Evolution and Its Mechanisms
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Evolution and Its Mechanisms

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Questions and Answers

What effect does climate have on the body size of fruit flies?

  • Body size is determined solely by genetic factors.
  • Climate has no effect on body size.
  • Colder environments produce larger body sizes. (correct)
  • Hotter environments produce larger body sizes.

    • What occurs when chromosomes fail to separate during meiosis?

  • Gametes have normal chromosome numbers.
  • No genetic variation is produced.
  • Polyploidy can result. (correct)
  • Cellular duplication occurs.

    • Which of the following statements is true about wild type alleles?

  • They always result in a homozygous genotype.
  • They are always dominant over mutant alleles.
  • They are the most common alleles in a population. (correct)
  • They have the lowest fitness in a population.

    • What happens if a diploid organism mates with a tetraploid organism?

    <p>Offspring are likely to become triploid.</p> Signup and view all the answers

    Which term describes the variation in chromosome number greater than two sets?

    <p>Polyploidy</p> Signup and view all the answers

    How is allele frequency determined?

    <p>By dividing the number of alleles of interest by the total number of alleles.</p> Signup and view all the answers

    Which type of organisms typically exhibit higher levels of genome duplication?

    <p>Plants</p> Signup and view all the answers

    What defines a mutant allele?

    <p>Any allele that is different from the wild type.</p> Signup and view all the answers

    What is a key perspective of evolution regarding individuals and populations?

    <p>Evolution focuses on the population level rather than individuals.</p> Signup and view all the answers

    Which statement best summarizes the concept of pre-adaptation in evolution?

    <p>Traits must already exist in a population to be selected for new functions.</p> Signup and view all the answers

    What is the relationship between gonopodia length in fish and mating success?

    <p>Long gonopodia are advantageous for catching prey but can reduce survival.</p> Signup and view all the answers

    What misconception about evolution does the content correct?

    <p>That evolution can predict future environmental changes.</p> Signup and view all the answers

    What occurs in lion populations as a result of infanticide?

    <p>Female lions become fertile sooner with the killing of the cubs.</p> Signup and view all the answers

    What was the contribution of Thomas Hunt Morgan to the field of genetics?

    <p>He identified the genetics behind mutations as being unlimited.</p> Signup and view all the answers

    What does the modern synthesis of evolution emphasize?

    <p>The combination of genetics and evolution provides a clearer understanding of variation.</p> Signup and view all the answers

    In the study of evolution, why is it important that variation is heritable?

    <p>Only heritable variations can be passed down to future generations.</p> Signup and view all the answers

    What is the observed mutation rate in the nuclear DNA of elegans during replication?

    <p>2.1 mutations per replication</p> Signup and view all the answers

    Which type of mutation is most common in elegans?

    <p>INDL mutations</p> Signup and view all the answers

    Why do mitochondria accumulate more mutations compared to nuclear DNA?

    <p>Mitochondrial DNA lacks repair mechanisms.</p> Signup and view all the answers

    What factor affects the rate of mutations introduced during DNA replication?

    <p>Speed of DNA polymerase</p> Signup and view all the answers

    What is the relationship between mutation rate and fitness in populations?

    <p>Higher mutation rates can lead to a decline in fitness with no natural selection.</p> Signup and view all the answers

    In the context of evolution, what is gene duplication considered to be?

    <p>An important source for evolution</p> Signup and view all the answers

    What impact do repair mechanisms have on mutation rates?

    <p>More efficient repair mechanisms lower mutation rates.</p> Signup and view all the answers

    How does natural selection affect deleterious mutations in a population?

    <p>Natural selection decreases harmful mutations over time.</p> Signup and view all the answers

    What is the significance of genetic variation in evolution?

    <p>It provides the raw material on which evolution can act.</p> Signup and view all the answers

    What major discovery did Watson and Crick make regarding DNA?

    <p>They discovered the structure of DNA.</p> Signup and view all the answers

    How do point mutations differ from each other?

    <p>Transversions swap a purine for a pyrimidine.</p> Signup and view all the answers

    Which condition is an example of a genetic disease linked to mutations?

    <p>Huntington's disease</p> Signup and view all the answers

    What describes a synonymous mutation?

    <p>It leads to no change in the amino acid sequence.</p> Signup and view all the answers

    What does the wobble effect refer to in genetic coding?

    <p>The ability of the third base in a codon to encode similar amino acids.</p> Signup and view all the answers

    What role do mutations play in the evolution of species?

    <p>They are a source of genetic variation.</p> Signup and view all the answers

    What was the outcome of the Butler Act regarding the teaching of evolution?

    <p>Evolution was banned until its reintroduction in 1968.</p> Signup and view all the answers

    What was the primary focus of Linus Pauling's research related to sickle cell anemia?

    <p>The effects of mutation on the molecular structure of hemoglobin.</p> Signup and view all the answers

    What causes a nonsynonymous mutation?

    <p>A point mutation that alters the amino acid sequence.</p> Signup and view all the answers

    How is the CCR5 gene analyzed to detect variations between populations?

    <p>Using PCR to replicate DNA followed by restriction enzyme digestion.</p> Signup and view all the answers

    What does mean heterozygosity measure in a population?

    <p>The average fraction of gene loci that are heterozygous in individuals.</p> Signup and view all the answers

    What happens to lethal dominant alleles in a population over generations?

    <p>All individuals carrying them are eliminated quickly.</p> Signup and view all the answers

    What condition causes the CFTR receptor to malfunction in certain individuals?

    <p>Mutations in the CFTR gene impacting mucus membranes.</p> Signup and view all the answers

    What is the primary role of a restriction enzyme in genetic analysis?

    <p>To cut DNA at specific sequences.</p> Signup and view all the answers

    What is observed in populations where mutation selection balance is present?

    <p>Constant mutation and elimination of deleterious alleles at equilibrium.</p> Signup and view all the answers

    What is the result of underdominance in genetics?

    <p>Heterozygous individuals experiencing lethality.</p> Signup and view all the answers

    How does selection contribute to changes in allele frequency?

    <p>It eliminates non-beneficial alleles over time.</p> Signup and view all the answers

    What factor significantly impacts the expression of cystic fibrosis symptoms?

    <p>The presence of specific mutations in the CFTR gene.</p> Signup and view all the answers

    What is the significance of studying E. Coli to understand mutations?

    <p>It accumulates mutations rapidly due to fast replication.</p> Signup and view all the answers

    Which condition is associated with a mutation in the telSMN gene?

    <p>Spinal muscular atrophy causing muscle degeneration.</p> Signup and view all the answers

    What happens when selection is removed but mutations continue to occur?

    <p>Accumulation of mutations without observable change.</p> Signup and view all the answers

    What could result from the sterilization practices aimed at feeblemindedness over generations?

    <p>Minimal change in allele frequencies over time.</p> Signup and view all the answers

    What is a common measure of gene polymorphism in populations?

    <p>Percentage of genes that have at least two alleles.</p> Signup and view all the answers

    Study Notes

    Evolution

    • Evolution affects populations (species) not just individuals, even though natural selection affects individuals.
    • Evolution works on existing genetic traits that are already in a population. These traits do not develop because they are needed.
    • Evolution can't predict the future.
    • Pre-adaptations are characteristics that exist in a population and acquire a new function due to selection; working on existing variations.
    • Pre-adaptation example: giant panda's sesamoid bone, modified for grasping bamboo.

    Infanticide

    • A male lion kills another male's cubs from a different pride, which causes the female to go into heat and reproduce with him.
    • Causes more offspring for the male.

    Gonopodia

    • The longer the gonopodia (in fish), the more likely the fish is to find a mate.
    • Longer gonopodia are more likely to catch food.
    • Longer gonopodia are also detrimental to survival.

    Mutations and DNA

    • Mutations are not all bad, some are beneficial.
    • Mutations are changes in the DNA that can lead to a new protein product.
    • Mutations are key sources of variation for evolution.
    • DNA consists of a sugar phosphate backbone.
    • A + T pair (2 H bonds), C + G pair (3 H bonds)
    • Phosphodiester bond links them together.
    • DNA → mRNA → Protein
    • Watson and Crick stole Rosalind Franklin's lab and discovered DNA.
    • Kornberg figured out how DNA replicates.

    Sickle Cell Anemia

    • This disease occurs due to a mutation in the 6th amino acid of hemoglobin, valine was inserted instead of glutamic acid.
    • One base change causes the cells to be sickled.

    Point Mutations

    • Two types: transitions and transversions.
    • Transitions swap a purine for a purine or a pyrimidine for a pyrimidine. They are more likely to persist to the next generation, causing less disruption to DNA.
    • Transversions swap a purine for a pyrimidine. They cause more disruption to DNA and are more likely to be repaired.

    Codons

    • 3 base pairs create a codon, which determines which amino acid is incorporated.
    • A change in the first or second base of a codon is less likely to be tolerated than a change in the third base, due to the wobble effect.

    Synonymous and Nonsynonymous Mutations

    • Nonsynonymous mutations (replacement substitution) change the amino acid sequence.
    • Synonymous mutations (silent mutations) do not change the amino acid sequence, often due to the wobble effect.

    Mutation Rate

    • DNA polymerase makes 1 error per 100 million base pairs.
    • Mutation rate depends on DNA synthesis and repair mechanisms.
    • The faster DNA polymerase works, the more mutations accumulate.
    • The more mutations in repair mechanisms, the higher the rate of mutations.
    • Familial cancers are inherited and associated with double-stranded DNA repairs.

    Evolution

    • Evolution is a predicted idea that goes against the Law of Thermodynamics

    Genome Duplication

    • The entire chromosome set (genome) is duplicated.
    • This duplication is caused by chromosomes failing to separate during meiosis 1 or sister chromatids failing to separate during meiosis 2.
    • Polyploidy : more than 2 sets of chromosomes.
    • Gametes have double the number of chromosomes.
    • Genome duplication can lead to speciation.
    • If a diploid and tetraploid organism mate, the offspring is triploid, which has a low survival rate.
    • Many plants are polyploids.
    • Angiosperms are one of the most diverse plants due to genome duplication.

    Genetic Variation

    • We look at the alleles to measure genetic variation.
    • Wild type allele: most common allele with the highest fitness.
    • Mutant allele: less common and any allele that is different from the wild type.
    • Allele frequency: determine the genotype of a large sample of individuals and look at their alleles.

    CCR5

    • CCR5 is a receptor on the surface of white blood cells, helps fight off viruses, but is mutated in individuals with high resistance to HIV.
    • The mutant allele of CCR5 emerged in Europe and led to increased resistance to specific strains of HIV.

    Statistical Summaries of Gene Variation

    • Mean heterozygosity: fraction of gene loci that are heterozygous in the genotype of the average individual.
    • Percentage of polymorphic genes: the fraction of genes in a population that have at least two alleles.

    CFTR Receptor

    • CFTR receptor is mutated in individuals with cystic fibrosis.
    • Lines the GI and respiratory tract.
    • When a CFTR receptor mutates, it causes issues with the mucus membranes.
    • 500 different mutations cause a mutated CFTR receptor.

    Cystic Fibrosis

    • Most common mutation studied.
    • 4% of the population are carriers for a mutated CFTR gene.
    • Mutation occurs on chromosome 7.
    • Individuals used to die young, but new treatments have prolonged life.

    Hardy-Weinberg Equilibrium -

    • P2+2PQ+Q2=1
    • Going against Hardy-Weinberg Equilibrium means evolution!
    • No mutation, drift, selection, migration, or huge population.

    Selection

    • Even minimal amounts of selection can cause a change.
    • Example: Food spiked with ethanol led to more ADH F (alcohol breakdown).

    Kuru

    • Kuru is a degenerative brain disease that is caused by a prion, which is a type of misfolded protein.

    Malaria

    • Placental inflammation due to malaria selection pressure.

    Dominant vs Recessive Alleles

    • Dominant allele lethal - wiped out in one generation.
    • Recessive allele will persist.

    Sterilisation Statue

    • Attempted to sterilize individuals who were deemed "feebleminded".
    • There was a slight allele frequency change over 250 years, but very small.

    Mutation is a weak mechanism of evolution -

    • Slow effects.
    • Creates slightly different alleles, creating very little change in genetic material.

    E. CoIi

    • Used to study mutations due to fast reproduction rate and no conjugation.
    • Accumulated one mutation in populations over 10,000 generations.
    • Study of three generations of E. Coli showed that selection helped cause a significant change, while mutation alone did not.

    Mutation Selection Balance

    • Mutations are created and selection eliminates deleterious mutations.
    • The rate at which copies of deleterious alleles are eliminated by selection = the rate at which new copies are created by mutations in allele frequencies and are at equilibrium.

    Spinal Muscular Atrophy

    • A neurodegenerative disease that causes wasting and weakening of muscles.
    • Mutation in the telSMN gene on chromosome 5.
    • Second most lethal autosomal recessive disease (after cystic fibrosis).
    • It is still prevalent due to mutation selection balance with deleterious mutations.

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    Evolution Exam 2 PDF

    Description

    This quiz explores key concepts of evolution, including how natural selection impacts populations rather than individuals. It discusses examples such as infanticide in lions and the role of gonopodia in fish mating, highlighting the importance of mutations and pre-adaptations. Test your understanding of these fundamental biological principles.

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