Genetic cross

2. Figure 13.9 The results of alternative arrangements of two homologous chromosome pairs on the metaphase plate in meiosis I

4. Genetic cross

5. Mended tracked heritable characters for three generations Mendel deduced: Discrete genetic determinants from each parent. Some dominant over others.

6. Alleles, alternative versions of a gene (Dominant) (Recessive)

7. Mendel’s law of segregation

8. Mendel’s law of segregation Punnett square

9. Genotype versus phenotype

10. How could you determine the genotype of a purple flower?

11. A testcross

12. The Results of Mendel’s F1 Crosses for Seven Characters in Pea Plants

13. Dihybrid Cross

14. MENDEL’S LAWS OF INHERITANCE • Segregation of alleles • Independent assortment of different traits

15. Mendel was not only smart, but extremely lucky. All his traits were dominant/recessive and on different chromosomes (or were far apart on a chromosome)

16. Genes that are on the same chromosome are said to be “linked” Closely linked genes do not assort independently in meiosis, they are inherited together.

17. Crossing-over “unlinks”genes

18. Human Genetics How do geneticists study human genetics?

19. Some Human traits that are inherited in a Mendelian fashion (dominant and recessive) • Tongue Rolling • Widow’s Peak • Mid-digit finger hair • Unattached ear lobes • Asparagus pee Recessive trait Dominant trait (Attached earlobes) (Widow’s peak)

20. Human Genetic Disorders inherited in Mendelian fashion Autosomal Recessive disorders: • Albinism • PKU (phenylketonuria) • Cystic Fibrosis • Sickle cell anemia • Tay-Sachs • Hereditary deafness

22. Typical autosomal dominant pedigree

23. Autosomal Dominant disorders: How do mutant alleles act in a dominant fashion? Most serious dominant disorders are not passed on. One exception is Huntington’s Disease

24. Achondroplasia Is it possible for this couple to have normal height children?

25. SCREENING FOR HUMAN GENETIC DISORDERS Amniocentesis and karyotyping for gross chromosomal abnormalities

26. Molecular Screening: -adolescents and adults -Fetal -Pre-implantation What is your opinion on in-vitro fertilization and pre-implantation screening?

27. The relationship between genotype and phenotype is not always so simple

28. Sex-Linked Traits Humans have 22 pairs of autosomes and 1 “pair” of sex chromosomes

29. Sex-linked traits were discovered in fruit flies. Male fly with white eyes (mutant) Normal (wild-type) fly

30. Sex-linked inheritance Sex-linked traits “skip a generation”. Phenotype comes from maternal grandfather. Color-blindness, hemophilia examples in humans.

31. Incomplete dominance in snapdragon color

32. Knowledge of the molecular basis of gene expression gives us a handle on understanding these different types of gene (allele) interaction and phenotypic expression. Genes code for proteins! Functional vs. nonfunctional enzymes, dosage affects, etc.

33. A and B are codominant, O is recessive to A and B Multiple alleles for the ABO blood groups

34. PLEIOTROPY One gene (or genotype) results in multiple phenotypes. Many different outward effects on the organism.

35. Pleiotropic effects of the sickle-cell allele in a homozygote

36. POLYGENIC INHERITANCE -Multiple genes resulting in one phenotype. Ex. Skin color, eye color.

37. At least 2 genes invloved in pigment formation. (Location of color also important)

38. A simplified model for polygenic inheritance of skin color Environmental effects also affect the range of phenotype (multifactorial trait)

39. The effect of environment of phenotype Soil acidity effects the color of hydrangeas. Temperature sensitive mutations for pigment formation