Deck 5: Beyond Mendels Laws

Question 1

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

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

Answer 1

C

Question 2

In Addam's family,there is 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 members who have inherited 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.

Answer 2

C

Question 3

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

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

Answer 3

C

Question 4

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." Farm animals often mate with their close relatives.So,three of the dams (mothers of the stillborns)are also Morris' daughters,and the fourth is his half-sister.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 alleles that Morris shares with his mates.
C)multiple lethal alleles that Morris shares with his mates.
D)co-dominance between two lethal alleles.

Question 5

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)recessive
B)pleiotropic
C)epistatic
D)dominant

Question 6

When the cystic fibrosis gene was discovered in 1989,only one mutation was described,and a diagnostic test was 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.Which of these is reflected by the given facts?

A)The presence of multiple alleles
B)The presence of pleiotropy
C)The presence of phenocopy
D)The presence of lethal alleles

Question 7

Different alleles that are both expressed in a heterozygote are

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

Question 8

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.

Question 9

Familial hypercholesterolemia illustrates incomplete dominance in humans because

A)heterozygotes have an intermediate number of low-density lipoprotein receptors on their liver cells.
B)homozygous wild type individuals have an intermediate number of low-density lipoprotein receptors on their liver cells.
C)heterozygotes have an intermediate number of low-density lipoprotein receptors on their kidney cells.
D)heterozygotes have the minimal number of high-density lipoprotein receptors on their liver cells.

Question 10

Clara has alkaptonuria.Her symptoms include back spasms,dark urine,arthritis,hearing loss,kidney stones,heart valve damage,and darkened ear tips.This condition is therefore

A)genetically heterogenic.
B)pleiotropic.
C)dominant.
D)epistatic.

Question 11

Epistasis and multiple alleles differ in that

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

Question 12

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 highly abnormal brains and spinal cords.Marbles has one copy of a dominant _____ allele.2-14-2013

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

Question 13

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 in this family is

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

Question 14

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.

Question 15

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

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

Question 16

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 environment and other genes.
D)he didn't count enough peas to draw conclusions.

Question 17

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.The most likely 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.

Question 18

Hairlessness in dogs is inherited from a single dominant allele.Inheriting two dominant alleles is lethal for an embryo.Penelope,a hairless dog mates with Arnold,a dog with hair.The probability Penelope will have hairless puppies is

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

Question 19

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.

Question 20

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 genotype is haploid because of meiosis.
D)having more than two alleles unbalances the chromosomes.

Question 21

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.

Question 22

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

Question 23

Mitochondrial disorders are probably very rare because

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

Question 24

Marfan syndrome can be caused by mutations in either of two genes involved in the disorder,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.

Question 25

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

Question 26

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

A) $\frac { A a } { B b }$
B) $\frac { A B } { a b }$
C) $\frac { A b } { a B }$
D) $\frac { B b } { B B }$

Question 27

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 the transmission of

A)two genes that have the same effect.
B)two genes on different chromosomes.
C)two genes on the same chromosome.
D)genotype and phenotype to an offspring.

Question 28

When researchers analyzed the remains of Tsar Nicholas II of Russia and his family,they found that the suspected Tsar and his living great-grandniece Xenia differed at nucleotide position 16169 in the mitochondrial DNA.Retesting the remains showed that for this site in the mitochondrial genome,the purported Tsar had thymine (T)in some samples and cytosine (C)in others.The most likely cause of this finding is
2-14-2013

A)the samples were too old.
B)incomplete dominance.
C)pleiotropy.
D)heteroplasmy.

Question 29

The mitochondrial genome consists of _____ genes.

A)12
B)37
C)250
D)370

Question 30

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

A)recombination.
B)repulsion.
C)cis.
D)trans.

Question 31

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%.

Question 32

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

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

Question 33

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.

Question 34

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.

Question 35

Two different alleles for the same mitochondrial gene is called

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

Question 36

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)lysosomes dismantle the mitochondria in muscle cells.

Question 37

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

A)Duchenne muscular dystrophy
B)Hemophilia
C)Leigh syndrome
D)Marfan syndrome

Question 38

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.

Question 39

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)is poorer at DNA repair.

Question 40

Genes that are situated close on a chromosome
2-14-2013

A)do not affect one another.
B)do not cross over.
C)do not assort independently.
D)produces Mendelian ratios for crosses tracking two or more genes.

Question 41

In the context of linkage,the higher the LOD score,the closer are two genes.

Question 42

Genetic heterogeneity refers to mutations in different genes that cause the same symptoms.

Question 43

A popular 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.

Question 44

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

Question 45

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.