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Questions and Answers
What is the role of an oncogene in cancer development?
What is the role of an oncogene in cancer development?
How many copies of a tumor-suppressor gene usually need to be inactivated for cancer to occur?
How many copies of a tumor-suppressor gene usually need to be inactivated for cancer to occur?
Which statement correctly differentiates between tumor-suppressor genes and proto-oncogenes?
Which statement correctly differentiates between tumor-suppressor genes and proto-oncogenes?
What characteristic do malignant cancerous cells exhibit?
What characteristic do malignant cancerous cells exhibit?
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What happens when a tumor-suppressor gene experiences a loss of function mutation?
What happens when a tumor-suppressor gene experiences a loss of function mutation?
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What is the main effect of stabilizing selection on phenotypic distribution?
What is the main effect of stabilizing selection on phenotypic distribution?
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How does directional selection impact allele frequencies in a population?
How does directional selection impact allele frequencies in a population?
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Which of the following best describes heterozygote advantage?
Which of the following best describes heterozygote advantage?
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What factor does NOT significantly influence genetic drift in a population?
What factor does NOT significantly influence genetic drift in a population?
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What is the coefficient of inbreeding (F) desired for healthy populations?
What is the coefficient of inbreeding (F) desired for healthy populations?
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Which type of selection allows for the coexistence of multiple genotypes?
Which type of selection allows for the coexistence of multiple genotypes?
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What is meant by the term 'threshold traits' in the context of diseases?
What is meant by the term 'threshold traits' in the context of diseases?
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What is the relationship between variance and standard deviation?
What is the relationship between variance and standard deviation?
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In the context of polygenic inheritance, which statement is true?
In the context of polygenic inheritance, which statement is true?
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The bottleneck effect primarily leads to what outcome in a population?
The bottleneck effect primarily leads to what outcome in a population?
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What role do proto-oncogenes play in cellular growth?
What role do proto-oncogenes play in cellular growth?
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Which of the following is NOT a major tumor-suppressor gene?
Which of the following is NOT a major tumor-suppressor gene?
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Which of the following statements about mutations in genes and cancer is true?
Which of the following statements about mutations in genes and cancer is true?
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What are morphogens responsible for during development?
What are morphogens responsible for during development?
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How do homeotic genes function during development?
How do homeotic genes function during development?
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In Drosophila, what does the Sxl gene govern?
In Drosophila, what does the Sxl gene govern?
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What are the mechanisms that can alter existing genetic variation in a population?
What are the mechanisms that can alter existing genetic variation in a population?
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What does directional selection favor in a population?
What does directional selection favor in a population?
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What is broad sense heritability (hB2) primarily concerned with?
What is broad sense heritability (hB2) primarily concerned with?
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Which of the following definitions best describes polymorphism?
Which of the following definitions best describes polymorphism?
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Which relationship results in the highest expected phenotypic correlation (rexp)?
Which relationship results in the highest expected phenotypic correlation (rexp)?
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What is the relationship between allele frequency and genotype frequency in a population?
What is the relationship between allele frequency and genotype frequency in a population?
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What is the result of inbreeding in a population?
What is the result of inbreeding in a population?
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How is narrow sense heritability (hN2) calculated?
How is narrow sense heritability (hN2) calculated?
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Which of the following mechanisms is a prezygotic isolating mechanism?
Which of the following mechanisms is a prezygotic isolating mechanism?
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What does the principle of parsimony in constructing phylogenetic trees emphasize?
What does the principle of parsimony in constructing phylogenetic trees emphasize?
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Which concept best describes a species' ecological role within its environment?
Which concept best describes a species' ecological role within its environment?
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What happens during cladogenesis?
What happens during cladogenesis?
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What characterizes orthologous genes?
What characterizes orthologous genes?
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In the context of genetic variation, what does heterosis refer to?
In the context of genetic variation, what does heterosis refer to?
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Which of the following statements about the Kimura ‘neutral theory of evolution’ is correct?
Which of the following statements about the Kimura ‘neutral theory of evolution’ is correct?
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What is the main purpose of constructing phylogenetic trees?
What is the main purpose of constructing phylogenetic trees?
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What happens when two populations are separated by geographic barriers in allopatric speciation?
What happens when two populations are separated by geographic barriers in allopatric speciation?
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Study Notes
Cancer: Cellular and Genetic Processes
- Cancer is a multistep process at the cellular and genetic levels.
- Malignant cells are invasive, able to invade healthy tissues.
- Malignant cells are metastatic, able to migrate to other parts of the body.
- Oncogenes are mutant genes that are overexpressed or hyperactive, contributing to cancer growth.
- Tumor suppressor genes prevent cancer; loss-of-function mutations allow cancer growth.
- Proto-oncogenes, involved in the cell cycle, can mutate into oncogenes causing unregulated division.
- Tumor suppressor genes, regulating the cell cycle, can be inactivated causing unregulated division.
- One copy of a proto-oncogene needs mutation to cause cancer, while both copies of a tumor suppressor gene typically need inactivation.
- Oncogenes promote abnormal cell growth.
- Proto-oncogenes are normal genes that can mutate into oncogenes.
- Tumor suppressor genes prevent cancer cell proliferation.
- Major tumor suppressor genes include: rb, p16, NF1, APC, p53, BRCA-a, BRCA-2.
- Most cancers result from mutations in multiple genes. The order of mutations is not critical.
- Tumor cells often have missing, extra, or rearranged chromosomes.
- Inherited mutations in oncogenes or tumor suppressor genes can predispose individuals to cancer.
- Chromatin modification abnormalities are common in cancer cells.
Embryonic Development
Stages of Development
- Morula: 16-cell stage
- Blastula: 32-cell stage
- Gastrula: 64-cell stage
Developmental Factors
- Morphogens are molecules specifying positional information and driving developmental changes.
- Morphogens can influence development in unfertilized oocytes.
- Homeotic genes determine the final identity of body regions.
Developmental Axes and Genes
- Adult flies have four axes: anteroposterior (head-tail), dorsoventral (up-down), left-right, and proximodistal (limb attachment).
- Segmentation genes are categorized as: gap genes, pair-rule genes, and segment-polarity genes.
- Maternal effect genes influence gap, pair-rule, and segment-polarity genes.
- Homeotic mutants replace one body part with another.
- Polycomb genes repress homeotic genes in inappropriate regions.
- Trithorax genes promote homeotic gene expression in appropriate regions.
Sex Determination in Nematodes
- Male nematodes (XO) have 1031 somatic cells in adulthood.
- Hermaphrodites (XX) have 959 somatic cells in adulthood.
- Hermaphrodites have both male and female reproductive organs.
Plant Development
- Plants have a root-shoot axis and a radial axis.
- The root-shoot axis defines tips of shoots and bottoms of roots.
- The radial axis defines buds that form branches, leaves, and flowers.
Sex Determination in Insects
- In insects, XX is female, XY and XO are male.
- X chromosome controls femaleness via the Sxl gene.
- An insect with no two X chromosomes is male.
- In most animals, XX or X0 is female and XY is male.
- Y chromosome determines maleness via the SRY gene.
- In Drosophila, the Sxl gene determines femaleness.
- In animals, the SRY gene determines maleness.
Population Genetics
Polymorphism
- Polymorphism refers to trait variation within a population.
- Polymorphism at the DNA level occurs when two or more alleles influence a phenotype.
- A polymorphic gene commonly exists with two or more alleles.
Allele and Genotype Frequencies
- Allele frequency = (Number of allele copies) / (Total allele copies)
- Genotype frequency = (Number of individuals with a genotype) / (Total individuals)
- Allele and genotype frequencies are always less than or equal to 1.
- For polymorphic genes, the allele frequencies sum to 1.0
- The Hardy-Weinberg equation (p² + 2pq + q² = 1) mathematically describes the results of a Punnett square.
Mechanisms of Genetic Variation
- Natural selection, genetic drift, migration, and nonrandom mating can alter genetic variation.
- Natural selection favors beneficial alleles.
- Darwinian fitness (w) measures reproductive success.
Types of Selection
- Directional selection favors one extreme phenotype.
- Balancing selection maintains multiple alleles.
- Disruptive selection favors multiple phenotypes.
- Stabilizing selection favors intermediate phenotypes.
Genetic Drift
- Genetic drift is random change in allele frequencies due to chance fluctuations.
- Genetic drift affects allele frequencies more quickly in small populations. - Bottleneck and founder effects significantly impact genetic drift.
Inbreeding
- Inbreeding occurs between related individuals.
- Inbreeding coefficient (F) assesses relatedness.
- Low inbreeding coefficients (F < 5%) are preferred for animal health.
Mutations
- Mutations can be beneficial, neutral, or deleterious.
- Neutral and deleterious mutations are more common than beneficial mutations.
DNA Fingerprinting
- DNA fingerprinting uses repetitive sequences to identify individuals. -Matches are used in crime scene investigations.
Quantitative Traits
- Complex traits involve multiple genes and environmental factors.
- Quantitative traits are numerically measurable (e.g., height, weight).
- Quantitative traits can be meristic (whole numbers, e.g., bristles).
- Diseases can be threshold traits with contributions from multiple genes.
Biometrics
- Biometrics statistically analyzes biological traits.
- Mean is the average value.
- Variance (VX) measures deviation from the mean.
- Standard deviation (SD) is a useful measure derived from variance.
- Correlation coefficient (r) evaluates the association between variables.
- Covariance (CoV) underlies the calculation of r.
Polygenic Inheritance
- Polygenic traits involve multiple genes influencing a phenotype.
- Environmental factors influence polygenic traits.
- Genetic and environmental variance both affect the observed phenotypic variance.
Heritability
- Heritability measures how much phenotypic variance is due to genetics.
- Broad-sense heritability (hB²) considers all genetic sources.
- Narrow-sense heritability (hN²) considers only additive genetic variance.
Selective Breeding
- Selective breeding (artificial selection) manipulates traits.
- Inbreeding can reduce genetic variation and increase risk of deleterious alleles (inbreeding depression).
- Heterosis (hybrid vigor) occurs when crosses between different inbred lines create offspring that are more vigorous.
Speciation
Biological Species Concept
- Species are groups whose members can interbreed.
- Members of one species cannot interbreed with members from different species.
Modes of Speciation
- Prezygotic isolating mechanisms prevent zygote formation.
- Postzygotic isolating mechanisms prevent viable offspring development.
- Allopatric speciation (geographic isolation) is common.
- Parapatric speciation involves partial geographic separation.
- Sympatric speciation occurs without geographic separation.
Species Concepts
- Evolutionary species concept emphasizes lineage divergence.
- Ecological species concept relates species to ecological niches.
- General lineage concept is a widely-accepted approach to define species.
Phylogeny
- Phylogeny traces the evolutionary history of species.
- Phylogenetic trees depict species relationships.
- Phenetic method uses overall similarities to build trees (phenograms).
- Cladistic method uses evolutionary pathways to build trees using parsimony
Homologous Genes
- Homologous genes originate from a common ancestral gene.
- Orthologous genes are found in different species.
- Paralogous genes are found within a single species.
- Neutral mutations account for much genetic variation.
- Kimura's neutral theory suggests that most evolution occurs due to random mutation fixation
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Description
Explore the intricate cellular and genetic mechanisms that lead to cancer development. This quiz covers key concepts such as oncogenes, tumor suppressor genes, and the differences between malignant and benign cells. Understand how mutations can result in uncontrolled cell growth and proliferation.
