Objectives Know how to complete a Punnett Square (monohybrid cross) comparing one trait at a time when the traits are: Dominant and Recessive Incompletely.

Objectives Know how to complete a Punnett Square (monohybrid cross) comparing one trait at a time when the traits are: Dominant and Recessive Incompletely dominant Co-dominant

Challenge Question Write your answer on a blank sheet of paper to turn in at the end of class
Taryn has blue eyes. Her parents & 2 older brothers all have brown. How is this possible??? WRITE your scientific explanation.

Gregor Mendel First to investigate how traits are inherited
Studied pea plant height (tall or short) Each parent contributes a factor – either strong or weak (later became dominant/recessive)

Important terms A. Gene - The basic unit of inheritance
- Codes for specific protein - Located on DNA - Inherited from Parents B. Allele – One of several possible forms of a gene. (ex: brown hair or blonde hair) C. Sexual Reproduction 1. One allele inherited from dad/Male parent (Y) 2. One allele inherited from mom/Female parent (X)

Dominant v. Recessive A. Some traits may be determined by a single gene Ex. Petal Color B. Other traits require many genes. Ex. Skin Color C. For Traits with only 2 options - Dominant = it completely masks the other (Gg or GG) - Recessive = it is masked by the Dominant trait (gg) D. We use Letters to represent traits - Capital letters represent Dominant D,R,T,S - Lower case letters represent recessive d,r,t,s

Classroom “Inventory of Traits”
We will find out which traits are Dominant and Recessive for our class!!! Tongue Rolling (Y/N) Handedness (L/R) Hand Clasping (Rt over Lt or Lt over Rt) Widows Peak (hairline) Hitchhikers Thumb Earlobes (Detached/Connected)

Monohybrid Cross A. Shows ratio for 1 Trait B. Genotype – the actual gene combination that determines the phenotype…(HH, Hh, hh) Genetic Make-up C. Phenotype – physically exhibiting a trait…(The trait you can physically see) Physical Make-up *** How we predict the genetic make up of offspring*** D. A monohybrid cross shows: 1. # of offspring with each phenotype 2. # of offspring with each genotype

Homozygous vs Heterozygous
A. Homozygous -Has both dominant (HH) OR recessive (hh) - Known as Purebred B. Heterozygous - Has one dominant and one recessive (Hh) - Known as Hybrid

Probability Likelihood that a specific event will occur

Punnett Squares Way to predict the number of different genotypes; Shows different ways in which genes can combine B b B b P Generation= Parent Generation Example: Bb X Bb BB Bb bb F1 Generation= Offspring of the P Generation Example: BB, Bb, bb

Monohybrid Crosses A cross between individuals that involves one pair of contrasting traits Example: Pure Tall x Pure Short AA x aa A A a Aa

Monohybrid Cross Example
Example: Pure Black x Hybrid BB x Bb B B B b Punnett square is use for predicting probabilities Genotype = Phenotype = BB Bb

Think check If we cross two hybrid plants (Aa), how would we know the offspring’s genotypes/phenotypes? What would their genotypes/ phenotypes be?

Punnett Squares **How we determine a ratio of the expected results in a Cross ** Ratio – shows the relative sizes of two or more values -Ex. If the class has 25 students, and there are 12 boys and 13 girls…what is the ratio of girls to boys? - Answer: The ratio is 12 boys to 13 girls OR 12:13 (12 boys : 13 girls)

Practice In guinea pigs, short hair, H, is dominant to long hair, h.
Set up a Punnett Square for the following One guinea pig is Hh and one is hh. List the genotype and phenotype percentages.

More Practice Hornless (H) in cattle is dominant over horned (h). A homozygous hornless bull is mated with a horned cow. What will be the percentages of genotypes and phenotypes of the first generation (F1)? In tomatoes, red fruit (R) is dominant over yellow fruit (r). A plant that is homozygous for red fruit is crossed with a plant that is heterozygous. What would be the percentages of genotypes and phenotypes of the F1 generation?

More More Practice In humans, being a tongue roller (R) is dominant over non-roller (r). A man who is a non-roller marries a woman who is heterozygous for tongue rolling. Father’s phenotype ______ Mother’s phenotype______ Father’s genotype ________ Mother’s genotype _______ What is the probability of this couple having a child who is a tongue roller? ________ What are the percentages of each genotype and phenotype?

Question 1 There is a male and female Labrador retriever. Dad has black fur (BB) and the mom has yellow fur (bb). Name the phenotypes & genotypes of mom & dad. What is the probability that the offspring will get black fur? What is the probability that the offspring will get yellow fur?

Question 2 Mom dog and Dad dog both have spots versus no spots. Dad is heterozygous for spots, and Mom is homozygous dominant for spots. What are Mom & Dad’s genotypes? What is the probability the offspring will be homozygous dominant? Heterozygous? Homozygous recessive?

Question 3 A mother has homozygous alleles for straight eyebrows. Keep in mind arched eyebrows are the dominant trait. The father is heterozygous for arched eyebrows. What are the parents’ genotypes? What is the probability the offspring will possess arched eyebrows? What are the odds the offspring will have straight eyebrows?

Question 4 A scientist cross-breeds two pigs, one with the homozygous recessive trait for a curly tail, and one with heterozygous dominant alleles for a straight tail. What are the phenotypes of the parents? What is the possibility the offspring will have a curly tail? What is the probability the offspring will have heterozygous alleles?

Question 5 In the following problem about pea plants, smooth is dominant to wrinkled, and green is dominant to yellow. Cross two plants that are heterozygous for both traits. Create a genotype legend for all the traits. Identify the parent plants’ genotypes? What is the phenotypic ratio of the possible offspring?

Steps to Solve a Punnett Square problem
Find/Determine each of the parents’ alleles (hint: genes represented by letters) Correctly label the Punnett square: Parent #1: label across the top (one allele/letter per box!) Parent #2: label down the left (one allele/letter per box!) Fill in the Punnett Square. Re-read the question!! (Think: “What do I need to figure out?”) ANSWER!!

Reading a Punnett Square
Punnett squares are used to determine PERCENT PROBABILITY of potential offspring. That means interpreting a Punnett square depends on the fraction of squares representing a given genotype or phenotype: One square= 1/4 = 25% Two squares= 2/4 = 50% Three squares= 3/4 = 75% Four squares= 4/4 = 100%

Genotype vs. Phenotype For each of the following genotypes, indicate whether it is homozygous or heterozygous. HH Gg bb hh BB Having no magical powers (M) is dominant over having magical powers (m). For each of the following genotypes, indicate what the phenotype would be. MM Mm mm

Dihybrid Cross Cross between individuals that involves two pairs of contrasting traits Punnett square will have a total of 16 squares Each square will contain 4 alleles

Example: Dihybrid Cross
R = smooth r = wrinkled Y = yellow y = green Dad = Homozygous smooth, heterozygous yellow Mom = Heterozygous wrinkled, homozygous green RRYY x rryy

Example: Dihybrid Cross
S = Short hair s = long hair B = Black hair b = brown hair Dad = Heterozygous short, heterozygous black Mom = Heterozygous short, heterozygous black What is the probability the offspring would have brown, short hair?

Set up a punnett square using the following information:
Dominate allele for black fur in guinea pigs = B Recessive allele for white fur in guinea pigs =b Dominate allele for rough fur in guinea pigs = R Recessive allele for smooth fur in guinea pigs = r Cross a heterozygous parent (BbRr) with a heterozygous parent (BbRr) Using the punnett square in question #1: What is the probability of producing guinea pigs with black, rough fur? Possible genotype(s)? What is the probability of producing guinea pigs with black, smooth fur? Possible genotype(s)? What is the probability of producing guinea pigs with white, rough fur? Possible genotype(s)? What is the probability of producing guinea pigs with white, smooth fur? Possible genotype(s)?

Frozen Genetics Queen Elsa has power over ice and snow. This ability is a recessive trait. Both of her parents, Agnarr and Iduna, are heterozygous for this trait. Identify the genotypes of the parents Complete a Punnett Square Give the genotype and phenotype percentages

Frozen Genetics Ana has blue eyes, and Kristoff has brown eyes. Having brown eyes is the dominant trait. Both of Kristoff’s parents are Homozygous for brown eyes. Identify the genotypes of the parents Complete a Punnett Square Give the genotype and phenotype percentages

Frozen Genetics In reindeer long antlers are dominant to short antlers. Complete a cross between a short antler male and a heterozygous female. Identify the genotypes of the parents Complete a Punnett Square Give the genotype and phenotype percentages

Incomplete Dominance A condition that results when genes produce a trait somewhere in between the traits of the parents (blended results) EXAMPLE: A cross between a red carnation & a white carnation results in a pink carnation

INCOMPLETE DOMINANCE A. When genes are neither dominant or recessive B. Traits are expressed as a blend of two traits Ex. Red Flowers x White Flowers = Pink **For Punnett Squares** A. Same rules as Monohybrid Cross B. Symbolization is Different! 1. Choose two dominant alleles for one parent phenotype 2. Choose two different dominant alleles for the other parent phenotype

Flowers can be Red (RR) White (WW) or Pink (RW)
Incomplete Dominance Flowers can be Red (RR) White (WW) or Pink (RW) Cross a Pink flower with a Pink Flower. Complete the Punnett Square and Answer the Questions. List the possible genotypes for the offspring B. List the possible phenotypes for the offspring What percentage of the offspring will be Red __ Pink __ White __ R W R W

RR RW WW Incomplete Dominance
Flowers can be Red (RR) White (WW) or Pink (RW) Cross a Pink flower with a Pink Flower. Complete the Punnett Square and Answer the Questions. R W List the possible genotypes for the offspring List the possible phenotypes for the offspring What percentage of the offspring will be Red __ Pink __ White __ RR RW WW R W

RR RW WW Incomplete Dominance
Flowers can be Red (RR) White (WW) or Pink (RW) Cross a Pink flower with a Pink Flower. Complete the Punnett Square and Answer the Questions. R List the possible genotypes for the offspring RR & RW & WW List the possible phenotypes for the offspring Red & Pink & White What percentage of the offspring will be Red __25%_ Pink __50%_ White __25%_ W RR RW WW R W

Think Check In your groups decide whether each of the following are complete or incomplete dominance. 1. A curly haired parent and a straight haired parent have an offspring with wavy hair. 2. A black hamster is crossed with a white hamster. 100% of the offspring are black. 3. A light-skinned person and a dark skinned person produce a child with a skin color that is in between each.

Co-dominance Exists when the alleles of both parents are visible, but not blended in the offspring EXAMPLE 2: Blood Types Type A crossed with Type B = Type AB EXAMPLE 1: A cross between a white cow & a red cow results in a roan (red and white spotted) cow Red cow = RR; White Cow = WW; Roan (Red and White)= RW

Discuss with your neighbors the difference between co-dominance and incomplete dominance.

Exit Ticket 1/16/18 Number 1-5 For the following descriptions, determine whether each statement is an example of complete dominance, incomplete dominance or co-dominance.

Pigs can have straight tails, curly tails, or wavy tails.

Smurfs can be dark blue or light blue.

Daisies can be red, blue, or purple.

Some fish can be blue, yellow, or yellow with blue spots.

Aliens can be green or silver.

Sex Determination Females X X Males X Y
Females can only donate X chromosomes Males can donate either X or Y chromosomes Males determine the sex of the child

Sex-Linked Traits Traits controlled by genes located on sex chromosomes Alleles for sex-linked traits are written as superscripts of the X or Y chromosomes (Xh)

More than 100 sex-linked genetic disorders have been mapped to the X chromosome.
The Y chromosome is much smaller than the X chromosome & contains only a few genes.

HUMAN KARYOTYPE

Colorblindness- inability to distinguish certain colors
Sex-linked disorders Colorblindness- inability to distinguish certain colors Hemophilia- missing a protein necessary for important blood clotting

Example: Sex-Linked Traits
A man with hemophilia marries a homozygous normal woman. Predict the genotypes & phenotypes of their children. Female XX Male XY Xh – recessive hemophilia XH -- normal dominant Y -- N/A XhY x XH XH

Practice Problem In fruit flies, the gene for white eyes is sex-linked recessive. (R) is red and (r) is white. Cross a white-eyed female with a normal red-eyed male. What percent of the males will have red eyes? White eyes? What percent of the females will have red eyes? White eyes? What total percent of the offspring will be white-eyed? What percent of the offspring will be carriers of the white eye trait?

Practice Problem In cats, the allele (B) produces black color but (b) produces a yellow color. These alleles are incompletely dominant to each other. A heterozygote produces a tortoise shell color. The alleles (B) and (b) are sex-linked as well. Cross a tortoise shell female with a yellow male. What percent of their offspring will be yellow? What percent of their offspring will be black? What percent of their offspring will be tortoise shell? Why is it impossible to have a tortoise shell male offspring?

Use the information below to answer the following questions.
XH- X chromosome with normal dominant allele (no hemophilia) Xh - X chromosome with recessive hemophilia allele Y - Y chromosome (does not contain comparable gene) XB - X chromosome with normal dominant allele (not colorblind) Xb - X chromosome with recessive colorblind allele Y -Y chromosome (does not contain comparable gene)

Write the genotypes for the following phenotypes of red- green color blindness
normal male _____________ normal female carrying no colorblind alleles (Homozygous) _____________ colorblind male _____________ normal female carrying the colorblind allele (Heterozygous) _____________ colorblind female _____________

1. Coat color in mice is incompletely dominant. Yellow and white-colored mice are homozygous, while cream-colored mice are heterozygous. If two cream-colored mice mate, what phenotypic ratio can we expect of their offspring? Show the Punnett Square.

2. Two parents think their baby was switched at the hospital. Its 1968, so DNA fingerprinting technology does not exist yet. The mother has blood type “O,” the father has blood type “AB,” and the baby has blood type “B.” Mother’s genotype: _______ Father’s genotype: _______ Baby’s genotype: ______ or ________ Punnett square showing all possible genotypes for children produced by this couple Was the baby switched?

3. In some chickens, the gene for feather color is controlled by codominance. The allele for black is B and the allele for white is W. The heterozygous phenotype is known as erminette (black and white spotted). What is the genotype for black chickens? ____ What is the genotype for white chickens? ____ What is the genotype for erminette chickens? ____

4. The bison herd on Konza Prairie has begun to show a genetic defect. Some of the males have a condition known as "rabbit hock" in which the knee of the back leg is malformed slightly. This condition is controlled by a sex-linked gene and it is recessive. Now, suppose that the herd bull (the dominant one which does most of the breeding) who is normal (XN) mates with a cow that is a carrier for rabbit hock. What are his chances of producing a normal son (bull)? What percentage of their daughters will have normal knees? What percentage of their daughters will be carriers of rabbit hock?

5. Attached ear lobes are recessive to free ear lobes. Answer the following questions if both parents are heterozygous. What is the genotype of the male parent? __________ & the female parent?___________ Fill in the Punnett square for this cross: What is the phenotypic ratio of the offspring?

6. Clouded leopards are a medium sized, endangered species of cat, living in the very wet cloud forests of Central America. Assume that the normal spots are a dominant, sex-linked trait and that dark spots are the recessive counterpart. Suppose as a Conservation Biologist, you are involved in a clouded leopard breeding program. One year you cross a male with dark spots and a female with normal spots. She has four cubs and, conveniently, two are male and two female. One male and one female cub have normal spots and one each have dark spots. What is the genotype of the mother? Suppose a few years later, you cross the female cub that has normal spots with a male that also has normal spots. How many of each genotype will be found in the cubs (assume 4)? Will any of the cubs from this latest cross have dark spots? If so, how many and of what sex will they be?

7. In shorthorn cattle, when a red bull (RR) is crossed with a white cow (WW), all the offspring are roan—a spotted, red and white or milky red color. What offspring are expected from mating a roan bull and a roan cow? Show the Punnett Square.

8. Black hair is dominant to brown hair. Cross a black rabbit and a brown rabbit. The black rabbit had a brown haired mother. If the black rabbit had a brown haired mother what is the genotype of the black rabbit? _________ What is the genotype of the brown rabbit? ________ What is the genotypic ratio from this cross?

9. In Andalusian fowls, black individuals (B) and white individuals (W) are homozygous. A homozygous black bird is crossed with a homozygous white bird. The offspring are all bluish-gray. Show the cross as well as the genotypes and phenotypes of the parents and offspring.

10. In humans, the allele for normal blood clotting, H, is dominant to the allele for hemophilia, h. This is a sex-linked trait found on the X chromosome. A woman with normal blood clotting has four children. The father has normal blood clotting. What are the possible genotypes of each of the kids?

Genetic Pedigrees A. Pedigree – The ancestry or lineage of an individual B. Pedigree Chart – Shows all the known phenotypes of an individual and its ancestors. ( Basically a family tree) C. We use Pedigree Charts in the place of genetic crosses to analyze inheritance of traits in humans.

How to Make a Pedigree Chart
A. represent females, represent males B. Horizontal lines represent mating (marriage lines) C. Vertical lines off marriage lines represent offspring D. Every generation should be numbered with Roman Numerals (I, II,III,IV) E. Children should be numbered left to right starting with the oldest (1,2,3,4,5) F. Shade in the individuals who exhibit the trait in question.

What A Pedigree Chart Tells Us
A. Determine whether a trait is inherited B. Show how a trait is passed on from one generation to the next C. Determine whether an allele is dominant or recessive

Clues for Autosomal Dominant Inheritance
Every affected person has at least one affected parent Each generation will have affected individuals Will see both sexes affected

Clues for Autosomal Recessive Inheritance
Individual expressing trait has 2 normal parents Two affected parents cannot have an unaffected child May see “skipping” of generations Will see both sexes affected

Clues for sex-linked recessive inheritance
No father to son transmission Predominantly males affected Trait may skip generations

Objectives Know how to complete a Punnett Square (monohybrid cross) comparing one trait at a time when the traits are: Dominant and Recessive Incompletely.

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Objectives Know how to complete a Punnett Square (monohybrid cross) comparing one trait at a time when the traits are: Dominant and Recessive Incompletely.

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Presentation on theme: "Objectives Know how to complete a Punnett Square (monohybrid cross) comparing one trait at a time when the traits are: Dominant and Recessive Incompletely."— Presentation transcript:

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