Podcast
Questions and Answers
What is the significance of the HERC2 rs12913832*C single nucleotide polymorphism (SNP)?
What is the significance of the HERC2 rs12913832*C single nucleotide polymorphism (SNP)?
- It indicates a gene duplication event.
- It has no known phenotypic associations.
- It is associated with increased skin pigmentation.
- It is linked to blue eye color. (correct)
Which statement accurately describes the evolutionary history of light skin pigmentation in European populations?
Which statement accurately describes the evolutionary history of light skin pigmentation in European populations?
- The adaptive spread of light skin pigmentation was complete by the Mesolithic.
- Light skin pigmentation evolved in parallel with blue eye color.
- The evolution of light skin is a recently developed trait. (correct)
- Alleles associated with light/blue eye color spread after changes in skin pigmentation.
What might be one consequence of gene duplications and deletions?
What might be one consequence of gene duplications and deletions?
- They have no impact on human phenotypes.
- They can lead to dosage effects and gene disruption. (correct)
- They are always beneficial to the organism.
- They increase the overall genetic diversity of a population.
What historical trait combination is unique and no longer present in contemporary European populations?
What historical trait combination is unique and no longer present in contemporary European populations?
What is one of the theories for the evolution of lighter skin at high latitudes?
What is one of the theories for the evolution of lighter skin at high latitudes?
Which of the following conditions may be associated with copy number variants?
Which of the following conditions may be associated with copy number variants?
How does folate sensitivity relate to skin pigmentation in varying latitudes?
How does folate sensitivity relate to skin pigmentation in varying latitudes?
In the context of mammalian evolution, what is the relevance of gene duplications?
In the context of mammalian evolution, what is the relevance of gene duplications?
What role does the SLC24A5 gene play in pigmentation?
What role does the SLC24A5 gene play in pigmentation?
What type of homology is associated with speciation events?
What type of homology is associated with speciation events?
What is a consequence of having darker skin at higher latitudes?
What is a consequence of having darker skin at higher latitudes?
Which process is NOT typically a result of unequal crossing-over?
Which process is NOT typically a result of unequal crossing-over?
What evolutionary adaptation is associated with populations that have lower constitutive skin pigmentation?
What evolutionary adaptation is associated with populations that have lower constitutive skin pigmentation?
Which factor is NOT associated with the variation of skin color among human populations?
Which factor is NOT associated with the variation of skin color among human populations?
Which of the following statements about racial pigmentation differences is true?
Which of the following statements about racial pigmentation differences is true?
What historical factor is suggested to influence allelic frequency in pigmentation?
What historical factor is suggested to influence allelic frequency in pigmentation?
What role does the SLC24A5 allele play in relation to skin pigmentation among Europeans and Asians?
What role does the SLC24A5 allele play in relation to skin pigmentation among Europeans and Asians?
Which gene makes a significant contribution to light skin in Chinese populations?
Which gene makes a significant contribution to light skin in Chinese populations?
What does the evidence suggest about the evolution of lighter pigmentation in Europeans and Asians?
What does the evidence suggest about the evolution of lighter pigmentation in Europeans and Asians?
Which of the following statements is supported by the information on pigmentation variation?
Which of the following statements is supported by the information on pigmentation variation?
How is the concept of convergent evolution illustrated in terms of skin pigmentation?
How is the concept of convergent evolution illustrated in terms of skin pigmentation?
Which statement correctly describes the genetic architecture in the context of human pigmentation?
Which statement correctly describes the genetic architecture in the context of human pigmentation?
What can be inferred about the allelic frequency of light skin alleles?
What can be inferred about the allelic frequency of light skin alleles?
Which evolutionary perspective is relevant when analyzing the genetic basis of human skin color?
Which evolutionary perspective is relevant when analyzing the genetic basis of human skin color?
Flashcards
SLC24A5 allele
SLC24A5 allele
A genetic variant of the SLC24A5 gene that is linked to skin colour.
OCA2 gene
OCA2 gene
A gene playing a key role in defining skin tone.
Light skin in Europeans
Light skin in Europeans
The evolution of a light skin color in European ancestors, influenced by genetic variations.
Light skin in Asians
Light skin in Asians
Signup and view all the flashcards
Convergent skin lightening
Convergent skin lightening
Signup and view all the flashcards
Genetic architecture of pigmentation
Genetic architecture of pigmentation
Signup and view all the flashcards
Mesolithic European
Mesolithic European
Signup and view all the flashcards
Human pigmentation variation
Human pigmentation variation
Signup and view all the flashcards
Skin color and latitude
Skin color and latitude
Signup and view all the flashcards
Vitamin D and latitude
Vitamin D and latitude
Signup and view all the flashcards
Folate and latitude
Folate and latitude
Signup and view all the flashcards
Tanning as adaptation
Tanning as adaptation
Signup and view all the flashcards
SLC24A5 gene
SLC24A5 gene
Signup and view all the flashcards
Vitamin D synthesis
Vitamin D synthesis
Signup and view all the flashcards
Folate depletion
Folate depletion
Signup and view all the flashcards
Human skin variation
Human skin variation
Signup and view all the flashcards
HERC2 rs12913832*C SNP
HERC2 rs12913832*C SNP
Signup and view all the flashcards
Light Skin Evolution
Light Skin Evolution
Signup and view all the flashcards
Gene Duplication
Gene Duplication
Signup and view all the flashcards
Unequal Crossing-Over
Unequal Crossing-Over
Signup and view all the flashcards
Deleterious Duplications/Deletions
Deleterious Duplications/Deletions
Signup and view all the flashcards
Copy Number Variants (CNVs)
Copy Number Variants (CNVs)
Signup and view all the flashcards
Mammalian Hemoglobins
Mammalian Hemoglobins
Signup and view all the flashcards
Orthology vs. Paralogy
Orthology vs. Paralogy
Signup and view all the flashcards
Study Notes
Codan Usage and Adaptive Protein Divergence
- Codan usage is determined mostly by mutation bias.
- More sensitive methods exist for detecting adaptive protein divergence than dN/dS, such as the McDonald-Kreitman (MK) test.
The McDonald-Kreitman (MK) Test
- This test assesses neutral evolution versus adaptive evolution.
- Under the null hypothesis (neutral evolution), polymorphism and divergence are from genetic drift.
- Rapidly evolving proteins show high polymorphism levels within species compared to fixed variants.
- Compares protein polymorphism/fixed variants to synonymous variants.
- Effective only if there are many selectively fixed amino acids and multiple variants within a gene.
Logic of the MK Test
- Under neutrality, the ratio of polymorphic to fixed nonsynonymous variants equals the ratio of polymorphic to fixed synonymous variants.
- An example dataset following neutrality will have a ratio of 5/10 = 10/20 = 0.5.
Datasets Incompatible with Neutral Protein Variation
- Datasets showing disparities between the ratios of polymorphic to fixed nonsynonymous and synonymous variants indicate adaptive evolution.
- A significant Fisher's exact test (G-test) p-value (<10^-5) suggests the data is incompatible with neutral evolution.
Effects of Directional Selection on Linked Genomic Regions
- Polymorphism is positively correlated with recombination rate.
- Directional selection on linked genomic regions influences protein divergence.
- In mammals, the effects of directional selection on mammalian genomes are smaller than effects on fly genomes.
9 Polymorphism = ↑ Mutation Rate = ↑ Divergence
- Increased polymorphism often correlates with higher mutation rates and greater divergence.
Hitchhiking Effect (Selective Sweep)
- The hitchhiking effect allows mutations to spread alongside beneficial mutations.
- The spread of beneficial mutations can lead to the reduction in variation within a genome.
- A dataset incompatible with neutral protein variation can be due to selective sweeps driving changes in allele frequency.
No Recombination
- No recombination near a gene can result in the fixation of the gene near by due to strong selection pressure.
- Recombination can reduce the strength of natural selection and lead to more diversity.
What Fraction of Protein Divergence is due to Directional Selection?
- In D. simulans, 20% of genes evidence adaptive protein evolution
- 30-50% of amino-acid fixations are due to directional selection, not neutral (drift) events.
Current Evidence Suggests...
- Adaptive evolution of non-coding DNA is common in flies.
- Effects of directional selection on mammalian genomes are smaller than effects on fly genomes.
Evolution of Lactase Persistence
- Data indicates that the evolution of lactase persistence is comparatively recent.
- The presence of specific genetic variants (alleles) correlates with the ability to digest lactose.
- The ability to digest lactose is not present in all humans.
Map of Recent Positive Selection in the Human Genome
- Various genomic regions show evidence of recent positive selection.
Adaptation to Low Oxygen Pressure
- Tibetans have adapted to low oxygen pressure by recent selection for specific genetic variants.
Geographic Location and Genetic Affinities
- The geographic location of individuals and their genetic affinities are related to the presence or absence of specific alleles
Evolution of Human Skin Pigmentation
- The development of darker skin is thought to be a result of complex selection pressures, including the need to maintain folate levels and regulation of vitamin D synthesis in locations with lower UV radiation.
Pigmentation Alleles
- Certain alleles (e.g., SLC24A5) correlated are associated with differences in pigmentation in various populations
De Novo Gene Evolution
- Genes can originate from non-genic DNA regions through cis-acting regulatory mutations.
Genome Size Variation
- Genome size variation is often unexplained by gene content but is affected by repetitive DNA.
Mammalian HemoGlobin
- Mammalian hemoglobin subfamilies arose by duplication.
Two Types of Homologies
- Orthology (speciation)- related by gene duplication events.
- Paralogy (duplication): related by ancestral duplicated genes, and diverged.
Gene Duplications
- Duplications can result in deleterious effects from gene dosage but can also create new functions.
Anti-Freeze Protein Evolution
- Anti-freeze proteins in antarctic fish result from non-coding regions of a digestive enzyme.
- These proteins are derived from an existing protein, which subsequently acquires a new function.
Homologous Sequence Identification
- Homologous sequences that are present in all species, but exhibit expression and open reading frame in one species, represent recently evolved genes.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz explores the principles of codon usage and adaptive protein divergence, focusing on the McDonald-Kreitman (MK) test. It examines how the MK test differentiates between neutral and adaptive evolution by comparing polymorphism and fixation rates. Test your understanding of these important concepts in evolutionary biology!
