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Exercise 3: Mendelian Genetics. Objectives (see page 27). Crosses Monohybrid Autosomal and Sex-Linked Dihybrid Autosomal Punnett Squares Scientific Method Chi-squared test Drosophila and Pea Genetics. When Meiosis goes afoul…. Karyotype: Trisomy 21. From Meiosis to Mendel.
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Objectives (see page 27) • Crosses • Monohybrid Autosomal and Sex-Linked • Dihybrid Autosomal • Punnett Squares • Scientific Method • Chi-squared test • Drosophila and Pea Genetics
From Meiosis to Mendel • Meiosis produces haploid (n) gametes • Only 1 chromosome of each type (homologue) • Mendelian genetics concerns the recombination of these chromosomes
Allele: One of two or more molecular forms of a gene that code for different versions of the same trait P p
Genotype dictates Phenotype • P=purple • dominant • p=white • recessive
True Breeding Individuals: Genetic line always produces same type of progeny when crossed within the line Homozygous Homozygous
Results Cross F1
How?? Started with truebreeders • F1 Generation • All Heterozygous • F2 Generation • Determine probability of each genotype and Phenotype • Punnett square
ww Ww W? ww Ww ww Ww Ww ww Ww Ww W? W? Pedigrees
Problems with Mendel’s Laws • Environmental influences
Problems cont • Not all traits are independently assorted • Pleiotropy: 1 gene Many traits • Epistasis: Many genes 1 trait
Problems cont • Multiple Alleles • ABO • AB codominant
Problems cont • Incomplete dominance
Sex-linked Traits • Located on the X chromosome • Females XX, Males XY • Other chromosomes are AUTOSOMAL
Today’s Lab: Computer Simulation • Monohybrid crosses • Autosomal or Sex-linked • Use reciprocal cross • Dominant or recessive • Dihybrid crosses • Dominant or recessive • Test with Chi-square statistical test
Describe Phenomenon Formulate Falsifiable Hypotheses to Explain the Phenomenon Design and Implement Tests of Hypotheses Analyze Results (statistics) Draw Conclusions and/or Modify Hypotheses Classical Scientific Method