Mendel and Heredity

Genetics The study of how traits are passed from parents to offspring.

Traits Characteristics that are inherited controlled by genes Attached Earlobe Free Earlobe

Genes Found on the chromosomes inside the nucleus of the cell. Made up of DNA

passing of traits to offspring Heredity passing of traits to offspring D M pedigree

History of Genetics Gregor Mendel (1800’s): “Father of Genetics” Studied traits of pea plants Came up with 3 Laws of Inheritance

Alleles Different forms of a gene for a trait Dominant or Recessive

Dominant vs. Recessive Alleles Dominant - the allele that dominates, or covers up, another allele (written with a capital letter EX: T – tall plant Trait: Height Recessive - the allele that is covered up, or hidden by another allele and seems to disappear (written in lowercase) EX: t – short plant Trait: Height

Genotype vs. Phenotype Genotype - the actual genetic makeup of an organism (TT, Tt, or tt) Phenotype - the physical trait that shows as a result of the genotype (tall, short)

Genotype vs. Phenotype Genotype Phenotype TT Tall plant Tt tt Short plant

Homozygous vs. Heterozygous You have 2 alleles for a trait, so there are three possible combinations you could have. Homozygous Dominant Homozygous Recessive Heterozygous Dominant

Homozygous vs. Heterozygous Homozygous or purebred an organism with 2 alleles for a trait that are exactly the same. There are 2 types: Homozygous Dominant (TT, tall) Homozygous recessive (tt, short) Heterozygous or hybrid - an organism with 2 different alleles for a trait. Heterozygous Dominant (Tt, tall)

Punnett Square Chart used to predict genetic outcomes

A monohybrid cross involves inheritance of only one specific trait. The TT and tt that were the original parents are called the P1 generation. The four Tt are called F1 GENERATION

Steps for Using a Punnett Square 1. Write the genotype of one parent along the top of the square & the genotype of the other parent along the side of the square.

Punnett Squares 3. Bring over the alleles over from the side 2. Bring down the alleles down from the top 3. Bring over the alleles over from the side

Punnett Squares Genotypes: 2 Rr, 2 rr Ratio= 2:2 %= 50% Fractions= 1/2 3. Analyze the results. Genotypes: 2 Rr, 2 rr Ratio= 2:2 %= 50% Fractions= 1/2 Phenotypes: 3 red, 1 white Ratio= 3:1 %= 75% & 25% Fractions= 3/4 & 1/4

3 chances to get red = 3/4 or 75% Punnett Squares 4. Answer any questions given. What is the probability (chance) of the new plant having a red flower? 3 chances to get red = 3/4 or 75%

Experiment 1: Parents = Tall x Short Offspring = 100% tall  X

Experiment 2: Parents = Tall x Tall Offspring = 3 tall : 1 short practice Experiment 2: Parents = Tall x Tall Offspring = 3 tall : 1 short

#4 on Bikini Bottom Genetics SpongeBob Squarepants recently met SpongeSusie Roundpants at a dance. SpongeBob is heterozygous for his square shape, but SpongeSusie is round. Create a Punnett square to show the possibilities that wouldresult if SpongeBob and SpongeSusie had children. HINT: Read question #2! A. List the possible genotypes and phenotypes?

#4 on Bikini Bottom Genetics P: Ss & ss & Squarepants Roundpants

#4 on Bikini Bottom Genetics Ss Ss S ss ss B. What are the chances of a child with a square shape? ____ out of ____ or ____% C. What are the chances of a child with a round shape? ____ out of ____ or ____% 2 4 50 2 4 50

Dihybrid Punnett Squares A dihybrid cross is a cross between 2 individuals that differ in two traits of particular interest. For example: S = spherical seeds & s = wrinkled seeds Y = yellow seeds & y = green seeds

Bring down both alleles across the top

Bring down both alleles down the side

Bring down both alleles from the top Bring over both alleles from the side

Determine the PUREBRED DOMINANT phenotypes based on the genotype

Determine the HYBRIDS

Determine the PUREBRED recessive phenotypes based on the genotype

What is the phenotypic ratio of wrinkled green seeds? 9:3:3:1 What is the phenotypic ratio of spherical green seeds? 3 What is the phenotypic ratio of wrinkled green seeds? 1 What is the phenotypic ratio of wrinkled yellow seeds? What is the phenotypic ratio of spherical yellow seeds? 9 3

DYHYBRID EXAMPLE A father is heterozygous for black hair and heterozygous for tongue rolling. The mother is light haired and heterozygous for tongue rolling. What is the probability of having a child with light hair who is a tongue roller?

PARENT’S GENOTYPES FATHER: BbTt Heterozygous for black hair: Bb Heterozygous for tongue rolling: Tt MOTHER: bbTt Light hair: bb

FATHER BbTt BT, Bt, bT, bt MOTHER bbTtbT, bt, bT, bt POSSIBLE GAMETES FATHER BbTt BT, Bt, bT, bt MOTHER bbTtbT, bt, bT, bt

Punnett Square BT Bt bT bt bT Bt bt

Black hair/Tongue Roller - 6 Black hair/non-roller - 2 BT Bt bT bt bT Bt bt BbTT BbTt bbTT bbTt BbTt Bbtt bbTt bbtt BbTT BbTt bbTT bbTt BbTt Bbtt bbTt bbtt Black hair/Tongue Roller - 6 Black hair/non-roller - 2 Light hair/Tongue Roller - 6 Light hair/non-roller - 2