Genetics Notes

Heredity:The study of genetics started with

observations made by GREGOR MENDEL, a monk who noticed that pea plants passed certain traits from one generation to the next.

Heredity is the passing of genes from one generation to the next. We all inherit DNA from both our parents, and their parents and so on.

DNA contains genes that code for all of our characteristics.

Genes:Provide genetic information, passed on from parents to offspring.

Genes provide traitsEx: hair color, eye color, height, seed shape, etc.

AllelesAlleles are different forms of a trait. We

use letters to represent a particular trait. Example: Height T= Tall t= Short

Dominant Allele: Fully Expressed (Always in Capitalized letter)Recessive Allele: Not shown when paired with a dominant allele; only noticeable when paired with another recessive allele (Always in lower case letter)

Genotype:Is the combination of genes from each parentHomozygous = Same alleles. Ex: TT (Dominant)

Same or tt (Recessive)

purple PP homozygous dominant

Heterozygous= Different alleles. Ex: Tt (Hybrid)

different also called a CARRIER.purple Pp heterozygous

Phenotype:Is the way an organism physically looks.

Ex: Blonde hair, brown eyes, tall, purple flowers, etc.

TT or Tt= Tall phenotype tt = Short phenotype

RR Red feathers

What is the phenotype? What is the genotype?

Punnett Squares Allow us to find the probability of the

genotype and phenotype passed from parents to offspring

Letters OUTSIDE of the Punnett Square are from the parents

Letters INSIDE of the Punnett Square represent the probability of the parents’ offspring’s genotypes

Punnett Squares:

Ex: Parents: Tt x tt (T=Tall, t=short)

T t Genotype:

t Tt=50% , tt= 50%

Phenotype:

t Tall=50%, Short=50%

T t

tt

Tt

tt

Can you think of any traits that identify you and the rest of your family?