Genetics additional notes: Chapter 5.1 Mendel’s work Chapter 5.2

Describe 3 traits that were passed to you from your Mom or Dad. Warm Up

Describe 3 traits that seem inherited but were more likely from experiences in the environment. Warm Up

Born in 1822 in Austria Worked as a math teacher and a gardener in the monastery where he lived

Mendel used pea plants to study inherited traits Why pea plants? Grow quickly and have a fast life cycle (from seed to offspring)

Pea plants have both male and female reproductive parts Fertilization = egg (female sex cell) and sperm (male sex cell) join Egg - from female part called pistil Sperm - from male part called stamen Pollination = pollen delivers sperm to pistil Pea plants are self- pollinating but can also be cross pollinated.

In pea plants, there are a variety of traits which come in two forms Tall or short stems Round or wrinkled seeds White or purple flowers Green or yellow seed pods

Mendel’s 1 st Experiment Mendel crossed purebred plants with plants that had the opposite forms of a trait. For instance, purebred tall plants were crossed with purebred short plants. Purebred = the organism can only pass on one form of the trait to offspring.

X Parent Tall P generation Parent Short P generation All Offspring Tall F1 generation

Mendel’s 2 nd Experiment Mendel crossed two of the offspring tall plants (F1) produced from his first experiment.

. Tall F1 generation X 3⁄4 Tall & 1⁄4 Short F2 generation Parent PlantsOffspring

Mendel’s Conclusion 1. Individual “factors” must control the inheritance of traits 2. The factors for each trait come in pairs 3. One factor of the pair is contributed by each parent 4. Some factors can hide the other (ex. - tall factor overshadows the short factor in pea plants)

An organism’s traits are determined by the genes it inherits from its parents.

We now call Mendel’s “factors” that control each trait a gene. Alleles are different forms of a gene (ex. - tall or short; white or purple flowers) An organism inherits one allele from each parent for each trait

Dominant & Recessive Alleles Some alleles are dominant - this trait always shows up in the organism when this allele is present Some alleles are recessive - this trait is hidden when the dominant trait is present

Letters are used to represent alleles Dominant alleles are represented by uppercase letters Recessive alleles are represented by lowercase letters Brown eyes are dominant so we use “B” Blue eyes are recessive so we use “b”

If a child inherits a dominant allele from each parent then the trait will be written “BB” (purebred brown) If a child inherits a recessive allele from each parent then the trait will be written “bb” (purebred blue) If a child inherits a dominant allele from one parent and a recessive allele from the other parent then the trait will be written “Bb” (hybrid) Hybrid = there are two different alleles for a trait

Gregor Mendel is called the “Father of Genetics” He determined that traits are determined by individual alleles inherited from each parent Alleles can be dominant or recessive He changed the way scientists explained human traits

Example of Codominance BB W W BW Example: feather color in chickens BB = Black feathers WW = white feathers BW = black & white speckled feathers

Incomplete dominant alleles are written as capital letters with superscripts

Genetic terms to know: Genotype = an organism’s genetic makeup or allele combination for a trait (genotype for stem height is TT or Tt or tt) Phenotype = the physical appearance of a trait (the characteristic you can see)

Genetic terms to know: Homozygous = a trait that has two identical alleles ( ex. - TT; bb; RR; ee) Heterozygous = a trait that has two different alleles (ex. - Tt; Bb; Rr; Ee)

Probability and Heredity Chapter 5 Sec. 2

What is probability? A number that describes how likely it is that a certain event will occur If you toss a coin, what is the probability that it will land on heads?

1 in 2 1/2 50% If you toss a coin, what is the probability that it will come up heads?

The Mathematics of Probability The laws of probability predict what is likely to occur, not necessarily what will happen. If you toss a coin 20 times, you might expect it to land w/ heads up 10 times and tails 10 times, but you might not always get these results. The more tosses you make, the closer your actual results will be to the results predicted by probability.

Independence of Events When you toss a coin more than once, the results of one toss do not affect the results of the next toss. Each toss is an independent event If you toss a coin 5 times and it lands heads each time, is there a greater chance of tossing heads on the 6th toss?

Punnett Squares Punnett squares are charts that help geneticists predict genotypes in offspring by showing probabilities. Male Allele A (Distribute down) Male Allele B (Distribute down) Female Allele A (distribute to the right) Genotype AA: 25% chance Genotype AB: 25% chance Female Allele B (distribute to the right) Genotype BA: 25% chance Genotype AB: 25% chance

Punnett Squares Ex: If two brown eyed heterozygotes produced offspring what would be their chances a blue eyed phenotype? 25% chance homozygous brown. (BB) 50% chance heterozygous brown. (Bb) 25% chance homozygous blue. (bb) Male Allele B (Distribute down) Male Allele b (Distribute down) Female Allele B (distribute to the right) Genotype BB: 25% chance Genotype Bb: 25% chance Female Allele b (distribute to the right) Genotype bB: 25% chance Genotype bb: 25% chance Centromere Genes with eye color allele