DO NOW: Quietly…….. Take a poll of how many of you have the following traits: - brown hair -blonde hair -red hair - black hair - blue/green eyes -brown eyes
Alien activity • http://www2.edc.org/weblabs/BabyBoom/babyBoom.html
What is Genetics??? • Genetics • is the scientific study of heredity. • Heredity • is what makes each species unique.
Key Vocabulary • Dominant: • inherited characteristic that appear in an organism • Represented with capital letter. • Ex: B, X, R • Recessive: • inherited characteristics often masked • Represented with lowercase letter. • Ex: b, x, r
Example: Dominate Recessive • Brown Eyes: B • Blue Eyes: b
Phenotype: • physical traits that appear in an individual as a result of its genetic make-up • How to remember……. Phenotype= Physical • Ex: brown eyes, blonde hair
Genotype: • genetic Make Up of an individual • How to remember…. GENotype= GENEtic • Ex: • B- brown eyes • b- blue eyes
Homozygous Heterozygous • having two identical alleles • Ex: BB or bb • having two different alleles for a trait • Ex: Bb
Phenotype vs. Genotype A little girl has blue eyes Genotype Phenotype bb Blue Eyes
Allele • different forms of a gene for a specific trait • 2 for each trait
Chromosome for Flower Color ALLELE Could code for a PURPLE flower Could code for a WHITE flower
Gregor Mendel • Austrian Monk • Famous for his work with pea plants • WHY????? • They weren’t messy • Rapid results • Many generation • He is known as the father of genetics
Mendel’s Work • Mendel used true-breeding plants • True Breeding: • When bred with themselves they would produce identicaloffsprings. • He studied 7 different traits in pea plants. • Trait: • is a specific characteristic that can vary from one individual to another.
More on Mendel’s Work • Hybrids • are offspring from parents with different traits. • Genes • are the chemical factors that determine a trait.
Mendel’s Experiments: 3 Principles • Principle of Dominance • Segregation • Independent Assortment
Principle 1: The Principle of Dominance • States that some alleles are dominant and others are recessive. • Dominant alleles are always expressed. • Recessive alleles are only expressed if both alleles are recessive.
Principle 2: Segregation • The two alleles for a trait separate • HELP…… • Segregate means to separate • Happens during meiosis • form gametes (sex cells)
Principle 3: Independent Assortment • states that genes for different traits separate independently during the formation of gametes. • EX: • the color of the flower has nothing to do with the length • They separate INDEPENDENTLY
Summarize Mendel’s Principles • The inheritance of biological characteristics are determined by genes. • For two or more forms of a gene, dominance and recessive forms may exist • (Principle #1). • Most sexually reproductive organisms have two sets of genes that separate during gamete formation • (Principle #2). • Alleles segregate independently • (Principle #3).
Probability & Genetics • Probability • is the likelihood that an event will happen. • The principle of probability can be used to predict the outcomes of genetic crosses.
Punnett Squares • Diagram used to predict genetic crosses. • REVIEW: • Homozygous individuals with identical alleles • Heterozygous individuals with different alleles are called • Phenotype physical characteristic • Genotype genetic makeup
How to use Punnett Squares…… • Choose a letter to represent the alleles in the cross. • Write the genotypes of the parents. • Enter the possible gamete at the top and side of the Punnett square. • Complete the Punnett square by writing the alleles from the gametes in the appropriate boxes. • Determine the phenotypes of the offspring. • Using the results of step 4. write down the genotypic and phenotypic ratios.
Example: What is the probability that two heterozygous purple flowers will produce a white flower? • Choose a letter to represent the alleles in the cross. • Write the genotypes of the parents. • Enter the possible gamete at the top and side of the Punnett square.
What is the probability that two heterozygous purple flowers will produce a white flower? 4. Complete the Punnett square by writing the alleles from the gametes in the appropriate boxes. 5. Determine the phenotypes of the offspring. 6. Using the results of step 4. write down the genotypic and phenotypic ratios
Review Quiz on Probablity and Punnett Squares • http://anthro.palomar.edu/mendel/quizzes/mendqui2.htm
What is a Test Cross????? • Test that is conducted to determine if the genotype of an organism • HOMOZYGOUS DOMINANT for a trait • HETEROZYGOUS for a trait
5 Key Points…… • The organism with the dominant trait is always crossed with an organism that is HOMOZYGOUS RECESSIVE • If ANY offspring shows the recessive trait than the unknown genotype is heterozygous. • Recessive trait seen heterozygous • If ALL offspring have the dominant trait, the unknown is homozygous dominant. • Dominate trait homozygous • Large numbers of offspring are needed for reliable results • Start by making a key and writing down what you know.
Example: • If fire breathing is dominant to not fire breathing in Gregorous Dragon, how can we determine if Mendelia is homozygous dominant or heterozygous?????
So what do we know…………. • Let’s say • F= fire breathing • f= can’t fire breathe. • Set up a two different Punnett squares • Both with a homozygous recessive ff • Then as the other parent place a: • FF in one Punnett square • Ff is another • Essentially, your two Punnett squares will have: • Ff crossed with ff • FF crossed with ff
Interpretation • If all of the Gregorous dragon babies can firebreathe we can assume that Mendelia is HOMOZYGOUS DOMINANT • If any of the babies DO NOT fire breathe than Mendelia is HETEROZYGOUS
Dihybrid Crosses • Cross that involves two traits • Gives 16 offsprings • Example: • Pea color and wrinkles
Steps for Solve for Dihybrid Cross • Make a key for the two traits that you are crossing • Write out the different genotypes of the parents • Figure out the possible gametes • similar to FOIL • there are four for each parent • each gamete must have one allele from each trait • Set up and Solve the Punnett Square
Example Problem: A mother is heterozygous brown hair and blue eyes. The father has blonde hair and is heterozygous for brown eyes. What are the possible genotypes and phenotypes of their offsprings? • Step 1 (assume brown hair & brown eyes are dominant) • Make a key for the traits • Brown Hair (B) vs Blonde Hair ( b) • Brown Eyes (E) vs Blue eyes (e) • Step 2 • Genotypes of the parents • Mother Bbee • Father bbEe • Step 3 • Figure out the possible gamete • Mother Gamete’s Be, Be, be, be • Father’s Gamete’s bE, be, bE, be
Step 4 Set up and Solve punnet Square Be Be be be bE be bE be bbEe bbee bbEe bbee BbEe Bbee BbEe Bbee BbEe Bbee BbEe Bbee bbEe bbee bbEe bbee
Count up the possible genotypes and phenotypes that you have from your punnett square Genotypes Phenotypes • BbEe • 4/16 • Bbee • 4/16 • bbEe • 4/16 • bbee • 4/16 • Brown Hair; Brown eyes • Brown Hair; Blue eyes • Blonde Hair; Brown eyes • Blonde Hair; Blue eyes