Heredity & Genetics Heredity parent to offspringHeredity = the passing of traits from parent to offspring genes inherited oTraits are controlled by genes, so therefore, GENETICS is the study of how traits are inherited through the action of alleles

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 scientific method oHe made careful observations, and strictly adhered to the scientific method

pollinator oHe performed cross-pollination by becoming the pollinator himself, and controlling which plants mixed. shapepea color seedsheight position oSome traits Mendel worked with were shape of pea and it’s pod, color and shape of seeds, plant height, flower position and flower color.

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

oExample dominant brown hides oExample: Eyecolor—Brown color is dominant and blue is recessive. 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 homozygousFor instance: BB or bb. o“Purebred” species have two alleles of the same trait, and therefore would be represented by two of the same letters. This is called homozygous. For instance: BB or bb. letters For instance: Bb oSpecies with two different alleles or two different forms of the gene would have 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.

My Mom has blue eyes (bb) My Dad has brown eyes (BB or Bb) Miss Hemphill has blue eyes (bb) Therefore, my dad must have the Bb genotype, because he must have given me the “b” allele. His “b” allele is masked by his “B”/dominant allele. Genetics by Brainpop

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!

Why is it that if a couple has 2 children, they don’t always have one boy and one girl? 2 is a really small trial #…so won’t always “see” the ratio! …we will investigate this more later on!

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. 4)See Below:

Steps for using the Punnett square: Let’s say the parents are Bb and Bb (the same genotype). What would be their phenotype? Brown Eyes BbBb B b So you would predict: 1/4 1/4 offspring to be BB, or Brown Eyes 1/2Brown 2/4 or 1/2 to be Bb, or Brown Eyes 1/4Blue and 1/4 to be bb or Blue eyes BB bbBb

So, if Miss Hemphill had children with her husband to be …what color eyes would they have? Mr. Ellinger Blue eyes (bb) Miss Hemphill Blue eyes (bb) All of our kids would have blue eyes! bb b b

Using a Punnett Square Clip

Heredity Heredity by Brainpop 1What do we call different forms a gene may have for a trait? 2What height of pea plant (tall or short) did Mendel find to be dominant? 3Which kind of trait can’t be passed from parent to child? a)Eye colorb) heightc) broken arm

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 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