Genetics Exam 1
In guinea pigs, the allele for dark color (B) is dominant to the allele for light color (b). In a cross between two heterozygous organisms, the chance for producing a light colored offspring is
1/4
The combined length of all of the DNA present in a single cell of your body is approximately
2 meters
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%
From the cross Aa x Aa, the probability of producing a homozygous dominant offspring is _____
25%
The DNA double helix is equivalent to the ____
2nm fiber
In the DNA double helix, if 20% of the bases are A, then G would make up what percent?
30%
The haploid number of an organism is 16. The number of chromosomes in its body cells, if they have one trisomy, is
33
Sickle-cell anemia 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? (Note: A Punnett square may be useful.)
50%
A pea plant that is heterozygous for the flower color gene makes gametes. What is the probability that a specific gamete contains the recessive white allele for flower color?
50% FEEDBACK: Heterozygotes can make two kinds of gametes, each with equal probability.
A woman with blood type O has a child with blood type O. The father could have the blood type
A or B
Assuming your blood type is AB, you can donate blood to people with type ________ blood and can receive blood from people with type ________.
AB, O
Consider the X-linked dominant disorder congenital generalized hypertrichosis (CGH). What can you determine about the potential offspring of a couple in which the father has CGH and the mother does NOT?
All daughters will have the disorder.
Which of the following statements regarding crossing-over is FALSE? Crossing-over disrupts the linkage between genes on the same chromosome. Crossing-over disrupts the linkage between genes on different chromosomes. Crossing-over produces new genetic combinations. Crossing-over produces nonparental chromosomes.
Crossing-over disrupts the linkage between genes on different chromosomes. FEEDBACK: Recall that crossing-over occurs only between homologous chromosomes and that linked genes are found only on the same physical chromosome. Therefore, these processes do not affect genes found on different chromosomes.
Patients with XP possess a recessive allele that produces a nonfunctional
DNA repair enzyme FEEDBACK: In XP, a recessive allele codes for the production of a faulty protein in the normal DNA repair mechanism. Thus, when ultraviolet light damages DNA in skin cells, the damage cannot be repaired, and the physical symptoms of XP, such as severe blisters and skin cancer, emerge.
Which of the following statements regarding genes is FALSE? Genes are located on chromosomes. Genes consist of a long sequence of DNA. Genes contain information for the production of a single protein. In sexually reproducing species, each somatic cell contains a single copy of every gene.
In sexually reproducing species, each somatic cell contains a single copy of every gene. FEEDBACK: In sexually reproducing species, each cell (except for gametes) contains two copies of every gene, one copy inherited from each parent.
A botanist crossed a white snapdragon flower with a red snapdragon and produced pink offspring. This type of cross is an example of
Incomplete dominance
A purple-flowered pea plant has the genotype PP. Which of the following statements about this plant is FALSE?
Its phenotype is white.
Which of the following ideas or events related to the chromosomal theory of inheritance is FALSE?
Mendel was the first to discover that chromosomes contain genes.
Consider the pedigree for a family with brachydactyly shown in Figure 10.9. On what basis can we conclude that the allele that causes brachydactyly is likely dominant?
None of the affected individuals have unaffected parents.
An individual with the genotype ii would have blood type
O FEEDBACK: In the case of blood type in humans, the i allele does not produce any cell surface proteins. Therefore, for an individual that is ii, no cell surface proteins would be present on red blood cells and the person would have blood type O.
Which of the following statements about mutations is FALSE? Mutations are the source of new alleles for genes. Organisms are able to create mutations to meet their specific needs. Mutations are random events and can happen in any cell at any time. Most mutations tend to be harmful or have no effect on organisms, but occasionally a mutation can be beneficial to organisms.
Organisms are able to create mutations to meet their specific needs.
The observation that individuals afflicted with albinism also always have vision problems is an example of
Pleiotropy refers to situations in which a single gene has influence over multiple, different traits. A pleiotropic gene is one that can influence two or more different traits simultaneously, such as in the example with albinism and vision problems.
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?
RRYY x rryy True breeding means homozygous for both traits, with the parents of opposite phenotypes.
Which of the following represents a housekeeping gene that would be expressed in a human pancreas cell?
Ribosomal RNA genes are needed in all cells that carry out protein synthesis and so qualify as housekeeping genes.
Genetic mutations that are never passed to the next generation occur in
Somatic mutations occur in cells other than the sex cells. Somatic mutations are not passed to the next generation because somatic cells do not produce gametes.
A person is genetically XX and develops as a male. How can this be explained?
The SRY gene is also present in this individual FEEDBACK: It is possible (although rare) for the portion of a Y chromosome that determines maleness (the SRY gene) to become associated with an X chromosome and thus produce male characteristics in an individual who does not have a Y chromosome.
Which of the following would you NOT expect to find in a sample of DNA from one of your liver cells?
The crystalline protein FEEDBACK: Liver cells are representative of your body cells in general, and therefore all of the DNA components would be present. However, crystalline is a protein used in the eye and is not expressed in the liver.
Which of the following is NOT true of DNA repair? The damaged area must be up-regulated. The damaged area must be recognized. The damaged area must be removed. The damaged area must be replaced.
The damaged area must be up-regulated The three steps of DNA repair are recognition, removal, and replacement of the damaged DNA segment. Up-regulation of expression of the damaged gene is not involved in DNA repair.
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?
The offspring are either 100 percent homozygotes or 100 percent heterozygotes.
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?
These diseases usually take effect later in life after people have had children.
TRUE OR FALSE: The substitution of one RNA nucleotide for another RNA nucleotide in a codon, does not always result in the formation of a different amino acid.
True
Select the syndrome whose genetic makeup is a monosomy (XO)?
Turner syndrome
The DNA base sequence AAGCGATCG would code for which mRNA transcript?
UUCGCUAGC
Which of the following statements about the process of DNA replication is FALSE? Many different enzymes are needed for the process to function properly. Mistakes can be corrected at multiple steps in the process. Uncorrected mistakes introduce mutations into the DNA base sequence. Mistakes in the copying process are very common occurrences.
Uncorrected mistakes introduce mutations into the DNA base sequence
An uncorrected mismatch error during human DNA replication can result in all of the following EXCEPT a DNA sequence identical to the original DNA molecule. the potential for a genetic disorder. a new allele. a harmless mutation.
a DNA sequence identical to the original DNA molecule.
Down syndrome in humans is an example of
a change in overall number of chromosomes Down syndrome results when an individual receives three copies of chromosome 21 as the result of an error during meiosis.
A sample of DNA from an unknown organism is analyzed and found to contain histone proteins, more than 2 billion base pairs, and large segments of noncoding DNA. From this information, one can conclude that the organism is
a eukaryote
A diploid organism that is heterozygous for a given gene carries ________ an organism that is homozygous for that gene.
a larger number Of alternative alleles than does FEEDBACK: Because both organisms are diploid, both individuals would have the same number of alleles, just different combinations of alleles. The heterozygote would carry two alternative versions of the gene, while the homozygote would carry two identical versions of that gene.
In humans, the protein insulin is produced in specialized pancreatic cells. In an individual human, the gene for insulin is located in
all cells (the gene for insulin is present in all of a human's cells but is only expressed in the specialized pancreatic cells.)
In humans, X-linked genetic diseases
can be seen in both males and females.
In humans, the genetic commonality of height and skin tone is that they are both
controlled by multiple genes with a strong environmental influence
Genes located on the same chromosome tend to be inherited as a group. Which of the following can disrupt this pattern of inheritance?
crossing over
Cri du chat syndrome results when a portion of chromosome 5 is missing. This is caused by which of the following structural changes to chromosomes?
deletion
Genetically identical plant clones can exhibit dramatic phenotypic variation
depending on the environmental conditions under which they are grown
Two genes are linked and crossing-over does not occur. In this situation, the two genes
do not assort independently of each other. FEEDBACK: Linked genes (those present on the same chromosome) do not show independent assortment, unless they are located very far apart from one another on the chromosome so that crossing-over is likely to occur.
An organism has the genotypes DD. How many kinds of gametes can this organism produce?
four
All of the following are characteristics of RNA, except ______ single stranded polynucleotide highly stable molecule ribose sugar contains A,C,G and U directs the synthesis of protein
highly stable molecule
Noncoding DNA
includes spacer DNA and introns.
A chestnut-colored horse is mated with a cremello (cream-colored) horse. During a 10-year period, all of their offspring are palominos. This pattern of inheritance is best explained by
incomplete dominance
The only known violation of Mendel's law of independent assortment is flower color in snapdragons, which is best explained using the concept of
incomplete dominance
Members of one pair of factors separate independently of the members of another pair of factors. This is a statement of Mendel's law of
independent assortment
Being able to use a Punnett square to track the pattern of inheritance in a two-trait cross (for example, pea seed color and seed shape) demonstrates Mendel's idea of
independent assortment.
Even though you and your brothers or sisters are all humans, odds are that each of you has a somewhat different genetic makeup. The molecular basis for this inherited genetic variation
is related to the difference in the DNA nucleotide sequence of your genes.
Which of the following conditions is NOT an example of a chromosomal mutation?
linkage
Who determines the sex of offspring?
male
Mendel's laws of segregation and independent assortment both have their biological basis in events that take place during ________
meiosis
The diseases of cancer, heart disease, diabetes, and asthma are similar because they are all caused by
multiple genes and external factors
Which of the following parts of a DNA molecule are held together by hydrogen bonds?
nucleotide bases on opposite strands of the double helix FEEDBACK: Hydrogen bonds connect the bases on opposite strands of the DNA molecule, which is the reason the double helix can be unwound and separated relatively easily. All other bonds in the molecule are covalent.
Two genes are known to be on the same chromosome, yet analysis of genetic crosses involving these genes suggests that they assort independently. The most plausible explanation for this observation is that they are
on opposite ends of the same chromosome.
When a molecule of DNA replicates without error, each of the resulting molecules contains
one new strand and one old strand
Which type of genetic crosses will produce a continuous variation of phenotypes resembling a bell shaped curve?
polygenic inheritance
The X chromosome in humans is
present in both human males and females.
Because they are large, varied, and complex biomolecules, scientists initially thought that the genetic material consisted of
proteins
Mendel's primary contribution to our understanding of genetic inheritance was
providing a mechanism that explains patterns of inheritance.
In bacteria, genes are typically turned on and off
response to environmental changes
The two factors for each trait separate when gametes form, so that each gamete contains only one factor for each trait. This statement is part of Mendel's law of
segregation
In eukaryotic cells, histones
serve as structures around which DNA is spooled for packaging
_____ transports the correct amino acid to the ribosome in the process of translation.
tRNA
Refer to Figure 11.11 in your textbook. The structure labeled metaphase chromosome at the top of the diagram would not be able to undergo successful gene transcription because
the DNA is packed too tightly
On chromosomes, a pair of linked genes will be found only on
the same chromosome
The Punnett square method is useful as a tool for analyzing genetic crosses because ________
the two alleles of a gene separate and recombine randomly during gamete formation.
If two parents are heterozygous for an autosomal recessive disease,
they are both considered carriers
The first step of gene expression is
transcription
Which process(es) occurs in the cytoplasm in eukaryotes?
translation only
Recall the genetic determination of coat color in mice, as discussed in the textbook. A cross between a male with the genotype BBcc and a female with the genotype bbcc will produce offspring with which coat color(s)?
white only FEEDBACK: Because both individuals are homozygous recessive for the c allele, their offspring will also be homozygous recessive for c. As c has more influence over pigmentation than does the B gene, their offspring will not deposit coat pigment and therefore will all be white.