Bio 191 Ch 21 HW

What is the frequency of the A1A2 genotype in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals? 0.5 80 0.1 0.4

0.4 The calculation to determine the frequency of the A1A2 genotype is: 80 A1A2 individuals / (20 + 80 + 100) total individuals = 0.4, the frequency of the A1A2 genotype.

In the beetles described in the animation, there were two alleles for color, brown and green. Suppose that you discover a very small population of these beetles, consisting of the individuals shown below. How can you calculate the frequency of each allele in this population?

1. To calculate the frequency of the brown allele, count the number of brown alleles and divide by the total number of alleles in this population. 2. In this beetle population, the number of brown alleles is 8. 3. In this beetle population, the total number of alleles is 20. 4. The frequency of the brown allele in this beetle population is 0.4. 5. The frequency of the green allele in this beetle population is 0.6.

What is the frequency of the A1 allele in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals? The frequency of the A1 allele is 0.3. The frequency of the A1 allele is 0.5. The frequency of the A1 allele is 0.7. The frequency of the A1 allele is 0.1.

The frequency of the A1 allele is 0.3. The frequency of the A1 allele is p = (number of A1 alleles) / (total of all alleles) = [(2 ( 20) + 80] / [(2 × 20) + (2 × 80) + (2 × 100)] = 0.3.

In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following? Time The value of a particular characteristic; characteristics of an organism can include such traits as size and color. The number of individuals

The value of a particular characteristic; characteristics of an organism can include such traits as size and color. The value of the characteristic increases from left to right.

True or false? The Hardy-Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating. True False

True These are the five assumptions of the Hardy-Weinberg model.

Homologous pairs of chromosomes are lined up independently of other such pairs during _____. prophase II telophase II metaphase II metaphase I anaphase I

metaphase I

Part BPart complete Generation-to-generation change in the allele frequencies in a population is _____. mutation macroevolution microevolution natural selection genetic drift

microevolution Generation-to-generation change in the allele frequencies in a population is the definition of microevolution.

Which of the following are causes of evolutionary change? Select all that apply. natural selection gene flow mutation genetic drift

natural selection gene flow mutation genetic drift

In human gamete production there is an average of _____ crossover events per chromosome pair. 9-10 5-6 10+ 2-3 0-1

2-3 These crossover events increase the genetic variation among gametes.

True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population. True False

False Heterozygote advantage results in more genetic variation in the population.

Which of the following are basic components of the Hardy-Weinberg model? Frequencies of two alleles in a gene pool before and after many random matings Allele frequencies in a subset of the population Allele frequencies, number of individuals in the population Allele frequencies, phenotype frequencies

Frequencies of two alleles in a gene pool before and after many random matings Hardy and Weinberg were trying to determine how and whether allele frequencies in a population change from one generation to the next.

Which of these gametes contain one or more recombinant chromosomes? B, C, D, and G B, C, F, and G B, C, and G C, D, E, F, and G A, B, and C

B, C, F, and G These gametes carry chromosomes produced as a result of crossing over.

Which of the following evolutionary forces could create new genetic information in a population? Selection Mutation Genetic drift Nonrandom mating

Mutation Mutations, which are changes in a cell's DNA, can introduce new genetic information in a population.

Populations evolve for many reasons. Suppose there is a population of plants that have either purple flowers or white flowers, and the allele for purple flowers is dominant. This means that plants with two purple alleles have purple flowers. Plants with one purple allele and one white allele also have purple flowers. Only plants with two white alleles have white flowers. For each event or condition described below, answer the following questions. Which mechanism of evolution is at work? How does this event affect the population's gene pool? Do the frequencies of the two alleles change, and if so, how?

1. During an extreme heat wave, plants with white flowers survive better. Mechanism: Natural selection Effect: Frequency of white allele increases 2. A person uproots the five closest plants, which all happen to have white flowers. Mechanism: Genetic Drift Effect: Frequency of purple allele increases 3. A storm kills many plants at random. Mechanism: Genetic Drift Effect: allele frequencies change but not predictably 4.Plants with purple flowers attract more insects, which pollinate the plants. Mechanism: Natural selection Effect: Frequency of purple allele increases 5. Workers from a nearby greenhouse accidentally introduce white flower seeds to this population's habitat. Mechanism: Gene flow Effect: Frequency of white allele increases

Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today? Directional selection Disruptive selection Stabilizing selection

Directional selection Directional selection drives the average of the population in one direction, in this case, toward longer necks.

Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers? Stabilizing selection Disruptive selection Directional selection

Disruptive selection Disruptive selection causes both extreme phenotypes (large and small beaks) to be favored over the intermediate phenotypes.

Which type of selection tends to increase genetic variation? Disruptive selection Directional selection Stabilizing selection

Disruptive selection Disruptive selection eliminates phenotypes near the average and favors the extreme phenotypes, resulting in increased genetic variation in a population.

How did Dr. Allison test his hypothesis that sickle cell disease was connected to malaria? Select all that apply. He expanded his study area beyond Kenya to the rest of East Africa to see if malaria and sickle disease were connected. He looked for the underlying genetic mechanism causing sickle cell disease. He evaluated blood samples for malaria parasites and the presence of sickle cells. He studied the way that the malaria parasite interacts with sickle cells.

He expanded his study area beyond Kenya to the rest of East Africa to see if malaria and sickle disease were connected. He evaluated blood samples for malaria parasites and the presence of sickle cells. Dr. Allison gathered blood samples from more than 5,000 children in East Africa. He analyzed the samples to identify malaria parasites and sickle cells. He found that children carrying the sickle cell character (or trait) had a lower parasite count, as if they were partially protected against malaria.

In 1949, Dr. Tony Allison observed a high frequency of Kenyans carrying the sickle cell allele in coastal areas and near Lake Victoria, but a lower frequency in the highlands. What did he hypothesize? He hypothesized that sickle cell disease was an environmental, not a genetic disease. He hypothesized that there was a connection between malaria and sickle cell disease. He hypothesized that malaria is a genetic disease. He hypothesized that malaria causes sickle cell disease.

He hypothesized that there was a connection between malaria and sickle cell disease. On the basis of this hypothesis, Dr. Allison predicted high frequencies of sickle cell disease only in areas where malaria is common.

How does Dr. Allison's work provide an example of natural selection in humans? Select all that apply. In areas with malaria, individuals with one sickle cell allele reproduced at higher rates than those with no sickle cell alleles. In areas without malaria, individuals with two sickle cell alleles reproduced at lower rates than those without sickle cell disease. Natural selection caused the sickle cell allele to appear in east African populations. In areas with malaria, natural selection causes individuals to acquire the sickle cell allele as protection against malaria.

In areas with malaria, individuals with one sickle cell allele reproduced at higher rates than those with no sickle cell alleles. In areas without malaria, individuals with two sickle cell alleles reproduced at lower rates than those without sickle cell disease. In different environments, natural selection favors different characteristics. In areas with malaria, the reproductive advantages of having one sickle cell allele (and some protection from malaria) kept the allele at high frequencies in the population. In areas without malaria, the reproductive disadvantages from sickle cell disease reduced the allele in populations.

In some populations, 1 in 500 people have sickle cell disease. What reason does the film give for why a potentially deadly, inherited disease is found at such high frequencies? Sickle cell alleles are new mutations and not enough time has gone by for these alleles to be eliminated from the population by natural selection. Individuals with one sickle cell allele are protected from malaria and do not have sickle cell disease, thus keeping the allele in the population. Individuals with two sickle cell alleles have an evolutionary advantage because they do not get sickle cell disease or get infected with malaria. Individuals with two normal hemoglobin alleles get both sickle cell disease and are susceptible to malaria, so these alleles are eliminated from the population.

Individuals with one sickle cell allele are protected from malaria and do not have sickle cell disease, thus keeping the allele in the population. Individuals with two sickle cell alleles have an evolutionary advantage because they do not get sickle cell disease or get infected with malaria. People with one sickle cell allele are protected from malaria, but do not have sickle cell disease. Protection from malaria comes at the cost of more sickle cell disease in the population.

The three major mechanisms of evolution differ in how they work, and as a result often have different effects on a population. Review your understanding of natural selection, genetic drift, and gene flow by sorting the statements below into the correct bins. Drag each statement into the appropriate bin depending on whether it applies to natural selection, genetic drift, or gene flow.

Natural Selection: Consistently causes a population to become better adapted to its environment Cannot cause a harmful allele to become more common A result of differential success in reproduction Genetic Drift: Causes allele frequencies to fluctuate randomly Responsible for the bottleneck effect Responsible for the founder effect Gene Flow: A result of the movement of fertile individuals or their gametes Can introduce new alleles into a population's gene pool

Which of the following evolutionary forces consistently results in adaptive changes in allele frequencies? Selection Mutation Inbreeding There is no evolutionary force that results in adaptive changes in allele frequencies.

Selection Selection is the only evolutionary force that consistently results in adaptation. Mutation without selection and genetic drift are random processes that may lead to adaptive, maladaptive, or neutral effects on populations.

Compare sickle cell disease and malaria. Sickle cell disease and malaria are both potentially lethal diseases. Sickle cell disease and malaria are both infectious diseases. Sickle cell disease and malaria are both genetic diseases. Sickle cell disease and malaria are both inherited diseases.

Sickle cell disease and malaria are both potentially lethal diseases. Though malaria is an infectious disease and sickle cell disease is inherited, both can cause life-threatening conditions.

Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies? Directional selection Stabilizing selection Disruptive selection

Stabilizing selection Stabilizing selection causes no change in the average of the population; extreme phenotypes (in this case, large and small babies) become less common.

Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards? Disruptive selection Directional selection Stabilizing selection

Stabilizing selection Stabilizing selection causes no change in the average of the population; extreme phenotypes (large and small lizards) become less common.

What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q = 0.2 for a particular gene? The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2 , and A2A2 , respectively. The expected genotype frequencies are 0.25, 0.5, and 0.25 for A1A1, A1A2 , and A2A2 , respectively. The expected genotype frequencies are 0.32, 0.64, and 0.04 for A1A1, A1A2 , and A2A2 , respectively. The expected genotype frequencies are 0.33, 0.33, and 0.33 for A1A1, A1A2 , and A2A2 , respectively.

The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2 , and A2A2 , respectively. The expected frequency of the A1A1 genotype is p 2 = (0.8)(0.8) = 0.64; the expected frequency of the A1A2 genotype is 2pq = 2(0.8)(0.2) = 0.32; the expected frequency of the A2A2 genotype is q 2 = (0.2)(0.2) = 0.04. To verify your calculations, confirm that the three frequencies add up to one.

Which of the following statements is not a part of the Hardy-Weinberg principle? If allele frequencies in a population are given by p and q, then genotype frequencies will be given by p 2, 2pq, and q 2 for generation after generation. When alleles are transmitted according to the rules of Mendelian inheritance, their frequencies do not change over time. The genotype frequencies in the offspring generation must add up to two. Even if allele A1 is dominant to allele A2 , it does not increase in frequency.

The genotype frequencies in the offspring generation must add up to two. This statement is not true; the genotype frequencies in the offspring generation must add up to one.

If a person has two normal copies of the hemoglobin allele, which statements are true? Select all that apply. The person is susceptible to malaria. The person is homozygous at the hemoglobin locus. The person is protected against malaria. The person is heterozygous at the hemoglobin locus.

The person is susceptible to malaria. The person is homozygous at the hemoglobin locus. A person with two copies of any allele is homozygous. A person with two normal copies of the hemoglobin allele is more susceptible to malaria than someone with a sickle cell hemoglobin allele.

Predict what will happen to the frequency of the sickle cell allele in areas where malaria has been eradicated. The sickle cell allele will decrease in frequency. The sickle cell allele will increase in frequency. The sickle cell allele frequency will not be affected.

The sickle cell allele will decrease in frequency. Without malaria, selection for the sickle cell allele decreases. As a result, the frequency will likely decrease.

Crossing over, resulting in an increase in genetic variation, occurs between _____. nonsister chromatids of homologous chromosomes sister chromatids of nonhomologous chromosomes sex cells and somatic cells sister chromatids of homologous chromosomes nonsister chromatids of nonhomologous chromosomes

nonsister chromatids of homologous chromosomes This process produces chromosomes containing genes inherited from both parents.