Genetics Basics Making predictions about future generations Objective

Genetics Basics Making predictions about future generations…

Objective • I will be able to use Punnett squares to predict the genotype and phenotype of offspring.

Gene vs. Allele • Gene: A specific region of the DNA that codes for a particular trait • Allele: Any of the alternative versions of a gene that occur at specific locations on a chromosome – Example: The alleles for pea flowers are purple and white – What are some alleles for eye color?

Introducing the Father of Genetics… • Gregor Mendel! • A monk that lived in Austria in the 1860 s • Mendel bred peas to study inheritance. • He discovered the founding principles of heredity.

The technique…

The results… Experiment 1 • Purple and white makes…? • Purple! Experiment 2 • Purple and purple makes…? • Purple and white! X

The discovery… • The dominant allele, is fully expressed in the organism’s appearance. – Shown with a CAPITAL LETTER • The recessive allele, has no noticeable effect on the organism’s appearance. – Shown with a lowercase letter Purple = dominant = P White = recessive = p

Two Alleles for Each Trait • For each trait, an organism inherits two alleles – One from MOMMY one from DADDY • Homozygous: When the two alleles are the same – AA or aa • Heterozygous: When the two alleles are different: – Aa Aa AA aa

Genotype vs. Phenotype • Genotype: all the organism’ genetic information that codes for traits – “what’s in the DNA” – Example: BB, Bb, bb • Phenotype: the organisms physical characteristics – “what it looks like” – Example: Brown or blue eyes

Vocab. Practice… 1. If T = tall and t = short, what is the genotype of each of these: • Homozygous dominant: TT • Homozygous recessive: tt • Heterozygous: Tt 2. • • • What is the phenotype for each of these? TT = Tt = tall tt = tall short

More practice: N = Straight hair, n = curly hair 3. A man that is heterozygous for straight hair, marries a woman who is homozygous recessive for curly hair. – Man genotype: Nn – Man phenotype: Straight hair – Woman genotype: nn – Woman phenotype: Curly hair

One more: B = brown eyes, b = blue eyes 4. A man with blue eyes marries a woman who is homozygous dominant for brown eyes. – Man genotype: bb – Man phenotype: Blue eyes – Woman genotype: BB – Woman phenotype: Brown eyes