Introduction to Genetics Why you are you and not anybody else! However, children born from the division of one fertilized egg ARE genetically identical!

Are you Unique? Dimples? Able to roll your tongue or not? Curly or straight hair?

Are You Unique? Widow’s Peak or not? Free or attached lobes?

Are You Unique? Second toe longest or not?

Are YOU Unique? Complete table of your own traits (Anyone with a tail and blue skin?) Complete table of the class traits

Traits Individuals have many characteristics or traits that make each of us unique. Trait = specific characteristic that varies from one individual to another

Genetics – The Study of Heredity Interest in the passing of traits from one generation to the next is not new Agriculture was developed around 12,000 years ago. People selected the plants and animals with the best traits to raise. Example: Farmers selected wild grass plants with the largest seeds to produce corn

Gregor Mendel – Father of Genetics Born in 1822 in what is today the Czech Republic. At university he studied for the priesthood, as well as, math and science.

Gregor Mendel – Father of Genetics As an adult he lived in a monastery. He taught high school and worked in the monastery garden. Between , Mendel conducted experiments on inheritance with the common garden pea.

Pea Plants

Mendel’s Genetic Work Mendel experimented with 7 different traits of peas.

Mendel’s Genetic Work Mendel was extremely lucky in his choice of the garden pea for his study. This was a perfect organism for the study of inheritance.

What made the Pea so Perfect? Several of the characteristics were controlled by individual genes. –height of plant –color of pea pod

What made the Pea so Perfect? Reproduce sexually Large number of offspring (peas on a pod) Easy to handle in a lab

What made the Pea so Perfect? Genetic crosses are easily controlled Peas are True Breeding plants (=the parent plant normally produces offspring identical to itself), because they self-pollinate.

Mendel’s Genetic Research Mendel published his findings in the 1860’s but his ideas were ignored. At the time of Mendel’s publication of his work, scientists believed ALL inheritance worked through “blending.” What happened to Copernicus and Galileo when they had new ideas ?

Blending Example: White animals live in a meadow An animal is born with a mutation making it red

Blending Red animal breeds with white animals  results in some pink animals Pink animals breed with white animals  results in light pink animals

Blending Light pink animals breed with white animals  results in white animals. Mendel’s work with garden peas proved that blending did NOT explain the transfer of traits from one generation to the next.

Mendelian Genetics Mendel studied 7 traits He studied one trait at a time He began his work by breeding together two True Breeding plants. A True Breeding plant self-pollinates and always has offspring that share its traits. Example: Tall plants always produce tall plants. Short plants always produce short plants.

Mendel’s Experiments Mendel asked, “What happens if I cross a true breeding tall plant with a true breeding short plant?” _________________________________ According the theory of blending, what will be the results of this cross? Medium tall plants

Mendel’s Results What were the ACTUAL results of a cross between a true breeding tall and a true breeding short plant? All of the offspring were TALL. Definitions True breeding plants are the –Parents or P generation The offspring of the P generation are the –First Filial (filial = son in Latin) or F 1 generation

How did Mendel conduct his Experiment? Flower Worksheet ♂ = male ♀ =female

Pea Flower

Mendel’s Experiment Mendel removed the stamen (♂) from a SHORT plant. He then removed pollen from the anther of a tall plant and brushed it on the stigma (♀) of a SHORT plant.

Mendel’s Results The plants produced seeds. The seeds were planted Every seed produced a TALL plant Mendel’s First Conclusion: biological inheritance is determined by factors that are passed form one generation to the next. Today we know these factors as genes. P generation F 1 generation

Mendel’s Second Experiment Mendel crossed plants from the F 1 generation together. He created thousands of crosses this way. Each flower produced seeds. Thousands of these seeds were planted and grew into the F 2 generation.

Mendel’s Results of the F 1 Cross Mendel observed the thousands of plants he grew from seeds. He found the missing trait had reappeared!! Among the new F 2 generation there was a 3:1 ratio of Tall to Short Plants P generation F 1 generation F 2 Generation

Mendel’s Second Conclusion Second Conclusion: Principle of dominance – Some alleles are dominant and some are recessive. An organism with one or two dominant alleles for a particular form of a trait will always have that form. ********************** An organism inherits TWO alleles for every trait. One from its mother and one from its father.

Vocabulary Gene – Allele – Dominant - Recessive - Hybrid = Pure = True breeding =

Vocabulary Gene - unit of heredity information Allele – form of a gene (Tall/Short). Dominant - stronger of two alleles Recessive - weaker of two alleles Hybrid = offspring of parents with different traits. A hybrid has one recessive gene and one dominant gene Pure = both genes are the same (2 recessive or 2 dominant) = homozygous True breeding = P generation = pure

Rules for Genetic Problems Two alleles for a gene are represented with the same letter. Dominant alleles are represented with an uppercase letter, and recessive alleles are represented with a lower case letter. The letter representing the gene is usually the first letter of the dominant trait. For example: Tall allele = T; Short allele = t

Rules for Genetic Problems Try this: –A pea plant has two alleles for seed color. –Yellow is the dominant seed color –Green is the recessive seed color. –What is the symbol for yellow seed color?_____________ –What is the symbol for green seed color? _____________ Y y

Rules for Genetic Problems Since a plant inherits two alleles for seed color it may be –YY = yellow seeded plant –Yy = yellow seeded plant –yy = green seeded plant.

More Vocabulary Homozygous genes = same alleles for the trait (YY, yy) = pure Heterozygous genes = different alleles for the trait (Yy) = hybrid Genotype = genetic make-up of an organism. Phenotype = physical characteristic of an organism.

Punnett Squares Named after R.C. Punnett, British geneticist, Used to understand the probability of the outcome of a genetic cross.

Punnett Square F 1 generation cross

Worksheets Genetic Crosses