repair.
E) is present only in females.

Question 25

A trait caused by an environmental influence that appears to be inherited is

A) pleiotropic.
B) a phenocopy.
C) incompletely penetrant.
D) multigenic.
E) completely lethal.

Question 26

The mitochondrial genome consists of ___ genes.

A) 12
B) 37
C) 250
D) 370
E) 3,700.

Question 27

A mitochondrial trait passes from

A) mothers to all children.
B) fathers to daughters only.
C) mothers to daughters only.
D) fathers to sons only.
E) fathers to all children.

Question 28

Mitochondrial disorders tend to cause great fatigue because

A) nerve cells are filled with mitochondria.
B) muscle cells are normally filled with mitochondria.
C) affected cells do not use their mitochondrial DNA.
D) affected cells do not use their nuclear DNA.
E) lysosomes dismantle the mitochondria in muscle cells.

Question 29

In a heterozygote for two linked genes,both dominant alleles are on one chromosome and both recessive alleles are on the homologous chromosome.The genes are said to be in

A) recombination.
B) repulsion.
C) cis.
D) trans.
E) the mitochondria.

Question 30

Of nearly 200 forms of hereditary deafness,132 are autosomal recessive,64 autosomal dominant and 4 X-linked recessive.Hereditary deafness is therefore genetically

A) heterozygous.
B) heterogenic.
C) heterogametic.
D) heterosexual.
E) heterostatic.

Question 31

A,B and C are linked genes.Recombination between A and B is 3%; between A and C is 6%; and between B and C is 9%.What is the order of these genes on the chromosome?

A) A-B-C
B) A-C-B
C) B-C-A
D) B-A-C
E) Aa-Bb-Cc

Question 32

Mitochondrial disorders are probably very rare because

A) people have many mitochondria, so the healthy ones can substitute for the affected ones.
B) as oocytes formed, those with harmful mitochondrial mutations did not have sufficient energy to survive.
C) they are difficult to diagnose because most physicians have forgotten what mitochondria are.
D) they do not produce symptoms.
E) they are not inherited from the father.

Question 33

Geneticists construct linkage maps of chromosomes by

A) correlating a phenotype to an observable chromosomal abnormality.
B) determining the number of crossovers between genes on different chromosomes.
C) calculating the percent recombination between two genes on the same chromosome.
D) observing the number of genes on a chromosome.
E) observing environmental factors that cause a condition.

Question 34

Which of the following is an illness caused by a mutation in mitochondrial DNA?

A) cystic fibrosis
B) Duchenne muscular dystrophy
C) hemophilia
D) Leber optic atrophy
E) Marfan syndrome

Question 35

A and B are linked genes.In a study of 100 offspring,94 had parental genotypes for A and B,while 6 were recombinants.A and B are __ map units apart.

A) 4
B) 6
C) 9.4
D) 94
E) an unknown number of

Question 36

In common English,"linkage" refers to one event that tends to occur when another does.In genetics,linkage has a precise meaning.It refers to

A) two genes that have the same effect.
B) two genes that have opposite effects.
C) two genes on different chromosomes.
D) two genes on the same chromosome.
E) genotype and phenotype.

Question 37

Two different alleles for the same mitochondrial gene is called

A) heterosexuality.
B) heterogamy.
C) heteroplasmy.
D) heterogeneity.
E) heterozygosity.

Question 38

A and B are linked genes.A heterozygote for both genes would show which configuration if the genes are in cis?

A) $\frac { A b } { a b }$
B) $\frac { A a } { B b }$
C) $\frac { A B } { a b }$
D) $\frac { A b } { a B }$
E) none of these choices

Question 39

In many species,lens crystalline protein aggregates in the eyes to form lenses,yet in other cell types,functions as an enzyme.The gene that encodes this protein is therefore

A) pleiotropic.
B) incompletely penetrant.
C) eclectic.
D) mutant.
E) variably expressed.

Question 40

A man who has normal hearing and has a recessive deafness allele on chromosome 17 marries a woman who also has normal hearing and also has a recessive deafness allele,but this allele is on chromosome 3.The probability that their children will be deaf due to either of these mutated genes is closest to

A) 100%.
B) 50%.
C) 25%.
D) 0%.
E) 200%.

Question 41

Types of genetic markers include

A) places in the genome where a base varies among individuals in a population.
B) places in the genome where all people have identical base sequences.
C) the types of mRNAs in a cell.
D) the proteins produced in a cell.
E) how many centromeres chromosomes have in a population.

Question 42

A widely-used research technique used to associate patterns of genetic variation with phenotypes that is based on the concept of linkage,but considering all of the chromosomes at once,is

A) gene expression profiling.
B) genome sequencing.
C) genome-wide association studies.
D) assisted reproductive technologies.
E) genetically modified organisms.