Solving Genetics Problems

Phenotype: physical appearance Ex: Brown Hair, Purple flowers, White fur, produces lactase Genotype: what genes an organism has Ex: TT, Tt, tt, Gg, hh, SS

3. Solving Genetics Problems Genetics Problems Goal: to predict the traits of offspring

3. Solving Genetics Problems 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)

3. Solving Genetics Problems 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. Solving Genetics Problems 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

3. Solving Genetics Problems 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

4. Allele: 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 F f T t

5. Solving Genetics Problems a) Example: a. In humans there are two alleles for thumb type: hitchhikers thumb which is dominant or a straight thumb which is recessive. For this example assume that the father has two recessive genes, while the mother has one dominant gene and one recessive gene. 1. Assign letters: Hitchhikers = T Straight Thumb = t 2. Parents’ genotypes Father = tt Mother = Tt

Solving Genetics Problems 3. Draw Punnett Square Example: the father has two recessive genes, while the mother has one dominant gene and one recessive gene. tt t T TtTt TtTt tt Father = tt Mother = Tt

Solving Genetics Problems 4. Calculate probabilities TT = _____ Tt = ________ tt = _________ Hitchhikers = ____ StraightThumb= _____ Tt tt TtTt 0/4=0% 2/4=50%

Solving Genetics Problems Homozygous: organism with two identical alleles for a trait (tt, TT) Heterozygous: organism with two different alleles for a trait (Tt)

Homozygous dominant: organism with two dominant alleles (TT) Homozygous recessive: organism with two recessive alleles (tt)

Humans can have unattached earlobes (picture B) or attached earlobes (picture A). 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). Free 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 Free

1) A mother is homozygous dominant for ear type and a father is heterozygous:  C. 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 2/4=50% 0/4=0%

Tongue Rolling: Dominant  If a mother can roll her tongue and a father can not. What do we know about their genes?

Tongue Rolling: Dominant  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. what will this tell you? d. Draw a punnett square: r r r R RrRr RrRr r r Yes! Dad= rr Mom=RR or Rr

Tongue Rolling: Dominant e. Which people in the family would be considered hybrids? f. 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

Complete the rest of the problems on your own:  HW: Monohybrid Crosses