Dichotomy, Alleles, and Genes:
Dichotomous keys: allow for the comparison of potential breeding of two individuals, and the potential
characteristics their offspring would carry.
For example, a blue eyed and brown eyed couple have 3 kids; what are the chances that they would
have a blue eyed child?
Genes: a string of DNAor RNAthat determines a certain trait. They are responsible for the colour of
your hair, your height, your eye colour, etc.
Alleles: Variations of Genes. Several alleles can belong to the same gene, but are varied in their ability
for expression of what that gene is. Ex: red haired, blonde haired, black haired, auburn hair alleles all
belong to a hair colour gene.
Homozygous: Homo (same)- the alleles are the same for the particular gene
Heterozygous: Hetero(different)- the alleles are different for that particular gene.
Genotype: The genetic make up of that gene: determines phenotype
Phenotype: The visually observable trait of that gene: cannot always determine genotype based on
An example of Mendel's Law, or how the ratios of offspring are determined:
G= Green coloured, g=white coloured. Although there are
some pairs that are both G and g, because the G is the
dominant allele, the heterozygous offspring will appear
green. Only when there are two recessive alleles (g) will
the offspring demonstrate a white colour.
DNAis wrapped around the spherical Histones, which are
threaded together to become chromatin: chromatin is then
packaged again into chromosomes, which determine the
genes a species will exemplify. Humans contain 23 pairs
(46 in total) of chromosomes, which determine everything
from body shape to sex.
Human reproduction occurs when two gametes, a sperm and an egg
(vehicles that allow for safe travel of chromosomes) combine to form
But first, the chromosomes duplicate, with the egg removing its'
duplicate (explained later) and the sperm subdividing into several
sperm. This ensures that there are more sperm then eggs: the route to
the egg is highly acidic as a means to kill bacteria, and most sperm
will die before they make it to the egg. When the egg is fertilized, due
to its' lack of a pair of chromosomes, the sperms chromosomes
readily integrate with the eggs to form the zygote: this ensures eggs
readily fertilize, but also do not allow in other sperm after one makes
DNAstands for DeoxyribonucleicAcid. Deoxyribose is a binding
agent that holds the double stranded helix (the form most DNAtakes)
together, while the NucleicAcids are random assortments of proteins
caused by the arrangement of 4 bases that occur in pairs: Adenine and
Thymine, and Guanine and Cytosine. These acids must occur in these
pairs, or else mutations may happen! DNAreplicates by “unzipping” itself and then replacing the other side of it with the base pair that is
supposed to be there: this ensures that both strands are almost identical.
Two types of Genes: structural and operator. Structural are the most common, creating proteins using
ribosomes (“protein factories”). Operators regulate structural genes: only ever are on or off.
Structural Genes are created by the unzipping of DNA, but instead, do not make a double helix
structure: a copy is made of one side, with the base Thymine being replaced by Uracil. This single
stranded copy is known as RNA(RibonucleicAcid). RNA, if being used as a way to create proteins,
works as a messenger (thus called mRNA) and passes through a Ribosome. Every three base pairs tells
the Ribosome which protein to make, which are then stringed together like beads.
Don't worry! There are ways to make sure everyone isn't a mutant:
Splicing: RNAhas sections removed that would produce either no protein or a harmful protein.
Alt. Splicing: RNAsections are rearranged to code for a different protein.
miRNA: Micro RNAregulate protein production, stopping any that don't make sense.
How does the RNAknow? Other proteins that have been made can either illicit a “response element” to
let the Ribosomes to make more or less of that protein. Or there are DNA-binding domains, where if
there are too many proteins, one will bind to a region that will cease production of that protein.
Epigenetics: genes that change phenotype even though there is no change in genotype. Ex: caterpillar to
butterfly, child birth. Occurs either through DNAmethylation (Methyl represses gene activity on base
pairs) or Histone modifications (Histones altered to affect chromatin, either repress(closed chromatin)
or activate transcription(open chromatin)).
Lower methyl levels= less stress hormones, lower anxiety.Always present, but levels change.
Evolution: Behaviour acquired by natural selection; behaviours that encourage survival and
reproduction are passed on, others lead to death of both behaviour and those that practice it. Nature vs.
Nurture is not true: both work together to foster behaviours. Behaviour can either be categorized as
Phylogeny (Species through evolution) or