Population genetics.txt

• extra nuclear inheritance
• traits conditioned by genomes OTHER than nuclear one
• these genes are called CYTOPLASMIC genes - they arise in organelles such as mitochondria or plastids

• Organelles contributed to zygota via EGG, not sperm:
• 1. chloroplasts or
• 2. mitochondria inherited from MOTHER

• Genotype of mother determines phenotype of progeny
• ie snail shells: coiling dominant to maternal - mother's trait present in every offspring
• in a diagram, mother's circle will be shaded in every case

• XX: one female X chromosome in each cell is inactivated
• During development remains inactivated
• In diff development lineages, a different X becomes inactivated
• 1st recog. by Mary Lyon

• 1. Females have a chromatin body in interphase nucleus, but not in males
• 2. Female cats are mosaic for coat color on gene X (calico cats), human (anhidrotic ectodermal dysplasia, red-green color blindness)
• w/colorblindness, XR Xr, although every cell can't see color, as long as you have some of both you won't be colorblind.
• 3. Female mice w/a translocation b/w X and an autosome w/a coat color gene are MOSAIC

• continuous traits showing a distribution of phenotypes
• continuous traits are affected by many genes and are also called POLYGENIC or MULTIGENIC traits

• 1. Matings b/w extremes in phenotypes will usually result in INTERMEDIATE phenotype (usually occurs when both parents are homozygous for different sets of alleles affecting different characteristics) - ie AA x aa = Aa (tall x short = medium HEIGHT)
• 2. Matings b/w intermediate phenotypes can result in F1 outside the range of parents. (produce progeny from one extreme to the other & in between)

Phenomenon that progeny can be OUTSIDE the range of the two parents for a particular trait. ie 8ft tall child from 2 tall parents

• includes Mean and Variance to analyze polygenic traits
• Mean: sum of sample measures / n
• n = # in sample
• Variance: s^2 = (mean - x)^2 / n-1
• x = number ur looking at
• Standard Deviation: Square root of Variance

• 1. If variance increases from F1 to F2, Multiple genes are involved.
• 2. Magnitude of increase gives indication of how many genes
• if only a FEW genes, Variance will increase A LOT
• if MORE genes, Variance will increase LESS
• Prob of a few genes getting to extremes is HIGHER than lots of genes getting to extremes

if offspring resemble parents as result of genetic similarity

• Has both an environmental VS genetic component
• ie - environmental can be improper nutrition leading to less growth

Study of genes in population of a species w/regards to allele freq and how they change

Shared genes in a population

• Test of assumptions about a population
• Allows calculation of genotypic frequencies from allele freq. (and vice versa)
• Need to hold the following true:
• 1. Organisms are diploid
• 2. Reproduction is Sexual
• 3. Large populations
• 4. Random mating
• 5. No evolutionary forces, no mutations, no migration, no natural selection
• p^2 + 2pq + q^2 = 1

• Positive assortment mapping: individuals w/similar phenotypes mate preferentially. (ie humans and height)
• Negative assortment mapping: phenotypically dissimilar individuals mate more often than at random
• Rare male advantage: in fruit flies, an UNUSUAL phenotypic male will be selected by females more often than at random (ie guitar playing band member syndrome)
• Inbreeding: mating among relatives increases homozygosity at expense of heterozygosity. Progeny is small in populations...Makes detrimental mutations homozygous
• Outbreeding: mating b/w non-related individuals. Maintains detrimental mutations heterozygous, but if no mates in small population, no progeny.

Ability to pass on genes

• 1. new genes come from gene duplication
• 2. new alleles come from MUTATION
• 3. Allele freq can change by selection, migration, or in small population, genetic drift
• 4. Genotypic freq can change by in/outbreeding, assortive mating

• Can change allele freq thru SEXual selection and environmental factors (migration)
• or can be done through Human selection (ie humans select dogs for pure breeding)