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Genetics

This overview explores the foundational concepts of genetics, focusing on Gregor Mendel's principles of heredity and the variation of traits. It discusses the blending hypothesis, monohybrid crosses, and the significance of dominant and recessive alleles. The principles of segregation and independent assortment are explained alongside exceptions like intermediate inheritance, codominance, and polygenic traits. Additionally, it touches on chromosome theory, genetic linkage, and the implications of sex-linked traits. The role of the environment in shaping phenotypes is also examined.

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Genetics

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  1. Genetics

  2. Genetics- study of heredity • Trait - variation of a particular character • Blending Hypothesis • Flowers: White + Red= Pink • Not true

  3. Gregor Mendel • Bred pea plants • Hypothesis- parents pass on separate/distinct genes

  4. Identify true breeders - Self-Fertilization • Crossed true breeders - Cross Fertilization - Developed seeds 3. Mendel planted seeds - recorded flower color that was produced

  5. Hybrids- offspring of 2 dif true breeding varieties • Monohybrid cross- one characteristic • P gen. - parent plants • F1 gen. - hybrids • F2 gen. - hybrids self fertilize/fertilize each other

  6. Conclusion • F1- plants carried 2 genes for flower color

  7. Developed 4 hypothesis 1. Alternate forms of genes = alleles • Ex: Purple and White form 2. Two alleles control gene characteristic Homozygous- 2 alleles the same (PP) or (pp) Heterozygous- 2 different alleles (Pp)

  8. 4 Hypothesis 3. Dominant and Recessive alleles (Pp) 4. Principle of Segregation- 2 alleles for a trait segregate during formation of gametes

  9. Punnet SquaresShows all outcomes of a genetic cross PP X pp = P P p p Pp Pp Pp Pp

  10. Cross F1 Gen. Pp X Pp = P p P p PP Pp Pp pp

  11. Phenotype-observable trait • Genotype-genetic makeup or combo of alleles Genotype: 1:2:1 Phenotype: 3:1

  12. Pp X pp= P p p Genotype: 2:2 or 1:1 Phenotype: p 2:2 or 1:1 Pp pp pp Pp

  13. Principle of Independent Assortment • During gamete formation in an F₂ cross, an allele from one character can be paired with either allele from another character • Ex: RrYy RY Ry • Alleles of dif gametes are sorted into gametes indep. of each other

  14. Exceptions • Intermediate inheritance- neither allele is dominant • Heterozygous = intermediate phenotype • C is paired with superscripts • Ex: Chickens CBCB CwCw CBCw pg 215

  15. Exceptions • Multiple Alleles- multiple alleles control traits • Ex: Human Blood type • A, B, AB, O O= ii A= IAIA or IAi B= IBIB or IBi AB= IAIB

  16. Exceptions • Codominace- heterozygote exhibits both traits Ex: AB blood type Polygenic Inheritance- 2 or more genes affect a single trait Ex: height, skin color

  17. AABBCC –dark aabbcc- fair AaBbCc- intermediate

  18. Nature/Nurture • Environment affects phenotypes/genotypes • Ex: Trees genotype never changes but size/color of leaves change yr to yr based on temp./sun • Ex: Identical twins- dif environments

  19. Chromosome Theory Inheritance • Genes located on chromosomes • Behavior of chromosomes during meiosis and fertilization= inheritance pattern • Homologous chromosomes- • Gene locus- alleles of a gene found on same location

  20. Genetic Linkage • Tendency of alleles on one chromosome to be inherited together • Closer 2 genes are < genetic linkage • Further apart 2 genes are > genetic linkage • Crossing over

  21. Sex-linked gene • Genes located on a sex chromosome • Ex: Red-Green Color blindness Hemophilia Both sex linked (x linked) recessive traits

  22. Pedigree • Family tree that records/traces occurrence of a trait • Figure out Genotypes of an indiv. by examining patterns

  23. Pedigrees

  24. aa Aa aa A__ Aa Aa A_ A_ aa aa aa aa aa

  25. aa Aa aa Aa Aa / AA

  26. Solution • a) aa • b) Aa • c) Aa • d) A?  (in other words AA or Aa)

  27. Aa Aa A__ aa

  28. Solution • a) Aa • b) Aa • c) aa • d) aa • e) A?  (in other words AA or Aa)

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