Chapter 20
If the frequency of an autosomal recessive trait in humans is 1 out of 100 births, what would be the expected frequency of heterozygote carries for the trait if we assume that the gene is in Hardy Weinberg equilibrium?
0.18
Antigens on red blood cells are herditary traits that allow blood to be typed in different ways. One system is based on a gene with two alleles, M and N. If the frequency of the M allele in a popullation is 0.4, then according to the Hardy Weinberg rule, the expected frequency of the heterozygous MN genotype is ?
0.48
The recessive phenotype of a trait occurs in 16% of a population. What is the frequency of the dominant allele?
0.60
A human autosomal recessive trait appears in 1 in 100 births. What percent of people homozygous dominant for this trait?
0.81
A fur color gene in rabbits has a white dominant and brown recessive allel. The enviorment changes suddenly and none of the white rabbits survive. In a population of 10,000 rabbits the initial frequency of W in the pool was 0.7. How many generations would be required to eliminate all W alleles from the population? Assume that there is no mutation and the population meets all other Hardy-Weinberg conditions.
1
For a gene with two alternative alleles, A (p) and B(q), the term in algebraic form of the Hardy-Weinberg equilibrium for the heterozygote gentoype frequency is?
2pq
In a large population of randomly reproducing rabbits, a recessive allele r comprises 80% of the alleles for a gene. What percentage of the rabbits would you expect to have the recessive phenotype?
64%
A population of flowers is in Hardy weinberg equilibrium with an allele frequency for white flowers of 40%. What percentage of the flowers will have the colored or dominant phentoype?
84%
The observation that most pureblood Native Americans have type O blood is best explained by ?
A founder effect
Being born with extra fingers on a hand is called polydactyly. this is more common in some populations in north america than others due to _____.
A founder effect because their ancestors from Europe carried the alleles
In the graph above, how can the change in infant mortality be explained as birth weight increases from 2 to 7 pounds?
A larger baby will have more developed organs and thus have greater fitness
Moths that can evade a bat's echolocation have ___ that increase their likelihood of survival and reproduction.
Adaptations
In the Hardy-Weinberg equation p and r are ?
Allele frequencies
The organism with the highest fitness is :
An animal that lives ten years and produces ten offspring per year
Some flowering plants cannot self polinate which increases their tendency to mate with phenotypically different mates, a process called disassortative mating. what effect would this have on a population in Hard-Weinberg equilibrium?
An increase in heterozygotes would be observed.
A restriction in genetic variability caused by a drastic reduction in population size is called ?
Bottleneck effect
You spray your kitchen with an insecticide to kill the cockroaches. A few survive and reproduce, producing a large healthy population in a few generations that all have similar genetic backgrounds. This is an example of ?
Bottleneck effect
Assortative and disassortative mating are similar in that both _____.
Change only the expected hardy-weinberg frequencies in a population.
Natural selection, as a mechanism of evolution that, acts on variants within populations and ultimately leads to the evolution of different species was proposed by ?
Darwin
During a drought on the Galapagos islands, finches with larger beaks were able to crack the large tough seeds produced by plants that survived the dry conditions. This is an example of ?
Directional selection
In a forest, trees that get more sunlight grow taller than the other nearby trees. this is a form of _____.
Directional selection
In early ancestors of the modern giraffe, longer necks allowed animals to reach higher tree branches as food. This would lead to _____ in the ancestral giraffe population.
Directional selection
____ could not be involved in gene flow?
Disassortative mating within a population
The key point in Darwin's proposal is that the _____ imposes the conditions that determine the direction of selection.
Enviorment
Darwin proposed that natural selection occurs in an enviorment by ?
Favoring heritable features that make the organism better suited to survive and reproduce
Reproductive success of an individual is known as ?
Fitness
Certain small towns in the western United States have remained isolated and inbred since their settlement many years ago. Some alleles are more common in these communities as compared to the rest of the population. This effect is known as ?
Founder effect
The several hundred species of picture winged fruit flies of the Hawaiian islands are genetically very similar, yet they all differ markedly from their ancestral population in Asia. This is probably an example of _____.
Founder effect
Large ears is a rare trait in a mainland population of mice. A female mice homozygous for very large ears arrives at an island that already contains mice after sneaking onto a boat. This will lead to a population with a higher incidence of big ears than the mainland population because of ___.
Gene flow
In a small population of cockroaches living in your kitchen, only a few roaches mate in one year. This can lead to random changes in allele frequency in the population through?
Genetic drift
There are more than 30 blood group genes in humans, in addition to the ABO locus. This increases ____ in human populations.
Genetic variability
Gentoypes are said to be in _______ equilibirium if there is random mating and no other forces tend to alter the proportions of alleles from one generation to the next.
Hardy-Weinberg
People homozygous for the sickle cell anemia allele develop a life threatening disease, while those homozygous for the normal allele are at the highest risk of dying from malaria. Carriers have some resistance to malaria, but do not develop sickle cell anemia. This is an example of ?
Heterozygote advantage
Two parents who do not have sickle cell anemia have a child that has the disease. The parents are both:
Heterozygous for the sickle cell allel.
The percentage of different colored water boatmen eaten by fish were graphed relative to the frequency of that color in the population. Based on the graph, a population of water boatmen would _____.
Increase in rare genotypes
The disease sickle cell anemia is common in malaria-infested areas because individuals that are heterozygous for the gene have enhanced resistance to malaria over normal individuals. Individuals with sever sickle cell anemia usually die before reproduction. If this population moves to an area without malria, what will happen to the allele frequency of the A allele over time?
It will go up because there is no malaria.
"The inheritance of acquired characteristics" proposal was put forward by?
Lamark
Gene flow, defined as the movement of genes from one population to another, can take place by migration, as well as ?
Mating between individuals of adjacent populations.
______ would be expected to produce the largest evolutionary change in a given period of time in a population of birds.
Migration
Animals that select mates that are phenotypically similar will have ____ when compared with Hardy-Weinberg predictions.
More homozygotes
______ would produce the smallest evolutionary change in a given period of time in a population of birds.
Mutation
An insect population that becomes resistant to a commonly used insecticide is an example of _____.
Natural selection
The genetic preservation of the features that increase the likelihood of survival and reproduction of some individuals within a population is called the process of?
Natural selection
Many male songbirds are brightly colored. However, the color of the birds is determined by a balance of ___.
Natural selection against bright colors by predation and sexual in favor of bright colors.
If a population was in Hardy-Weinberg equilibrium then ___ would occur in that population.
No evolutionary changes
Hardy-Weinberg pointed out that the original proportions of the genotypes in a populatin would remain constant from generation to generation if certain assumptions are met. Which one of the following is not a Hardy-Weinberg condition?
No polymorphic loci exist in the population
An island is on the migration route of sea birds. This island also has abundant tree nesting birds that live on the island permanently and are not found on any other island. The tree nesting birds are more likely than the sea birds to be in Hardy-Weinberg equilibrium because:
Of high immigration in the sea bird population
In order for natural selection to occur within a population, certain conditions must be met. One such condition is ?
Phenotype variations that are genetic
In the experiment above, guppy color patterns were measured in populations exposed to increasing amounts of predation. From this you could conclude that ______.
Predators are more likely to catch and eat brightly colored guppies
_____ would keep a population in Hardy-Weinberg equilibrium.
Random mating
The presence of the disease sickle cell anemia illustrates that natural selection does not always eliminate ____ alleles.
Recessive
The frequency of a particular allele within a population can be changed, over time, by ?
Selection
The midrange of an array of phenotypes is favored in ______.
Stabilizing selection
In the graph above, which aspects of fitness would explain the percent infant mortality curve?
The baby needs to be large enough to survive after birth, but small enough for a safe delivery.
Female cardinals select male mates in part based on their bright red color. What effect would this have on a cardinal population that was in Hardy-Weinberg equilibrium?
The frequency of red alleles would be greater than those predicted by Hardy-Weinberg equilibrium.
Cheetahs have been through a genetic bottle neck; evidence for this is that?
There is very little genetic variability
A population of lizards lives in a rocky area next to a desert. Some lizards are light colored and blend into the sand. Others are dark and blend into the rocks. What may happen in this population of lizards over time?
They may evolve into two seperate species as a result of disruptive selection.
The total of all the alleles of a gene in a population affects the :
allele frequency
Natural selection for a certain phenotype will affect the ____.
allele frequency of a population
Based on the graph above, the color of male guppies can be seen as a balance between positive and negative selections. Bright colors are an advantage in ___, buyt a disadvantage in ___.
attracting mates; avoiding predators
Both extremes of an array of phenotypes are favored in _____.
disruptive selection
Average human males are most likely to be attracted to women with a waist to hip ratio of 0.72. Women with this waist to hip ratio are also the most fertile. By being attracted to women with a waist to hip ratio, a male is increasing his chances of having children and thus improve his ___.
fitness
When fisheries managers move fish from one lake to another, this causes gene ?
flow
About 80% of the alleles present in thoroughbred horses can be dated back to 31 known ancestors from the late eighteenth century. As a result, one would expect ______
little variation in physiology and behavior.
In the Hardy-Weinberg equations, the frequencies of two alleles in a population can be designated as?
p and q
The California populations of the Northern elephant seal are descendants froma very small population of seals that was over-hunted in the 1890s. Heterozygosity in this population would be expected to be _____ due to _____.
slight; bottleneck effect
In some instances enviormental change causes a situation where one phentoype is favored for a period of time, and then a different phentoype is favored. This oscillating selection causes ?
the maintenance of genetic variation in the population
In disruptive selection, over time ?
the population is strongly selected for in two directions
