Genetics

The study of patterns and mechanisms of heredity and variation of inherited characteristics.

heredity

The transmission of genetic characteristics from P to F₁.

variation

inherited differences among species

"Father of Genetics"

blending inheritance

-how inheritance was viewed prior to Mendel

-problem: uniformity

true breeding

offspring have same traits as parents

variety

true breeding line

hybridization

crossing of two varieties

qualitative traits

traits with 2 character states

example: yellow vs. green seeds

example: wrinkled vs. smooth seeds

character

heritable feature

filial generation

offspring

trait

character variant

first part of

Particle Theory of Inheritance

Inheritance of each trait is determined by units (genes).

(these genes are passed to descendents unchanged)

second part of

Particle Theory of Inheritance

Individuals inherit one unit for each trait from each parent.

(unit for each trait = alleles)

third part of

Particle Theory of Inheritance

A trait may not show up but can still be passed down.

(recessive allele)

Law of Segregation

alleles segregate into seperate gametes

sister chromatids

either of two copies of a duplicated chromosome attached to each other by proteins at the centromere (and sometimes along the arms)

homologous pair

a pair of chromosomes of the same length and centromere position that posses genes for the same characters at corresponding loci

genotype

the genetic makeup or set of alleles of an organism

phenotype

an organism's physical and physiological appearance (determined by its genotype)

locus

-specific location ("address") of a gene

-location of a gene on a chromosome

alleles

alternate forms (variants) of a gene

homozygous

vs.

homozygote

same alleles at a given locus on homologous chromosomes

vs.

an individual with homozygous alleles

heterozygous

vs.

hybrid/heterozygote

different alleles at given locus on homologous chromosomes

vs.

individual with different/heterozygous alleles at a given locus

Law of Independent Assortment

each pair of alleles segregates itno gametes independently

Complete Dominance

Simple Mendelian Dominance

-alleles are dominant OR recessive (recessive alleles are there but NOT EXPRESSED)

Incomplete Dominance

F₁ generation individuals have appearance somewhere between that of their parents

example: P-red and white; F₁- pink; F₂-1 red, 2 pink, 1 white

Codominance

both alleles contribute to the phenotype and are expressed to the same extent

ex: human blood groups M,N,MN

Multiple Alleles

-multiple allelic forms on genes

ex: A B O blood groups

(see table 14.11)

Polygenic Inheritance

-additive effect of two or more genes on a single phenotypic character

-based on quantitative characters (vary along continuum)

ex: skin color, height, multiple sclerosis

linkage

Genetic loci on same chromosome are physically connected, tend to segregate together during meiosis.

karyotype

arrangement of homologous pairs of chromosomes from longest to shortest