S OLVING G ENETICS P ROBLEMS Honors Biology Unit 5 Powerpoint #1 / Chapter 11

T RAITS What are some of your traits? Where did they come from? Do you look like one of your parents, a combination, or neither? Do certain traits “run” in your family? Or pop up after skipping a generation What traits are common in our class? why do you think that is?

Mendel’s Pea plant Observations

P Generation F 1 Generation F 2 Generation TallShortTall Short Mendel’s Experiment TTTt tt TTTt tt

H YBRID : OFFSPRING OF CROSSES BETWEEN PARENTS WITH DIFFERENT TRAITS. Example: Cross pollinate a true-breeding purple flower and a true breeding white flower. Seedlings=hybrid (even though they are purple) X =

H YBRID C ARS Gas + Electric

T ERMINOLOGY Gene: segment of DNA that determines a trait Alleles: different forms of a gene (ex: Height: tall allele, or short allele)

Allele

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) (aka Hybrid)

Homozygous dominant has 2 dominant alleles (TT) Homozygous recessive has 2 recessive alleles (tt) 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

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 * remember 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 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 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 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 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 Tall = 4/4 Short = 0/4 what % will be tall? : 100% Tt t t TTTT

P ROBLEM #1 Brown hair is dominant to blonde hair. If two heterozygous brown hair parents have 8 children, how many of them do you expect to have blonde hair? Use the letter B to solve the punnett square Parents Genotypes: Bb

S OLVING G ENETIC P ROBLEMS BBBb bb BbBb BbBb 3. Draw Punnett Square

S OLVING G ENETICS P ROBLEMS 4. Calculate probabilities BB = ¼ (25%) Bb = 2/4 (50%) bb = 1/4 (25%) How many do you expect to have blonde hair? 2 BBBb bb Bb BbBb

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.

Determine 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: ___

Determine 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: ___

Determine 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: ___

Determine 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 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

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. If you know that they have 2 children, one that can roll and one that can not. Will 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

Humans can have unattached earlobes (picture A) or attached earlobes (picture B). Attached earlobes are dominant. Use the letter ‘E’ to complete the following questions. Ear Lobes

Humans can have unattached earlobes (picture A) or attached earlobes (picture B). Attached earlobes are dominant. Use 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%

Co and Incomplete Dominance

DEFINITIONS Co-dominance: Both alleles are dominant and contribute to the phenotype of a heterozygous individual

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

C O - DOMINANCE

2. F R = R ED F UR F W = W HITE F UR What do you think a F R F W 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 F R F W : ______________ Red and White spots FRFRFRFR Red Fur FWFWFWFW White Fur 100%

F ILL IN THE P UNNETT S QUARE FWFW FRFR FWFW FRFR FRFWFRFW FRFWFRFW FRFWFRFW FRFWFRFW Genotypes Phenotypes

S OLVE THE FOLLOWING CROSSES : C O -D OMINANCE In mushrooms there is a gene for Purple Spots (S P ) and a gene for Green spots (S 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 SPSPSGSGSPSGSPSPSGSGSPSG

S ICKLE C ELL HEMOGLOBIN ALLELE IS C O - DOMINANT TO N ORMAL H EMOGLOBIN ALLELE Hb A Hb S

S ICKLE C ELL : C ROSS TWO HETEROZYGOUS INDIVIDUALS Normal Hemoglobin: _____ Sickle Cell Trait: _____ Sickle Cell Anemia: _____ Hb A Hb S Hb A Hb A Hb S Hb S 25% 50% Hb A Hb S

S ICKLE C ELL : A UTOSOMAL C O -D OMINANT D ISORDER Sickle shaped cells are resistant to Malaria

Hb S and Malaria Frequency

I NCOMPLETE D OMINANCE One allele is NOT completely dominant over the other 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= Black (Incomplete Dominance) b = Yellow (Recessive) 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 = Black Fur (Incomplete Dominance) b= White Fur (Recessive) 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: ________%

BbBb BbBb BBBb Bbbb BB: ________% Bb: ________% bb: ________% Black:_______%

BbBb BbBb BBBb Bbbb BB: 25% Bb: 50% bb: 25% Black: 25%