Punnet’s Squares, Probability & Pedigrees Practice, Practice, Practice! 

Warm Up on the Whiteboards Set up a punnet square for the cross. Warm Up on the Whiteboards An aquatic arthropod called a Cyclops has antennae that are either smooth or barbed. The allele for barbs is dominant. In the same organism, resistance to pesticides is a recessive trait. Make a "key" to show all the possible genotypes (and phenotypes) of this organism A Cyclops that is resistant to pesticides and has smooth antennae is crossed with one that is heterozygous for both traits. Show the genotypes of the parents. Set up a Punnet’s Square for the cross. What are the phenotypic ratios for the offspring?

In Rabbits, grey hair is dominant to white hair In Rabbits, grey hair is dominant to white hair. Black eyes are dominant to red eyes. What are the phenotypes of the rabbits that have the following genotypes? Ggbb__________ b) ggBB__________c) ggbb________d)GbBb__________ 2. A male rabbit with the genotype GGbb is crossed with a female rabbit with the genotype ggBb . Set up a Punnet Square to determine the following: What % have grey fur and black eyes? What % have grey fur and red eyes? What % have white fur and black eyes? What % have white fur and red eyes? 3. A male rabbit has the genotype GgBb. Determine the gametes made by this rabbit. 4. Set up a punnet’s square for a male rabbit GgBb mated with a female rabbit GgBb. What are the phenotypic proportions?

Probability Rules 1) Multiplication Rule- for this AND that together Ie) What is the probability of flipping 3 coins and getting all tails? 1/2 x 1/2 x 1/2 = 1/8 2) Addition Rule- for “This and That”.. Different ways of getting the same thing Ie) What’s the probability of getting one tail and two heads? First find the probability of each event THEN add them up!

Ie) What’s the probability of getting one tail and two heads? First find the probability of each event THEN add them up! Probability of tail, heads, heads: ½ x ½ x ½ = 1/8 Probability of heads, tail, heads:½ x ½ x ½ = 1/8 Probability of heads, heads, tail: ½ x ½ x ½ = 1/8 Answer: 1/8 + 1/8 +1/8 = 3/8

What’s the probability of having two girls and one boy? Probability of boy, girl, girl: ½ x ½ x ½ = 1/8 Probability of girl, boy, girl Probability of girl, girl, boy Answer: 1/8 + 1/8 +1/8 = 3/8

Try this! In peas yellow seed colour is dominant over green seed colour Round seed shape is dominant over wrinkled seed shape. A round yellow seeded plant was crossed with a green wrinkled plant producing 20 plants. Of these 11 were yellow with round seeds and 9 had green round seeds What was the probable genotype of the parents?

Genotype of parents? Known Info: R- round shape rr-wrinkled Y- Yellow yy- green Parents: Round yellow seed x Round green wrinkled Genotype? R_?_Y_?_ x R__yy F1 info: 11/20 = 55% Round and yellow  genotype? 9/20= 45% Round and Green genotype? SINCE F1 has no wrinkled there must not be any recessive gene in the Round Yellow parent  RRYy x RRyy

Pedigrees Males are square Females are circles Filled in = have the trait

Example

Is a widow`s peak dominant or recessive

In class: Pedigree Problems HW: More genetics Qs  Practice, Practice , Practice!