Mendelian Genetics Gregor Mendel

Introduction Genetics is the study of heredityGenetics is the study of heredity Gregor Mendel used mathematics to study the inheritance of traitsGregor Mendel used mathematics to study the inheritance of traits

Phenotypes These are features you exhibit physically ( your looks) Example: Eye color - green

Alleles The different versions of a characteristic Example: blue, green, and brown eyes

Inheritance Occurs when traits are passed down from parent to child. Gametes (sex cells like sperm or ovaries) carry traits to offspring.

Genes Bits of information passed down from parent to child. Made of chemicals called DNA.

Heredity The chromosome theory of heredity states that the inheritance of traits is controlled by genes, located on chromosomes

Key Terms  Genotype - gene combination for a trait (e.g. RR, Rr, rr)  Phenotype - the physical feature resulting from a genotype (e.g. red, white)

The Average American Phenotype

Alleles T – is considered a dominant allele t – is considered a recessive allele TT – is homozygous dominant Tt or tT – is heterozygous dominant tt - is Homozygous recessive recessive

Genotype & Phenotype in Flowers Genotype of alleles: R = red flower r = yellow flower All genes occur in pairs, so 2 alleles affect a characteristic Possible combinations are: GenotypesRR Rrrr PhenotypesRED RED YELLOW

The Law of Dominance Law states that the dominant allele, if present, will be expressed.  Dominant - capital letter (R)  Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R)  Recessive - lowercase letter (r)  Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r)

Predicting traits Probability is used to predict traits in offspring Punnett squares are diagrams used to predict outcomes from a cross

Types of Genetic Crosses  Monohybrid cross - cross involving a single trait e.g. flower color  Dihybrid cross - cross involving two traits e.g. flower color & plant height

How to do a monohybrid cross

Law of Segregation During the formation of gametes (eggs or sperm) during meiosis, the two alleles responsible for a trait separate.During the formation of gametes (eggs or sperm) during meiosis, the two alleles responsible for a trait separate. Alleles for a trait are then "recombined" at fertilizationAlleles for a trait are then "recombined" at fertilization.

Applying the Law of Segregation

Make a Cross for the following: Imagine you are crossing two vampire bats. –The dominant trait for skin color is black (S). –The recessive trait for skin color is white (s). It you have one parent with the genotype Ss and one with the genotype ss, what kind of offspring would they have? s s S s

Answer S s s S s s S s s s

Group Assignment Let’s imagine we found a new species of dog called a Gir. –We are going to practice crossing this new species to get a better knowledge of how Punnett Squares work. A pure breed GREEN Gir has the genotype GG A pure breed RED Gir has the genotype gg A Gir with the genotype Gg will have a GREEN phenotype because green is dominant over red.

Breed the P 1 generation Green (GG) x Red (gg)Green (GG) x Red (gg) G G gg

Solution: G G gg GgGg GgGg GgGg GgGg All Gg = Green (heterozygous Green) produces the F 1 generation Green (GG) x Red (gg) dogs

Breed the F 1 generation Green (Gg) x Green (Gg)Green (Gg) x Green (Gg) G g Gg

Solution: GG GgGg GgGg gg G g Gg produces the F 2 generation 1/4 (25%) = GG 1/2 (50%) = Gg 1/4 (25%) = gg 1:2:1 genotype 3:1 phenotype 3:1 phenotype Green (Gg) x Green (Gg)

Punnett Squares can also be used to determine the sex. X Y XX XX XY 50% possibility of female XX 50% possibility of male XY

Dihybrid Cross A breeding experiment that tracks the inheritance of two traits.A breeding experiment that tracks the inheritance of two traits. Follows Mendel’s “Law of Independent Assortment”Follows Mendel’s “Law of Independent Assortment” –Each pair of alleles segregates independently during gamete formation

Dihybrid Cross Traits: Seed shape & Seed colorTraits: Seed shape & Seed color Alleles:Alleles: R round r wrinkled Y yellow y green RrYy x RrYy RY Ry rY ry All possible gamete combinations shape color

Law of Independent Assortment Alleles for different traits (like eye color and hair color) are distributed to sex cells (& offspring) independently of one another.Alleles for different traits (like eye color and hair color) are distributed to sex cells (& offspring) independently of one another.

Dihybrid Cross RYRyrYry RYRy rY ry

Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1

Pedigrees Pedigrees use symbols to track a trait. Trait is then tracked through generations.

Example Generation 1 Generation 2 Generation 3

Pedigree Pedigree: is a diagram of family relationships that uses symbols to represent people and lines to represent genetic relationships. These diagrams make it easier to visualize genetic relationships within families. Pedigrees are often used to determine the mode of inheritance (dominant, recessive, etc.) of genetic diseases.

Incomplete Dominance and Codominance

Incomplete Dominance F1 hybrids in betweenphenotypesF1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties. Example:snapdragons (flower)Example: snapdragons (flower) –red (RR) x white (rr) RR = red flowerRR = red flower rr = white flower R R rr

Incomplete Dominance RrRrRrRr R Rr All Rr = pink (heterozygous pink) produces the F 1 generation r

Incomplete Dominance

Codominance Multiple alleles are expressed in heterozygous individuals.Multiple alleles are expressed in heterozygous individuals. Example: blood typeExample: blood type 1.type A= I A I A or I A i1.type A= I A I A or I A i 2.type B= I B I B or I B i2.type B= I B I B or I B i 3.type AB= I A I B3.type AB= I A I B 4.type O= ii4.type O= ii A and B are types of antigens. O type blood does not have these antigens.

Codominance Problem Example: Type B (I B I B ) x Type A (I A i) What blood types are possible in offspring? IBIB IAIA i IBIB

Codominance Problem Example: Type B (I B I B ) x Type A (I A i) IAIBIAIB IBiIBi IAIBIAIB IBiIBi 1/2 = I A I B 1/2 = I B i IBIB IAIA i IBIB

Another Codominance Problem Example:Example: male Type O (ii) x female type AB (I A I B ) What are the possible blood types? i IAIA IBIB i

Another Codominance Problem Example:Example: male Type O (ii) x female type AB (I A I B ) IAiIAiIBiIBi IAiIAiIBiIBi 1/2 = I A i 1/2 = I B i i IAIA IBIB i

Sex-linked Traits Traits (genes) located on the sex chromosomes Sex chromosomes are X and Y XX genotype for females XY genotype for males Many sex-linked traits carried on X chromosome ONLY. –Color blindness, Hemophilia (can’t clot blood), Kabuki syndrome, baldness This means males get genes on X gene from MOTHER.

Sex-linked Traits Sex Chromosomes XX chromosome - femaleXy chromosome - male fruit fly eye color Example: Eye color in fruit flies

Sex-linked Trait Problem Example: Eye color in fruit flies (red-eyed male) x (white-eyed female) X R Y x X r X r Remember: the Y chromosome in males does not carry traits. RR = red eyed Rr = red eyed rr = white eyed XY = male XX = female XRXR XrXr XrXr Y

Sex-linked Trait Solution: X R X r X r Y X R X r X r Y 50% red eyed female 50% white eyed male XRXR XrXr XrXr Y

Alien Lab You will spend 2/3 class periods creating this booklet. DO NOT LOSE YOUR BOOKLET. –TURN IT IN TO ME after each class period so you won’t lose it. –There are NO EXTRA COPIES.

You will create a booklet of an Alien you create and its FAMILY HISTORY in terms of genetics. EVERYONE will have a DIFFERENT alien. Things to complete (look at rubric on page 11) –1. Cover page (Day 1) –2. Alien Trait Key (Day 1) –3. Alien Personal Data (Day 1) –4. Alien Personal Ad (Day 2) –5. Alien Mate Data Sheet (Day 2). –6 & 7 Alien Matchmaking Traits (Day 2) –8. Alien Offspring Trait Key (Day2/3) –9. Alien Offspring Drawings (Day 3) –10. Discussion Questions (Day 3) I will discuss each thing the DAY we will do them. I will only cover items 1-3 today.

Alien Trait Key We will do this AS A CLASS. We will discuss what we want our ALIEN SPECIES TO LOOK LIKE.

#TraitHomozygous Dominant Heterozygous Dominant Homozygous Recessive Example  HH (heads/heads) Hh (heads/tails) hh (tails/tails) 1Hair ColorBlue Yellow 2Eye Color 3# Heads 4Tall? Short? 5# Fingers 6# Toes 7Skin Color SexFemaleMale  Circle one

Alien Personal Data Using a penny (Heads = H) (Tails = h) flip a coin to find out your personal genotype. Fill in column 1 with genotypes flipped. Using the information from the “alien trait key” fill in column 2 with your personal phenotype. Draw and color YOUR COVER PAGE based off this information on the cover of your Alien Lab Booklet.

# YOUR Alien’s Traits (Genotype) YOUR Alien’s Traits (Phenotype) Mate Information (Genotype) Mate Information (Phenotype) 1 hhyellow

Cover Page Have the students put their parent drawing here. They will get this information from the “alien personal data” sheet to be filled out on page 3.