Heredity Chapter 11 1 Gregor Mendel Father of

Heredity: Chapter 11. 1

Gregor Mendel. Father of Genetics • Heredity- the passing of traits from parents to offspring • Genetics- the branch of biology that focuses on heredity

A little bit about Mendel • Austrian monk born 1822 • Published work that became the basis for modern genetics in 1866 • Studied at the University of Vienna to study math and science- learned how to experiment and use math to explain natural phenomena • Experimented with pea plants using quantitative analysis!

Traits Studied by Mendel

Why pea plants? Reason #1: Many traits that have only 2 choices. Example: flowers can either be purple or white. Reason #2: Easy to control pollination- reproductive parts are enclosed within the flower. Mendel pollinated them himself! Reason #3: Pea plants are small, easy to grow, produce many offspring quickly!

The Reality of “Round and Wrinkled” – Two Alternative Traits of the Seed Shape Character Note that each of seed is a new individual of a different generation – seeds are not of the same generation as the plant that bears them.

Mendel’s Model Organism – the Garden Pea

Monohybrid Cross • Cross that involves one pair of contrasting traits. • Step 1: – Pea plants self pollinated ensuring truebreeding: all offspring would only display one form of a trait. Example- all purple flowers. – Called P generation (parent) Step 2: – Cross pollinated P generation plants that had different traits. Offspring is F 1 (fillial) Generation Example- one parent has green seeds, the other parent has yellow seeds

Mendel’s Monohybrid Cross – P to F 1 A Punett square,

Step 3: Continued Crosses to the F 2 (the grandchildren) The green trait was not lost or altered, even though it disappeared in the F 1. One trait is dominant to the other in its expression. The reappearance of the recessive trait is ¼ of the F 2

Mendel’s Results • F 1 plants only showed 1 form of a trait • The trait reappeared in the F 2 generation in a ration of 3: 1 • For each of the 7 traits he found the same ratio!

Calculating Mendel’s Ratios Contrasting Traits F 2 Generation Results Flower Color 705 purple 224 white Seed Color 6022 yellow 2001 green Seed Shape 5474 round 1850 wrinkled Pod Color 428 green 152 yellow Pod Shape 882 round 299 constricted Flower Position 651 axial 207 top Plant Height 787 tall 277 dwarf Fraction Ratio 705/224 3. 15: 1

Assignments Classroom Assignment Homework Assignment Design a newspaper ad • In your notebook, do that would have 11. 1 section review attracted someone like questions (1 -3). Mendel to purchase • You may write in peas for genetic complete sentences research. The ad or write the question. should mention all of • This will be checked the benefits of pea in at the beginning of plants (Pisum sativum) class tomorrow, as a that make it useful for homework check. genetic research. Illustrated please

Mendel’s Theory Bio B 11. 2 p. 164

Mendel’s Hypotheses: Foundation of Modern Genetics • Hypothesis #1: For each inherited trait, an individual has 2 copies of the gene- one from each parent. • Hypothesis #2: There alternative versions of genes. These are called alleles. Example: allele for brown eyes, allele for blue eyes. Different versions of eye color.

Mendel’s Hypotheses: Foundation of Modern Genetics • Hypothesis #3: When 2 different alleles occur together, one of them may be completely expressed, while the other may have no observable effect on the organism’s appearance. dominant- expressed form of trait recessive- trait that is not expressed

Mendel’s Hypotheses: Foundation of Modern Genetics • Hypothesis #4: When gametes are formed, the alleles for each gene in an individual separate independently of one another. Thus, gametes carry only one allele for each inherited trait. When gametes unite during fertilization, each gamete contributes 1 allele. (During meiosis)

Capital=Dominant Lower Case=Recessive In pea plants: The allele for violet flower color (B) is dominant The allele for white flower color (b) is recessive

Terminology Homozygous- If an individual has 2 alleles for a gene that are the same. Ex: blue eyes from mother, blue eyes from father=blue eyes Heterozygous- If an individual has 2 alleles that are different. Example: blue eyes from mother, brown eyes from father=brown eyes

Do you have dominant or recessive traits? Dominant Trait Recessive Trait Cleft Chin No cleft Dimples No dimples Hair above knuckles No hair Freckles No freckles You? (Yes or No) # of Dominant Classmates # of Recessive Classmates

• Genotype- set of alleles that individual has(codes) • Phenotype- physical appearance of a trait Examples: Ff Genotype: heterozygous for freckles Ff Phenotype: has freckles ff Genotype: homozygous for no freckles ff Phenotype: doesn’t have freckles

Different Genotypes Can Produce the Same Phenotype

Genotype vs. Phenotype Genotype BB Homozygous dominant Bb Heterozygous bb Homozygous recessive Phenotype

Law of Segregation • Organisms inherit two copies of each gene, one from each parent • Organisms donate only one copy of each gene in their gametes • Two copies of each gene segregate, or separate, during gamete formation

Principle of Segregation Demystified Segregation The principle of segregation is explained by the behavior of homologous chromosomes at meiosis.

Segregation and Inheritance

Law of Independent Assortment • The inheritance of one trait does not affect the inheritance of any other trait • Example: eye color does not affect hair color or texture…

Assignment: Concept Map • Directions: Use the following words, connected by ideas, diagrams and lines to make a concept map. Allele recessive Homozygous heterozygous Genotype phenotype Law of segregation Law of dominant independent assortment

Classwork: Notebook 11. 2 Section Review Questions p. 318 (1 -4) Write question or answer in complete sentences

8. 3 Studying Heredity

A Punnett Square

CF - An Autosomal Recessive Trait

Carrier mother Punnett Square Carrier father G g GG Gg 25% 50% Gg gg 50% 25% Child with CF

Autosomal Recessive: A Pedigree

Inheritance of an Autosomal Dominant Trait

Incomplete Dominance In snapdragons red flower color is due to gene (R) and white to its corresponding allele (r). The heterozygous (Rr) condition results in pink flower color. This is referred to as “incomplete dominance. ”