Foundations of Genetics  Main idea: Gregor Mendel discovered the basic principles of genetics.

Gregor Mendel

Why do we look like our family members?  The answer is DNA  DNA determines everything about you

What does DNA determine?  DNA determines traits  Traits are physical characteristics that we inherit from our parents  Heredity is the passing of traits from parents to offspring.  Genetics is the study of heredity.  Examples of traits: hair color, eye color, height

Mendel’s Experimental Methods  Studied seven traits of each pea plant

Controlled Experiments  Cross-fertilization- transferred pollen from the stamen of one pea flower to the stigma of a pistil in another flower

Genes and Alleles  Gene- A section of DNA that has information about a specific trait  Allele (factor)- Each form of a gene with different information

Purebred and Hybrid  True breeding plants (purebred)-offspring of many generations with the same trait  Hybrid- offspring inherits two different alleles from 2 parents

Mendel’s Experimental Results  One genetic factor for purple flowers and one genetic factor for white flowers

Dominant & Recessive alleles Dominant  An allele whose trait always appears  Example: Mendel’s experiment, purple flowers Recessive  An allele whose trait can be hidden by the dominant allele  Example: Mendel’s experiment, white flowers

Phenotype  Phenotype is the physical appearance or visible traits

Genotype  An organism’s combination of alleles

Genotype & Phenotype

Heterozygous and Homozygous Phenotype Smooth SmoothWrinkled Homozygous (SS) Heterozygous(Ss) Homozygous dominant recessive (ss) Genotype Uppercase letters= dominant alleles Lower case letters= recessive alleles

Phenotype or Genotype ? Red hairCleft Chin RR Dd Blue EyesBB BbHair on Fingers Cc Brown skin Curly Hair Bb WwGG Straight Hair

Homozygous or Heterozygous ? HHyy Rrdd GGKK WwFf WWss XXNN XxNn

Punnett Square ✦ A Punnett square is a chart that shows all the possible combination of alleles that can result from a genetic cross. You can use a Punnett Square to calculate the probability that offspring with a certain combination of alleles.

EXAMPLE

Results of Cross