BIO Exam 3

Consider a gene with two alleles that show complete dominance. When two heterozygotes for this gene breed, they have a 25 percent chance of producing a homozygous recessive offspring. The next time these two individuals breed, what are the chances that they will once again have a homozygous recessive progeny?

. 25 percent

The source of the gene needed for gene therapy treatment of the sex-linked adrenoleukodystrophy (ALD) would be a(n) ________ chromosome with a ________ copy of the ALD gene.

.X; functional

The genotype of a female carrier of the X-linked recessive gene for Duchene muscular dystrophy is represented as

.XDXd

Mendel's manuscript discussing his pea-breeding results is considered one of the two most important scientific papers of the nineteenth century because he was the first to explain how

.traits are passed from one generation to the next.

The gene for a certain sex-linked trait is found only on the Y chromosome. If the male parent has this gene, the trait will be expressed in

100 percent of the male offspring.

A pea plant that is heterozygous for the flower color gene makes gametes. What is the probability that a specific gamete contains the recessive allele for flower color?

50 percent

Among children with parents who are both carriers of Tay-Sachs, an autosomal recessive disorder, chances are that

50 percent will be carriers.

Suppose D were dominant and d were recessive, and you could label the D allele in the P generation with a radioactive substance that could be inherited over several generations. You create hybrids by mating your radioactive DD individuals to dd individuals. Finally, you cross two F1 individuals (with the Dd genotype). In 1,000 offspring, how many would you predict would be radioactive?

750

A female who is a carrier of the sex-linked gene A has the genotype

AA XX

If a father is affected by an X-linked recessive condition and the mother is a carrier, what is the probability of their children being affected?

All sons will be affected. xx

Which of the following statements explains how genetically identical plant clones can exhibit dramatic phenotypic variation?

Environmental conditions under which plants are grown can cause variations in phenotypes.

Which of the following statements regarding genes is NOT true?

Genes are found as single copies in cells other than sperm or egg.

During cell division a piece of a chromosome breaks off and reattaches to the same chromosome, but the piece is now in reverse order. How would this abnormality affect the chromosome?

Genes in the section that was inverted could lose normal function.

Based on Mendelian inheritance, would it be necessary to have both the genotype and phenotype for an organism when attempting to predict the inheritance pattern for a trait, such as hair color, in offspring?

No; knowing the genotype will indicate the phenotype.

In humans, the "master sex switch" that determines whether an embryo will become a male is the

SRY gene.

If a recessive allele causes a fatal disease that kills the affected individual before he or she can reproduce, why doesn't that allele quickly become extinct in the population?

The recessive allele is carried in the genome of heterozygotes, who do not suffer from the disease

Which of the following statements is a basic summary of one of Mendel's laws?

The separation of alleles for one gene does not affect the separation of alleles for other genes

When comparing a human sperm cell to a skin cell from the same individual, what differences would be expected?

The sperm cell would contain only one allele for a given gene; the skin cell would contain two alleles.

Which of the following is true of the genetic cross shown in the figure below?

Their sons have a 50 percent chance of having the disorder.

Which of the following statements about homologous chromosomes is true?

They contain the same genes in the same locations.

In which of the following situations would looking at a pedigree be MOST useful?

Three young boys who are first cousins show symptoms of a neurological disorder.

Which of the following expresses Mendel's law of segregation?

Two alleles of a gene separate during meiosis and end up in different gametes.

Which of the following statements is NOT true?

Two organisms with the same phenotype may have different genotypes. xx

The figure shown below illustrates

a dihybrid cross. xx

A karyotype from an adult male indicates a chromosomal abnormality, which does not affect his health. Which of the following abnormalities is MOST likely seen?

a translocation between chromosome 14 and chromosome 15

If the male in generation II of the figure below was affected, what would the pattern of inheritance MOST likely be?

autosomal recessive xx

The 9:3:3:1 ratio of phenotypes that occurs in the F2 generation of the cross shown below can be explained using

both the laws of segregation and independent assortment.

A hammer is needed to pound nails into a board. Even if one has the nails, they cannot be used without first getting ahold of a hammer. This is similar to the genetic relationship known as

codominance. xx

Most human genetic characters are

controlled by more than one gene.

The leaf color of a certain plant is controlled by one gene. For that gene, the allele G = orange and g = green. You have a plant with orange leaves but do not know whether that plant's genotype is GG or Gg. Which of the following would help you determine the plant's genotype?

cross the plant to a plant with green leaves

Two copies of the same gene on a single chromosome would indicate a(n) ________ had occurred

duplication

It would become nearly impossible to predict the phenotype of an individual with a known genotype if the

environment affects the phenotype.

The X chromosome in humans is

found as a pair in females.

In the Punnett square shown below, the lettered circles on the top and left of the square (indicated by the arrows) represent the

gametes that may be produced by each parent involved in the cross

Mendel used ________ as his research organism to study patterns of genetic inheritance.

garden peas

What information is NOT visible in a karyotype?

genetic mutations

A chestnut-colored (red-colored) horse is mated with a cremello (cream-colored) horse. Over a 10-year period, all of their offspring are palominos (gold-colored). This pattern of inheritance is best explained by

incomplete dominance.

Phenylketonuria (PKU) is a metabolism disorder that can result in mental retardation if untreated. This recessive disorder is caused by a defective gene located on chromosome twelve. The most reliable source for the functional gene needed for gene therapy would be a(n)

individual that is homozygous dominant for the functional gene.

The karyotype shown below is from a(n)

male.

In a genetic cross of Gg with Gg guinea pigs, none of the four offspring were gg. This

neither supports nor disproves Mendel's law of independent assortmen

One of the first medical tests a newborn receives determines if the child has phenylketonuria (PKU). PKU is the result of a mutation in a single gene that causes mental retardation and a host of other phenotypes (light hair and skin color, eczema, and a "mousy" smell). By detecting PKU early, doctors are able to reduce the effect of this condition with a modified diet. PKU is an example of

pleiotropy.

If two different alleles for the same trait have an equal effect on the phenotype, the alleles are

recessive. xx

Which of the following genetic changes would NOT be passed from parent to child?

the addition of a chromosome in an egg cell xx

One chromosomal abnormality that is usually fatal is

the addition of an extra autosomal chromosome.

Which of the following does NOT represent a phenotype?

the alleles in a mouse that control hair color

Which of the following information is available in a Punnett square showing the inheritance pattern for an autosomal recessive disorder?

the percentage of all children likely to be affected by the disorder

If two parents are heterozygous for an autosomal recessive disease,

they are both considered genetic carriers for the disease.

In a karyotype of a male, which of the following would indicate an abnormality?

three copies of chromosome 22

What is the smallest number of traits that are needed to test Mendel's law of independent assortment?

two

On chromosomes within an individual, there are ________ alleles for a given gene found on ________ chromosomes.

two; homologous