Biology Exam 3
predict the outcome of a genetic cross.
A Punnett square is used to
pedigree
A ________ is a chart that shows genetic relationships within a family over several generations.
heterozygous
A carrier is an individual with a ________ genotype who does not express the recessive trait but can pass it along to offspring.
incomplete dominance
A chestnut-colored horse is mated with a cremello (cream-colored) horse. Over a 10-year period, all of their offspring are palominos. This pattern of inheritance is best explained by
XAXa
A female who is a carrier of the sex-linked gene A has the genotype
A translocation between chromosome 14 and chromosome 15.
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?
Half of her eggs will contain an extra copy of the x chromosome.
A karyotype of an individual with mild mental retardation shows three copies of the X chromosome. If this individual decides to have children, how is her chromosomal abnormality likely to affect her offspring?
inversion
A karyotype shows a chromosomal abnormality that does not change the length of any of the chromosomes. Which abnormality is indicated?
50 percent
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?
A piece of a Y chromosome has become attached to one of the X chromosomes.
A person is genetically XX and develops as a male. How can this be explained?
2
A thoroughbred racehorse could have at most ________ alleles of the same gene.
50 percent will be carriers.
Among children with parents who are both carriers of Tay-Sachs, an autosomal recessive disorder, chances are that
sex-linked.
An allele that appears more frequently in males is most likely
These diseases usually take effect later in life after people have had children.
Autosomal dominant diseases are exhibited by anyone who carries at least one dominant allele for that gene. How is it that dominant lethal genes, such as the one that causes Huntington disease, can persist in a population?
No, because the Y chromosome contains the gene that makes an embryo male.
Because an individual with an XX genotype is a female, is an individual with an XO (no second sex chromosome) a male?
Fifty percent of the children could be carriers of the disease.
Both members of a couple are carriers for a recessive disease allele. If the couple has four children, which of the following statements must be true?
autosomes
Chromosomes that are NOT involved in determining gender are known as
25 percent
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?
Genes in the section that was inverted could lose normal function.
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?
gray
Feather color in a certain species of bird is controlled by a pair of alleles that exhibit incomplete dominance. If birds that are homozygous for one allele are black and birds that are homozygous for the other allele are white, then heterozygous birds would be
23
Humans have ________ pairs of homologous chromosomes.
Half of the sons will be affected.
If a father is affected by an X-linked condition and the mother is a carrier, what is the probability of their children being affected?
AA and Aa
If a genetic disorder is caused by a dominant allele, individuals with which of the following genotypes would be affected by the disorder?
The recessive allele is carried in the genome of heterozygotes, who do not suffer from the disease.
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?
autosomal dominant
If the male in generation II was affected, what would the pattern of inheritance most likely be?
Codominant
If two different alleles for the same trait have an equal effect on the phenotype, the alleles are
they are both considered genetic carriers for the disease.
If two parents are heterozygous for an autosomal recessive disease,
The sperm cell would contain only one allele for a given gene; the skin cell would contain two alleles.
If you compare a sperm cell in a human to a skin cell from the same individual, which of the following differences would you expect to find?
the F1 generation.
In Mendel's controlled mating experiments the individuals produced by crossing two true-breeding parents are referred to as
neither supports nor disproves Mendel's law of independent assortment.
In a genetic cross of Gg with Gg guinea pigs, none of the four offspring were gg. This
Three copies of chromosome 22
In a karyotype of a male, which of the following would indicate an abnormality?
tend to be expressed more in males than in females.
In humans, X-linked genetic diseases
SRY gene.
In humans, the "master sex switch" that determines whether an embryo will become a male is the
gametes that may be produced by each parent involved in the cross.
In the Punnett square shown below, the lettered circles on the top and left of the square (indicated by the arrows) represent the
healthy female.
In the pedigree shown, the individual indicated represents a(n)
The environment affects the phenotype.
In which of the following situations would it become nearly impossible to predict the phenotype of an individual with a known genotype?
Three young boys who are first cousins show symptoms of a neurological disorder
In which of the following situations would looking at a pedigree be most useful?
garden peas
Mendel used ________ as his research organism to study patterns of genetic inheritance.
meiosis
Mendel's laws of segregation and independent assortment both have their biological basis in events that take place during
traits are passed from one generation to the next.
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
controlled by more than one gene.
Most human genetic characters are
recessive mutations of genes located on autosomes.
Most inherited human disorders are the result of
recessive
Most inherited human genetic disorders are inherited as ________ alleles.
two; homologous
On chromosomes within an individual, there are ________ alleles for a given gene found on ________ chromosomes.
the addition of an extra autosomal chromosome.
One chromosomal abnormality that is usually fatal is
pleiotropy
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
50%
Sickle-cell disease is an inherited chronic blood disease caused by an autosomal recessive allele. Suppose a man who is homozygous recessive for the sickle-cell gene fathers a child by a woman who is a carrier for sickle-cell. What are the chances their children will exhibit the disease?
750
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?
both of Mendel's laws of genetic inheritance
The 9:3:3:1 ratio of phenotypes that occurs in the F2 generation of the cross shown can be explained using
found as a pair in females.
The X chromosome in humans is
Alleles are used to produce proteins that function best in specific temperature ranges.
The coat color in a Siamese cat is determined by a temperature-sensitive allele that allows the brownish pigment melanin to be produced in extremities of the body. What might explain this phenomenon?
This is an example of epistasis.
The figure shown indicates two Labrador retrievers that are both homozygous recessive for fur color. Why is one dog brown and the other is yellow?
these diseases are most likely affected by environmental factors in addition to genes.
The figure shown indicates two diseases with genetic links that are common in industrialized nations. The fact that both are about 80-90% avoidable indicates that
sperm
The gender of a human child is determined by the
The trait will be expressed in 100 percent of the male offspring.
The gene for a certain sex-linked trait is found only on the Y chromosome. If the male parent carries this gene, which of the following statements about the inheritance of that trait is true?
recessive and autosomal.
The genetic disorder followed through the pedigree shown is
male
The karyotype shown is from a(n)
Cross the plant to a plant with green leaves.
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?
pleiotropy
The observation that individuals afflicted with albinism also always have vision problems is an example of
autosomal
The parents in the figure shown are carriers of a genetic disorder. Based on the Punnett square, the allele that causes the disorder must be
heterozygous
The pedigree shown diagrams an X-linked gene. The individual indicated is ________ for the gene.
the skeletal traits are related in the overall function of the dog.
The pleiotropy that occurs when a single gene controls multiple skeletal traits in dogs, such as leg bone length and skull size, may be explained because
hydrogen
The two strands of a DNA molecule are held together by ________ bonds between their base pairs.
duplication
Two copies of the same gene on a single chromosome would indicate a(n) ________ had occurred.
epistasis
Two genes control fur color in Labrador retrievers. The first gene determines whether the pigment to be deposited in the hairs will be black or brown. The second gene determines whether the pigments are put into the dog's hairs at all. A dog homozygous for the recessive allele of this second gene will be yellow because no pigment is deposited in its hairs. This is an example of
The offspring are either 100 percent homozygotes or 100 percent heterozygotes.
Two organisms that are true-breeding for a certain genetic characteristic are mated and their offspring analyzed. Which of the following statements about this situation is true?
epistasis
We need a hammer to pound nails into a board. Even if we have the nails, we cannot pound them without first getting hold of a hammer. This is similar to the genetic relationship known as
None of the affected individuals have unaffected parents.
What information in a pedigree would indicate a condition is likely dominant?
whether the individual carries genetic mutation.
What information is NOT visible in a karyotype?
two
What is the smallest number of traits that are needed to test Mendel's law of independent assortment?
knowledge of the location of the alleles for flower color
When Mendel proposed the law of segregation, which of the following pieces of information did he NOT have?
BbCCdd
Which of the following choices represents the genotype of an individual diploid organism?
Some plants always produced offspring with flowers that were the same color as the parent plant's flowers.
Which of the following did Gregor Mendel notice in garden peas?
dihybrid crosses between pea plants
Which of the following did Mendel use to help him form the law of independent assortment?
the alleles in a mouse that control hair color
Which of the following does NOT represent a phenotype?
Two alleles of a gene separate during meiosis and end up in different gametes.
Which of the following expresses Mendel's law of segregation?
a mutation in a skin cell
Which of the following genetic changes would NOT be passed from parent to child?
XY
Which of the following genotypes represents a human male?
percentage of all children likely to be affected by the disorder
Which of the following information is available in a Punnett square showing the inheritance pattern for an autosomal recessive disorder?
the separation of alleles for two different genes during meiosis
Which of the following is the mechanism described by Mendel that results in a new combination of alleles in a pea plant seed?
Mutations will affect the genotype, which may affect the phenotype.
Which of the following is true for mutations?
Their sons have a 50 percent chance of having the disorder.
Which of the following is true of the genetic cross shown in the figure?
There are two genes to control two separate steps in a pathway.
Which of the following might explain how two separate genes control a single trait?
All of her eggs will contain one allele or the other, but not both alleles.
Which of the following must be true for a woman who is heterozygous for a given gene?
FGH, FgH, fGH, fgH
Which of the following represents all of the possible gametes that can be formed by an individual with the genetic makeup FfGgHH?
They contain the same genes in the same locations.
Which of the following statements about homologous chromosomes is true?
Environmental conditions under which plants are grown can cause variations in phenotypes.
Which of the following statements explains how genetically identical plant clones can exhibit dramatic phenotypic variation?
A genotype is always expressed in the phenotype.
Which of the following statements is NOT true?
Two organisms with the same genotype are homozygous.
Which of the following statements is NOT true?
The separation of alleles for one gene does not affect the separation of alleles for other genes
Which of the following statements is a basic summary of one of Mendel's laws?
They correctly explain how genes are inherited.
Which of the following statements is true of Mendel's laws?
In sexually reproducing species, each cell contains a single copy of every gene.
Which of the following statements regarding genes is NOT true?
Most affected individuals are males.
Which of the following statements would indicate a pedigree that shows the inheritance pattern of a recessive X-linked disease?
A chromosomal alteration has occurred.
Which of the following would explain two chromosomes in an individual cell that contain some, but not all, of the same genes at the same loci?
Females must receive two copies of the recessive allele to exhibit the disorder, but males need only one copy.
Why are X-linked recessive genetic disorders more commonly seen in males?
The likelihood of seeing a clear pattern is higher with a larger data set.
Why did Mendel analyze thousands of plants while conducting his research?
No; knowing the genotype will indicate the phenotype.
Would it be necessary to have both the genotype and phenotype for an organism if you are attempting to predict the inheritance pattern for a trait, such as hair color, in offpsring?
An allele is
a version of a gene.
RRYY x rryy
in a particular plant, two genes control leaf shape and color. Round leaves (R) are dominant to jagged leaves (r). Yellow fruits (Y) are dominant to white fruits (y). A true-breeding round-leaved, yellow-fruited plant is mated with a jagged-leaved, white-fruited plant. What are the genotypes of the plants involved in this cross?
