Genetics Exam 4 Final- Ch. 22 and 24
The kernel color in wheat is a continuous trait determined by two additive genes, each with two alleles, that equally contribute to kernel color determination. The red kernels are determined by two genes and two dominant alleles (R1R1R2R2), and white kernels are determined by two recessive alleles at the same two genes (r1r1r2r2). The duplicate dominant alleles R1 and R2 contribute equally to kernel color and cumulatively control the intensity of the red kernel phenotype. Both these alleles are dominant over the recessive white alleles r1 and r2. (A) A true breeding red plant and true breeding white plant are crossed, and the resulting F1 progeny are selfed. What is the expected phenotypic ratio of the kernel progeny of the F2 offspring? (B) Determine which statement best describes the relationship between the phenotypes of the r1r1R2r2 and r1R1r2r2 genotypes.
(A) 1:4:6:4:1 (B) The phenotypes of the r1r1R2r2 and r1R1r2r2 genotypes will be the same because the same number of dominant and recessive alleles are contributing in each genotype.
Select the statements that accurately describe different ways that translocations could lead to cancer.
-A gene for a protein that regulates the cell cycle is placed next to the regulatory sequence of a different gene. The gene is now expressed at inappropriate times. -A new sequence is added to a proto-oncogene. The modified gene now produces a new protein that increases the rate of cell division. AND -A translocation disrupts the sequence of a gene for a protein that stimulates apoptosis. The resulting protein cannot function properly.
Both genes and environmental factors contribute to cancer. The table below shows that prostate cancer is 30 times more common among Caucasians from Utah as among Chinese from Shanghai. Briefly outline how you might determine if these differences in the incidence of prostate cancer are due to differences in the genetic makeup of the two populations or to differences in their environments. Select all that apply.
-If the differences are due to genetic makeup only, then people who migrated from Utah or Shanghai to elsewhere would have a similar cancer rate as people who stayed in Utah or Shanghai. AND -If the differences are due to the environment only, then people who migrated from Utah or Shanghai would have rates of cancer determined by their location and not by their place of origin.
Which of the following mutations have the potential to cause cancer?
-a loss-of-function mutation in a tumor suppressor gene AND -a gain-of-function mutation in a proto-oncogene
What are the methods by which apoptosis can be regulated.
-an intrinsic pathway that is activated by enzymes called caspases AND -an extrinsic pathway that is activated by local signals to the cell's membrane receptors
Suppose Nicole recently learned that she inherited a mutant RB1 allele from her mother, who had retinoblastoma. RB1 is a tumor suppressor gene that is related to retinoblastoma. Why would Nicole be at higher risk for getting retinoblastoma at an earlier age than her sister, Francine, who inherited a normal RB1 allele from their mother?
A person who inherited two functioning alleles of a tumor suppressor gene needs both alleles to mutate for tumors to develop.
Which of the following takes place in a signal-transduction pathway?
An activated membrane-bound receptor undergoes a conformational change. An external signaling molecule binds to a specific receptor. Proteins in the pathway add or remove phosphate groups from other proteins. Activated proteins move into the nucleus to activate transcription factors.
Bloom syndrome is an autosomal recessive disease that exhibits haploinsufficiency. A recent survey showed that people heterozygous for mutations at the BLM locus are at increased risk of colon cancer. Suppose you are a genetic counselor. Suppose that a young woman is referred to you whose mother has Bloom syndrome but the young woman's father has no family history of Bloom syndrome. The young woman asks whether she is likely to experience any other health problems associated with her family history of Bloom syndrome. What advice would you give her?
Based on her family history, she is heterozygous for a mutated BLM allele and will have an increased risk of colon cancer.
What do egg polarity genes in Drosophila specify?
Both the anterior-posterior and dorsal-ventral axes
Which of the following is true regarding cancer cells?
Cancer cells rob healthy tissues of nutrients Cancer cells divide rapidly and continuously Cancer cells can travel to distant sites within the body and set up new tumors AND Most, if not all, cancer cells arise from defects within the DNA
Cloning in plants and animals demonstrates that _________.
Cells retain their nuclear genome during development
Which of the following statements is true regarding epigenetic changes that are associated with cancer?
Changes in DNA methylation are observed in many cancer cells.
Genes that control development of flowers in Arabadopsis include _____________.
Class A genes, which are expressed in whorls 1 and 2 of the flower Class B genes, which are expressed in whorls 2 and 3 of the flower AND Class C genes, which are expressed in whorls 3 and 4 of the flower
quantitative characteristics are also known as __________.
Continuous characteristics
Which of the following are genes that, when mutated, could lead to cancer?
Cyclins Cyclin-dependent kinases DNA-repair Genes AND genes that promote vascularization
What type of virus is associated with cervical cancer?
DNA virus
Some cancers have been treated with drugs that demethylate DNA. Explain how these drugs might work. Do you think the cancer-causing genes that respond to the demethylation are likely to be oncogenes or tumor-suppressor genes? Explain your reasoning.
Demethylation would transcriptionally activate any genes that had been silenced by methylation and would have variable effects depending on whether tumor suppressors or oncogenes or both were activated.
One early (and incorrect) concept of the genetic control of development was that _________.
Development consists of cells losing genes, specifying their identity with the remaining genes
Which of the following types of genes do not regulate development in Drosophila?
Dextro-sinestral genes
Quantitative traits include all of the following except _____________.
Discrete traits, such as seed shape in pea plants
Cancers may be either inherited or they may be induced by environmental factors such as carcinogens and radiation. Select the statement that explains how diverse factors such as hereditary events and environmental agents can both cause cancer.
Hereditary and environmental factors involve mutations that affect the cell cycle.
Which of the following genes control development in Drosophila through the regulation of the expression of other genes?
Homeobox genes Egg-polarity genes Segmentation genes
Nielsen-Ehles experiment with corn kernel color, where he demonstrates polygenic inheritance, ___________.
Involved wheat varieties that differed in only two kernel color loci
How might a retrovirus lead to cancer?
It integrates into the host chromosome and mutates proto-oncogenes.
Which of the following statements are true about apoptosis, or programmed cell death?
It is distinct from necrosis It is a normal part of development It is controlled by genes that can be activated in most cells AND It can be inactivated in some cancers
Which of the following statements about apoptosis, or programmed cell death, is incorrect?
It results in the spillage of cell contents
Cancer is a genetic disorder. How does cancer differ from most other genetic disorders?
Most genetic disorders are inherited through germ cells from parents. Most cancers are, to some extent, the result of mutations in somatic cells that occur during an organism's lifetime.
conservation of developmental genes in evolution is supported by all of the following observations
Mutations of homeotic genes often have similar phenotypic effects in animals Mutations of homeotic genes often have significant, non lethal phenotypic effects AND almost all animals have the same homeobox genes expressed at equivalent anterior-posterior locations
Mutant versions of genes that are normally involved in driving the cell cycle are known as ___________.
Oncogenes
Which of the following does not take place in a signal-transduction pathway?
Proteins are activated when histones are deacetylated
Explain why maternal effects are exhibited by bicoid and nanos, but not runt and gooseberry.
RNA transcripts of bicoid and nanos are made maternal DNA during oocyte formation, whereas runt and gooseberry are transcribed after fertilization.
Tumor-suppressor genes typically act in a _____________ manner, and oncogenes typically act in a ______________ manner.
Recessive; dominant
Which of the following statements are accurate about cell determination in animals?
Regulation of transcription can be involved AND Cells lose totipotency
Which of the following statements best describes Alfred Knudson's two-hit hypothesis?
Retinoblastoma results from two separate genetic defects, both of which are necessary for cancer to develop
Which of the following types of genes regulate development in Drosophila?
Segmentation genes Homeotic genes AND Egg-polarity genes
A genetic counselor determines that patients with a deletion in a particular region of a chromosome are more likely to develop cancer than other people. Is the gene responsible for the increased risk of cancer a tumor suppressor or a proto-oncogene?
The gene is a tumor suppressor, because tumor suppressor genes induce apoptosis in abnormal cells.
Which of the following statements is true of cyclins?
The levels of cyclin oscillate during the course of the cell cycle.
What do evo-devo studies indicate about development in distantly related organisms?
The same genes often control development
Which of the following explains why Hox genes are highly conserved between species?
They are critical for proper development.
Which statements best describes quantitative traits?
They are often polygenic.
Which of the following statements is true of cyclin-dependent kinases?
They regulate the cell cycle by phosphorylating other proteins.
Quantitative traits include all of what?
Threshold traits, which are either on or off Meristic traits, which can only be expressed in whole numbers Truly continuous traits, such as height in humans AND Polygenic traits, which show a range of phenotypes
Which of the following is a way in which chromosome mutations could lead to cancer?
Translocation of a proto-oncogene to a new location puts it under the control of a strong promoter. Inversions cause breaks within a tumor-suppressor gene. Chromosome rearrangements create fusion proteins that are more active and upregulate cell division. AND Deletions can remove or inactivate tumor-suppressor genes.
Which of the following is not a way in which chromosome mutations could lead to cancer?
Translocation of a tumor suppressor gene to a new location puts it under the control of a strong promoter
Genes that normally produce factors that inhibit cell division are called ____________.
Tumor-suppressor genes
conservation of developmental genes in evolution is supported by all of the following observations except that _____________.
Tunicates have homeotic genes in distinct chromosomal locations from other animals
What is a morphogen?
a protein that varies in concentration along a gradient and brings about different developmental responses based on its concentration
Which of the following is not true regarding cancer cells?
cancer cells respond to normal cell cycle controls but proliferate at an abnormal rate
What is the function of Hox genes during development?
direct the formation of the appropriate structure at a given location in the embryo
Suppose a researcher hypothesizes that the homeotic gene ey is expressed in the eye region because ey is known to be important in eye formation in Drosophila melanogaster. In the image below, anterior is to the left and posterior is to the right. Click on the area of the embryo where ey is expressed. How would you test your hypothesis?
generate a fluorescent reporter using the ey promoter and examine the expression pattern
In general, what causes normal cells to become cancer cells?
loss of cell cycle control
Anterior-posterior development in Drosophila is regulated by ___________.
mRNA that is deposited at one end of the egg
Select the best definition of apoptosis.
programmed cell death
How might a mutation in a gene that regulates telomerase lead to cancer?
the mutation could allow telomerase to be expressed when it should not be
Which of the following statements best describes the clonal evolution of tumors?
tumor cells acquire more somatic mutations that allow them to become increasingly more aggressive in their proliferative properties