GENETICS

GENETICS

• Study of genes
• Mendel
• discovered particles (chromosomes and DNA)
• trait (color of eyes, hair) 
• heredity (passing traits)
• genetics study heredity
• alleles: different genes for the same trait (dominant and recessive)
• dominant: stronger one (R)
• recessive: shows up less often (r)
• WHEN BOTH GENES OF A PAIR ARE THE SAME THEY ARE HOMOZYGOUS
• heterozygous a dominant and a recessive
• monohybrid cross (1 trait)
• dihibryd cross (2 traits)
• genotype: gene combination for a trait (RR)
• phenotype: physical characteristic from a genotype( red)

Genetics is the study of genes.

Gregor Mendel  Man of science  discovered how genes act from generation to generation. Father of genetics.

Mendel stated that physical traits are inherited as “particles”. He didn’t know that the “particles” were chromosomes and DNA.

•Gene: is a segment of DNA that determines a trait.  As chromosomes come in homologues (matching genes. One from mother and other from father) pairs, thus genes come in pairs. Homologous regions code for the same gene. 

•Trait: any characteristic that can be passed from parent to offspring. They are determined by the genes on chromosomes. 

•Heredity: passing of traits from parent to offspring.

•Genetics: study of heredity. 

Designer genes

•Alleles: two forms of a genes (dominant and recessive). Different genes (possibilities) for the same trait (blue eyes or brown eyes). Always use the same letters for the same alleles. 

•Dominant: stronger of two genes expressed in the hybrid, represented by a capital letter. One copy of the gene. Gene that prevents the other gene from “showing” .

Straight thumb is dominant to hitchhiker thumb T=Straight thumb. t= hitchhikers thumbs. 

•Recessive: gene that shows up less often in a cross; represented by a lowercase letter. Two copies of the gene. Gene that does not “show” even though it is presented. Must have 2 recessive alleles for a recessive trait to “show”.

Both genes of a pair are the same. Homozygous or purebred. 

TT= homozygous  dominant

tt= homozygous  recessive.

One dominant and one recessive gene, heterozygous or hybrid. Combination of dominant and recessive. 

Dark color is dominant over lighter colors. 

Types of genetic crosses:

•Monohybrid cross: cross involving a single trait.  (flower color)

•Dihybrid cross: cross involving two traits. (flower color and plant height)

•Genotype: gene combination for a trait. 

•Phenotype: the physical feature resulting from a genotype 

•Punnett square: used to predict the possible gene makeup of offspring