Genetics and Evolutionary Biology Final Exam

Questions and Answers

Why do rare recessive alleles like albinism persist in a population?

They are more advantageous than dominant alleles.

They only occur in specific environments.

They are subject to strong natural selection.

Most individuals carrying the allele do not exhibit the trait. (correct)

What does genetic load refer to?

The ability of a population to adapt to changes.

The difference between the fittest genotype and the average genotype. (correct)

The total number of genes in a population.

The frequency of dominant alleles in a population.

How can a deleterious allele persist in a population despite natural selection?

It provides immediate benefits to the individuals carrying it.

It is always the most common allele.

An equilibrium is reached between the deleterious and wild type alleles. (correct)

Natural selection has no impact on allele frequency.

What is the proportion of polymorphism (P) calculated from 4 polymorphic genes out of 10 surveyed genes?

0.4 Signup and view all the answers

What is a characteristic of a population with low genetic load?

It has fewer carriers of deleterious genes. Signup and view all the answers

What would be the result if natural selection completely eliminated a deleterious allele from a population?

The population may lose genetic diversity. Signup and view all the answers

Which of the following best describes the difference between polymorphic and monomorphic genes?

Polymorphic genes can have multiple alleles, while monomorphic genes have only one. Signup and view all the answers

What is indicated by a high proportion of carriers of a rare recessive allele within a population?

The allele remains present despite its rarity. Signup and view all the answers

What is the likely outcome when the mutation rate for a deleterious allele is reduced by natural selection?

An equilibrium between the wild-type and deleterious alleles will be achieved. Signup and view all the answers

What is the average number of alleles per locus calculated for the given loci?

2.33 Signup and view all the answers

Which process involves a sharp decline in population size leading to decreased genetic diversity?

Bottleneck effect Signup and view all the answers

How is the average heterozygosity (H0) calculated from the given proportions of heterozygosity?

0.045 Signup and view all the answers

What is the main consequence of genetic drift in small populations?

Random fluctuation in allele frequencies Signup and view all the answers

What percentage of the population is fixed based on the FST value calculated?

18% Signup and view all the answers

Which of the following best describes conservation genetics?

The application of genetics to preserve species and enhance genetic diversity Signup and view all the answers

In the context of alleles at a diploid locus, what does 'p' refer to in the Hardy-Weinberg equilibrium?

The frequency of the allele in the population Signup and view all the answers

What is the expected frequency of carriers for sickle cell anemia assuming Hardy-Weinberg equilibrium?

0.48 Signup and view all the answers

Which type of DNA is characterized by high mutation rates and is commonly located in centromeres and telomeres?

Minisatellite DNA Signup and view all the answers

What effect does non-random mating, such as inbreeding, typically have on a population's gene pool?

Decrease in heterozygosity Signup and view all the answers

Study Notes

Rare Recessive Alleles

Rare recessive alleles, like the one causing albinism, persist due to high carrier rates; most carriers are unaffected.
Genetic variation remains in populations, making it difficult for rare alleles to vanish completely.
Albinism occurs in 1 in 20,000 individuals; carriers are approximately 1 in 70, leading to a genetic load phenomenon.

Genetic Load

Defined as the difference between the most fit genotype and the observed average in a population; low genetic load indicates a healthier population.
Also refers to the accumulation of deleterious, hidden genes that can be passed to offspring, mostly seen in heterozygous individuals.

Mutation-Selection Balance

Deleterious alleles may persist despite natural selection favoring wild-type alleles.
An equilibrium is reached between the normal (A1) and harmful (A2) alleles; some A2 genes survive due to limited selection pressure.

Proportion of Polymorphism

Proportion of polymorphic genes (P) is calculated by dividing the number of polymorphic genes by the total loci surveyed.
In a survey of 10 genes, 40% (4/10) are polymorphic.

Allelic Diversity

Average alleles per locus (A) can be calculated by summing alleles across loci and dividing by the number of loci.
For six loci in African lions, A is 2.33 alleles per locus.

Average Heterozygosity

Average heterozygosity (H0) reflects the proportion of heterozygous individuals at multiple loci.
Calculated as the average of heterozygosity values across the loci, yielding 4.5%.

Genetic Diversity Measures

In a study of 12 loci in big belly seahorses, the measures are:
- Proportion of polymorphic genes (P) is 67% (8/12).
- Average alleles per locus (A) is 1.75 (21/12).
- Average heterozygosity (H0) is 22% (2.63/12).

Genetic Drift and Bottleneck Effect

Genetic drift refers to random fluctuations in allele frequencies due to population size.
Smaller populations experience larger fluctuations, making them more vulnerable to genetic drift.
The bottleneck effect results from sudden population size reduction, leading to decreased genetic diversity and accelerated genetic drift.

Genetic Diversity in a Structured Population

FST value helps determine genetic differentiation between subpopulations.
Metrics include average heterozygosity within subpopulations (Hs = 0.41) and total heterozygosity (Ht = 0.50); resulting FST is 0.18, indicating some gene flow.

Effects on Gene Pool

Genetic drift can lead to loss of allele frequency diversity or fixation.
Gene flow through migration increases diversity, while mutation introduces new alleles.
Inbreeding reduces heterozygosity and overall fitness, increasing genetic load.

Hardy-Weinberg Equilibrium

Sickle cell anemia frequency is approximately 0.16, leading to a calculated frequency of the HbA allele (p) at 0.6.
Carrier frequency for sickle cell trait under Hardy-Weinberg is approximately 48% (HbAHbS).

Conservation Genetics

Conservation genetics is the application of genetic principles to maintain species amid environmental changes.
Key areas include genetic management of populations, understanding taxonomy, and creating molecular markers for forensics.
Primary concerns encompass extinction risk, inbreeding depression, and loss of genetic diversity.

Techniques in Conservation Genetics

Common techniques include methods such as Alloenzymes, RFLPs, AFLPs, RAPDs, microsatellites, and DNA fingerprinting.
Minisatellite DNA: Repetitive motifs (10-60 bp) present in over a thousand genome locations with high mutation rates.
Microsatellites: Very short tandem repeats (2-5 bp) crucial for studying genetic diversity due to their high variability.

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Description

Prepare for your Final Exam in Genetics and Evolutionary Biology covering all modules from weeks 1 to 12. This exam consists of 40 questions, including multiple-choice and short answer formats, designed to test your understanding of key concepts in the field.