Understanding Genetics: Key Concepts of Genotype, Phenotype, and Inheritance Patterns

1. Natiwya Saddler Mitchell Loll 4.3.2 - 4.3.11

2. Background Info • Genotype: the alleles of an organism • Phenotype: all characteristics of an organism • Punnett Square: means of finding the expected ratio of the offspring, given certain parental phenotypes • Monohybrid: cross of parents that are homozygous except for a single gene locus that has two alleles (RR and rr)

3. Cont. • Allele: member of a pair or series of genes that occupy a specific position on a specific chromosome • Homozygous: having the same alleles at a particular gene locus on homologous chromosomes • Heterozygous: having different alleles at on or more corresponding chromosomal loci. • Locus: position a gene occupies on a chromosome

4. 4.3.2 • Determine the genotypes and phenotypes of the offspring of a monohybrid cross using a Punnett Grid • http://www.siskiyous.edu/class/bio1/genetics/monohybrid_v2.html

5. What is a Punnett Square? • Created in early 1900’s by Reginald Punnett • depicts the number and variety of genetic combinations • All possible offspring of two parents for each gene

6. 4.3.3 • State that some genes have more than two alleles (multiple alleles). • Multiple Alleles: When more than two alleles control a trait these are known as multiple alleles.

7. 4.3.4 • Describe ABO blood groups as an example of co-dominance and multiple alleles

8. Co-Dominance: Situation in which two different alleles for a genetic trait are both expressed Red plant + White plant =

9. 4.3.5 • Explain how the sex chromosomes control gender by referring to the inheritance of X and Y chromosomes in humans • Both males and females have X • Only males have Y • Receive Y from your dad • ½ chance of being male

10. 4.3.6 • State that some genes are present on the X chromosome and absent from the shorter Y chromosome in humans • X chromosome is much larger • X-linked genes only appear on X chromosome • Colorblindness • Hemophilia • More common in males

11. 4.3.7 • Define Sex Linkage • Sex Linkage: the phenotypic expression of an allele that is dependent on the gender of the individual • directly tied to the sex chromosomes. • Occurs when genes carried on sex chromosomes • Most often on X chromosome

13. 4.3.8 • Describe the inheritance of color blindness and hemophilia as examples of sex linkage • Both most common in males • Produced by recessive sex-linked allele on X chromosome • ½ of males receive colorblindness

14. 4.3.9 • State that a human female can be homozygous or heterozygous with respect to sex linked genes • Females have two X chromosomes • Homozygous: both alleles are the same • Dominant or Recessive • Heterozygous: different alleles. • One dominant, one recessive

15. Males have only one X chromosome • Homozygous and heterozygous do not apply

16. 4.3.10 • Explain that female carriers are heterozygous for X-linked recessive alleles • Woman can carry traits without being effected • Men have one chromosome, one allele will be expressed

17. This mother was a carrier for hemophilia but was not effected by the condition. • Half of her sons will carry have hemophilia • Y chromosome carries no allele

18. 4.3.11 • Predict the genotypic and phenotypic ratios of offspring of monohybrid crosses involving any of the above patterns of inheritance ¼ = GG Homozygous Dominant ½ = GgHeterozygous ¼ = ggHomozygous Recessive

19. Practice

21. Genotype: ½ Homozygous Dominant ½ Heterozygous • Phenotype: 100% Tall Plant

24. Genotype: ¼ Homozygous Dominant ¼ Homozygous Recessive ½ Heterozygous • Phenotype: ¾ Brown eyes ¼ Blue eyes

27. Genotype: ½ Heterozygous ½ Homozygous Recessive • Phenotype: ½ Curly Hair ½ Bald

30. Genotype: ½ Heterozygous ½ Homozygous Recessive • Phenotype: ½ Dwarf ½ Normal Proportion

33. Genotype: ½ A blood ¼ AB blood ¼ B blood • Phenotype: ½ A blood ¼ AB blood ¼ B blood