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Set up today’s page in your journal… • • Page: 50 Title: Mendelian Genetics Date: 11 -18 -14 Essential Question: Can genetic outcomes be predicted with 100% accuracy? **Do NOT leave a summary space on the first page! We will be using multiple pages today. **

Standard: predict possible outcomes of various genetic combinations (B. 6 F)

Trait: a specific characteristic that varies from one individual to another For example…

Inheritance is determined by biological factors that are passed from one generation to the next. In other words, which traits you pass on depends on what genes you get from your parents. Genes: chemical factors that determine traits (small sections of your DNA strand…remember? ? ) Alleles: different forms of a gene

Principle of Dominance: some alleles are dominant and others are recessive [ [ • the dominant allele will always be expressed when it is present • a capital letter is used to represent a dominant allele Y = Dominant y = Recessive

• the recessive allele will only be expressed when the dominant is not present • a lowercase letter is used to represent a recessive allele Y = Dominant y = Recessive

Phenotype: appearance Brown Eyes vs Blue eyes Genotype: the actual genes *Two organisms can have the same phenotype but different genotypes* BB Bb bb

Homozygous = purebred BB Bb bb Heterozygous = hybrid BB Bb bb

Name that Genotype! PP Homozygous Dominant

Name that Genotype! nn Homozygous Recessive

Name that Genotype! Tt Heterozygous

Name that Genotype! Dd Heterozygous

Name that Genotype! BB Homozygous Dominant

Name that Genotype! qq Homozygous Recessive

Name that Genotype aa Homozygous Recessive

Principle of Independent Assortment: the way alleles separate during meiosis is completely random and cannot be predicted **This is why you never know for sure which traits will be passed on to which offspring!**

Probability: the likelihood that a particular event will occur We can predict possible genetic outcomes using probability.

Punnett square: a diagram that shows the probability of certain traits being passed on to offspring

• The letters in the Punnett square represent alleles passed on from parent to child. Punnett squares are used to predict and compare the genetic variations that will result from a cross.

How to complete a Punnett Square 1 st = Use information to IDENTIFY and EXTRACT THE GENOTYPES *”homo”/”hetero”, “dominant”/”recessive”, “pure”/”hybrid” are all clues to the genotype • Extract: remove or take out, especially by effort or force.

How to complete a Punnett Square 2 nd = Arrange the genotypes on the top and side of the Punnett square. *the male genotype is usually written on top and the female on the side

How to complete a Punnett Square 3 rd = Cross the Genotypes to discover the possibilities. *the male genotype is usually written on top and the female on the side

How to complete a Punnett Square 3 rd = Cross the Genotypes to discover the possibilities. *the male genotype is usually written on top and the female on the side

Let’s sum it up…. . 1 st = Identify the trait and what letter will represent it 2 nd = Assign the dominant/recessive trait for your letters 3 rd = Match the letters to the correct parent 4 th = Now fill in your Punnett square

Punnett Square practice… 1. What would be the possible outcomes for the offspring of a cross between pink flower (PP) and a white flower (pp)? p p P P Pp Pp P = Pink p = White DAD = PP MOM = pp **When using the letters like “P and p” OR “C and c”, draw the lowercase letter in cursive or just make sure you make them look different. Otherwise, you might confuse the dominant for the recessive **

2. Long fingers are dominant (F) to short fingers (f). Complete the Punnett square for a homozygous recessive mom and a heterozygous dominant dad. f f Ff ff F = Long f = Short ff DAD = Ff MOM = ff Ff

3. In a plant, long stems are dominant (L) to short stems (l). If a homozygous dominant flower and a homozygous recessive plant are crossed, what would be the phenotypic ratio of their offspring? l l L L Ll Ll L = Long L = Short Ll DAD = LL MOM = ll Ll

4. Straight hair (C) is dominant to curly hair (c). What would be the probability that a child would have curly hair if both parents are heterozygous dominant? C c CC Cc Cc cc C = Straight c = Curly DAD = Cc MOM = Cc

5. Having a hitchhiker's thumb is a dominant trait (T). If a woman with a straight thumb has a child with a man who is heterozygous for the trait, what are the chances their child will have a hitchhiker's thumb? T t t Tt tt T = Hitchhiker t = Straight DAD = Tt MOM = tt

6. What would the phenotypic and genotypic ratios be for two purple (Pp) flowers that were bred together? P p PP Pp Pp pp P = Purple p = White DAD = Pp MOM = Pp

Can you identify your own genotypes and phenotypes? Hairline: Widow’s peak is dominant to straight hairline Eye Shape: Almond eyes is dominant to round eyes

Eyelash Length: Long eyelashes is dominant to short eyelashes Tongue Rolling: CAN roll the tongue is dominant to cannot

Hitchhiker’s Thumb: Hitchhiker’s thumb is dominant to straight thumb Lip Thickness: Thick lips are dominant to thin lips

Quick Write What are the chances of a homozygous recessive genotype when two heterozygous phenotypes are crossed? Explain.