Patterns of Inheritance Beyond Mendel Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Mendel and the Garden Pea Advantages of Garden Pea for research: Many hybrids previously produced. Large number of true-breeding varieties. Small and easy to grow. Short generation time. Sexual Organs enclosed in flower. Self-fertilization Cross fertilization Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

TestCross If you cross a plant with an unknown genotype (PP or Pp) with a homozygous recessive individual, the two possible genotypes will yield different results. pp x PP = 100% (Pp) pp x Pp = 50% (pp) : 50% (Pp) Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Mendelian Inheritance Phenotype Considerations Continuous Variation The greater the number of genes influencing a character, the more continuous the expected distribution of character variation will be. Example: eye color, hair color, height Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Phenotypic Considerations Incomplete Dominance Heterozygotes are intermediate in color. Ex: four o’clock flowers RR=red WW=white RW=pink Environmental Effects Degree of allele expression may depend on the environment. Ex: lung cancer gene and smoking Epistasis One gene interferes with the expression of another gene. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Multiple Alleles: ABO Blood Group Codominance - No single allele is dominant, and each allele has its own effect. ABO Blood Groups Human gene that encodes enzyme that adds sugar molecules to lipids on the surface of red blood cells. IB adds galactose IA adds galactosamine i adds no sugar Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Chromosomes and Inheritance A trait determined by a gene on the sex chromosome is said to be sex-linked. In Drosophila, sex is determined by the number of copies of the x chromosome. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Human somatic cells normally have 23 pairs of chromosomes. Human Chromosomes Human somatic cells normally have 23 pairs of chromosomes. Divided into seven groups characterized by size and shape. 22 pairs of autosomes 1 pair of sex chromosomes XX = Female XY = Male Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Karyotype A karyotype is an organized profile of a person's chromosomes Picture is taken of chromosomes during prophase of mitosis. They are cut out and matched up using size, banding patterns, and centromere position Helps scientists quickly identify chromosomal alterations that may result in a genetic defects. Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

Copyright © McGraw-Hill Companies Permission required for reproduction or display Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies