Chapter 11: Introduction to Genetics (p.306)

Q: Are all mutations harmful? Write an answer with ONE SENTENCE explaining your response. Include an example that supports your claim.

Gregor Mendel (July 20, 1822 – January 6, 1884) Austrian Friar Monastery gardener who raised pea plants and traced their genes through hundreds of generations “Father of genetics” His work was not widely accepted until the mid 1900’s http://www.youtube.com/watch?v=aDpLDBaEBjk&feature=related http://www.youtube.com/watch?v=aoVeSncKFAY&feature=related

Mendel’s Peas Anthers = Male structure, produce pollen Pistil = Female structure, produces ova (eggs) Peas can self-pollinate Or cross-pollinate

Cross-pollination Mendel used true- breeders (purple) He cut off the anthers of some before they developed pollen Then he cross- pollinated plants with paintbrushes Offspring now had 2 parents instead of 1

B. Genes and Dominance P = Parental generation F1= First filial or first “child” generation F2 = Second Filial generation, and so on. Filius is Latin for “son”

Genes and Dominance Gene: chemical factors that determine traits locus (loci)=location of gene on the DNA Allele: different forms of a single gene ex. White or purple flowers

Principle of Dominance some alleles are dominant and others are recessive--recessive traits are “masked” by dominant ones. Hybrids are offspring produced by two parents with different traits

Pea Traits Mendel studied 7 traits in peas and tracked how they were passed down for many generations He recorded the information each season for over 40 years!

Inheritance of Color in Pea Seeds Yellow peas are dominant Green peas are recessive

Gametes Sex cells only carry one allele each One allele will come from each parent Humans have sperm and eggs, plants have pollen and ova

Other Vocabulary words. . . Phenotype = visible expressed trait (what does it look like or do?) Genotype = combination of genes (letters) The genotype determines the phenotype Homozygous = an individual with 2 alleles for the same gene (AA or aa) Heterozygous = an individual with both alleles (Aa)

II. Genetics and Probability Probability= the likelihood that a particular event will occur Coin Flip (Ratio of heads:tails) Once: 50:50 (1/2 of the time it is heads, ½ tails) Q: If you flip a coin 3 times, what is the likelihood of getting three heads? Multiply the probability of each event ½ x ½ x ½ = 1/8

Punnett Squares A table of the possible outcomes from a cross between 2 parents

Rules for Punnett Squares (p.316) Start with the parents Figure out the possible gametes Line them up on the square Fill in the table by combining the traits Determine the possible genotypes and phenotypes of each offspring Write the RATIO and PERCENT CHANCE of these possibilities

Punnett Squares (continued) True-breeding = Homozygous (TT or tt) Heterozygous (Tt) means they have both alleles Phenotype: physical expressed characteristic Ex: Yellow or green peas; blue or brown eyes Genotype: genetic makeup (TT, tt, Tt) The genotype determines the phenotype

C. Other genetic factors Incomplete dominance Cases in which neither trait is dominant and the heterozygous individual expresses an even mix of the trait Miribalis flowers Red = R White = W Pink = RW

Incomplete Dominance RW In Miribalis flowers, a red parent + white parent results in all pink offspring Red = R White = W R R Pink = RW W Phenotype = 4:0 Genotype = 4:0 W RW

Codominance A mix of dominant and recessive trait is expressed like a blend (ex. Roan cattle) + =

Codominance (use capital letters) In cattle, a red parent + white parent results in both traits being expressed equally Red = R White = W R R Roan (spots) = RW W Phenotype = 4:0 Genotype = 4:0 W RW

Codominance In people a parent with straight hair + a parent with curly hair results in both traits being expressed equally (Wavy hair) Straight = S S S Curly = C C Wavy = SC Phenotype = 4:0 C Genotype = 4:0 SC

Multiple alleles more than 2 alleles control the expression of the gene (Fur color in rabbits, see p. 273 in Blue text)

Polygenic traits Traits controlled by more than 2 different genes (ex. Skin color in humans)

III. Exploring Mendelian Genetics Are there relationships between the different alleles? Mendel wondered if wrinkled seeds must always be yellow or if smooth seeds must also be round Crossed plants and looked for patterns with 4 different alleles (2 traits) DIHYBRID CROSS

Dihybrid Cross (RrYy x RrYy) Mendel tracked two traits to see if there were links between the inheritance of traits Round = R Wrinkled = r Yellow = Y Green = y Phenotype = 9:3:3:1 RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy Round Yellow: wrinked Yellow:Round green:wrinkled green

A. Independent Assortment Principle of independent assortment: genes for different traits can segregate independently during the formation of gametes We end up with a phenotype ratio of 9:3:3:1 Genotype ratio of 2:2:2:2:2:2:1:1:1 Out of 16 offspring looking at 2 traits

B. Mendel’s Principles Inheritance of traits is determined by genes. In sexual reproduction, genes are passed from parents to their offspring There are dominant and recessive forms of most genes that are expressed by different traits Each adult has 2 alleles for each gene (1 from each parent). Genes are segregated in gametes (sex cells only carry one allele) Alleles of genes segregate independently of one another

Genetic Diseases: Muscular Dystrophy Genetic muscle disease Dominant allele 50% chance of inheritance in offspring between an affected and an unaffected pair