Hardy-Weinberg (Lecture 1-4) Flashcards
What is blending inheritance? (Concept of Heredity before Mendel)
The idea that offspring’s traits are a blend of parental traits
What is the inheritance of acquired characteristics? (Concept of Heredity before Mendel)
Parents develop traits over a lifetime, offspring inherit these novel traits
Define Heredity
The transmission of traits from parents to their traits
Trait
Any characteristic of an indivdiual
What is Genetics
Branch of biology that focuses on inheritance of traits
Why did Gregory Mendel choose peas as his model organism
- Controlled crosses were easy
- Short generation times
- Cheap
- Could produce a lot of seeds
What is the principle of segregation?
Diploid individuals have 2 alleles of each gene and these alleles separate into gametes at meiosis
Is the “Principle of Segregation” due to random chance, or it’s orchestrated/planned
A) Random Chance
B) Orchestrated/Planned
A; Offspring receive an allele of a trait from the parent generation due to random chance
How many gametes does a parent generation contribute to each offspring?
A) 1
B) 2
C) 4
D) 6
A; 1
Are the traits that are inherited from the parent generation…discrete or does blending occur
A) Discrete
B) Blending
A; Discrete
What is the definition of “pure line” species?
Species that have homozygous genotypes
What is the maximum numbers of alleles that a parent carries for a given trait…
A) 1
B) 2
C) 4
D) 8
2; Think of alleles of G or g
What was the point of Mendel’s Dihybrid Cross experiment?
To test the hypothesis that traits are inherited independent of one another
What is the expected/“magic” ratio number resulting from an independent assortment of traits
9:3:3:1
9: Expected offspring with both dominant traits
3 & 3: Expected offspring with combination of dominant and recessive traits
1: Expected offspring with recessive traits
What is “Independent Assortment”
Alleles of different genes (traits) separate independently during the formation of gametes (if on different chromosomes)
How many traits does “Independent Assortment” deal with?
2 or more traits (think of Mendel’s Dihybrid Cross experiment)
What are the different implications of Independent Assortment
- Allows for different combinations of traits to occur in offspring
- Allows for genetic variation in population –> Evolution
What is the formula for the chi-square test
(Observed - Expected)^2/Expected
Do you accept or reject the null hypothesis if your calculated chi-square is higher than the chi-square critical value…
A) Accept
B) Reject
B; Reject the null hypothesis. Meaning one trait most likely does affect the other trait
What is the meaning of the “null hypothesis” in the chi square test?
There is no significant difference between observed and expected frequencies (i.e. genes are unlinked). Meaning one trait doesn’t affect the outcome of the other
What is the meaning of the “alternative hypothesis” in the chi square test?
There is a significant difference between observed and expected frequencies (i.e., genes are linked). Meaning one trait most likely affects the outcome of another
What are Darwin’s 4 Postulates
1) Variation exists among individual organism that make up a population (ex: Variation in shape and size)
2) Trait differences are heritable (ex: Parent flowers with long petals tend to have offspring with long petals)
3) Survival and reproductive success are highly variable (ex: Many more offspring are produced than can possibly survive)
4) The individuals that survive and reproduce the best aren’t due to chance/or random (ex: Individuals with certain heritable traits are more likely to survive & reproduce)
Define natural selection
Individuals with certain heritable traits produce more offspring than individuals without those traits
Define adaptation
A heritable trait that increases relative fitness of an individual in an environment compared to the other individuals that don’t have that trait
Do you accept or reject the null hypothesis if your calculated chi-square is lower than the chi-square critical value…
A) Accept
B) Reject
A; Accept the null hypothesis. Meaning that one trait doesn’t affect the other trait
In regard to “Independent Assortment”, what does it mean when you accept the null hypothesis (traits are unlinked to one another)
This means that Independent Assortment is happening. Which means that offspring have an equal chance to inherit any potential phenotypic combination
What is “Pleiotropy”
A single gene affects 2 or more traits
What is “Linkage”
Typically when traits are determined by genes on the same chromosomes.
What are the things that determine the frequency of crossing over (recombination) and the time for the linkage to be broken?
Physical distance
What is absolute fitness?
Average contribution to the gene pool of the next generation that is made by individuals of the specified genotype or phenotype
What are the 4 mechanism of evolution (things that change allele frequencies in populations)
1) Genetic Drift – Causes allele frequency to change randomly
2) Gene Flow (from migration) – Can introduce new alleles into the population
3) Mutations – Introduces alleles that are both deleterious and beneficial
4) Natural/Sexual Selection
What was the point of the Hardy-Weinberg Equation
To show/prove that no evolutionary forces were acting on a population
What is the general HW equation
p^2 + 2pq + q^2 = 1
What are the assumptions under the HW theory
1) Random mating (no mate choice based on genotype/phenotype of an individual)
2) No genetic drift (large population)
3) No mutation
4) No gene flow
5) No natural selection
What are the 2 common causes of Genetic Drift in natural populations
1) Genetic Bottleneck: Severe reduction of genetic variation in a population by a chance event
2) Founder Effect: Loss of genetic variation when a new population is established by a small number of individuals from a larger population
Is Genetic Drift more prevalent/important in large or small population….
A) Large
B) Small
B; Small populations
Define divergence
Genetic based differences in a population
Genetic Drift can “outweigh” the effects of natural selection in a population; True or False
A) True
B) False
True; It can fix deleterious alleles in populations and result in loss of beneficial alleles
Define Evolutionary Adaptation
Feature/Trait that evolved in a population over time that was favored by natural selection
Are most traits Mendelian traits (discrete/categorical traits) or Polygenic Traits (complex/quantitative)?
A) Mendelian
B) Polygenic
Polygenic
Define Phenotypical Plasticity
The capacity of an individual organism to alter its behavior, physiology/gene expression, and/or morphology in direct response to changing environmental conditions
What are the keys to interpret plasticity as adaptive plasticity?
1) Environmental cues
2) Organism must be able to receive and process the cue
3) Response of the organism must increase their fitness
Are there variation in traits that increase fitness…
A) True
B) False
True; due to things like balancing selection mechanisms
What are the different types of balancing selection mechanism?
- Disruptive selection (individuals at the extreme ends of the stat chart are favored with selection)
- Negative Frequency Dependent Selection (rare/the least common traits get favored until it switches)
Describe Directional & Stabilizing selection
1) Directional (Individuals go in one direction away from the mean; loss of genetic variation)
2) Stabilizing (Individuals @ extremes go away, but mean is still maintained; loss of genetic variation)
Define Sexual Selection
Affects changes in frequency that influence mating success
Define Sexual Dimorphism
A difference in phenotype of females & males within a species (often elaborate and exaggerate these physical traits)
What are the general things that are associated with Sexual Dimorphism
- Happens during mating season
- Happens generally with males
- Only seen in mature individuals
- Often disadvantageous to fitness
Is the cost for reproduction greater for males or females…
A) Males
B) Females
B; Females usually invest more with parental care and the gametes situation (eggs are more precious than sperm)
What does it mean when it asks for asymmetries in cost of reproduction?
It means that there is not an even consistency between males and females in regard to the reproduction stages
What are the steps to sexual dimorphism traits?
1) Asymmetries in cost of reproduction
2) Males benefit more from mating success than females
3) Greater intensity of selection in males for traits that increase mating success
What are the steps to sexual dimorphism traits?
1) Asymmetries in cost of reproduction
2) Males benefit more from mating success than females
3) Greater intensity of selection in males for traits that increase mating success
4) Sexual dimorphism traits
What are the two main types of sexual selection
1) Intersexual selection (choosiness in one sex for particular traits in the competing sex)
2) Intrasexual selection (competition among members of the same sex to secure mates; male-male competition)
