Heredity

What is heredity?

• Heredity is the passing of traits from parent to offspring.• You inherit traits from your

parents

What are traits?• Eye Color• Hair Color• Height• Weight• Body Structure• Facial Features• Skin Color

What traits did you inheritfrom your parents?

• Complete the genetic scavenger hunt with the people at your table.

• List any unusual traits that your group members have on the back of the paper.

• You have 5 minutes to complete this assignment.

• Be ready to share with the class.

How are traits passed?• When organisms reproduce, traits

are passed from parent to offspring.• These traits are carried in DNA, the

genetic material found in a cell’s nucleus.• DNA acts like a blueprint.

Review• DNA is located on chromosomes.– You have 23 pairs of chromosomes…pairs 1-22 are

autosomes and the 23rd pair are sex chromosomes.

– Homologous chromosomes carry the same gene• Genes are pieces of DNA that carry a specific set of

instructions– Genes influence the development of traits

• Half of your genes come from your mom and half come from your dad.

Dominant and Recessive• Each parent has two genes (or letters) for a

trait. These letters are called alleles.• Capital letters are called Dominant alleles.• When these alleles are present, they take over

or show. They are the “stronger” alleles• Lower case letters are recessive alleles and are

the “weaker” of the alleles.

http://naturalsciences.sdsu.edu/classes/lab2.4/trait.jpg

Punnett Squares• Using Punnett

Squares allow us to show what the offspring could look like

• Allows us to calculate probability of certain genotypes and phenotypes to occur

Dominant/Recessive• Capital letters are called Dominant

alleles.– When these alleles are present, they take over or

show. They are the “stronger” alleles

• Lower case letter are recessive alleles and are the “weaker” of the alleles.

Dominant• B – brown eyes• T – tall• C – curly hair• W – widows peak

• F – freckles• D – dark skin

Recessive• b – blue eyes• t – short• s – straight hair• w – no widows

peak• f – no freckles• d – light skin

Genome• All of an organism’s

genetic material.

– Everyone has a unique genome that determines their traits…except for identical twins.

Genotype and Phenotype• Genotype – the

inherited alleles, genes.(letters)

• Phenotype – what the alleles look like when inherited (physical characteristics)

Genotype/PhenotypeGenotype

• ff • cc• Cc• tt • TT • bb• Bb

Phenotype• No Freckles• Straight Hair• Curly Hair• Short• Tall• Blue Eyes• Brown Eyes

Homozygous and Heterozygous

• If the genes are the same, they are homozygous– “homo” means same

• If the genes are different, they are heterozygous– “hetero” means different

• Look at SIZE of letter!!

Homozygous/Heterozygous??

• RR• Rr• rr• Tt• tt• BB• Bb

Dominant/Recessive & Homozygous/Heterozygous

• Dominant– Heterozygous • Bb-Brown eyes

– Homozygous dominant• BB-Brown eyes

• Recessive– Homozygous

recessive• bb-blue eyes