Quantitative Genetics and Population Genetics Lecture Review

These flashcards cover key concepts in quantitative and population genetics as discussed in the lecture.

What is the phenotypic ratio of dominant traits in a monohybrid cross according to Mendelian genetics?

The phenotypic ratio is 3:1.

What was Herman Nilsson-Ehle's contribution to genetics in 1908?

He revealed a departure from Mendelian expectations using wheat kernels, showing a 15:1 ratio for red to white kernels instead of 3:1.

In a dihybrid cross, what is the expected phenotypic ratio for two unlinked dominant traits?

The expected phenotypic ratio is 9:3:3:1.

What does the additive model of polygenic inheritance assume?

It assumes that each gene involved has an equal (small) effect on the phenotype.

What is a quantitative trait locus (QTL)?

A locus that affects a quantitative trait.

What are complex traits?

Traits that exhibit continuous variation and do not follow simple Mendelian ratios; examples include skin color, height, and blood pressure.

Define phenotypic variance (VP).

The variance of a trait's distribution in a population influenced by both genetic and environmental factors.

How do you calculate heritability (H2)?

Heritability is calculated as H2 = VG / VP, where VG is genetic variance and VP is phenotypic variance.

What measure describes how much variation in a trait is caused by genetic differences in a population?

Heritability (H2).

What is the importance of family studies in measuring genetic vs environmental contributions to complex traits?

They help to determine the genetic similarity between relatives to infer heritability.

What occurs in a correlative study of height between parents and offspring?

It shows the correlation of height and estimates heritability based on parental similarities.

What are monozygotic (MZ) twins?

Identical twins that arise from the splitting of a single fertilized egg, being 100% genetically identical.

What is genetic drift?

Random changes in allele frequencies in a population due to chance events, primarily affecting small populations.

Define effective population size (Ne).

The size of an idealized population that would lose genetic diversity via drift at the same rate as the actual population.

What does the Hardy-Weinberg equilibrium state?

The allele and genotype frequencies in a population remain constant from generation to generation under certain assumptions, like random mating.

What factors can disrupt Hardy-Weinberg equilibrium?

Non-random mating, finite population size, mutation, natural selection, and migration.

What is the significance of SNPs in population genetics?

Single nucleotide polymorphisms (SNPs) are the most common type of genetic variation among individuals.

What is balancing selection?

Selection that maintains genetic diversity in a population, often through heterozygote advantage.

How can migration affect genetic diversity in populations?

Migration can introduce new alleles into a population, decreasing genetic differences between populations.

What impact does genetic drift have on small populations?

It can lead to the loss of genetic variation and can fix or eliminate alleles by chance.

What is the difference between positive and negative selection?

Positive selection favors advantageous alleles, while negative selection eliminates deleterious alleles.

What is a founder effect?

A decrease in genetic variation when a small group establishes a new population.

What was the main finding of Rosenberg et al. regarding human populations?

They used genomic data to study the genetic structure and similarity among diverse human populations.

What is the relationship between phenotype and genotype frequencies in population genetics?

Phenotype frequencies can be derived from genotype frequencies using the Hardy-Weinberg equation.

How does natural selection affect allele frequencies?

Natural selection increases the frequency of advantageous alleles and decreases the frequency of deleterious ones.

What is the role of environmental factors in quantitative traits?

Environmental factors can influence the expression and variation of quantitative traits alongside genetic factors.

What does a high heritability estimate imply about a trait?

It suggests that a large proportion of the phenotypic variance is due to genetic differences among individuals.

What influences the heritability of traits like height and IQ?

Both genetic variance and environmental factors contribute to their heritability estimates, which can vary significantly.

Define polygenic inheritance.

A type of inheritance where multiple genes contribute to a single trait, leading to continuous variation.

What is the significance of twin studies in genetics?

Twin studies help assess the relative contributions of genetic and environmental factors to various traits.

How does the Hardy-Weinberg principle apply to allele frequencies?

It predicts the genetic variation from generation to generation in a population assuming no evolution occurs.

What is the relationship between allele frequency and fitness?

Allele frequencies can change over time based on the relative fitness of different genotypes in a population.

What is the effect of non-random mating on genetic variation?

It can lead to increased homozygosity and potentially decrease genetic diversity within a population.

How does phenotypic selection operate in populations?

It selects for individuals with advantageous traits that improve survival or reproductive success.

What factors contribute to the genetic structure of populations?

Historical, geographical, and environmental factors influence how populations diverge genetically.

Define the concept of a genetic bottleneck.

A sharp reduction in the size of a population due to environmental events leading to reduced genetic diversity.

What is the importance of understanding genetic drift in population genetics?

It helps explain how allele frequencies can fluctuate over time in small populations.

How do environmental conditions affect the principles of natural selection?

They shape which traits are advantageous, leading to differential survival or reproduction of individuals.

What is meant by 'gene flow'?

The transfer of alleles or genes from one population to another, usually through migration.

What are the implications of eugenics in the context of genetics?

Eugenics aims to improve the genetic quality of a population but raises ethical concerns and practical limitations.

How does selection pressure influence allele frequency in populations?

It results in changes to the frequency of advantageous alleles, driving evolution over time.

What does the concept of selection coefficient (s) measure?

It measures the fitness difference between genotypes and reflects the strength of selection against a particular genotype.

How do mutations contribute to genetic diversity?

Mutations introduce new alleles into a population, which can either be beneficial, neutral, or harmful.

What does it mean when a trait has a continuous variation?

It indicates that the trait is influenced by multiple genes and exhibits a range of phenotypes rather than distinct categories.

What is the role of the Human Genome Diversity Project in understanding human populations?

It provides insights into genetic variation, structure, and evolutionary history of human populations globally.