Genetics-study of heredity

Heredity- transmission of traits from parents to offspring

I. You are a unique individual2 things determine this:A. Heredity examples: hair color, eye color, body build and features, diseases, blood type, etc.

B. Environment- your surroundingsexamples: family, friends,school, community, country, environmental (sun, climate), and internal factors (hormones)

C. Heredity and Environment work together to determinewho you are.

!!! Heredity sets limits butenvironment determines ifyou reach those limits

Examples:sun(tan??)height (5’4” or 5’8”)

II. Characteristics inheritedA. Species-things that make youlike others

arms with fingers, hair, eyes

B. Individual things that make you different

length, curly or straight, color

III. Gregor Mendel “The Father of Genetics”

A. His work 1856-1865 withgarden peas

B. Observed 7 different traits

C. Experimented by breedingplants

D. Plant anatomy:1. male anther produces pollen with sperm cells

2. Female ovary produces the egg (ovules)

3. Pollination-movement of pollen from stamen to pistila. Self-pollination -same flowerb. Cross-pollination - different plants

E. Mendel’s ExperimentMendel controlled the crossesby removing the stamen

F. Mendel’s results:Tall + tall = tallShort + short = shortShort + tall = ?????

IV. Why???Mendel’s hypothesis:1. Concept of Unit Characters

- Hereditary characteristics arecontrolled by factors that occurin pairs

We call these factors genes, that are found in the homologous pairs of chromosomes in our cells

Alleles are different forms of a gene, often represented by capital or lowercase letters

Ex: Gene = plant height - Alleles: tall or short-Allele for tall = T- Allele for short = t

Examples:tall or shortdark hair or red hairType A blood or Type B blood

2. Principle of Dominance and Recessiveness - one factor mayprevent the expression of the other

Dominant - gene that prevents the expression of anothercharacteristic that always appearsin a cross between parents

Recessive- characteristic that does not appear if a dominant ispresent

V. TermsA. Pure - both genes are the same2 dominant, or 2 recessive- “Purebred”- TT, tt

B. Hybrid - genes are different;one dominant one recessive- “hybrid plants and animals”- Tt

C. Homozygous- the samesame as pure (TT, tt)D. Heterozygous- differentsame as hybrid (Tt)

F. Genotype - the genes of an organism; its genetic makeup- Use of symbols to represent genesEx: TT tt Tt

G. Phenotype - the physical characteristic or trait of the organism - written in words, descriptiveEx: short or talltype A blood type

VI. Law of segregation- a pair of genes separateduring the formation of sex cells

A. Punnett square-a method used to determinepossible combinationsof genes in offspring

B. Examples

C. Test-cross - crossing anindividual with an unknowngenotype but a known dominant phenotypewith a recessive to determineits genotype

VII. Law of Independent Assortment- chromosomes with their genes separate independently of each other- Genetics cannot be predicted to an absolute, but we can determine the probability

Dihybrid cross-crossing organisms differing in 2 characters