Human Genetics Test 4

the accumulation of cancer-promoting mutations that each progressively contribute to causing uncontrolled cell proliferation

how does cancer occur?

a mass of abnormal cells that are not cancerous

what is a benign tumor?

a mass of abnormal cells that are cancerous

what is a malignant tumor?

malignant cells enter the blood or lymph fluids and seed in other tissues to develop new tumors

what is metastasis?

• hyperplasia

• dysplasia

what can cells in a benign tumor display?

cells divide faster than normal and build up. the cells look normal under the microscope

what is hyperplasia?

cells divide faster than normal and build up. the cells do not look normal under the microscope, can be low grade or high grade

what is dysplasia?

cells that have high-grade dysplasia. cells are benign but have high risk of becoming malignant

what is carcinoma in situ?

rapid cell division rate, ability to invade new tissues, immortality, a high metabolic rate, and an abnormal appearance

how are cancer cells characterized?

spontaneous or induced mutations that occur throughout life

what are most cancer-causing mutations?

an agent that causes mutation

what is a mutagen?

an agent that can promote the development of cancer

what is a carcinogen?

an agent that can promote the development of cancer

what is a carcinogen?

normal genes that cause normal cells to become cancerous when they develop a gain of function mutation

what are proto-oncogenes?

mutated versions of proto-oncogenes

what are oncogenes?

• promote cell division

• inhibit cell death

what are the functions of the proteins encoded by proto-oncogenes/oncogenes?

apoptosis is prevented even when it shouldn’t be

what happens when a cell has a mutated oncogene?

genes encoding proteins that function in the signaling pathway that promotes cell division

what do proto-oncogenes include?

cancer-causing mutations that prevent GTP hydrolysis

what keeps the Ras protein in the active state?

cause normal cells to become cancerous when they develop a loss-of-function mutation

what is the function of tumor suppressor genes?

• inhibit cell division

• promote cell death

• involved in DNA repair

what are the functions of the proteins encoded by tumor-suppressor genes?

a master regulator of the cell cycle

what is the Rb tumor-suppressor gene?

E2F transcription factors and prevents transcription of genes that promote cell cycle progression

what does the Rb protein interact with?

Retinoblastoma

what do individuals who inherit a mutation in the Rb gene have a predisposition to develop?

a transcription factor

what is p53?

activates genes that promote DNA repair, and inhibits cell cycle progression

what does p53 do when DNA is damaged?

it promotes apoptosis

what happens if DNA is not repaired by p53?

cells with DNA damage will continue to survive and divide and accumulate more damage

what happens if the p53 gene is mutated?

it is due to an inherited mutation in a tumor-suppressor gene

how do individuals develop a genetic predisposition of cancer?

all interbreeding individuals of same species in the same location at the same time

what is population?

genetic variation in a population and how genetic variation changes over time

what does population genetics study?

all alleles of every gene in a population

what is a gene pool?

different

different populations have _________ gene pools

number of copies of a specific allele in a population/total number of all alleles for that gene in a population

what is allele frequency?

number of individuals with a particular genotype in a population/ total number of individuals in a population

what is genotype frequency?

allele and genotype frequency

what does the Hardy-Weinberg Equilibrium relate?

p² + 2pq + q² = 1

what is the Hardy-Weinberg Equilibrium?

frequency of dominant allele

what does p stand for in the Hardy-Weinberg Equilibrium?

frequency of recessive allele

what does q stand for in the Hardy-Weinberg Equilibrium?

frequency of homozygous dominant genotype

what does p² stand for in the Hardy-Weinberg Equilibrium?

frequency of heterozygous genotype

what does 2pq stand for in the Hardy-Weinberg Equilibrium?

frequency of homozygous recessive genotype

what does q² stand for in the Hardy-Weinberg Equilibrium?

the frequency of gametes carrying a particular allele is equal to the allele frequency for a population

what is the general rule of the Hardy-Weinberg Equilibrium?

multiplying the allele frequencies

what gives the proportion of each allele combination in the population?

• random mating

• no natural selection

• no migration between populations

• no genetic drift

• no new mutations

what conditions does the Hardy-Weinberg Equilibrium assume?

the allele and genotype frequencies will remain constant from generation to generation

what happens if the conditions of the Hardy-Weinberg Equilibrium are met?

changes in gene pool from generation to generation

what is microevolution?

individuals with beneficial alleles that enhance survival and/or reproductive success will be more likely to survive and/or reproduce and pass on their alleles

what is natural selection?

a measure of reproductive success

what does fitness mean in population genetics?

a phenotype/trait on one side of the mean

what does natural selection select for in directional selection?

the peak shifts in one direction

what happens on a graph of phenotype versus frequency?

change in environment, introduction of a new allele, or both

why might a peak shift in one direction on a graph of phenotype versus frequency?

loss of body hair in early humans

what is an example of natural selection favoring a trait on one side of the mean?

heterozygotes have a survival advantage over either of the homozygous genotypes

what is heterozygote advantage?

maintenance of both alleles in a population

what does natural selection favor in balancing selection?

it becomes present at a much higher frequency than would otherwise be expected

what happens to the recessive allele with heterozygote advantage?

mean phenotype

what does natural selection favor in stabilizing selection?

the mean peak gets taller and narrower

what happens during stabilizing selection?

• infant birth weight

• brain size after an initial period of directional selection

what are some examples of stabilizing selection in humans?

two or more phenotypes in a population that occupies a diverse enviroment

what does natural selection favor in disruptive/diversifying selection?

two or more peaks as there are two or more favored phenotypes

what does the population have in disruptive/diversifying selection?

dark pigmentation in areas with plentiful daily sunlight and light skin pigmentation in areas with less daily sunlight

what is a human example of natural selection favoring disruptive/diversifying selection?

a change in allele/genotype frequency due to random chance

what is genetic drift?

population size and initial allele frequencies

what does the rate of genetic drift depend on?

when they are in small populations

when are allele frequencies more susceptible to genetic drift?

• a population decreases dramatically in size due to a natural event

• individuals die randomly

• population size rebounds, but genetic composition is altered

what is bottleneck effect?

• a small groups of individuals separate from a larger population

• allele frequencies are not representative of original population

what is the founder effect?

when individuals migrate between populations with different allele frequencies

when does gene flow occur?

genetic variation within the receiving population and reduces genetic variation between populations

what does migration increase?

individuals choose mates with a similar phenotype or a different phenotype to their own

what is assortative mating?

the number of genes involved in producing the phenotype and the degree of assortative mating

what does the effect of assortative mating depend on?

mating between two closely genetically related individuals

what is inbreeding?

traits that are determined by more than one gene

what are polygenic traits?

traits influenced by several genes as well as environmental factors

what are complex traits?

• continuous traits

• meristic traits

• threshold traits

what are the 3 categories of complex traits?

do not fall into discrete categories

what are continuous traits?

can be counted and expressed in whole numbers

what are meristic traits?

traits that show a genetic predisposition but are determined by the contribution of several genes and environment

what are threshold traits?

can be described numerically

what are quantitative traits?

frequency distribution

what can continuous traits be described with?

a bell-shaped curve with symmetrical variation about an average value

what do normal distributions show?

average number found by adding all data points and dividing by the number of data points

what is mean?

a measure of the amount of variation in a group

what is variance?

also a measure of the amount of variation in a group

what is standard deviation?

bell-shaped curve with a peak at the mean value and symmetrical distribution about the mean; shape is determined by the mean and standard deviation

what is normal distribution?

a measure of the relationship between two variables

what is covariance?

the strength of association between two variables

what does the correlation coefficient measure?

it indicates there is a strong association between 2 variables

what happens if the correlation coefficient is significant?

cause and effect

what does significant association NOT imply?

scatter plots

what can be used to visualize the degree of correlation?

a genetic and environmental component

what does variance have?

the proportion of overall variance that is due to genetic variance

• a measure of the extent to which differences among individuals are due to genetic factors

• a measure of how much “nature” contributes to genetic variance

what is broad-sense heritability?

the proportion of overall variance that is due to additive genetic variance

• it is a measure of the extent to which phenotypic variation can be predictably transmitted to offspring

what is narrow sense heritability?

by comparing expected correlation coefficient values with observed correlation coefficient values

how can narrow sense heritability be estimated?

to amplify a DNA sequence

what is the purpose of a Polymerase Chain Reaction (PCR)?

• template DNA

• primers

• DNA nucleotides

• Taq polymerase

what does PCR require?

• denaturation of DNA template

• primer annealing

• primer extension

what are the steps of PCR?

• amplification of DNA

• detecting the presence of a DNA sequence

• isolating a gene for insertion into a vector

• research applications

what are some uses of PCR?

DNA produced from mRNA

what is complimentary DNA (cDNA)?

using the enzyme reverse transcriptase

how is cDNA produced?