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Assuming that blending inheritance, not particulate Mendelian inheritance, is operating in a safe form. An individual with a tail that is 10 cm long is crossed with an individual that has a tail 2 m long. What would the expected tail length be in the F2 progeny?
All individuals would have tails that are 6 cm long
What is the probability that a cross between a true breeding pea plant with spherical seeds and a true breeding pea plant with wrinkled seeds will produce F2 progeny with spherical seeds?
The cross AaBb x AaBb is an example of a _______cross, and the result of such crosses had Mendel to predict what we now call the law of _____
dihybrid, independent assortment
Whether a pea seed is round or wrinkled is due to a single Mendelian gene, with round seeds being dominant to wrinkled seeds. In the progeny of a test cross ____ of 80 seeds should be round if the unknown round seeded individual being tested is heterozygous.
What fraction of the offspring of the cross AaBb x AaBb would be homozygous for both the dominant alleles, assuming that they are on different chromosomes?
Unattached earlobes are a dominant trait in humans. Finn and Maggie both have unattached earlobes but their daughter does not. If they have a second child, what is the probability that this child will have attached earlobes?
results in phenotypic ratio of 1:2:1 in a monohybrid cross
A woman has B blood type of the ABO system. Her mother is type O. Form this, we can infer that her father
could not have O blood type
you have chosen t study the genetics of snapdragon flower color. True breeding red plants crossed with true breeding white plants generate all pink F1 offspring. When the F1 offspring are crossed, you get the following numbers of F2 offspring. 24 red, 54 pink, and 22 white. You interpret this inheritance pattern as
coat color in mice involved the effects of multiple gene interactions. If a mouse has two recessive alleles (aa) for coat color, it will always be albino no matter what the genotype of the other genes involved in coat color. This is an example of
penetrance and expressivity are related to
the influence of environment on the expression of a particular gentotype
the X7 allele in a species of plant has 75 percent penetrance for producing red spots and 60 percent penetrance for dwarfism. If these probabilities of penetrance are independent _____ percent of individuals with the X7 allele will have neither red spots nor will be dwarfs.
Wild type fruit flies have red eyes. A white-eyed female fly is crossed with a red eyed male fly. All of the females from the cross are red eyed, and all of the males are white eyed. What type of inheritance patterns this?
in tomatoes, tall is dominant to dwarf, and smooth fruits are dominant to hairy fruits. A plant homozygous for for both dominant traits is crossed with a plant homozygous for both recessive traits. The F1 progeny are test crossed with the following results in the F2 progeny. 96 tall with smooth fruits, 94 dwarf with hairy fruits, 6 tall with hairy fruits and 4 dwarf with smooth fruits. This data indicates that they genes are
linked and show 5 percent recombination
consider the case of X-linked inheritance of a recessive mutant allele. Among progeny from a cross of an unaffected male and a heterzygous female carrier
all male offspring who receive the recessive mutant x chromosome would show the trait
Genes located on mitchondrial DNA are usually inherited
from the mother
Which event in prokaryotes is most like the segregation of sister chromatids in eukaryotic mitosis?
Ori regions moving toward opposite ends of the cell
Which eukaryotic process has no analogue in prokaryotes?
A cell in G2 has 4.8 pg of DNA. In G1, this cell had _______ pg of DNA
Imagine that there is a mutation in the Cdk gene such that its gene product is nonfunctional. What effect would this mutation have on a mammalian white blood cell?
The cell would not be able to replicate its DNA.
The cell would not be able to enter mitosis.
The cell would not be able to reproduce itself.
The cell would not be able to phosphorylate the associated target protein.
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A mutation frequently causes a chromosome of a cell line to become detached from the spindle. The most likely consequence of this mutation is that _______ cells will be stopped at the _______ checkpoint.
An environmental change leads to cyclin being degraded at a rate much faster than normal. Such a change would tend to _______ the activity of the Cdk, which would lead to _______ phosphorylation of the target protein, which in turn would lead to _______ cells being stopped at the checkpoint.
decrease, decreased, more
A cell in G2 contains 36 sister chromatids. This same cell in G1 would have
In a cell in mitotic metaphase, there are 40 sister chromatids. How many centromeres are there in the cell?
Which of the following is true about anaphase of mitosis?
It is the phase when sister chromatids separate and move to opposite poles.
The spindle forms during _______ of mitosis.
If the haploid number of a mammalian cell is 32, there will be _______ sister chromatids during metaphase of mitosis.
In most sexually reproducing organisms, the diploid phase of the life cycle begins at
In meiosis II,
sister chromatids are separated.
Why is meiosis sometimes called "reductive division"?
It results in a reduction of the number of chromosomes.
A species of grass has a haploid number of 18. How many different types of gametes can be produced from meiosis in a diploid individual just with independent assortment (no crossing over)?
The normal haploid number of a plant species is 28. An individual is found with 55 chromosomes. This individual is most likely
is controlled by signal transduction pathways.
In addition to identifying the genetic material, the experiments of Avery, MacLeod, and McCarty with different strains of Streptococcus pneumoniae demonstrated that
DNA may be taken up by bacterial cells and be active.
In order to show that DNA in cell extracts is responsible for genetic transformation in Streptococcus pneumoniae, important corroborating evidence should indicate that _______ also destroy transforming activity.
enzymes that hydrolyze DNA
Based on what you have learned about the experiments conducted by Griffith and Avery and colleagues with bacteria, which of the following would result in transformation of living R cells?
Cell-free extracts from S cells
A-T base pairs in a DNA double helix
are chemically distinct from G-C base pairs.
If 23 percent of the bases in a sample of double-stranded DNA are adenine, what percentage of the bases are uracil?
The uniform diameter of the DNA structure provides evidence for
If a sequence of one strand of DNA is 5′-TGACTATC-3′, what is the complementary strand?
What structural aspect of the DNA facilitates dissociation of the two DNA strands for replication?
Hydrogen bonding between paired bases
If the Meselson-Stahl density gradient experiment had resulted in two bands of DNA molecules after only one round of replication, one containing only 15N and the second only 14N, this result would have indicated that replication was
The nucleoside analogue acyclovir, which is used to treat herpes simplex virus (HSV) infections, lacks a 3′ hydroxyl group (-OH). Predict what will happen if the host cell DNA polymerase incorporates a molecule of acyclovir into an elongating strand of HSV DNA.
DNA polymerase will not be able to link a successive nucleotide.
Which of the following does not demonstrate the stability of the DNA double helix?
DNA synthesis requires energy.
What effect would a primase inhibitor have on DNA replication?
Primase would not be able to provide primers for DNA polymerases.
To replicate their DNA in a timely manner, most eukaryotic chromosomes
have multiple origins of replication.
Which statement about DNA replication is false?
Okazaki fragments are synthesized as parts of the leading strand.
In many eukaryotes, there are repetitive sequences called telomeres at the ends of chromosomes. After successive rounds of DNA replication, the _______ strand becomes shorter. In some cells, an enzyme called _______ repairs the shortened strand.
A researcher studies normal human fibroblast cells. They can be maintained in culture but die off after about 30 cell generations. Unexpectedly, a colony of cells continues to survive and divide past 30 generations. Which scenario is most likely true for these cells?
The telomerase gene is being expressed.
If DNA polymerase III introduces an incorrect nucleotide, what is the first corrective action made by the DNA repair system?
The replication complex excises the incorrect nucleotide.
Choose the correct order of the following four events in the excision repair of DNA:
(1) Base-paired DNA is made complementary to the template.
(2) Damaged bases are recognized.
(3) DNA ligase seals the new strand to existing DNA.
(4) Part of a single strand is excised.
Which scenario supports Garrod's one-gene, one-enzyme hypothesis of metabolic disease causation?
The disease PKU is due to the failure to produce a functional variant of an enzyme.
A strain of Neurospora is able to grow on minimal medium. When substance A is added to the medium, however, the strain cannot grow. Supplying a small amount of substance B has no effect on the strain, but it cannot reverse the effect of substance A. Supplying a small amount of substance C, by contrast, enables the strain to grow with substance A. Which of the following statements best explains these facts?
Substance A is a toxin that the strain cannot break down, and substance C is an enzyme that breaks down substance A
Ribozymes are RNA molecules that have enzymatic activity. This conflicts with the belief of early molecular biologists that
each enzyme is a polypeptide.
Which statement about RNA is false?
Messenger RNAs are produced on ribosomes.
An mRNA sequence is 5′-CAGUUACGA...UAAGC-3′ ([...] denotes intervening sequences). What is the sequence of the template strand of DNA?
Comparison of the same gene and its product in two different animal species revealed that the amino acids are 98 percent identical but the nucleotides are only 86 percent identical. What accounts for the much higher amino acid identity than nucleotide identity?
The genetic code is redundant.
If the coding region of an mRNA is 2,400 nucleotides long, how many codons does it have?
Which single base substitution in the coding strand of DNA would result in premature termination of translation?
CGA to UGA
Suppose the DNA of a gene contains seven regions, A through G, in that order. Regions A, B, E, and G are located in exons, while regions C, D, and F are located in introns. What is the order of the regions in the mature mRNA transcribed from that sequence?
Which statement about pre-mRNA splicing is false?
It is common in prokaryotes.
Order the four steps shown as they would occur, from beginning to end, during expression of a eukaryotic gene.
(1) Pre-mRNA is processed to make mRNA.
(2) Ribosomes translate the mRNA message to make proteins.
(3) mRNA is transported to the cytoplasm.
(4) DNA is used as a template to make pre-mRNA.
The modified base inosine contributes to
the wobble effect
If the codon is 5′-GAA-3′, then the corresponding anticodon is
In the elongation stage of translation,
rRNA is catalytically active
The start codon is near the _______ end of the mRNA, and this corresponds with the _______ terminus of the polypeptide.
An environmental change leads a cell to start making proteins at high rates. Which scenario would be the most likely mechanism?
The cell would likely have increased numbers of polysomes
In eukaryotes, the first amino acid in a growing polypeptide chain is always _______ because the only codon for this amino acid is also the _______ codon. This amino acid is not always the first amino acid in a processed protein because of _______.
methionine; start; proteolysis
A protein that is destined to be secreted from the cell
has a signal sequence that targets its translation into the lumen of the RER.
Concerned about a skin mole that has increased in size and darkened in color, a man visits a dermatologist. Based on a biopsy, the mole is diagnosed as melanoma, a form of cancer. A genomic analysis reveals a mutation in the BRAF gene, a commonly mutated gene in melanoma. The BRAF gene is the wild type in surrounding noncancerous cells. These data are evidence that
somatic mutations may be passed to daughter cells by mitosis.
Loss-of-function mutations in one allele tend to show _______ inheritance because the normal enzyme activity of one wild-type allele usually _______.
recessive; is sufficient to produce the wild-type phenotype
Refer to the table
Ancestral cell: ...CTT...CCG...CAA...CTG...
Descendant (mutated cell):...ATT...CTA...CAG...CAG...
A bacterial cell has been exposed to a powerful mutagen. In the table shown, a sequence from this cell is compared with the same sequence from its ancestral cell. Intervening sequences where the ancestral and descendant cells have identical sequences are represented by dots. In the mutated cell there have been ________ transition(s) and _______ transversion(s).
The isoenzyme hexosaminidase A (HEXA) is composed of subunits α and β and breaks down molecules containing terminal N-acetyl hexosamines. Tay-Sachs disease is caused by a recessively inherited loss-of-function mutation in the gene coding for the α subunit, which is the subunit that hydrolyzes the lipid GM2 ganglioside. Accumulation of this lipid in the brain leads to progressive deterioration of the nervous system and death, usually by age 4. The most common mutation in the HEXA gene is an insertion of four base pairs in exon 11 that creates a nonfunctional truncated protein. HEXA activity is 0 to 6 percent in homozygous recessives and 7 to 35 percent in heterozygous carriers, compared with noncarriers (100 percent). What evidence presented here strongly suggests that this truncated α subunit can still associate with the normal β subunit, thereby inhibiting its association with functional α subunit?
HEXA activity in heterozygous carriers is significantly less than 50 percent of that in noncarriers.
Which mutation does not change the amount of genetic material on a chromosome?
In an experiment a culture of bacteria is plated onto six agarose plates with nutrients that support their growth. One set of three plates are exposed to visible light, and the second set of three plates are exposed to ultraviolet radiation. This experiment is appropriate for studying the effect of _______ on DNA replication.
covalent bonds between thymine bases
The infection of cells by the human immunodeficiency virus (HIV) requires the virus to bind to the cell surface molecule CD3 and a second coreceptor molecule, CCR5 or CXCR4. In Scandinavian populations a mutation in CCR5 results in functional loss of CCR5 expression and exists at an allelic frequency of about 10 to 18 percent. Homozygous loss-of-function carriers are protected from infection by HIV strains that bind CCR5, and this mutation is also believed to have been protective against smallpox infection. This CCR5 mutation is evidence that mutations
can provide selective advantage to an organism.
Which disease is due to a mutation in a gene whose product transports gases?
An adult, who is one of identical triplets, develops breast cancer at the age of 54. Neither of the other two identical siblings develops breast cancer. This scenario supports the notion that cancer development is
usually caused by interactions of many genes/proteins with one or more factors in the environment.
Gel electrophoresis is able to separate DNA fragments strictly by relative size assuming
the pH of the buffer is neutral.
In DNA fingerprinting,
single nucleotide polymorphisms (SNPs) are informative.
Individuals with PKU have _______ levels of phenylalanine before birth and _______ levels of phenylalanine shortly after birth if provided normal breast milk.
normal; abnormally high
Abnormal genes are detected most accurately by examining