How does this happen?

The answer?...GENETICS!

Genetics: The study of heredity. Heredity: passing traits from parents to offspring.

Gregor Mendel The father of genetics Austrian monk, born 1822 Performed experiments with the garden peas at his monestary

Why Pea Plants? 1.Mating, or crossing, can be easily controlled 2.Small, grows easily and quickly, and produces many offspring 3.Has many traits that have two different forms that are easy to tell apart

Mendel controlled the fertilization of his pea plants by removing the male parts, or stamens. He then fertilized the female part, or pistil, with pollen from a different pea plant. Mendel’s Experiments Did repeated, careful experiments Cross-pollinated lines with each other and observed the results From , Mendel grew and tested 28,000 pea plants!

705 purple: 221 white What did Mendel observe? Crossed those flowers. What do you think the next generation looked like? Crossed parental generation pure purple x pure white. What do you think the next generation looked like?

Mendel’s Vocabulary Gene: DNA that holds information for a trait Allele: one version of that trait Trait: observable characteristic Examples: Purple/white flower color Round/wrinkled shape Green/yellow pea color Tall/short height What are the traits? What are the alleles?

Mendel’s Conclusion Many in Mendel’s day thought traits were blended. Mendel disproved this with his experiments. Formed the Law of Segregation : You only pass on 1 copy of your genes to your offspring. Child gets second copy from parent #2.

Mendel’s Conclusion Law of Independent Assortment the alleles of different genes separate independently of one another during gamete formation. – Example: the allele that an individual inherits for flower color has nothing to do with which allele is inherited for seed shape

Mendel’s Conclusion When two alleles occur together, one may be completely expressed while other has no effect. – Dominant allele: expressed (visible) form of the trait – Recessive allele: form of trait not expressed (not visible) when the dominant allele is also present

Two copies of each gene Two copies of each gene can be the same or different Same: homozygous Different: heterozygous

Writing Genotypes Each allele written as a letter. Letter comes from dominant trait. Dominant is UPPERCASE. Recessive is lowercase. Pea plant flower color. Purple is dominant so choose letter – P to show purple and p to show white. Write genotypes for 1.Homozygous dominant 2.Heterozygous 3.Homozygous recessive

Genotype is the genes Phenotype is the physical appearance What flower color would you see? P(Purple) and p(white) PP  ________? Pp  ________? pp  ________?

Punnett Squares Diagram that predicts the expected outcomes of a genetic cross by finding all the possible combinations of gametes of the cross. Can be accomplished in five steps.

Punnett Squares Cross a homozygous dominant purple flowered plant with a homozygous recessive white flowered plant. Step 1: Write out the genotypes, if not already given. – PP x pp

Punnett Squares Step 2: Draw the Punnett Square

Punnett Squares Step 3: Always write the first organism’s genotype across the top of the box; write the second organism’s genotype down the left side of the box.

Punnett Squares Step 4: For each box, write the allele from the top and the side. Always write the dominant allele first, if one is present. Step 5: Write the genotypes and phenotypes of all the offspring of the cross

Punnett Squares Example: Cross a short haired male cat (homozygous recessive) with a long haired female cat (heterozygous).

We can use what we know about genotypes and phenotypes to figure out our genes and how we will pass them on. – When would this information be important? Now: find out what some of your genes are!

Human Traits Lab - Y Trait Percent Dominant in Class Percent Recessive in Class Tongue Rolling85 15 Thumb Bending Ear Lobes Dimples Freckles Chin Thumb Folding Hairline Index Finger 6139 Ear Wiggling Polydactyly PTC Paper 8119

Human Traits Lab - X Trait# Recessive# Dominant Tongue Rolling 3 22 Thumb Bending13 12 Ear Lobes1411 Dimples1510 Freckles1410 Chin203 Thumb Folding1013 Hairline1312 Index Finger1113 Ear Wiggling915 Polydactyly250 PTC Paper 322

Word bank: allele, dominant, gene, genotype, heterozygous, homozygous, phenotype, recessive We have two copies of each gene. We got one from mom and one from dad. Each ______________ can have different versions (called _____________________). We can have two of the same alleles ( called__________________________) or two different alleles (______________________________). When different alleles are present, the _________________________ allele will mask the ________________________________ allele. With heterozygous genes (called your _____________________), only the dominant allele will be seen in the physical appearance (called _________________________).

We have two copies of each gene. We got one from mom and one from dad. Each gene can have different versions (allele) and the copies can be the same (homozygous) or different (heterozygous). When different alleles are present, the dominant allele will mask the recessive allele. With a heterozygous genotype, only the dominant allele will be seen in the phenotype.