Biology test 4
How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous?
cross the green pod plant with a yellow pod plant
Suppose that the botanist carried out the test cross described in Parts A and B and determined that the original green-pod plant was heterozygous (Gg). Which of Mendel’s findings does her test cross illustrate?
Law of segregation
During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur?
Meiosis I, anaphase
a. 3/4 Y 1/4 y
b. 1/2 Y 1/2y
c. 1/2 YY 1/2 yy
d. 1/2 Yy 1/2 Yy
e. 3/4 y 1/4 Y
f. 1/2 y 1/2 y
What is the probability that an F2 seed chosen at random will be yellow?
What is the probability that an F2 seed chosen at random from among the yellow seeds will breed true when selfed?
What is the probability that three F2 seeds chosen at random will include at least one yellow seed?
What is the probability that three F2 seeds chosen at random will include one green seed and two yellow seeds?
What is the difference between heterozygous and homozygous individuals?
All of the gametes from a homozygote carry the same version of the gene while those of a heterozygote will differ.
When constructing a Punnett square, the symbols on the outside of the boxes represent____________, while those inside the boxes represent_________.
True or false? The same phenotype can be produced by more than one genotype.
True or False? In diploid organisms, a dominant phenotype will only be expressed if the individual is homozygous dominant for that trait.
If an organism with the genotype AaBb produces gametes, what proportion of the gametes would be Bb?
Two mice are heterozygous for albinism (Aa) . The dominant allele (A) codes for normal pigmentation, and the recessive allele (a) codes for no pigmentation. What percentage of their offspring would have an albino phenotype?
A tall, purple-flowered pea plant (TtPp) is allowed to self-pollinate. (The recessive alleles code for short plants and white flowers.) The phenotypic ratio of the resulting offspring is 9:3:3:1. What is the genotype of the plant whose phenotype appeared once out of every 16 offspring (the “1” in the 9:3:3:1 ratio)?
What process is responsible for the independent assortment of alleles?
How do cells acquire homologous chromosome pairs that carry the alleles that are independently assorted?
fusion of gametes
Which of the following statements most accurately describes the process of independent assortment?
Alleles of different genes segregate from one another in a random manner.
True or false? The principle of independent assortment is best illustrated by events that take place during metaphase II, during which sister chromatids segregate independently of each other.
How many genetically unique types of gametes could be produced by an individual with the genotype RrYY?
Which of the following parental genotypes would yield a 1:1:1:1 phenotypic ratio in the offspring?
The mutent allele is dominant to its corresponding wildtype allele
the mutent allele is dominant to its corresponding wildtype allele
The mutent allele is neither dominant or completely recessive to its corresponding wild type allele.
Which of the following statements best explains the outcome of this cross?
The forked mutation and the twist mutation are codominant alleles of the same locus.
What defines a short sleeper?
they can function well on 6 hours or less of sleep
While it is estimated that less than 5% of the population are short sleepers,
an estimated 30% of the population sleep only 6 hours per night or less
The risks of sleep deprived include
The discovery of a gene associated with short sleepers means that
there is potential to manipulate sleep pathways with medication.
Since there is a genetic explanation for short sleepers, you would expect
that this trait appears more frequently among family members.
Hemophilia is caused by a sex-linked recessive gene, I am sure I do not have hemophilia, what genotype must I be ?
Consider the hypothetical sex-linked recessive baldness gene, if a bald woman has a child with a normal male, what are the odds their son will be bald?
Consider the following family history:
Bob has a genetic condition that affects his skin.
Bob’s wife, Eleanor, has normal skin. No one in Eleanor’s family has ever had the skin condition.
Bob and Eleanor have a large family. Of their eleven children, all six of their sons have normal skin, but all five of their daughters have the same skin condition as Bob.
Based on Bob and Eleanor’s family history, what inheritance pattern does the skin condition most likely follow?
A homozygous wild-type female fly is mated with a vermilion male fly.
Predict the eye colors of F1 and F2 generations.
F1 females : All wild type
F1 males : All wild type
F2 females : All wild type
F2 males : 1/2 wild type, 1/2 vermillion
Red-green color blindness is due to an X-linked recessive allele in humans. A widow’s peak (a hairline that comes to a peak in the middle of the forehead) is due to an autosomal dominant allele.
Consider the following family history:
A man with a widow’s peak and normal color vision marries a color-blind woman with a straight hairline.
The man’s father had a straight hairline, as did both of the woman’s parents.
Use the family history to make predictions about the couple’s children.
If the couple has a child, what is the chance that it will be a son with a widows peak ? 1/4
What is the chance that any son the couple has will be color blind with a straight hairline? 1/2
What is the chance that any daughter that the couple has will be color blind with a widows peak? 0
Suppose the couple had a daughter with normal color vision and a widows peak. What is the chance that she is heterozygous for both genes? 1
solid, normal, smooth :
solid, normal, peach :
solid, dwarf, smooth :
solid, dwarf, peach :
mottled, normal, smooth :
mottled, dwarf, smooth :
mottled, dwarf, peach :
Now, suppose that the three tomato genes from Part A did not assort independently, but instead were linked to one another on the same chromosome. Would you expect the phenotypic ratio in the offspring to change? If so, how?
All eight possible phenotypes could occur, but a greater proportion of the offspring would have the parental phenotypes.
What is a nondisjunction?
An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell
When can nondisjunction occur? Choose the best answer.
In meiosis, when homologous chromosomes fail to separate
In meiosis, when sister chromatids fail to separate
In mitosis, when sister chromatids fail to separate
Which syndrome is characterized by the XO chromosome abnormality?
What kind of cell results when a diploid and a haploid gamete fuse during fertilization?
A triploid cell
Of the following chromosomal abnormalities, which type is most likely to be viable in humans?
If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred?
A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.
If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two gametes with n− 1 chromosomes, what type of error occurred?
A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.
The following table illustrates some structural mutations that involve one or both of these chromosomes. Identify the type of mutation that has led to each result shown.
Meiosis occurs normally (no nondisjunction)
Nondisjunction of one chromosome pair in meiosis I
2 or 4
Nondisjunction of all three chromosome pairs in meiosis I
0 or 6
Nondisjunction of one chromosome in one daughter cell in meiosis II
2 3 or 4
Nondisjunction of all three chromosomes in one daughter cell in meiosis II
0 3 or 6
Cystic fibrosis is an inherited disorder that affects which of the following?
How long can sperm be cryogenically stored and still be viable?
for more than 20 years
Which federal agency ensures that sperm donors are tested for communicable diseases?
Food and Drug Administration
Which of the following is true?
Both women and men can be carriers for genetic disorders
Which of the following is a leading cause of sudden death among young athletes
Binds at the replication fork
breaks H-bonds between bases
binds ahead of the replication fork
breaks covalent bonds in DNA backbone
Single-strand binding protein
binds after the replication fork
prevents H-bonds between bases
only one primer needed
daughter strand elongates toward replication fork
multiple primers needed
made in segments
daughter strand elongates away from replication fork
synthesized 5′ to 3′
Drag the labels to their appropriate locations in the flowchart below, indicating the sequence of events in the production of fragment B
pol III binds to 3′ end of primer b -> pol III moves 5′ to 3′, adding DNA nucleotides to primer B -> pol I binds to 5′ end of primer A -> pol I replaces primer A with DNA -> DNA ligase links fragments A and B
During DNA replication, the leading strand is synthesized continuously, whereas the lagging strand is synthesized as Okazaki fragments. Why is this so?
DNA synthesis can take place only in the 5′ to 3′ direction.
Who demonstrated that DNA is the genetic material of the T2 phage?
Hershey and Chase
The radioactive isotope 32P labels the T2 phage’s
Hershey and Chase used ___ to radioactively label the T2 phage’s proteins
After allowing phages grown with bacteria in a medium that contained 32P and 35S, Hershey and Chase used a centrifuge to separate the phage ghosts from the infected cell. They then examined the infected cells and found that they contained___, which demonstrated that ___ is the phage’s genetic material
labeled DNA… DNA
In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.
thymine … cytosine
DNA is a self-replicating molecule. What accounts for this important property of DNA?
The nitrogenous bases of the double helix are paired in specific combinations: A with T and G with C
Short segments of newly synthesized DNA are joined into a continuous strand by _____
After DNA replication is completed, _____.
each new DNA double helix consists of one old DNA strand and one new DNA strand
The first step in the replication of DNA is catalyzed by _____.
The action of helicase creates _____.
replication forks and replication bubbles
Why is the new DNA strand complementary to the 3′ to 5′ strands assembled in short segments?
DNA polymerase can assemble DNA only in the 5′ to 3′ direction
The synthesis of a new strand begins with the synthesis of a(n) _____.
RNA primer complementary to a preexisting DNA strand
An old DNA strand is used as a _____ for the assembly of a new DNA strand.