TOPIC: Genetics AIM: What are Punnett Squares?

TOPIC: Genetics AIM: How do we use Punnett Squares to determine the traits of offspring? DO NOW: P = purple flower, p = white flowers Identify the 3 possible gene combinations and for each, give the phenotype and genotype.

Do you have your mothers eyes? Do you have your father’s eyes? Both! While your eye color may match they eyes of only one of your parents, you actually inherited a PAIR of eye color genes from EACH PARENT. Your mother and father each gave you two eye color genes called BEY and GEY in different forms (alleles). Your BEY gene may have 2 brown alleles (BB) or two blue alleles (bb) or one of each (Bb). Your GEY gene can have 2 green alleles (GG), two blue alleles (gg) or one of each (Gg). Your eye color depends on the combination you have.

Brown (B) is dominant over all other alleles, green (G) is dominant over blue (b and g) and blue alleles are never dominant. BBGG = brown BBgg = brown BbGg = brown BBGg = brown BbGG = brown Bbgg = brown bbGG = green bbGg = green bbgg = blue This 2 gene model works for most eye colors but not for people with grey, hazel or dark eyes.

Possibility that an event may/may not happen probability Possibility that an event may/may not happen

¼ = 25% 2/4 = 50% 3/4 = 75% 4/4 = 100%

Shows possible gene combos of offspring on inside. Special chart Shows possible gene combos of offspring on inside. Parent Gamete possibilities go on the outside. Punnett Square

Example: 1. T = tall t = short TT x tt T T t t T t T T t t T t

T T T t t T t t T t T t Phenotype = 100% (4/4) tall Genotype = 100% hybrid

2. B = Black fur b = white fur Bb x Bb B b B B B B b b B b b b

B b B b B B B b B b b b Phenotype= 75% black, 25 % white Genotype= 50% hybrid 25% pure dominant 25% pure recessive

3. Red is dominant in flowers & white is recessive 3. Red is dominant in flowers & white is recessive. Cross a heterozygous flower with a homozygous dominant flower. R = red r = white Rr x RR

Rr x RR R r Phenotype= R r R R R 100% red R R R R r Genotype = 50% pure dominant 50% hybrid

4. One dog carries heterozygous, black fur traits, and the other carries homozygous recessive white traits. What are the chances of having a puppy with black fur? B = black, b = white Bb x bb

Bb x bb B b b b b B b Answer: 50% chance of having a puppy with black fur b B b b b

Review: 1. What is the difference between a genotype and a phenotype? 2. What did Mendel use in his first experiment to test his hypothesis about genes?  ­ 3. A person is very short.  They are homozygous recessive for this trait.  Give the genotype (letters) for this person.  4. Correctly cross a  blue eyed person with a  heterozygous brown eyed  person.  Give the phenotype and genotype.    

5. Red hair (R) is dominant over blonde hair (r) 5. Red hair (R) is dominant over blonde hair (r). Make a cross between a heterozygous red head and a blonde. R r r Rr rr

Bb x bb Phenotype: Genotype: 6. Cross a heterozygous brown haired rabbit with a homozygous recessive white haired rabbit. Determine phenotype & genotype. Bb x bb Phenotype: 50% brown haired 50% white haired b b Bb Bb B b Genotype: 50% hybrid 50% pure recessive bb bb

0% Rr R R r What is the possibility of a red eyed offspring? 7. Black eyes (R) is dominant over red eyes (r) in rats. Make a cross between a homozygous rat with black eyes and a rat with red eyes. R R Rr What is the possibility of a red eyed offspring? r 0% Discuss with students other possible answers

Phenotype: LL x Ll Genotype: 8. Cross a homozygous dominant long haired guinea pig with a heterozygous long haired guinea pig. Phenotype: LL x Ll 100% long hair L l Genotype: LL Ll L 50% hybrid 50% pure dominant LL Ll

Phenotype: Ww x Ww Genotype: 9. Cross a heterozygous wrinkly elephant with another heterozygous wrinkly elephant. Phenotype: Ww x Ww 75% wrinkly 25% no wrinkles W w W w WW Ww Genotype: 50% hybrid 25% pure dominant 25% pure recessive Ww ww

Ff x ff Phenotype: Genotype: 50% freckles 50% no freckles 50% hybrid 10. The freckles trait is considered to be dominant. A couple a wonders if their children will have freckles. The man has freckles but his mother did not. The woman in this couple has no freckles. Create a Punnett Square and determine the phenotype and genotype of their possible offspring. Phenotype: Ff x ff 50% freckles 50% no freckles F f f Ff ff Genotype: Ff ff 50% hybrid 50% pure recessive

Phenotype: Genotype: F f 75% free 25% attached FF Ff F ff f Ff 11. The gene for free ear lobes is dominant. The gene for attached ear lobes is recessive. Complete the Punnett square to show the cross between two heterozygous parents and determine genotype & phenotype. Phenotype: F f 75% free 25% attached FF Ff F Genotype: ff f Ff 50% hybrid 25% pure recessive 25% pure dominant

Phenotype: Genotype: 12. I = cleft chin i = smooth chin Cross these 2 parents: Ii x ii Determine phenotype & genotype. Phenotype: I i 50% cleft chin 50% smooth chin Ii ii i Genotype: 50% hybrid 50% pure recessive Ii ii i

13. WHICH OF THE FOLLOWING HAS THE hh GENOTYPE? A. 1 & 3 C. 4 B. 2 D. NONE H h H 4 1 h 3 2 14. WHICH OF THE FOLLOWING IS A TRUE STATEMENT? INDIVIDUAL 4 IS RECESSIVE INDIVIDUALS 1 & 3 ARE HETEROZYGOUS INDIVIDUAL 2 IS DOMINANT ALL INDIVIDUALS ARE FEMALE

16. WHAT FRACTION IS HOMOZYGOUS DOMINANT IN THE ABOVE CROSS? 15. IF B IS THE ALLELE FOR BLACK FUR AND b IS THE ALLELE FOR WHITE FUR, WHAT PERCENT WOULD BE BLACK? A. 25% C. 100% B. 50% D. 75% B b B BB Bb b Bb bb 16. WHAT FRACTION IS HOMOZYGOUS DOMINANT IN THE ABOVE CROSS? A.1/2 B. ¼ C. 1/3 D. 4/4

DD x dd Dd x dd Dd Dd Dd dd Dd Dd Dd dd D D D d d d 17. In dogs, hereditary deafness is caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding if possible. The dog can hear, so the owner knows his genotype is either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the deafness gene will not be passed on. This can be tested by breeding the dog to a deaf female (dd). A. Draw the Punnett squares to illustrate these two possible crosses. DD x dd Dd x dd D D D d d Dd Dd d Dd dd Dd Dd Dd dd

DD x dd Dd x dd Dd Dd Dd dd Dd Dd Dd dd B. Hearing = 100% Deaf = 0% B. In each case, what percentage of the offspring would be expected to be hearing? deaf? C. What is the genotype of the male dog the owner can use? DD x dd Dd x dd D D D d d Dd Dd d Dd dd Dd Dd Dd dd B. Hearing = 100% Deaf = 0% B. Hearing = 50% Deaf = 50% C. pure dominant (DD)

Review: 1. What is the difference between a genotype and a phenotype? 2. What did Mendel use in his first experiment to test his hypothesis about genes?  ­ 3. A person is very short.  They are homozygous recessive for this trait.  Give the genotype (letters) for this person.  4. Correctly cross a  blue eyed person with a  heterozygous brown eyed  person.  Give the phenotype and genotype.    

Phenotype= T t Genotype = t Tt tt PUNNETT SQUARES WORKSHEET T = tall, t = short Cross a heterozygous tall plant with a short plant. Phenotype= Tt x tt 50% tall, 50% short T t Genotype = t Tt tt 50% pure recessive 50% hybrid

GG Gg Phenotype= G G G Genotype = g 50% hybrid 100% green PUNNETT SQUARES WORKSHEET 2. G = green, g = yellow Cross a pure green plant with a hybrid plant. GG x Gg Phenotype= G G 100% green G g GG Gg Genotype = 50% pure dominant 50% hybrid

Bb bb b b Phenotype= B b Genotype = bb x Bb 50% chance of blue eyes PUNNETT SQUARES WORKSHEET 3. A man with blue eyes marries a woman who is heterozygous for brown eyes. If brown eyes are dominant, what are the chances of having a blue eyed child? Also, give the phenotypes and genotyes. bb x Bb 50% chance of blue eyes b b Phenotype= 50% brown, 50 % blue B b Bb bb Genotype = 50% pure recessive 50% hybrid

Rr R R Phenotype= r Genotype = RR x rr 100% red 100% hybrid PUNNETT SQUARES WORKSHEET 4. In tomatoes, red fruit color is dominant to yellow fruit color. Predict the phenotypes and genotypes of the offspring by crossing a homozygous dominant parent with a homozygous recessive parent. RR x rr R R Phenotype= 100% red r Rr Genotype = 100% hybrid

B b BB Bb B 1. B = brown eyes, b = blue eyes Mom = Bb Dad = BB Punnett Squares: Human Characteristics 1. B = brown eyes, b = blue eyes Mom = Bb Dad = BB B b Genotype= Phenotype= BB Bb B 50% pure dominant 100% brown eyes 50% hybrid

Punnett Squares: Human Characteristics 2. Curly hair is recessive, and straight hair is dominant. A woman with curly hair marries a man who is homozygous dominant for straight hair. cc x CC c c Genotype= Phenotype= Cc C 100% hybrid 100% straight hair

Punnett Squares: Human Characteristics 3. Black hair is homozygous dominant. Brown hair is heterozygous. Blonde hair is homozygous recessive. A woman with brown hair marries a man with brown hair. Bb x Bb B b Genotype= Phenotype= BB Bb bb B b 50% hybrid 50% brown hair 25% pure dominant 25% black hair 25% blonde hair 25% pure recessive

Bb B B b Punnett Squares: Human Characteristics 4. Attached earlobes are dominant over free hanging earlobes. Mom = BB Dad = bb BB x bb B B Genotype= Phenotype= Bb b 100% hybrid 100% attached

7R Punnett Squares Homework 1. A green pea plant (Gg) is crossed with a yellow pea plant (gg).   G g Phenotype= 50% green Gg gg g 50% yellow Genotype= 50% hybrid 50% pure recessive

TT Tt T T T t 2. A tall plant (TT) is crossed with a tall plant (Tt). 7R Punnett Squares Homework 2. A tall plant (TT) is crossed with a tall plant (Tt). T T Phenotype= 100% tall TT Tt T t Genotype= 50% hybrid 50% pure dominant

T t Tt tt t 3. A tall plant (Tt) is crossed with a short plant (tt). 7R Punnett Squares Homework 3. A tall plant (Tt) is crossed with a short plant (tt).   T t Phenotype= 50% tall Tt tt t 50% short Genotype= 50% hybrid 50% pure recessive

R r Rr rr r 4. A red flower (Rr) is crossed with a white flower (rr). 7R Punnett Squares Homework 4. A red flower (Rr) is crossed with a white flower (rr). R r Phenotype= 50% red Rr rr r 50% white Genotype= 50% hybrid 50% pure recessive

rr r r r 5. A white flower (rr) is crossed with a white flower (rr). 7R Punnett Squares Homework 5. A white flower (rr) is crossed with a white flower (rr).   r r Phenotype= 100% white rr r Genotype= 100% pure recessive

BB B B B 6. A black chicken (BB) is crossed with a black chicken (BB). 7R Punnett Squares Homework 6. A black chicken (BB) is crossed with a black chicken (BB).   B B Phenotype= 100% black BB B Genotype= 100% pure dominant

7R More Punnett Squares continued… 1. A homozygous dominant brown mouse is crossed with a heterozygous brown mouse (tan is the recessive color). BB x Bb Phenotype= 100% brown B B Genotype= BB Bb B b 50% hybrid 50% pure dominant

7R More Punnett Squares continued… 2. Two heterozygous white (brown fur is recessive) rabbits are crossed. Bb x Bb Phenotype= 75% white B b 25% brown Genotype= BB Bb bb B b 50% hybrid 25% pure recessive 25% pure dominant

7R More Punnett Squares continued… 3. Two heterozygous red flowers (white flowers are recessive) are crossed. Rr x Rr Phenotype= 75% red R r 25% white Genotype= RR Rr rr R r 50% hybrid 25% pure recessive 25% pure dominant

7R More Punnett Squares continued… 4. A homozygous tall plant is crossed with a heterozygous tall plant (short is the recessive size). TT x Tt Phenotype= 100% tall T T Genotype= TT Tt T t 50% hybrid 50% pure dominant

7R More Punnett Squares continued… 5. A heterozygous white rabbit is crossed with a homozygous black rabbit. Ww x ww Phenotype= 50% white W w 50% black Genotype= Ww ww w 50% hybrid 50% pure recessive

TOPIC: Genetics AIM: Review DO NOW: D = dimples, d = no dimples Identify the 3 possible gene combinations and for each, give the phenotype and genotype.

P p PP Pp pp P p Pp x Pp Punnett Squares Worksheet Phenotype= #1. In a certain species of mouse, pointed ears are dominant over round ears. Predict the genotypes and phenotypes of a cross between two hybrid pointed-eared mice. Pp x Pp Phenotype= 75% pointed P p 25% round Genotype= PP Pp pp P p 50% hybrid 25% pure recessive 25% pure dominant

Bb B B b BB x bb Punnett Squares Worksheet Phenotype= Genotype= #2. In a certain species of dog, a black nose is dominant over a pink nose. Predict the genotypes and phenotypes of a cross between a purebred dominant male dog and a purebred recessive dog. BB x bb Phenotype= 100% black nose B B Genotype= Bb b 100% hybrid