Chapter 2 The Genetic and Evolutionary Roots of Behavior
Genetics of DNA
Living things are made of cells.
There is a large amount of diverse cells within the living thing. These cells hace different
shapes, size and function. The proteins on these cells also makes them immensly different from
one another. Each cell produces the specific proteins necessary for its role in the body.
There are a few exceptions.
all cells in a plant or animal contain a nucleus
inside the nucleus are the cell's chromosomes (structures in the nucleus of each cell that
contain the genes, the units of heredity transmission. A human cell has 46
chromosomes arranged in 23 pairs)
o these are complex structures that each contain a single long molecule of DNA
o DNA governs the cells structure and its chemical processes by providing a set of
detailed instructions for making the structural proteins that give each cell its
shape and for making proteins called enzymes that govern the cell's functioning.
DNA molecule constructed like a twisted ladder.
this shape is known as a double helix
Rungs of this ladder are made up of chemical subunits (referred to by single letter
o A - adenine
o T - thymine
o C - cytosine
o G - guanine
Each rung has a pair of these subunits.
o A is always paired with T
o C is always paired with G
o These can be in any order up and down the rungs
Gene: a section of DNA molecule that contains instructions for how and when to assemble a
protein. Genes are located on chromosomes.
Gene Expression Genome: every cell in a person's body contains a copy of the same 46 chromosomes
Genotype: the complete set of an organism's genes.
Phenotype: the overt chararteristics and behaviors of an organism.
Genes inherited from parents.
23 from the egg (mom) and 23 from the sperm (dad) to make a total of 46 chromosomes.
Each egg and each sperm contain different kinds of chromosomes. Because of this each
offspring is likely to represent a new combination of genes. Otherwise known as sexual
Interactions amound Genes
Gene's Locus: each gene that occupies a specific position within its chromosome.
For each gene, there is a partner gene located at the corresponding locus on the other
half of the chromosomal pair.
o One is from mom, the other is from dad.
o The pair may differ or may be identical.
If they differ they are called heterozygous.
If they are identical they are called homozygous.
o In all cases though, the variations of a specific gene are referred to as alleles(an
alternative form of a specific gene) of that gene.
Dominant: a term for a gene that directs the development of a particular characteristic even when the
corresponding gene on the othe chromosome is different.
Recessive: A term for a gene that directs the development of a particular characteristic only if the
corresponding gene on the other chromosomes matches it.
Single recessive gene on chromosome 12 causes an illness known as Phenylketonuria (PKU) which is
profound mental retardation.
Codominant: a relationship in which both genes in the pair affect the phenotype.
Incomplete Dominance: a person with two different alleles will have a phenotype that's intermediate
between the favored types favored by each allele on its own.
Polygenic Inheritance Polyogenic Inheritance: a pattern