Biology Chapter 4: Genetic Inheritance and Evolution Flashcards
Directional selection
where a more extreme phenotype is favored
Allopatric speciation
occurs because of physical barriers. Geographic isolation, separating the Asian and European samples, is a common cause of allopatric speciation
Sympatric speciation
describes reproductive isolation that emerges when no physical barrier separates a population (ie behavioural and ecological differences)
If one parent is homozygous recessive, what is the probability that an offspring will carry one or more recessive alleles?
100%
Genetic bottleneck occurs when
A population experiences a sharp reduction in size, leading to a loss of genetic diversity, increased genetic drift, potential inbreeding
Allele
Variation of a gene
Law of independent assortment
Inheritance of various genes are not correlated with each other
Linkage is an exception to
Independent assortment because genes that are physically close to each other on the same chromosome tend to have alleles inherited together
What is hemizygousity?
Only 1 allele (like on x Y chromosomes in males)
Why perform a test cross? And how?
To find the genotype of dominant allele (either AA or Aa). Cross the unknown dominant with a known recessive
What is a back cross and why perform it?
To obtain offspring more similar to the parent. Cross a hybrid from F1 with a parent
Penetrance
Probability that genotype actually manifests
Expressivity
The extent of the intensity of the gene expression
On a pedigree analysis, circles, squares and shaded shapes refer to what?
Circles = females, squares = males, shaded = manifest a certain phenotype. Half shaded means that the person is a carrier
Chiasmata
The point of crossing over. Occurs at random
Recombination frequency
Describes how often a single crossover will occur between 2 genes during meiosis
If the recombination frequency of two genes is exactly 50% then the genes? Less than 50%? Greater than 50%?
Obey the law of independent assortment at exactly 50%.
Less than 50% - genes are linked, meaning that the genes are close enough together that they don’t assort independently. Closer the genes, lower the rf
Not possible to have rf greater than 50%
Distance associated with 1% increment in the recombination frequency
Centimorgan (cM)
Difference in inheritance between autosomal mutations and somatic mutations
Autosomal mutations are found on chromosomes 1-22 and ARE inheritable if in germ line cells like egg and sperm (such as cystic fibrosis, Huntington’s disease)
Somatic mutations are located in body cells, NOT germline cells and therefore aren’t inherited. Ie cancer mutations, UV-induced skin damage etc
Autosomal dominant inheritance patterns
Do not skip generations
Autosomal recessive inheritance pattern
Can skip generations
X-linked inheritance patterns
More males affected
Dihybrid cross ratio
9:3:3:1
Fitness
Chance of reproduction associated with a certain phenotype. Must be defined by specific environment constraints
Inclusive fitness
Chance of reproductive success of an entire group of organisms (not just the individual)
Gene pool
All the genotypes in a population
Hardy-Weinberg equilibrium definition
Determines the genotype and allele frequency in a population.
AND can use to predict the phenotypes in the population and vice versa
Hardy-Weinberg equilibrium criteria
Hardy-Weinberg equations
And p + q = 1
Polygenic
Multiple genes collective contribute to a trait. Often involved with traits that show variation along a spectrum such as height
Stabilizing selection
Extreme phenotypes selected against
Disruptive selection
Extreme phenotypes selected for, median phenotype selected against
Directional selection
Occurs only if one extreme phenotype is selected against and the other is favoured
Genetic drift
Role of CHANCE in determining the reproductive fitness of various alleles
Polymorphism
Phenotypic variations can exist in a single species ie ABO blood group systems
Example of post zygotic barrier
Hybrid sterility
Leakage
On the level of the gene pool, genes can sometimes travel between species
Accumulation of random changes in genome over time
Molecular clock. Can be used as a method for dating divergence from last common ancestor
Differential reproduction
means individuals with traits better suited to their environment are more likely to survive, reproduce, and pass on their genes to the next generation.
“Survival of the fittest, through reproduction”
parsimony
which seeks the simplest explanation for the observed data—i.e., the phylotree that minimizes the number of evolutionary events (such as gene gains or losses)
Which phylums share the most genes?
simpsoni, mascarensis and aegypti
