Mendel and Autosomal Inheritance Complete Dominance

1. Mendel and Autosomal Inheritance Complete Dominance

2. Gregor Mendel (Born 1882) **An Austrian monk who was the first person to observe different inherited traits such as color and height using the reproduction of pea plants I’m a monk and I like peas, darn it !

3. Pea Plant Flower

4. Sexual Reproduction In Plants • **In plants, fertilization is called pollination (pollen from the male meets the female parts) • Self-pollination occurs when a plant is allowed to pollinate itself • Cross pollination – Different plants

5. Cross Pollination Female excepts the pollen Male Produces Pollen

6. Mendel’s Experiments **He studied only one trait at a time to control the variables ** He called these traits factors

7. Mendel’s Experiments He would cross-pollinate plants with two variations of one trait: For example, this dwarf plant was mated with this tall plant

8. Mendel’s Experiments P1  Parent Generation **tall plant mated with a short plant Their Offspring (F1)  Filial 1 (1st generation) **All Tall – allowed to self-pollinate Their offspring (F2) – Filial 2 (2nd) generation **3 tall and 1 short

9. What does this tell us?? F1 Must carry the tall AND the short “factors”

10. What else does this tell us???? ** Traits are inherited from generation to generation ** Also, a hybrid is the offspring that inherited both the tall “factor” and the short “factor”

11. Mendel’s Rules ~ Rule of Unit factors: Two factors (one from each parent) affect one trait in an individual ~ Rule of Dominance: The observed trait is called dominant and the trait that cannot be seen is recessive

12. Recall Chromosomes!!!! ~ We now call Mendel’s factors genes and are found on chromosomes • ~ Remember!!! We have a total of46 chromosomes • ½ from mom and ½ from dad ~ 44 are called autosomal chromosomes and 2 are called sex chromosomes (X’s and Y’s)

13. Alleles ** We call the alternate forms of a gene alleles ** Alleles inherited from the mother are in red. Those inherited from the father in blue. “A” Alleles aA are different, or alternate, forms of the “A” gene Homologues; Same chromosome from each parent; Just different forms of alleles D Alleles T Alleles

14. General Terms • Genotype  pair of alleles denoted by letters • TT = homozygous dominant (Upper Case) • Tt = heterozygous (hybrid, carrier…the recessive “t” is not expressed; the “T” dominnates over the “t”; the “t” cannot be seen • tt = homozygous recessive • Phenotype  how the alleles are expressed; what it “looks” like; such as tall and short or even a genetic disease or abnormality (like polydactyl fingers)

15. Genotypes – Combination of Alleles bb Homozygous Recessive BB Homozygous Dominant Remember!! Combination of alleles denoted by using a capital letter for dominant alleles and lower case letters for recessive traits

16. Genotypes and Phenotypes Codes For Genotype (AA, Aa,aa) Phenotype (Fur Color)

17. Dominant Recessive – Heterozygous and Homozygous

18. Mendel’s Principles Principle of Segregation: What it means: each gene has two copies (alleles) and a parent will give only one copy to a child. The other parent will give another copy, and thus the child will receive two copies (alleles) Segregation of alleles in the production of sex cells

19. Mendel’s Principles Principle Independent Assortment: Genes for different traits may assort independently of one another in gamete production  Leads to genetic diversity What it means: different genes are inherited separately. For example, the gene which codes for eye color is inherited separately from the gene which codes for nose shape.

20. Independent Assortment

21. Punnett Squares • Table that shows probability of offspring having a particular trait • Shows a cross (mating)between a male’s gamete with the female’s

22. Punnett Squares

23. Punnett squares **Cross a male with a Female – What are the probabilities of the sexes of the babies? X Y X XX XY X XX XY **Genotypic Ratio: 2 XY to 2 XX  1:1 (50/50 chance) **Phenotypic Ratio: 2 Males to females  2:2  1:1

24. Monohybrid Cross (crosses only 1 trait) Mom’s Genotype is Rr and her phenotype is Round Dad’s Genotype is Rr and his phenotype is Round R r RR Rr R Rr rr r **Genotypic Ratio: 1RR:2Rr:1rr  Write Homozygous Dominant 1st, then Heterozygous then Homozygous Recessive. **Phenotypic Ratio: 3Round:1Wrinkled3:1  Dominant first then recessive

25. Test Cross • Determine the genotypes of a parent based on offspring. • In a Test cross, cross an unknown genotype to a known recessive (below) T T t T t t T t T t T t t t t T t T t t T t t t If half of the offspring are short and the other half tall the unknown is Tt, heterozygous If all offspring are tall the unknown Is TT, homozygous dominant

26. Practice Punnett Squares- Write the Genotypic and Phenotypic Ratios • Cross the following and determine the genotypic and phenotypic ratios: • Homozygous yellow pod (YY) with heterozygous yellow pod (Yy) • 2 heterozygous tall plants (Tt) • 1 plant with wrinkled seeds (rr) with a plant that is heterozygous for round seeds (Rr) • A homozygous dominant purple flower (PP) with a homozygous white flower (pp)