Genetics and inheritance
- 2. Genetics ⢠What is genetics? study of inherited traits - âheredityâ ⢠What is heredity? passing of traits from parents to offspring (children) ⢠What is a trait? feature an organism can pass on to offspring ex) hair color, eye color, etc
- 3. Early Ideas - Heredity ⢠Originally believed⌠childâs traits were result of âblending between parentâs traitsâ ⢠Gregor Mendel decided to test this idea ⢠He knew nothing about DNA
- 4. ⢠Genes! ⢠Genes are⌠segments DNA on chromosome code for a trait by the production of a protein ⢠There are several genes on each chromosome.
- 6. Mendelâs Pea Plants Why did Mendel use pea plants? 1) Several contrasting traits 2) Understood method reproduction
- 7. Mendelâs Experiments ⢠The 1st thing Mendel did was cross purebred plants⌠⢠Purebred- produce young with same trait generation after generation ⢠What will happen if cross plants with different forms of a trait? ⢠Ex) trait â seed shape forms â round or wrinkled seed shape
- 8. Mendelâs Experiments conât ⢠Parental generation (P) âoriginal groupâ ⢠First filial generation (F1) offspring of the parental cross ⢠ALL offspring resulted were ROUND
- 9. Mendelâs Conclusion ⢠âNO blending- no ½ round ½ wrinkled seedsâ
- 10. We NOW know why⌠⢠Many traits have 2 alleles ⢠Allele- 2 contrasting forms of a trait ex) gene on chromosome for traitâseed shape 2 forms - round allele or wrinkled allele ⢠Principle of Dominance- one allele appears and causes contrasting allele NOT to appear ⢠dominant allele - hides the other allele; capital letter ⢠recessive allele- form often NOT expressed,
- 11. Mendelâs 2nd Experiment ⢠The next question Mendel wanted to answer was: Why didnât any of the recessive characteristics like (wrinkled) show up in the F1 generation? ⢠To answer this question Mendel extended his experiment and allowed F1 to reproduceâŚ
- 12. Mendelâs Results ⢠Second filial generation (F2)- offspring of F1 ⢠Some offspring showed recessive trait, some the dominant trait 3:1 ratio (round:wrinkled)
- 13. Mendelâs Conclusion ⢠Why did the recessive trait disappear in the F1 and then reappear in some of the F2? ⢠The dominant allele hides the recessive allele in the F1 ⢠Since the recessive allele reappeared in the F2 it must have âseparatedâ from the dominant allele ⢠Law of Segregation- when gametes form alleles for a trait are separated (each parent gives one allele to offspring)
- 14. Mendelâs Results Summarized ⢠Every trait is controlled by at least 2 different factors (1 gene / 2 allele) Use letters to represent contrasting forms (alleles) for a trait Example: Trait: Seed Color (letter Y) Y = yellow (dominant allele) y = green (recessive allele) ⢠Alleles occur in pairs (1 mom/1 dad) ⢠YY homozygous dominant â 2 same letter - capital Yy heterozygous â 2 different letters yy homozygous recessive - 2 same letter - lowercase ⢠Phenotype - outward appearance/physical characteristic ⢠Genotype - genetic makeup âlettersâ