2Learning goalsUnderstand the basic terminology of mendelian genetics, not limited to (phenotype, genotype, homozygous, heterozygous, P,F1,F2 generation(s), dominant, recessive, alleles, geneSolve monohybrid problems using Punnett square method
3Gregor Mendel ( )Used pea plants to study genetics, heredity and variation.Looked at 7 different traits that only had two variations (two different alleles)Discovered Mendel’s Laws of genetics
419th Century BritainBefore Mendel, from breeding ornamental plants, scientists believed in a blending theory of inheritance.4
5Charles Darwin theorized that offspring have variations of their parents' characteristics, but he was unable to explain why (1870s).5
6Gregor Mendel (1822-1884) Austrian monk Considered the father of genetics (now aka Mendelian Genetics)Why the pea plant?grows easily and quicklyhas seven traits that are easily identifiedit is easy to manipulate6
8Mendel's Pea Plant Experiment True breeding: Individuals that only contain one variation of a trait and therefore can only pass this one variation on to future generations.AKA homozygous: having two alleles that are the same.Mendel selected true bred plants for different traits and cross-fertilized them to see what would happen.For example:True bred Tall x true bred dwarfWhat do you think the offspring looked like?X
9100% of the offspring plants were tall 100% of the offspring plants were tall! (Instead of a blending – where all plants would be medium sized...)X9
10this time most were tall, but some were short and ALWAYS 3:1 ratio Mendel then let the F1 generation self-pollinate (fertilize themselves)F1 generation – (filial (son or daughter) generation) offspring from the cross (reproduction) of the Parent or P generation.this time most were tall, but some were short and ALWAYS 3:1 ratiox10
11Why?Each plant in the F1 generation carried an allele from the P generation; a tall allele and a dwarf allele. This is a hybrid.Hybrids: Individuals that contain more than one variation of a trait. Also known as heterozygous.Traits are dominant or recessive. If a dominant trait is inherited, it will be expressed.What is the dominant trait for height in pea plants?11
12Mendel’s “Key Terms”Phenotype: the appearance of traits in an organism (eg. short or tall)Genotype: the specific genes that an organism has (which alleles, dominant or recessive)Every individual has a phenotype and genotype for every trait.
21Monohybrid cross problem Curly hair is dominant over straight hair. If amother is homozygous dominant for curlyhair and the father has straight hair, whattype of hair will the children have?
22Test CrossesWhen geneticists want to know if an individual is heterozygous or homozygousWhy? For breeding purposesCross between unknown phenotype and homozygous recessive individual(Pp or PP) x ppPp x pp = 50% purple, 50% whitePP x pp = 100% purple
23Mendel's Laws and Principles Law of Segregation: when any individual produces gametes, the copies of a gene separate so that each gamete receives only one copy of a gene and therefore only one allele for all possible traits.23
24Law of Segregation Principle of Segregation Demystified Segregation Mendelian Genetics4/15/2017Law of SegregationPrinciple of Segregation DemystifiedSegregationThe principle of segregation is explained by the behavior of homologous chromosomes at meiosis.G. Podgorski, Biol 101024
25Law of Independent Assortment: alleles of different genes assort independently of one another during gamete formation, so different traits are inherited independently of each other