Chapter 1: The Molecular Basis of Heredity, Variation, and Evolution

Molecular Basis of Heredity (Chap 1) # questions 1. Mitosis and Meiosis 2. Development of modern Generics (How gametes are made) 3. Evolution has a genetic basis: know the 3 domains of life 4. The dsDNA structure and discovery and the mechanism for replication

Eukaryotic

more complex with membrane bound organelles

Prokaryotic

lack nuclear membrane and typically no membrane bound organelles

Gene

• fundamental unit of heredity

• come in multiple forms called alleles

• determines phenotypes

• defined DNA sequences

Chromosomes

are long molecules of double-stranded DNA and protein, which contains genes

• At the end of S-phase, consists of two replicated structures, joined at the centromere

Homologous pairs

carry genes for the same traits

Hereditary flow

DNA → transcription → RNA → translation → protein

nucleic acid structure

• phosphate

  • phosphodiester linkage

• Sugar

  • Ribose or deoxyribose

• Nitrogenous base (hydrogen bonds)

  • Purines

    • Adenine and Guanine

  • Pyrimidines

    • Cytosine and Thymine/Uracil

Chargaffs Rule

percentages of adenine and thymine are equal and the percentages of guanine and cytosine are equal

• complementary base pairs

  • A with T

  • C with G

RNA

Mostly similar to DNA but

1. Uracil replaces thymine

2. 2’ hydroxyl on all bases

3. usually single stranded

mRNA

messenger RNA

tRNA

transfer RNA

rRNA

ribosomal RNA

Protein Structure

Composed of amino acids linked together in a chain

Multiple chains combine to form a multimeric

Each of the 20 amino acids has a unique R-group

Phenotypic variation

a reflection of inherited genetic traits carried in the DNA

Evolutionary principles developed by Darwin

• Variation exists in populations

• Hereditary transmission allows that variation to be passed along to subsequent generations

• Variants survive differentially due to environmental pressures

• Variants that lead to increased survivorship increase in frequency in the population

Phylogenetics

study of evolutionary relationships

• Uses multiple markers but DNA is one of the most robust

• General principle – the most closely related species will have the smallest numbers of difference between shared genes

• The same principle as determining relatedness within human populations, just extended to other species