LECTURE 3: THE BIOLOGICAL BASIS OF LIFE AND HEREDITY
•the cell, identified by Robert Hooke (1665) as cellula, is the basic unit of life
⁃eukaryote: an organism consisting of a cell or cells in which the genetic material is
DNA in the form of chromosomes contained within a distinct nucleus
⁃structure of eukaryotic cells: cytoskeleton, nucleus, cell membrane, mitochondria,
ribosomes, and cytoplasm
⁃there are somatic cells and gametes
•Neoxyribonucleic acid - the Universal Code
⁃protein synthesis
⁃base pairs: A-T, G-C
⁃nucleotides
⁃double helix
•Protein Synthesis
⁃proteins have various applications:
⁃structure (ex. collagen)
⁃regulation of chemical reactions (ex. enzymes)
⁃affecting tissues and organs (ex. hormones)
⁃regulation of DNA
⁃amino acids are determined by a sequence of three DNA bases: a triplet
⁃transcription - the first step is to copy the DNA message into a form of RNA called
messenger RNA (mRNA)
⁃translation: turns mRNA into tRN, with the mRNA triplets, or codons, still
specifying one amino acid
•Genes are sequences of DNA bases that specify the order of amino acids for a protein, part
of a protein, or another functional product
⁃2% protein coding genes
⁃2% regulatory genes
⁃96% non-coding (doesn't code for a specific protein; formerly known as "junk"
DNA as its function is unclear - but it does fall under selective pressure so it may
have a role in evolution)
⁃mutations can be responses to environmental changes or genetic errors; they are
either beneficial, neutral, or deletarious
⁃they are a source for variation in populations, but they must be inherited and
become common in order for change to occur
⁃point mutation: a change in one of the four DNA bases
•Chromosomes are composed of DNA and protein
⁃the number of chromosomes in cells is species specific: humans have 46 (23 pairs)
⁃there are two types of chromosomes - autosomes (physical characteristics other than
sex determination) and sex chromosomes (determine maleness or femaleness)
⁃locus: where a gene is found on a chromosome; alleles are always found in the
same locus in paired (homologous) chromosomes