OCTOBER 21 Unit 5 Heredity 1. What is Heredity the passing on of physical or mental characteristics genetically from one generation to another. Agenda 1. Warm-up 2. Mendlian Notes pg 5-6 3. Lets Practice pg 7 Homework : pg 10-15
MENDEL & THE ORIGINS OF GENETICS
Heredity and Genetics What What is is Genetics? Heredity? The passing The branch of genetic of traits from Biology parent that to studies offspring heredity
Gregor Mendel The Father of Genetics Gregor Mendel studied genetics in the 1800 s. He was born in Austria to peasant parents who worked as gardeners. He studied at the University of Vienna and later became a monk. Conducted experiments in the garden studying traits in pea plants. Observed & recorded traits passed from parents to offspring.
Mendel Brainstorm What were Mendel s Experiments? What characteristics did Mendel study?
Mendel s Experiments
Mendel s Experiments - Hypotheses An individual has two Alleles copies of a gene one from each parent. the different versions of the gene; represented by letters One allele is dominant, one is recessive There are different versions of each gene. Dominant: expressed form of trait (capital allele) For example, the gene for flower color in pea plants can either be purple or white, represented by letters; P = purple and p = white. Recessive: not expressed form of trait (lower case allele)
Mendel s Experiments - Conclusions Homozygous Genotype Having identical alleles for a trait; either two dominant alleles the set or of two alleles recessive that alleles an individual has (the actual genes) Homozygous Dominant = BB or TT or QQ Ex: BB, Tt, or qq Homozygous Recessive = bb or tt or qq Phenotype Heterozygous Having the physical two different appearance alleles of a trait (how it actually appears) Ex: Brown eyes or blue eyes; tall or short Bb or Tt or Qq
Mendel s BIG Conclusions The Laws of Heredity Law of Segregation Two alleles for a trait separate when gametes are formed Law of Independent Assortment The inheritance of one trait does not influence the inheritance of another trait These both occur during Meiosis!
Mendel s Contributions On the left side of your IN, write a short paragraph about the importance of Mendel s research.
STUDYING HEREDITY
Punnett Square Simple diagram used to predict expected result of a genetic cross What is the genotype of parent 1? Punnett Squares consider all possible combination of gametes for that particular cross Heterozygous Genetic Cross Hh x hh What is the genotype of parent 2? Hh hh Homozygous Recessive Hh hh
Punnett Squares Monohybrid Cross What Cross is the the genotype following! of all of the offspring? Heterozygous What is the probability the offspring s RR x rr phenotype is Round? 100% Homozygous Dominant Female x Homozygous Recessive Male r r Seed of Pea Plants Key R Rr Rr R Round r- Wrinkled R Rr Rr
Punnett Squares Monohybrid Cross How Try 1 many more offspring cross! would What What is the is the you would Heterozygous expect have to the have Male the: x Heterozygous phenotypic genotypic Female ratio? ratio? following phenotype? Genotype RR 1:2:1 Rr x Rr 3:1 Round Seeds 1/4 or 25% 3/4 or 75% Genotype Rr Wrinkled Seeds 2/4 or 1/4 1/2 or or 25% 50% Seed of Pea Plants Genotype rr Key 1/4 or 25% R Round r- Wrinkled R r R RR Rr r Rr rr
Test Cross A test cross can be performed to determine whether a parent with a dominant phenotype is homozygous dominant or heterozygous. In a test cross, an individual whose phenotype is dominant, but whose genotype is unknown, is crossed with a homozygous recessive individual. One can then look at the offspring to determine the genotype of the parent.
Homozygous recessive Test Cross - examples Unknown with dominant phenotype Pea Plant Flower Color P = purple p = white p p P Pp= purple Pp= purple?p Pp= purple Pp= purple
Let s Practice
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