LFS100 Quiz 3 Flashcards
If the liver cells of an animal have 24 chromosomes, how many chromosomes do its sperm cells have?
12
A 9:3:3:1 phenotypic ratio is characteristic of which of the following?
a dihybrid cross
A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates
dominance.
Cystic fibrosis (CF) is a Mendelian disorder in the human population that is inherited as a recessive trait. Two normal parents have two children with CF. The probability of their next child having CF is which of the following?
1/4
A 1:2:1 phenotypic ratio in the F2 generation of a monohybrid cross is a sign of
incomplete dominance.
Chromosomes and genes are both present in pairs in all diploid cells
True
Hypophosphatemia (vitamin D-resistant rickets) is inherited as an X-linked dominant disorder. An unaffected woman mates with a male with hypophosphatemia. What is the expected phenotypic ratio of their offspring?
1 daughter with hypophosphatemia : 1 normal son
If nondisjunction occurs in meiosis II during gametogenesis, what will be the result at the completion of meiosis?
One gamete will be n + 1, one will be n - 1, and two will be n.
Which of the following statements does NOT apply to the Watson and Crick model of DNA?
The two strands of the helix are held together by covalent bonds.
You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent
leading strands and Okazaki fragments.
The Y-shaped structure where the DNA double helix is actively unwound during DNA replication is called the
replication fork.
RNA polymerase moves along the TEMPLATE strand of DNA in the ________ direction, and adds nucleotides to the ________ end of the growing transcript.
3’ to 5’; 3’
What are ribosomes composed of?
both rRNA and protein
When a cell releases a signal molecule into the environment and a number of cells in the immediate vicinity respond, this type of signaling is
paracrine signaling.
The general name for an enzyme that transfers phosphate groups from ATP to a protein is
protein kinase.
Which of the following most likely would be an immediate result of growth factor binding to its receptor?
protein kinase activity
Which of the following is the term for a human cell that contains 22 pairs of autosomes and two X chromosomes?
a female somatic cell
Crossing over usually contributes to genetic variation by exchanging chromosomal segments between
nonsister chromatids of homologues.
Mendel accounted for the observation that traits which had disappeared in the F1 generation reappeared in the F2 generation by proposing that
traits can be dominant or recessive, and the recessive traits were obscured by the dominant ones in the F1.
A sexually reproducing animal has two genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
HT
When a disease is said to have a multifactorial basis, it means that
many factors, both genetic and environmental, contribute to the disease.
SRY is
a gene present on the Y chromosome that triggers male development.
The strands that make up DNA are antiparallel. This means that
the 5’ to 3’ direction of one strand runs in the opposite direction to the 5’ to 3’ direction of the other strand.
Suppose one were provided with an actively dividing culture of E. coli bacteria to which radioactive thymine had been added. What would happen if a cell replicated once in the presence of this radioactive base?
DNA in both daughter cells would be radioactive.
A particular triplet of bases in the template strand of DNA is AGT. The corresponding codon for the mRNA transcribed is
UCA.
During translation, chain elongation continues until what happens?
A stop codon is encountered.
Paracrine signaling
involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular fluid.
The general name for an enzyme that transfers phosphate groups from ATP to a protein is
protein kinase.
A(n) ________ is an example of a signal molecule that can bind to an intracellular receptor and thereby cause a gene to be turned on or off.
steroid
Which of the following statements about genes is incorrect?
Under normal circumstances, each chromosome contains precisely one gene.
Sexual life cycles result in greater variation among the offspring than do asexual life cycles.
True
What are Punnett squares used for?
predicting the result of genetic crosses between organisms of known genotypes
P = purple, pp = white. The offspring of a cross between two heterozygous purple-flowering plants (Pp × Pp) results in
purple-flowered plants and white-flowered plants.
Chromosomes and genes have copy numbers in the cell that increase after meiosis, and decrease during fertilisation
False
A particular triplet of bases in the template strand of DNA is AGT. The corresponding codon for the mRNA transcribed is
UCA.
G proteins and G-protein-linked receptors
are thought to have evolved very early, because of their similar structure and function in a wide variety of modern organisms whose common ancestors diverged billions of years ago.
Independent assortment of chromosomes is a result of
the random and independent way in which each pair of homologous chromosomes lines up at the metaphase plate during meiosis I.
A 9:3:3:1 phenotypic ratio is characteristic of which of the following?
a dihybrid cross
A cross between homozygous purple-flowered and homozygous white-flowered pea plants results in offspring with purple flowers. This demonstrates
dominance.
In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?
tortoiseshell female; black male
Hypophosphatemia (vitamin D-resistant rickets) is inherited as an X-linked dominant disorder. An unaffected woman mates with a male with hypophosphatemia. What is the expected phenotypic ratio of their offspring?
1 daughter with hypophosphatemia : 1 normal son
Which of the following covalently connects segments of DNA
ligase
You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent
leading strands and Okazaki fragments.
The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?
A gene from an organism can theoretically be expressed by any other organism.
The old saying “one rotten apple spoils the whole barrel” is due to chemical signaling in plants via
release of ethylene gas, a plant hormone for ripening.
G proteins and G-protein-linked receptors
are thought to have evolved very early, because of their similar structure and function in a wide variety of modern organisms whose common ancestors diverged billions of years ago.
Which of the following is NOT part of the phosphorylation cascade model?
GTP donates a phosphate group to an inactive protein kinase.
Which of the following most likely would be an immediate result of growth factor binding to its receptor?
protein kinase activity
Consider this pathway: epinephrine → G-protein-linked receptor → G protein → adenylyl cyclase → cAMP. Identify the second messenger.
cAMP
Which of the following statements about genes is incorrect?
Under normal circumstances, each chromosome contains precisely one gene.
How many different combinations of maternal and paternal chromosomes can be packaged in gametes made by an organism with a diploid number of 8 (2n = 8)?
16