Exam 1 Flashcards
_________ is a change in allele or genotype frequency over time.
Evolution
How many homologous pairs of chromosomes in each somatic cell in your body?
23
How many total chromosomes in each somatic cell in your body?
46
What is the chromosome theory of inheritance?
A concept that explains how genetic information is transmitted from one generation to the next.
What is an allele?
Different version of the same gene.
What is a gene?
An instruction that tells your body what it needs to do.
Why is the pea wrinkled-seed allele a recessive allele?
The trait associated with the allele is not exhibited in htereozygotes.
Mendel’s experimental method involved using true breed parental plants for each of the traits he studied in the monohybrid cross. Why was this vital to the outcomes of the experiment?
By starting with a true breed pure line, Mendel could better understand the inheritance of the traits as only due to the result of the cross.
The alleles found in haploid organisms cannot be dominant or recessive. Why?
Dominance and recessiveness describe which of two possible phenotypes are exhibited when two different alleles occur in the same individual.
How did Mendel’s monohybrid cross with round and wrinkled seeds and other single traits tested, directly contradict the blending hypothesis?
The result of the cross between round and wrinkled pure breed cell lines was all round seeds in the F1 offspring, not partially round and wrinkled as blending theory would predict.
Mendel crossed plants that produced only round seeds to those that produced only wrinkled seeds. In the next generation, all the pea plants produced only round seeds. Which term describes how the round-seed allele is inherited?
Dominant
What is typically the purpose of drawing a forked-line diagram in genetics?
to determine what kinds of gametes an individual can produce
Name the fours evolutionary processes that change allele frequencies in populations.
Natural Selection.
Genetic Drift.
Gene Flow.
Mutation.
What is a “population”?
A group of individuals of the same species that live in the same area at the same time and can interbreed.
____________ changes the frequency of certain alleles if they influence reproductive success of organisms in a particular environment.
Natural Selction.
_______________ causes random changes in allele frequencies due to the chance survival and reproductive success in some individuals, even if they are less fit than other individuals.
Genetic Drift.
___________ occurs when individuals leave one population, join another, and breed.
Gene Flow.
___________ changes allele frequencies in a population when a random change in the DNA sequence creates a new allele of a gene.
Mutation.
Random Mating?
A model that assumes that gametes form the gene pool combine at random. This means individuals are mating by chance.
What are the five important assumptions about populations in the Hardy-Weinberg Equilibrium?
Random Mating.
No Natural Selection.
No Genetic Drift.
No gene flow.
No mutation.
In what sense is the Hardy-Weinberg Equilibrium a null hypothesis?
It defines what genotype and allele frequencies should be expected if evolutionary processes and nonrandom mating are NOT occurring.
what is a gene pool?
A hypothetical collection of all the genes that occur in a habitat.
Why isn’t inbreeding considered an evolutionary process?
It does not change allele frequencies.
What are the four main patterns, or modes, that affect genetic variation?
Directional selection.
Stabilizing Selection.
Disruptive selection.
Balancing selection.
Directional selection?
Changes the average value of a trait.
Stabilizing selection?
Reduces variation in a trait.
Disruptive selection?
Increases variation in a trait.
Balancing selection?
Maintains variation in a trait.
Which evolutionary mechanism results in adaptation?
Natural Selection.
How do stabilizing and disruptive selection differ?
Stabilizing selection reduces the amount of variation in a trait. Disruptive selection increases the amount of variation in a trait
Which mode of natural selection is most likely to contribute to speciation?
Disruptive selection.
In a population undergoing genetic drift, what is responsible for the changes in allele frequency?
Random chance due to sampling error.
In the context of genetic drift, what is meant by allele fixation?
The allele reaches a frequency of 1.0 in the gene pool.
True or false? Gene flow can either increase or decrease the average fitness of a population.
True
Which evolutionary process often favors certain alleles and leads to a decrease in overall genetic variation in a population?
Natural Selection.
Which evolutionary process tends to decrease genetic diversity over time, as alleles are randomly lost or fixed in a population?
Genetic Drift.
Which evolutionary process increases genetic diversity in a recipient population if new alleles arrive with immigrating individuals?
Gene Flow
Which evolutionary process decreases genetic variation in the source population if alleles leave with emigrating individuals?
Gene flow
Where do entirely new alleles come from?
Mutation.
What is point mutation?
A change in a single base pair in DNA.
Speciation?
The evolution of two or more distinct species from a single ancestral species.
_____________ occurs when some sort of barrier to gene flow isolates two populations within a species.
Genetic Isolation.
_________ makes allele frequencies more similar among populations
Gene flow
_____________ occurs when mutation, natural selection, and genetic drift occur in each of the isolated populations.
What does this mean?
Genetic divergence.
It means that the populations begin to evolve independently of each other.
According to the biological species concept, what is the main criterion for identifying species?
reproductive isolation.
Which mechanism of reproductive isolation causes postzygotic isolation?
Hybrid Sterility
What distinguishes a morphospecies?
It has distinctive characteristics, such as size, shape, or coloration.
Which species concept would be most useful to a team of biology students conducting a biodiversity survey on their campus?
The morphospecies concept
Which is the first step in allopatric speciation?
Physical isolation of two populations
Describe vicariance
A population is fragmented into isolated subpopulations.
How do autopolyploidy and allopolyploidy differ?
The chromosomes of an autopolyploid individual come from the same species, while an allopolyploid individual has sets of chromosomes from different species.
True or false? Speciation is a slow process.
False. Speciation is sometimes a slow process, but can occur rapidly, such as the formation of a new species of Tragopogon by allopolyploidy in a single generation.
Characteristics of life?
Life
Adaptation
Reproduction
Ability to live on it’s own
Cell theory of life?
Cells are the basic unit of structure of life.
All organisms are made of cells.
All cells come from pre-existing cells.
Are Viruses Alive?
No. They require a host.
What is selection?
What is adaptation?
Changing to survive in your environment.
Explain why Dr. Belayaev’s foxes changed from wild to tame over 10 generations.
We artificially selected for the docile foxes as opposed to the wild foxes.
Explain the process of evolution by natural selection.
There are multiple mechanisms of evolution.
Mutation.
Gene pool.
Genetic flow.
genetic drift.
Mendel’s first Law?
The law of segregation.
One allele is provided to offspring from each parent. The heredity is random.
Mendel’s second law?
Law of independent assortment.
Alleles from d
Incomplete dominance?
Some alleles are neither dominant nor recessive. A heterozygote has an intermediate phenotype.
codominant alleles?
When both alleles are present.
Is the ABO Blood group system an example of codominance or incomplete dominance? Why?
codominance because in codominance BOTH traits from the alleles show up.
Pleiotropic?
A single allele having multiple effects.
Epistasis?
Phenotypic expression of one gene is influenced by another gene. One gene is masking another gene that affects the same phenotype (like coat color for labradors)
What is the result of inbred offspring? why?
Low quality due to increase number of homozygous recessive loci.
Hybrid vigor or heterosis?
A cross between two different true-breeding homozygotes which can result in offspring with stronger, larger phenotypes.
Penetrance?
Proportion of individuals with a certain genotype that show the phenotype.
Expressivity?
Degree to which genotype is expressed in an individual.
Genes that determine complex continuous characters?
Quantitative trait loci (QTL)
When there is allelic variation at a gene locus, in a population, that population is _________ for that gene.
polymorphic.
Phenotypes are influenced by ?
genes and the environment.
The origin of genetic variation?
Mutation.
Any change in the genetic material?
Mutation.
Result of the migration of individuals and movements of gametes between population?
Gene Flow.
Results from random changes in allele frequencies?
Genetic Drift.
In large populations, ___________ can influence frequencies of alleles that don’t affect survival and reproduction.
Genetic Drift.
If populations are reduced to a small number of individuals, a _________________ can reduce the genetic variation quickly.
Population bottleneck (genetic drift)
A population forced through a bottleneck is likely to lose much _________________
genetic variation.
Conal monoculture (planting of a single species) results in what?
The stopping of evolution!
Which concept describes species based on their appearance?
Morphological species concept.
A concept that is useful when initially determinig the number of species.
Morphospecies concept.
The process by which one species splits into two or more daughter species, often gradually?
Speciation.
What is a required condition to determine if speciation has occurred?
Reproductive isolation.
Who proposed the Biological Species Concept?
Ernst Mayr.
Species are groups of actually or potentially interbreeding natural population which are reproductively isolated from other such groups?
Biological species concept.
Gene flow is interrupted when…
two populations are isolated, over time their genetic structure may change enough so that interbreeding is no longer possible.
Occurs when populations are separated by a physical barrier.
Allopatric Speciation.
A physical way that can populations become isolated.
Vicariance (barrier) via continental drift, sea level changes, etc.
Reduces the amount of variation in a trait.
stabilizing selection.
What does not require physical isolation and needs disruptive selection?
Sympatric speciation.
Increases the amount of variation in a trait.
Disruptive selection.
Which type of selection favors extreme phenotypes at both ends of the range of phenotypic variation?
Disruptive selection.
Which type of selection favors phenotypes near the middle of the range of phenotypic variation, maintaing average phenotype.
Stabilizing selection.
Which type of selection favors one extreme phenotype, causing the average phenotype in the population to change in one direction?
Directional selection.
Sympatric speciation most commonly occurs by ___________, duplication of the whole set of chromosomes.
polyploidy.
Chromosome duplication in a single species is ___________; combining of chromosomes from two species is _____________.
autopolyploidy.
allopolyploidy.
Can occur if a cell accidentally duplicates its chromosomes.
Autopolyploidy.
Two categories of reproductive incompatibility.
Prezygotic reproductive barriers.
Postzygotic reproductive barrieres.
Which reproductive barrier operates before fertilization occurs?
Prezygotic.
What is the strengthening of prezygotic barriers?
reinforcement.
A botanist studying the inheritance of flower color found that when she crossed the offspring of two pure-breeding flower lines, one purple and one white, she got the following F2 generation from planting 60 seeds: 17 plants with purple flowers, 26 plants with lavender flowers, and 15 plants with white flowers.
This is an example of __________.
incomplete dominance.
If an organism is heterozygous for two traits that are linked, how many genotypes are possible in the gametes produced from a single germ-line cell? Assume that no crossing over occurs.
two
If the first five seeds (offspring) grown from a cross between two heterozygous parent peas with the genotype Rr are all round, what is the probability that the next offspring from these parents will be wrinkled?
25 percent.
In snapdragon plants, T is the dominant allele for plant height (tall), t is the recessive allele for plant height (dwarf), RR flowers are red, rr flowers are white, and Rr flowers exhibit incomplete dominance and are pink.
A cross between Ttrr and TtRR results in what proportion of offspring with pink flowers on dwarf plants?
one quarter
The __________ hypothesis suggested that an offspring’s traits are intermediate between the egg-producing parent’s and the sperm-producing parent’s traits.
blending inheritance.
