HeredityHeredity : parent to offspring the passing of traits from parent to offspring genes Traits are controlled by genes, SO what is GENETICS? inherited Genetics: The study of how traits are inherited.

GREGOR MENDEL father oFirst known geneticist and “father of genetics” 1822 oWas an Austrian monk and was born in 1822 pea oDid most of his genetic studies on pea plants

WHAT ARE ALLELES? FORM oAre ONE FORM of a gene (there can be more than one form) one oSex cells have one form of a gene on their chromosomes two oBody cells have two forms or ALLELES for a single gene (you got one from Mom and one from Dad) dominant oOne may be dominant over another. If this happens, the dominant gene is the one expressed. If not, the recessive trait is expressed.

DOMINANT AND RECESSIVE oA Dominant trait: mask will always be expressed and will “mask” a recessive trait oA recessive trait dominant can only be expressed if there are no dominant alleles present.

Example Example: dominant Eyecolor—Brown color is dominant and blue is recessive. brown hides A person can have a brown allele and a blue allele but still have brown eyes because the brown allele is dominant and “hides” the blue allele.

Rr Example: R= dominant r = recessive capital lower caseGenerally, dominant alleles are represented with a capital letter, and recessive alleles are represented with a lower case letter.

TWO Each organism is represented by TWO letters, one for each allele.

same o“Purebred” species have two alleles of the same trait homozygousFor instance: BB or bb. oRepresented by two of the same letters. This is called homozygous. For instance: BB or bb. oSpecies with two different alleles or two different forms of the gene would be “hybrid” letters For instance: Bb oRepresented by two different “letters” and by called “heterozygous”. For instance: Bb genotype BB, Bb, or bb. oThe alleles present in the organism are referred to as its genotype. For instance, BB, Bb, or bb.

PHYSICAL PHENOTYPE oThe PHYSICAL trait that shows, regardless of genotype is called a PHENOTYPE. BlueBrown oFor instance, Blue or Brown Eyes.

PROBABILITY chance oHelps predict the chance that something will happen oExample 50% oExample: the probability of throwing heads or tails on a coin is 50% (1/2 chances) accurate oYour predictions become more accurate with the more trials you run!

Using a Punnett Square… oUsed to help predict Mendelian genetics

Steps for using the Punnett square: (genotype) 1)One parent’s alleles (genotype) go along the top 2)The other parent’s alleles go down the side. 3)You fill in the squares like doing the communicative property of multiplication. BbBb B b BB bbBb

Let’s try some practice problems…

Practice Problem #1 Predict the fur color of the offspring of a brown heterozygous hamsters and a white homozygous hamster. Brown is dominant. White is recessive. Use any letter you like.

Practice Problem #1 Bbbb Bbbb B b bbbb

Practice Problem #2 Predict the offspring of 2 white homozygous cows. Black is dominant over white. Use any letter you like.

Practice Problem #2 bb bbbb

Practice Problem #3 Predict the offspring of 2 Grey Heterozygous rats. Gray is dominant over white, which is recessive. Use any letter you like.

Practice Problem #3 GGGg gg G g GgGg

Practice Problem #4 Predict the pea shape of the offspring of one Heterozygous Round Pea plant and one homozygous wrinkled pea plant. Round is dominant over wrinkled. Use any letter you like.

Practice Problem #4 Rrrr Rrrr R r rrrr

Practice Problem #5 you don’t have to write this one down… What are the chances of having a boy or a girl? How would you solve this one?

Practice Problem #5 XXXY XXXY XXXX