Aim: Aim: How do your How do your genetics play a role in genetics play a role in the person you are the person you are today?today? Do Now: Do Now: What similarities do you What similarities do you

have with your parents or have with your parents or siblings? siblings?

Homework:Textbook 126-132 #1-5 Homework:Textbook 126-132 #1-5

Human GeneticsHuman Genetics

What is Heredity?What is Heredity? The transfer of characteristics from one The transfer of characteristics from one

generation to the nextgeneration to the next

What are Traits?What are Traits? A characteristic that is determined by A characteristic that is determined by

your genesyour genes A pair of genes will determine the traitA pair of genes will determine the trait

Examples:Examples: Tongue rollingTongue rolling EarlobesEarlobes Widow’s PeakWidow’s Peak Hair WhorlHair Whorl DimplesDimples

What is genetics?What is genetics? The science of how traits are inheritedThe science of how traits are inherited

Where do our genes Where do our genes come from?come from?• We had said that a pair of genes determines which traits

we will inherit from our parents• Why would it be a pair of genes?

•Each parent provides a sex cell in order for fertilization to occur

•The father will provide a sperm cell that has 23 chromosomes

•The mother will provide an egg cell that has 23 chromosomes

•When these two cells merge and become one, fertilization has occurred, and as a result, the new fertilized egg has 46 chromosomes (23 + 23 = 46)

23 chromosomes

+

46 chromosomes

23 chromosomes

How are traits determined?How are traits determined? Dominant GenesDominant Genes – the traits that will – the traits that will

usually appear in the individual usually appear in the individual (represented by an uppercase letter)(represented by an uppercase letter) If an organism has a gene for blue or If an organism has a gene for blue or

brown eyes, usually it will have brown brown eyes, usually it will have brown eyes because in is the dominant geneeyes because in is the dominant gene

Recessive GenesRecessive Genes – The gene hidden by – The gene hidden by the dominant gene the dominant gene (represented by a lowercase letter)(represented by a lowercase letter) Blue-eyed people need two recessive Blue-eyed people need two recessive

genes to show the blue-eyed traitgenes to show the blue-eyed trait

Who is Gregor Mendel?Who is Gregor Mendel? ““Father of Genetics”Father of Genetics” Studied pea plantsStudied pea plants He crossed pea plants with different He crossed pea plants with different

characteristics and studied their offspringcharacteristics and studied their offspring He was able to determine how He was able to determine how

traits get passed on from traits get passed on from generation to generationgeneration to generation

What is a Punnett What is a Punnett Square?Square? A table that shows A table that shows

the possible results the possible results when the genes of when the genes of two parents are two parents are crossedcrossed

It shows the It shows the probability of a trait to probability of a trait to be expressed in the be expressed in the offspring offspring

BB BB

BB BBBB BBBB

bb BbBb BbBb

B – Brown Eyes

b – Blue Eyes

What is a genotype?What is a genotype? The genetic code or make up of the The genetic code or make up of the

individualindividual Examples: Examples: BB, Bb, bbBB, Bb, bb

What is a genotype?What is a genotype? Homozygous dominantHomozygous dominant

– – a pair of dominant genes (BB)a pair of dominant genes (BB) Homozygous recessiveHomozygous recessive

– – a pair of recessive genes (bb)a pair of recessive genes (bb) Heterozygous or hybridHeterozygous or hybrid

– – a mixed pair of one dominant gene and a mixed pair of one dominant gene and one recessive gene (Bb)one recessive gene (Bb)

What is a phenotype?What is a phenotype? The way an organism looks or behavesThe way an organism looks or behaves

Examples:Examples:

GenotypeGenotype PhenotypePhenotype

BBBB Brown HairBrown Hair

BbBb Brown HairBrown Hair

Lets try some Punnett Lets try some Punnett Squares!Squares!

Examples:Examples: BB x bbBB x bb Bb x bb Bb x bb Bb x BbBb x Bb bb x bbbb x bb BB x BBBB x BB BB x BbBB x Bb

B = Brown EyesB = Brown Eyesb = Blue Eyesb = Blue EyesWhat we are looking for:What we are looking for:1.1. GenotypesGenotypes2.2. PhenotypesPhenotypes3.3. Percentage Brown eyesPercentage Brown eyes4.4. Percentage Blue EyesPercentage Blue Eyes