Genetics and modern evolutionary synthesis
what is blending inheritance
theory that phenotypes in offspring are a blend of their two parents
what version of blending inheritance did Darwin have
a version suggesting hereditary particles called ‘gemmules’ contributed by all body parts. they accumulate in gonads and are transfered to offspring
Fleeming Jenkin argued what about natruel selection
that blending inheritance made it ineffective because variation would soon be lost
what did Francis Galton's experiment with rabbits do
disproved Darwin’s ideas, leading to the decline of blending inheritance.
what was Weismann’s Germ Plasm Theory
that only germ cells transmit genetic information across generations, while somatic cells keep it for functional purposes but do not pass it on.
What did Weismans theory establish
a clear distinction between the reproductive and somatic cells
the germ plasm theory is different in
plants, corals, and sponges
how does Weismann's germ theory
germ cells produce new somatic cells each generation, information flows from germ cells to somatic but not the other way, soma is disposable but germ plasm is immortal
what is defined as the fundamental principles of inheritance
Mendel’s laws of dominance, segregation, and independent assortment
in the F2 cross mendel foud that
The ratios of phenotypes in offspring follow predictable patterns, such as the 3:1 ratio seen in some monohybrid crosses
mendel proposed a model in which
heredity was controlled by facteurs. distinct froms of these factors accoun for variation in phenotypes. every individual has to factors one from each of their parents
today we call these factors mendel called as ...
genes
what are genes
a specific sequence of DNA that encoddes RNA or a protein
what is a locus
broader term, means the location (sequence of DNA) on a chromosome
V ou7 F all genes are loci, but not all loci are genes
V
what are alleles
differnet sequences at a given locus. unique variants of a gene that differ in nucleotide sequence
how does inheritance occur
by discrete factors that are passed from generatons according to the rules of probability
what is mendels law of dominants
if you have two different locus the dominant allele determines the phenotype and the other is not expressed
what is mendels law of segregation
that during the formation of gametes, the two alleles for a trait separate from each other so that each gamete carries only one allele for each gene. This means that an individual with two different alleles for a trait will produce gametes that contain either one allele or the other, but not both
what is mendels law of independent assortement
the allele at a given locus, a gamete receives for one gene does not influence the allele at a given locus it receives for another gene.
what is a dihybrid
individuals heterozygous for both traits
what is monohybrid
individual that is heterozygous for one trait
V ou F probability governs mendelian inheritance
vrai!
what is incomplete dominance
a genetic phenomenon where the phenotype of a heterozygote is intermediate between the phenotypes of the two homozygotes. neither are dominant, therefore it becomes a blend of the two. EX red allele + white allele = pink allele
what is co-dominance
where both alleles at a locus contribute to the phenotype of the organism in a distinct and observable way. traits associated with both alleles are expressed simultaneously and independently in the phenotype.
what is meiotic drive
when a locus manipulates meiosis to favor the trasmission of one allele over another
what is Pleiotropy
processus that occurs when a single gene affects multiple phenotypic traits, illustrating the complexity of genetic interactions. EX ABO blood type
is segregation always fair?
NO
The assortment of alleles at one locus if often
not independent of those at another locus because genes are close together on a chromosome = physical linkage. usually inherited together
what inheritance patterns make it more complex
mendels law of complete dominance is not universal, alleles dont alway segregate indipendendlty, addition complicates for single genes, assortement of alleles at one locus if often not independant of those at another locus and epistasis
Many traits are quantitative, meaning they vary along a continuum rather than falling into discrete categories
Height and skin color serve as prime examples
Quantitative traits are often
polygenic, being influenced by multiple genes, alongside environmental factors that contribute to phenotypic expression
recombinatoin cane produce
the missing gamete types. the probability of recombination increases as the distance between them increases.
what is epistasis
when one locus alters the effect on the phenotype of another seperate locus. EX. colour of retreiver (dog) fur
why does quantative variations arise
multipule loci affect the trait (polygenic) an individuals environment affects expression of the trait
what is a polgenic trait
when multipule genes affect the trait. as loci increase phenotype variation becomes finely graded. EX. skin colour
environmenal impacts can change
finely garded discrete genetic variation into truly continous phenotypic variation
what is the Hardy-Weinberg principle
mathematically describes how allele and genotype frequencies relate in a population, indicating potential equilibrium states under specific assumptions
what is the Hardy-Weinberg equation
2^2 + 2pq + q^2 = 1
what is a gene pool
consist of all copies of each allele at a given locus
what assumptions need to be met for the Hardy-weinberg principle to be true
diploid organism reproduce sexually, random mating, no natrual selection, no mutation, no migration, no genetif drift (population infinitley large)