Chromosomal Basis of Inheritance

Topics

Reminders

• September 8, 1995
• chp 14, pp 280-297, Campbell
• Emphasis: class outline
• Study questions pp 297-298
• Examine study outline on pp 298-299

1. Introduction

• Genes
• Meiosis
• Chromosomes
• Homologous chromosomes
• Heterozygous and homozygous
• Gene frequency in mating
• Dominance and recessive
• These and all other factors relating to genes and chromosomes are fuel for evolution
  • -mutation
  • -chromosomal alterations

2. The chromosomal Theory for Inheritance

• Vehicle for carrying genes
• Genes are in linear sequence
  • linked genes and chromosomal mapping
• Diploid
  • two sets of chromosomes
• Meiosis
  • Law of Segregation
  • Law of Independent Assortment

3. Chromosomal Basis for Recombination

• Non-linked genes
  • Obey Law of Independent Assortment
  • Ratios 3:1, 9:3:3:1
• Linked genes and crossing over

4. Morgan and his flies

• Genes on the X chromosomes

5. Sex chromosome and sex-linked inheritance

• Humans
• Sex-linked disorders in humans
  • Hemophilia
  • color blindness
• X chromosome inactivation in females
  • Lyon's hypothesis
    • iris color in humans
    • calico cats

6. Chromosomal Alterations

• Chromosomal numbers
  • Aneuploidy (2N plus or minus 1 chromosome)
    Haploid
    Diploid
    Triploid
• Structure
  • Chromosomal mutations:

Deletions
Duplication
Translocation
Inversion usually deleterious

Point mutation, beneficial

• Human disease - nondisjunction

Down's syndrome

an extra autosomal chromosome
extreme mental retardation

• Human disease - nondisjunction in sex chromosomes

Metafemale, XXX, limited fertility

Klinefelter's syndrome, XXY, female appearance, sterile

Turner's syndrome, X_, female with only one X-chromosome, secondary sex characteristics do not develop