Genetics Flashcards
genotype
the combination of alleles a person has
alleles
the variants of a particular gene
phenotype
the expression of a genotype
the genotype interacts with the __________________ to produce the phenotype
external environment
sources of genetic variability
genetic recombination (random segregation & crossing over) mutation- change in DNA sequence
deme
local population that interbreeds
gene pool
all the genetic information in a breeding population
reproductive isolation
mechanism that prevents two populations from interbreeding
species
groups of reproductively isolated organisms
reproductive isolation is not always
absolute
ie. hybrids can happen
incomplete reproductive isolation
produces living but not fertile offspring
polygenic inheritance is not
mendelian
polygenic traits are also known as
continuous traits
continuous traits are governed by…
alleles at two or more loci, and each locus has some influence on the phenotype
examples of polygenic traits
hair, skin and eye colour
skin coloration is determine by pigment produced by special cells called…
melanocytes
EVERYONE has the same number and distribution of
melanocytes
the amount of melanin produced determines
how dark or light the skin will be
melanin production is influenced by
interactions between several different loci
how can melanin production vary
in amount produced and pattern it is produced in (ie. freckles)
factors that influence human skin colour
genetics and stress from solar radiation
why are skin colours darker near the equator
melanin protects from solar radiation
why is skin colour lighter farther from the equator
melanin prevents vitamin D synthesis
discontinuous distribution of mendelian traits
frequencies are easily counted, no blending occurs
continous expression of a polygenic trait
frequencies can’t be counted easily
ie. height, theres no set distinct phenotypes but instead a range
what traits cause more of the observable phenotypic variation in humans and serve as a basis for racial classification
polygenic traits
more examples of polygenic traits
stature, shape of face, fingerprints
Rh- mother with Rh+ baby
Rh antigens from developing fetus can enter mothers blood during delivery causing the mother to produce anti Rh antibodies
if this woman becomes pregnant with an Rh+ fetus, the anti rh antibodies will cross the placenta and damage fetal RBCs
Rh- is
recessive
