S OLVING G ENETICS P ROBLEMS Honors Biology Unit 5 Powerpoint #2 / Chapter 11

S OLVING G ENETICS P ROBLEMS Phenotype: physical appearance Example: Tall, Short, Blonde, Red, Brown Eyes Genotype: genes in the DNA (alleles) Example: TT bb Rr Bb

A LLELE : A VARIETY OF A GENE A gene for hair color could have the allele: _______ for Brown hair or _______ for Blonde hair A gene for flower color could have allele: ______for blue flower or ________ for red flower A gene for height could have the alleles: _______ for tall or _______ for short B b B b Tt

Dominant: An allele that causes its phenotype if at least 1 is present Examples: TT, Tt (Tall) Recessive: An allele that causes a phenotype only when there are 2 alleles Example: tt (short) S OLVING G ENETICS P ROBLEMS

Homo zygous: organism with 2 identical alleles for a trait (TT or tt) Hetero zygous : organism with 2 different alleles for a trait (Tt)

Homozygous dominant: has 2 dominant alleles (TT) Homozygous recessive: has 2 recessive alleles (tt) S OLVING G ENETICS P ROBLEMS

A B C D E F G H Plant A: a. Phenotype: b. Genotype: Tall TT

A B C D E F G H Plant B: a. Phenotype: b. Genotype: short tt

A B C D E F G H Plant C: a. Phenotype: b. Genotype: Tall Tt

S OLVING G ENETICS P ROBLEMS Genetics Problems Goal: to predict the traits of offspring

S OLVING G ENETICS P ROBLEMS Genetics Problems Goal: to predict the traits of offspring 1. Identify trait(s) and assign a letter to each (capital letter for dominant, lower case letter for recessive)

S OLVING G ENETICS P ROBLEMS Genetics Problems Goal: to predict the traits of offspring 1. Identify trait(s) and assign a letter to each (capital letter for dominant, lower case letter for recessive) 2. Determine parents’ genotypes

S OLVING G ENETICS P ROBLEMS Genetics Problems Goal: to predict the traits of offspring 1. Identify trait(s) and assign a letter to each (capital letter for dominant, lower case letter for recessive) 2. Determine parents’ genotypes 3. Draw Punnett square and fill in

S OLVING G ENETICS P ROBLEMS Genetics Problems Goal: to predict the traits of offspring 1. Identify trait(s) and assign a letter to each (capital letter for dominant, lower case letter for recessive) 2. Determine parents’ genotypes 3. Draw Punnett square and fill in 4. Determine the probabilities for offspring of each genotype and phenotype

S OLVING G ENETICS P ROBLEMS Example : In pea plants, the gene for tall height is dominant to the gene for short height. A short pea plant is cross pollinated with a true breeding tall pea plant. 1. Assign letters: tall = T short = t 2. Parents’ genotypes True breeding tall: TT True breeding short = tt

S OLVING G ENETICS P ROBLEMS 3. Draw Punnett Square

S OLVING G ENETICS P ROBLEMS 3. Draw Punnett Square t t TTTT

S OLVING G ENETICS P ROBLEMS 3. Draw Punnett Square Tt t t TTTT

S OLVING G ENETICS P ROBLEMS 4. Calculate probabilities TT = _____ Tt = ________ tt = _________ Tall = _________ Short = _________ Tt t t TTTT

S OLVING G ENETICS P ROBLEMS 4. Calculate probabilities 10) TT = 0/4 Tt = 4/4 tt = 0/4 11) Tall = 4/4 Short = 0/4 Tt t t TTTT

I DENTIFY TRAIT ( S ) AND ASSIGN A LETTER TO EACH ( CAPITAL LETTER FOR DOMINANT, LOWER CASE LETTER FOR RECESSIVE ) Examples: In guinea pigs, the gene for black fur is dominant to the gene for white fur. black = ____white = ____

I DENTIFY TRAIT ( S ) AND ASSIGN A LETTER TO EACH ( CAPITAL LETTER FOR DOMINANT, LOWER CASE LETTER FOR RECESSIVE. Examples: In guinea pigs, the gene for black fur is dominant to the gene for white fur.

D ETERMINE PARENTS ’ GENOTYPES. Example: In guinea pigs, the gene for black fur is dominant to the gene for white fur. A white guinea pig and a hybrid black guinea pig produce 20 offspring. Find the probability of offspring genotypes and phenotypes. 1. Black: ___White: ___ 2. White guinea pig: ___ Hybrid black guinea pig: ___

D ETERMINE PARENTS ’ GENOTYPES. Example: In guinea pigs, the gene for black fur is dominant to the gene for white fur. A white guinea pig and a hybrid black guinea pig produce 20 offspring. Find the probability of offspring genotypes and phenotypes. 1. Black: B White: b 2. White guinea pig: ___ Hybrid black guinea pig: ___

D ETERMINE PARENTS ’ GENOTYPES. Example: In guinea pigs, the gene for black fur is dominant to the gene for white fur. A white guinea pig and a hybrid black guinea pig produce 20 offspring. Find the probability of offspring genotypes and phenotypes 1. Black: B White: b 2. White guinea pig: bb Hybrid black guinea pig: ___

D ETERMINE PARENTS ’ GENOTYPES. Example: In guinea pigs, the gene for black fur is dominant to the gene for white fur. A white guinea pig and a hybrid black guinea pig produce 20 offspring. Find the probability of offspring genotypes and phenotypes. 1. Black: B White: b 2. White guinea pig: bb Hybrid black guinea pig: Bb

S OLVING G ENETIC P ROBLEMS Bbbb Bbbb BbBb bbbb 3. Draw Punnett Square

S OLVING G ENETICS P ROBLEMS 4. Calculate probabilities BB = 0/4 Bb = 2/4 (50%) bb = 2/4 (50%) How many of the babies will Probably be Black = 10 How many of the babies will Probably be White = 10 Bbbb Bbbb Bb bbbb

H UMANS CAN HAVE UNATTACHED EARLOBES ( PICTURE A) OR ATTACHED EARLOBES ( PICTURE B). A TTACHED EARLOBES ARE DOMINANT. U SE THE LETTER ‘E’ TO COMPLETE THE FOLLOWING QUESTIONS. Ear Lobes

H UMANS CAN HAVE UNATTACHED EARLOBES ( PICTURE A) OR ATTACHED EARLOBES ( PICTURE B). A TTACHED EARLOBES ARE DOMINANT. U SE THE LETTER ‘E’ TO COMPLETE THE FOLLOWING QUESTIONS. 1) A mother is homozygous dominant for ear type and a father is heterozygous: a) What is the mother’s genotype? ______ Father’s genotype? ____ b) What are their phenotypes? Mother: ___________ Father: _________ EE Ee Attached

1) A MOTHER IS HOMOZYGOUS DOMINANT FOR EAR TYPE AND A FATHER IS HETEROZYGOUS : Draw a punnett square: E E e E E E EeEe EeEe

1) A MOTHER IS HOMOZYGOUS DOMINANT FOR EAR TYPE AND A FATHER IS HETEROZYGOUS : d: What are the chances they will have children that are: Homozygous Dominant: ____ Heterozygous: ____ Homozygous Recessive: ____ E E eE E E EeEe EeEe 50% 0%

T ONGUE R OLLING : D OMINANT If a mother can roll her tongue and a father can not. What do we know about their genes?

T ONGUE R OLLING : D OMINANT If a mother can roll her tongue and a father can not. What do we know about their genes? Mother: _______ Father: _______ RR or Rr rr only

2) B. I F YOU KNOW THAT THEY HAVE 2 CHILDREN, ONE THAT CAN ROLL AND ONE THAT CAN NOT. W ILL THAT GIVE YOU MORE INFO ABOUT THE PARENT ’ S GENOTYPES ? c. Draw a punnett square: r r r R RrRr RrRr r r Yes!

T ONGUE R OLLING : D OMINANT d. Which people in the family would be considered hybrids? e. Are their any genotypes that this mother and father can not produce in their offspring? Why or why not? Mom and the child that can roll their tongue Yes, they can not produce a Homozygous Dominant (RR) child because the father only has recessive genes (r) to pass on

C O AND I NCOMPLETE D OMINANCE

DEFINITIONS Co-dominance: Both alleles are dominant and contribute to the phenotype of a heterozygous individual Incomplete Dominance: One allele is NOT completely dominant over the other

S OLVE THE FOLLOWING CROSSES : C O -D OMINANCE 3. In Cows the trait for coat (fur) color is expressed by R for Red fur and W for white fur. The hybrid of the two is called a Roan color (RW). a) Describe what you think the Roan cow’s fur will look like:

C O - DOMINANCE

F ILL IN THE P UNNETT S QUARE R W R WRW Genotypes Phenotypes

2. R= R ED F UR W= W HITE F UR What do you think a RW cow will look like: ____________________ If the mother cow is homozygous red for fur color. What is her genotype: _____ Phenotype?________________ If the dad is homozygous white for fur color. What is his genotype: _____ Phenotype?________________ What percentage of the offspring will be RW: ______________ Red and White spots RR Red Fur WW White Fur 100%

S OLVE THE FOLLOWING CROSSES : C O -D OMINANCE 4. In mushrooms there is a gene for Purple Spots (P) and a gene for Green spots (G). Cross a Homozygous purple with a Homozygous Green. a) What do you think their offspring will look like? Genotype? Phenotype? b) What will the genotype and phenotype percentages be in the F2 when you cross two from the F1 generation.

P HENOTYPES PPGGGP

I NCOMPLETE D OMINANCE The heterozygous (Rr) Does not look like the Homozygous recessive (rr) or the homozygous dominant (RR).

I NCOMPLETE D OMINANCE 1. In flowers there is a gene for Red (R) which has incomplete dominance to the recessive color white (r). The heterozygote plant produced by a white and red flower is pink RR rr Rr

S OLVE THE FOLLOWING CROSSES : I NCOMPLETE D OMINANCE

B= B LACK (I NCOMPLETE D OMINANCE ) B = Y ELLOW (R ECESSIVE ) What is the genotype for a dog that is Black : ______ What is the genotype for a dog that is Yellow :_____ What is the genotype for a dog that is Brown: ______ Show a cross between a Brown dog and a yellow dog. BB bb Bb

F ILL IN THE P UNNETT S QUARE B b b bBb bb Bbbb Genotypes Phenotypes

W HAT PERCENTAGE OF THE PUPPIES ARE BB=_________ Bb=__________ bb= __________ 0% 50%

B = B LACK F UR (I NCOMPLETE D OMINANCE ) B = W HITE F UR (R ECESSIVE ) What do you think the genotype would be for the mother sheep if she has white fur: ____________ What do you think the genotype would be for the father sheep if he has black fur:_______________ What color would a Bb sheep be: __________________________ bb BB Gray

F ILL IN THE P UNNETT S QUARE B b B bBb Genotypes Phenotypes

W HAT PERCENTAGES WILL THE F1 BE : BB: _______% Bb: ________% bb: ________% Black:_________% White:_________% Hybrid: ________%