Biology Chapter 12: Evolution and Genetics (4 Stars) Flashcards
Chromosomes contain genes in a _____ sequence.
linear
_____ are alternative forms of a gene.
Alleles
A ______ allele requires only one copy to be expressed.
dominant
A recessive allele requires ___ copies to be expressed.
two
A ______ is the combination of alleles one has at a given genetic locus.
genotype
Having two of the same allele is termed ______
homozygous.
Having two different alleles is termed _______
heterozygous.
Having only one allele is termed _______ (such as male sex chromosomes).
hemizygous
A _______ is the observable manifestation of a genotype.
phenotype
There are different patterns of ______
dominance.
______ has one dominant allele and one recessive allele.
Complete dominance
______ has more than one dominant allele.
Codominance
______ has no dominant alleles; heterozygotes have intermediate phenotypes.
Incomplete dominance
______ is the proportion of a population with a given genotype who express the phenotype.
Penetrance
_____ refers to the varying phenotypic manifestations of a given genotype.
Expressivity
______ states that an organism has two alleles for each gene, which segregate during meiosis, resulting in gametes carrying only one allele for a trait.
Mendel’s first law (of segregation)
_______states that the inheritance of one allele does not influence the probability of inheriting a given allele for a different trait.
Mendel’s second law (of independent assortment)
The Griffith experiment demonstrated the ______, converting non-virulent bacteria into virulent bacteria by exposure to heat-killed virulent bacteria.
transforming principle
The Avery–MacLeod–McCarty experiment demonstrated that DNA is the genetic material because degradation of DNA led to a cessation of _____
bacterial transformation.
The Hershey–Chase experiment confirmed that DNA is the genetic material because only ____ DNA could be found in bacteriophage infected bacteria.
radiolabeled
All of the alleles in a given population constitute the _____
gene pool.
_____ are changes in DNA sequence.
Mutations
______ include point mutations (the substituting of one nucleotide for another) and frameshift mutations (moving the three-letter transcriptional reading frame).
Nucleotide mutations
A _______ has no effect on the protein.
silent mutation
A ______ mutation results in the substitution of one amino acid for another.
missense mutation
A ______ mutation results in the substitution of a stop codon for an amino acid.
nonsense mutation
Insertions and deletions result in a ____ in the reading frame, leading to changes for all downstream amino acids.
shift
______ include much larger-scale mutations affecting whole segments of DNA.
Chromosomal mutations
______ occur when a large segment of DNA is lost.
Deletion mutations
_____ occur when a segment of DNA is copied multiple times.
Duplication mutations
_____ occur when a segment of DNA is reversed.
Inversion mutations
_____ occur when a segment of DNA is moved from one chromosome to another.
Insertion mutations
______ occur when a segment of DNA is swapped with a segment of DNA from another chromosome.
Translocation mutations
______ is a flow of genes between species through hybrid offspring.
Genetic leakage
______ occurs when the composition of the gene pool changes as a result of chance.
Genetic drift
The ______ results from bottlenecks that suddenly isolate a small population, leading to inbreeding and increased prevalence of certain homozygous genotypes.
founder effect
_____ visually represent the crossing of gametes from parents to show relative genotypic and phenotypic frequencies.
Punnett squares
A ______ cross accounts for one gene; a dihybrid cross accounts for two genes.
monohybrid
In sex-linked crosses, sex chromosomes are usually used to indicate sex as well as _____
genotype.
The ______ states that if a population meets certain criteria (aimed at a lack of evolution), then the allele frequencies will remain constant (Hardy–Weinberg equilibrium). Evolution
Hardy–Weinberg principle
______ states that chance variations exist between individuals, and that advantageous variations—those that increase an individual’s fitness for the environment—afford the most opportunity for reproductive success.
Natural selection
The modern synthesis model ______ accounts for mutation and recombination as mechanisms of variation and considers differential reproduction to be the mechanism of reproductive success.
(neo-Darwinism)
_____ considers an organism’s success to be based on the number of offspring, success in supporting offspring, and the ability of the offspring to then support others; survival of offspring or relatives ensures continuation of genes in subsequent generations.
Inclusive fitness
_____ equilibrium considers evolution to be a very slow process with intermittent rapid bursts of evolutionary activity.
Punctuated
Stabilizing selection keeps ____ in a narrow range, excluding extremes.
phenotypes
______ moves the average phenotype toward one extreme.
Directional selection
______ moves toward two different phenotypes at the extremes and can lead to speciation.
Disruptive selection
______ is the rapid emergence of multiple species from a common ancestor, each of which occupies its own ecological niche.
Adaptive radiation
A species is the largest group of organisms capable of breeding to form _____ offspring. Species are reproductively isolated from each other by pre- or postzygotic mechanisms.
fertile
___ species can evolve with different relationship patterns.
Two
_____ evolution occurs when two species sharing a common ancestor become more different.
Divergent evolution
______ evolution occurs when two species sharing a common ancestor evolve in similar ways due to analogous selection pressures.
Parallel
_____ evolution occurs when two species not sharing a recent ancestor evolve to become more similar due to analogous selection pressures.
Convergent
According to the ______ model, the degree of difference in the genome between two species is related to the amount of time since the two species broke off from a common ancestor.
molecular clock model
