heredity
the transmission of traits from one generation to the next
genetics
the scientific study of heredity
Gregor mendel
- worked in the 1860’s
- was the first person to analyze patterns of inheritance
- deduced the fundamental principles of genetics
Mendel studied garde peas because
- easy to grow
- came in many readily distinguishable varieties
- easily manipulated
- can self-fertilize
character
a heritable feature that varies among individuals
trait
a variant of a character
Mendel
- created purebred varieties of plants and
- crossed two different purebred varieties
hybrids
offspring of two different purebred varieties
P generation
the parental plants
F1 generation
the parents hybrid offspring
F2 generation
a cross of the F1 plants
Mendel’s four hypothesis
- the alternative versions of genes are called alleles
- for each inherited character, an organism inherits two alleles, one from each parents
- if two alleles of an inherited pair differ, one detrained the dominant all era done the recessive allele
- gametes carry only one allele for each inherited character
punnett square highlights
- the four possible combinations of games
- the four possible offspring in the F2 generation
phenotype
an organisms physical appearance
genotype
an organisms genetic makeup
dominant traits are not necessarily
- normal or
- more common
wild type traits
- those seen most often in nature and
- not necessarily specified by dominant alleles
many human traits
- show simple inheritance and
- are controlled by single genes on autosomes
carriers
individuals who have the recessive all but appear normal
cystic fibrosis
- most common lethal genetic disease in the US
- caused by a recessive all carried by about one in 31 americans
inbreeding
prolonged geographic isolation of certain populations caused by the mating of close relatives
-increases the chances of offspring that are homozygous for a hatful recessive trait
achrondoplasia
- form of dwarfism
- homozygous dominant genotype causes death of embryo
- only heterozygotes have this disorder
huntington’s disease
leads to degeneration of the nervous system, does not usually begin until middle age
incomplete dominance
F1 hybrids have an appearance between the phenotypes of the two parents
codominance
when both dominant alleles are expressed equally
ex: ABO blood types
polygenic inheritance
the additive affects of two or more genes on a single phenotype
many characteristics result from a combination of
- heredity
- environment
sex-linked gene
any gene located in a sex chromosome
most sex linked gene are found
on the X chromosome
red-green colorblindness
- a common human sex-linked disorder
- caused by a malfunction of light-sensitive cells in the eyes