Heredity Heredity by Brainpop

I. Heredity & Genetics parent to offspring oThe 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

II. 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.

III. 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.

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. Genes by Brainpop

IV. 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.

V. PROBABILITY chance oHelps predict the chance that something will happen 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!

VI. Using a Punnett Square oUsed to help predict Mendelian genetics oIn Punnett squares, dominant traits are represented with a CAPITAL letter, and recessive traits represented by a LOWER CASE letter. Take for instance, eye color. Choose to represent eye color with the letter b. Big B or “B” for dominant and little b or “b” for recessive. oEach organism is represented by TWO letters, one for each allele.

same homozygous 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 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 oThe alleles present in the organism are referred to as its genotype. For instance, BB, Bb, or bb.

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

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 Bbbb BbBb B b So you would predict: 1/4 ¼1/4 offspring to be BB, or Brown Eyes 1/2½Brown 2/4 or 1/2½ to be Bb, or Brown Eyes 1/4Blue and ¼1/4 to be bb or Blue eyes

So, if Miss Hemphill married and had children with her boyfriend …what color eyes would they have? Blue eyes (bb) All of our kids would have blue eyes! bb b b

Using a Punnett Square Clip

Heredity Heredity by Brainpop