Cell Genetics Unit 4 Exam
A linkage group is what?
A group of genes that usually stay together during meiosis.
In plants, most chloroplasts are inherited from the maternal plant because maternal gametes contribute the most ________ to the zygote.
cytoplasm
Eukaryotic DNA methylation occurs on which base?
cytosine
What is NOT a typical cellular change that occurs during lung cancer?
elevated gas transport
Small effector molecules are often what?
end products or key metabolites of a metabolic pathway
A modification of a gene or chromosome that occurs during gamete formation or early development that permanently alters the expression of that gene for the lifetime of the individual is called what?
epigenetic inheritance
Genomic imprinting does not actually involve a change in the genetic sequence of an inherited gene. True or false?
True
Larger genes are usually more likely to incur a mutation than smaller genes. True or false?
True
Loosely packed chromatin is said to be in an open conformation. True or False?
True
Maternal inheritance is the typical pattern of inheritance for mitochondria and chloroplasts because mitochondria and chloroplasts come from the large cytoplasm of the egg rather than the relatively miniscule cytoplasm of the sperm. True or False?
True
MicroRNAs (miRNAs) silence the expression of specific mRNAs. True or false?
True
Modifying the accessibility of chromatin leads to complex regulation of eukaryotic gene expression. True or false?
True
Most oncogenes encode proteins that function in cell growth signaling pathways. True or false?
True
Mutations can produce a polypeptide with increased function. True or False?
True
Oncogenes may occur due to a mutation in a gene regulatory region, such as a promoter, enhancer, or repressor. True or false?
True
Only a small group of cells within the organism is affected by the mutation. True or False?
True
When lactose becomes available the genes encoding b-galactosidase and lactose permease are upregulated in E. coli. True or False?
True
What type of physical mutagens produces thymine dimer mutations?
UV
Somatic cell mutations are heritable. True or false?
false
What is xeroderma pigmentosum associated with?
faulty DNA repair mechanisms
If the copy number of a proto-oncogene is increased by gene duplication then the proto-oncogene has undergone what?
gene amplification
A cell's ability to control its level of gene expression is called what?
gene regulation
Protein(s) that play a role in initiating transcription in eukaryotes include what?
general transcription factors, RNA polymerase II, mediators and RNA polymerase II.
Cancer results from cells that divide when they should not. A hallmark of cancer is high levels of DNA methylation in cell genomes. Methylation of which genes is MOST likely to lead to cancerous cell formation?
genes that prevent cell division
An actively dividing cell is missing an entire chromosome. How might this lead to cancer?
Various tumor suppressor genes may have been deleted from the genome, so cell proliferation occurs regardless of the damaged genome.
You breed a black, long-haired rabbit with a white, short-haired rabbit. All of the offspring have long, black hair. If the genes for hair color and length are closely linked on the same chromosome, what would you expect to see in the F2 generation?
15 black, long-haired: 1 black, short-haired: 1 white, long-haired: 5 white, short-haired
Assume that the F2 generation from the previous question had the following phenotypic ratios: Long stingers and bi-lobed wings (298); short stingers and tri-lobed wings (322); long stingers and tri-lobed wings (97); and short stingers and bi-lobed wings (77). What is the recombination frequency of these two genes?
22%
What is the MOST important reason a cell would have translational control over the regulation of gene expression?
At the translational level, protein synthesis can be turned on and off quickly to respond to the needs of the cell.
Why are people afflicted with xeroderma pigmentosa likely to develop skin cancer?
Because they are born with a mutation in their DNA repair system and they cannot repair DNA that is mutated by UV radiation.
Cancer progression can result from mechanisms other than mutation (change in the DNA sequence). Which of the following is not an example of such a mechanism?
Chromosomes could be lost during meiosis.
How can crossing over maintain the principle of independent assortment for alleles present on the same chromosome?
Crossing over produces recombinant chromosomes that will have new combinations of alleles different from the parental chromosomes, separating alleles that are on the same chromosome.
What characteristic of DNA makes nucleotide excision repair (NER) mechanisms possible?
DNA is a double helix so once a damaged region is recognized, it can be removed and synthesized based on the undamaged opposite strand.
In dogs, there is a hereditary deafness caused by a recessive allele, d. A kennel owner has a male dog that she wants to use for breeding purposes if possible. The dog can hear, but the owner is unsure of the genotype. She does a testcross (crosses it to a homozygous recessive dog), and two of the five offspring are deaf. This means that the male dog has what genotype?
Dd
Paternal inheritance occurs in plants but not animals because plants have chloroplasts instead of mitochondria. True or False?
False
Paternal inheritance occurs in plants but not animals because plants have chloroplasts instead of mitochondria. True or false?
False
Patients who suffer from xeroderma pigmentosum (XP) have a defective mismatch repair system. True or False?
False
Small effector molecules directly bind the DNA they regulate. True or false?
False
The movement of DNA polymerase continues unimpeded if a thymine dimer is present in the DNA double helix. True or False?
False
The timing of a mutation during development has negligible effects on the severity of the genetic defect. True or False?
False
The timing of a mutation during development has negligible effects on the severity of the genetic defect. True or false?
False
Two genes that are close together on the same chromosome will cross over more frequently than two genes that are further apart. True or False?
False
Two genes that are close together on the same chromosome will cross over more frequently than two genes that are further apart. True or false?
False
When oncogenes are silenced, the cell cycle may be able to proceed even when it should not. True or False?
False
When oncogenes are silenced, the cell cycle may be able to proceed even when it should not. True or false?
False
At what phase of the cell cycle does p53 halt cell division if it senses DNA damage?
G1
In the sweet pea crossing experiment by Bateson and Punnet, the F2 generation had many more offspring with the phenotypes of purple flowers with long pollen (PL) and red flowers with round pollen (pl) than expected from independent assortment. This is because what?
In sweet peas, the alleles for flower color and pollen shape are on the same chromosome.
The rate of transcription for a gene is found to be affected by a mutation. Where would you expect the mutation to appear on the DNA?
In the promotor for the gene
Sickle-cell anemia is a human disease that occurs as a result of what type of mutation in the b-globin gene?
Missense
A researcher determined that a strain of E. coli is producing a shortened version of a protein required for glucose metabolism. What type of mutation could be responsible for this shorter than normal protein?
Nonsense mutation
P, D, and Q are three genes found on a single chromosome in greyhounds. The recombination frequencies between the three genes are shown below. In which order are these genes found on the greyhound chromosome? P—D = 50% P—Q = 20% D—Q = 30%
P-Q-D
What is the MOST important reason a cell exhibits tight transcriptional control over the regulation of gene expression?
Regulation at the transcriptional level is energetically efficient for the cell.
A physician discovered a cancerous tumor in the cartilage of a patient. What type of tumor is this?
Sarcoma
In mice, the gene for insulin-like growth factor is imprinted. During embryonic development, only the paternal allele for insulin-like growth factor is expressed. This means what?
That the maternal allele is imprinted.
The lactose (lac) operon of E. coli is under both positive and negative control. How is the lac operon affected by positive control?
The CAP protein binds near the promoter in the presence of cAMP.
How is the lac operon affected by negative control?
The Lac Repressor binds to the operator in the absence of lactose.
A cell has a mutation such that UvrA is permanently attached to UvrB. What effect might this have on nucleotide excision repair (NER)?
The cell would be able to recognize damaged regions of the double helix, but it would be unable cut the DNA in the appropriate region in preparation for removing the damaged sequence.
You are trying to improve growth in an economically important fish species. These fish have a gene that controls their size. There are two size alleles; L and S. You cross a large female (LL) with a small male (SS) and get all large fish! The genotypes of the F1 are 100% LS so you assume that large size is dominant to small. You then cross a small female (SS) with a large male (LL) and get all small fish! The genotypes of this F1 are all LS. How do you explain this result?
The gene for large size is a maternally inherited.
Epigenetic inheritance can result in the expression of different alleles in different generations. True or false?
True
Genomic imprinting does not actually involve a change in the genetic sequence of an inherited gene. True or False?
True
A human mother's genes seem to influence brain development while a human father's genes seem to influence growth. What does this imply?
The mother imprints her growth genes and the father imprints his brain development genes.
In both the lac and trp operons of E. coli, a repressor binds to an operator to block transcription. Identify the most accurate description of these operons.
The trp operon is repressible while the lac operon is inducible.
The karyotype of a young patient shows two Barr bodies per cell. What condition might this child have?
Triple X
Both eukaryotes and prokaryotes require a promoter region for gene transcription. True or false?
True
Cancers originate from a single cell. True or false?
True
What is a testcross?
a cross between an organism of unknown genotype with a homozygous recessive individual
What would result from a single nucleotide deletion (point mutation) within the coding sequence of a structural gene?
a frameshift mutation, producing a different amino acid sequence altogether
What type of regulatory transcription factor binds DNA and increases the transcription of a gene?
an activator exerting positive control
A regulatory element that can function from a large distance (e.g. tens of thousands of base pairs) from a promoter is called what?
an enhancer
Which of the following is a possible mechanism by which an organism's diet can directly affect the expression of its genome?
attachment of methyl groups to bases of DNA
Which of the following is the cancer of epithelial cells?
carcinoma
What protein is activated during apoptosis?
caspase
Liver cells, mammary cells, and skin cells all contain the same genome; however, their respective proteomes vary drastically. This observation is best explained by what phenomenon?
cell differentiation
Should a genetic abnormality arise, ________ prevent a cell from progressing uncontrollably through the cell cycle.
checkpoint proteins
DNA methylation does what?
inhibits transcription.
What is a group of genes that usually stay together during meiosis?
linkage group
When cancer cells have the ability to migrate to other parts of the body, they are said to be what?
metastatic.
What would probably NOT increase the accessibility of the DNA for gene transcription?
methylation of DNA
What CANNOT be repaired by nucleotide excision repair (NER)?
mismatched bases
Assume each of the following letters represents an amino acid. What type of gene mutation occurred to produce the following protein sequence?Normal: JAYBIRDCATPAW Mutated: JAYBIRDBATPAW
missense
A(n) ________ operon is one whose transcription is decreased by effector molecules.
repressible
You see a recombination frequency of 0.3%. What does this indicate?
that the genes are located close together on the same chromosome
The relationship between loci and linkage that Morgan described is what?
the closer together two genes are on a chromosome, the more likely they will be inherited together.
What mutation(s) might result in the formation of an oncogene?
the duplication of a proto-oncogene, so that it occurs several times in a single chromosome
Which of the following mutations might result in the formation of an oncogene?
the duplication of a proto-oncogene, so that it occurs several times in a single chromosome
In rabbits, spotted coat (S) is dominant to solid color (s) and black (B) is dominant to brown (b). A true-breeding black spotted rabbit is mated to a true-breeding brown solid rabbit to produce a heterozygous F1 generation. Two F1 individuals are mated, and you do not see a 9:3:3:1 (black spotted: black solid: brown spotted: brown solid) ratio of offspring, but instead see that almost all offspring are a non-recombinant phenotype. This tells you that...
the genes for fur pattern (spotted vs. nonspotted) and fur color are on the same chromosome.
Genes that encode proteins are first transcribed to mRNA, and then are translated into protein. What is the MOST important factor determining the control of gene expression?
the level of transcription (when a gene is transcribed to mRNA)
Oncogenes could lead to uncontrolled cell division. True or false?
true
The molecule that functions as a corepressor for the trp operon is what?
tryptophan
What is an overgrowth of cells that serves no useful purpose?
tumor