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Primate Behavioral Ecology
Genetics, Protein Synthesis, and
Natural Selection
Darwin s Biggest Scientific Problem
• Darwin realized that
natural selection for
specific traits could lead
to changes in species
through time.
• However, Darwin lacked
information on how these
traits were passed from
generation to generation.
Genetics
Mendel was the first
to explore the units of
inheritance: genes.
Gregor&Mendel&(1822/1884)&&
What do GENES do?
They control the production specific
PROTEINS in living things…
By stringing up small amino acid
molecules into long protein strands…
Genetics and Protein Synthesis;
Bodies are made of protein and
other stuff…
Organisms Components
•  Organism = a living thing
•  Living things are made of matter
•  What kind of matter? Molecules…
–  Proteins, e.g., collagen, enzymes, etc.
•  there are some exceptions, e.g., viruses--but they are not relevant to our
simplified introductory discussion in this class--take upper division biology
classes if you are interested
–  Also: water, carbohydrates, fats, vitamins/minerals, DNA (nucleic
acids), etc.,
–  Proteins are long molecules that are folded over on themselves
–  The components of protein molecules are smaller molecules
called amino acids (AAs)
Amino Acids
•  There are 20 kinds of AAs
that make up all the proteins
that organisms have
–  Such as: alanine, asparagine, methionine…
– Made of Hydrogen,
Oxygen, Nitrogen,
Carbon, (HONC) and
Sulfur (S only in
methionine and cysteine)
Amino Acids
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• 
AAs are small molecules, but when strung up and folded over on
themselves to form a protein, they can be quite large
AAs are attached by peptide bonds
AAs are molecules whose properties are determines by their
electrochemical configurations
Amino acid strand
Each AA is like a bead on a necklace; electrochemical interactions
among neighboring AAs cause the strand to fold over on itself in
specific ways. The folded strand is a protein. Different AA sequences
will make different proteins.
Protein
•  Proteins interact with other substances
(including other proteins) in specific ways that
are determined by their electrochemical
properties.
•  There are only 20AAs out there—a finite number
(though in actuality the story is more complex
than this)
•  Different lengths and permutations of the AAs
that make up AA strands can lead to countless
varieties of proteins
Protein Functions
•  Structural proteins (collagen in skin, keratin in hair
and nails, proteins that make up muscle tissue, etc.)
•  Transport proteins (hemoglobin is a blood cell protein
that transports oxygen to body tissues)
•  Enzymes: proteins that catalyze (speed up) chemical
reactions in the body
•  Immune functions
•  Signaling functions: E.g., neurons in your brain
communicate with each other; these neurons are
proteins (and other substances)
Proteins
•  From where to organisms get the AAs
needed for body maintenance and
growth?
Food!
•  Foods are typically living
(or formerly living)
substances…
•  What substances are in
our food?
Lichtenstein 1962 Meat
Components of living things
(like food)
•  Protein: the stuff living things are made of, including
structural proteins like collagen, enzymes, etc.
•  Also water, carbohydrates, fats, vitamins/minerals, DNA
(nucleic acids), etc.
•  Proteins are long molecules that are folded over on
themselves
•  The components of protein molecules are smaller
molecules called amino acids (AAs)
Proteins to AAs
•  Organism A eats foreign protein that makes up organism B
•  Organism A breaks Organism B proteins into AAs:
digestion
•  Organism A s DNA restrings raw AAs up into Organism A
proteins
•  Organism A s DNA = blueprints
•  Organism B = the raw building blocks of proteins
Amino Acids to Proteins
…genes
Genes
Proteins
•  Genes determine what proteins get built from those raw AA
molecules
•  Genes are protein-coding units of DNA
•  You eat proteins of other living things, and break the protein into
amino acids; then, genes in your DNA re-string those amino
acids into proteins that YOU need to survive and reproduce
•  Bodies are made of proteins (fat and carbs and water are
essentially there to service these proteins)
•  Genes also code for enyzmes, which are proteins that regulate
everything, including development
•  Other parts of DNA do not code for proteins, and have either no
function (e.g. hitchhiker DNA), or function for self-regulation,
and other tasks—take advanced biology classes to learn about
these very cool things DNA does
•  What is DNA?
DNA
•  Deoxyribonucleic acid
•  A long molecule with a small number of constituent molecules
•  Shape is a double helix —think of a ladder that is twisted
DNA
• 
• 
• 
• 
• 
• 
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A sugar-phosphate
backbone, (I.e., the sides
of the ladder), and rungs”
made up of paired nucleic
acids
There are 4 nucleic acids:
adenine (A), thymine (T),
cytosine (C), and guanine (G)
[don’t worry about uracil (U),
for the purposes of this class
Note these are not AAs
A only bonds to T
C only bonds to G
A-T and C-G bonds are weak
Sugar-phosphate bonds are
strong
Lots of zipping action
Genes to Proteins
•  Protein synthesis
•  An elegant process…brief whiteboard illustration
• 
(RNA, Uracil, ribosomes: do not worry about these for this class)
•  Upshot: the sequence of nucleotides in DNA
determines the sequence of AAs in protein
manufacture (nucleic acid sequence maps to AA
sequence, but not one-to-one, and redundancy is built
into the system)
•  In other words, your DNA determines what proteins get
built out of the AAs that your body extracts from the
foreign proteins you eat
Genes
Proteins
Bodies
+
DNA
molecule
Amino acid
molecules
Cell parts, cells, and tissues
Amino acid strand
Organ
Protein
Body
DNA-Supercoil-Chromosome
Genes vs. Alleles
•  Genes: protein-coding regions of an
organism s DNA
•  Alleles: different forms of a gene at a particular
spot ( locus ) on the DNA; different allele
have slightly different DNA sequences, and
make slightly different versions of a protein
•  Here, the gene = eye pigment; with a few
exceptions, we all have eye pigment, and the
gene for this pigment is at the same spot on
our DNA strand for every person
•  Allele = brown eyes vs. blue eyes: even
though we all have eye pigment protein,
different people can have different versions of
the eye pigment protein
“Brown”
•  http://www.dailymail.co.uk/
sciencetech/article-2246888/
The-eyes-The-iris-picturedremarkable-incredible-closeshots.html
“Blue”
“Green”
“Green”?
Allele Frequencies
•  Allele frequency = the proportions of different alleles
among all the individuals in a specific population (in this
room, allele frequencies underlying eye color might be different from
frequencies in a Scandinavian population, which might have more
blue and green eyes people, or a population whose ancestors lived
near the equator, which might have more brown eyed people)
•  Whiteboard exercise on allele frequencies of eye color in
this class, in order to illustrate what evolution is; assume,
for now, that human eye color is determined by a single
gene with 3 possible alleles: brown, blue, and green
•  How many people total?
•  How many people with each of the (roughly) 3 colors of
eyes in this classroom?
Exercise:
Eye Color Allele Frequencies
•  100 people in class (assume, for now, that human eye color is
determined by a single gene with 3 possible alleles: brown, blue,
and green)
–  60 people have brown eyes
–  30 people have blue eyes
–  10 people have green eyes
•  The current generation of our classroom population, G1, has the
allele frequencies: 60% brown, 30% blue, and 10% green
• 
Everyone has the opportunity to reproduce. Many of us do. The
next generation s allele frequencies are…
Exercise:
Eye Color Allele Frequencies
•  The allele frequencies in the next generation, G2, are…
•  …again 60% brown, 30% blue, and 10% green
•  This means that allele frequencies have NOT changed over
generations: evolution has NOT occurred from generation 1 to
generation 2.
•  Now this 2nd generation has the opportunity to reproduce. Many do.
The allele frequencies in the next generation, G3, are…
Exercise:
Eye Color Allele Frequencies
• 
• 
• 
• 
The next allele frequencies in G3 are…
now 90% brown, 5% blue, and 5% green
(they had been 60% brown, 30% blue, and 10% green in G2)
This means that allele frequencies HAVE changed over generations:
evolution HAS occurred from G2 to G3.
•  Evolution is defined as a change in allele frequencies in a population
over generations
Exercise:
Eye Color Allele Frequencies
•  G3 allele frequencies are 90% brown, 5% blue, and 5% green
•  Now this generation has the opportunity to reproduce. Many do. The
next allele frequencies in the next generation, G4, are…
•  90% brown, 5% blue, 4% green, and 1% purple
•  This means that allele frequencies HAVE changed over generations:
evolution HAS occurred between G3 and G4.
•  But where did this new purple allele come from?
Mutations!
•  Where do new, different alleles come from? Mutations.
•  Mutations are random mistakes in the molecular sequence of DNA,
which can lead to changes in proteins that get built
•  A change in the DNA sequence of a gene will cause a change in the
protein that gets built
–  ATGCAAAATCGG=green eye pigment protein
–  ATGCAACATCGG=purple eye pigment protein
•  Origins of mutations include radiation (x-rays, solar rays, other cosmic
rays, nuclear waste), various non-living substances (asbestos, cigarette
smoke), living substances (viruses), unknown causes, etc.
•  Only heritable mutations are relevant to the evolutionary process
because evolution is a process that occurs over generations
•  Not all mutations that occur in living things are heritable; there is an
important difference in the heritability of mutations in multi-celled vs.
single-celled organisms...
Genes (DNA segments)
•  Genes are protein-coding regions of an organism s DNA
•  (1) They direct protein synthesis
•  (2) They ALSO replicate, or reproduce, over generations, as
they are passed from parents to offspring (offspring inherit
their parents genes)
–  (a) in single-celled organisms, one mother (or parental )
cell s genes double then divide and are passed on to two
daughter (or offspring ) cells (the parent cell no longer exists
—its body s proteins now make up the bodies of two offspring)
–  (b) in multicelled organisms, there are two kinds of cells: somatic
cells and germ cells:
freshwater paramecium
(single-celled)
•  (i) somatic cells (such as human skin cells), live only as a part of the parental
body; somatic cell genes build proteins for the parent s body; reproduction of
somatic cells involves gene replication, but the new cells remain a part of the
parental body
•  (ii) germ cells (such as sperm and eggs) are housed in the parental body; then,
at the time of reproduction, a germ cell leaves the parental body, and develops
a new multicelled body of its own
•  THE point: only germ cell genes can make it into the next generation for
multicelled organisms like humans
red-tailed hawk
(multicelluled)
Reproduction in
Single vs. Multi-celled Organisms
single-celled mother
multi-celled mother
Somatic line cells
All genes reproduce
by doubling
½ of reproduced
genes passed to
each of two
identical, singlecelled daughters
Germ line cell
*The somatic line cells ARE the
germ line cells
multi-celled daughter
At reproduction, germ line cell leaves
mother s body and multiplies, creating new
somatic cells for its daughter body, and, at
some point, a subsequent germ line of cells
that the daughter can transmit into the next
generation; germ line = eggs and sperm in
sexually-reproducing species
Germ line cell…
Heritability in
Multi-celled Organisms
•  Mutation must be in germ
line of cells to be passed to
offspring; only mutations in
the germ line heritable, and
thus subject to the process
of evolution
•  Mutations in the somatic line
can lead to new proteins
(usually bad) being built in
the maternal body
( cancer ), but these alleles
are NOT passed to the next
generation; they die with the
mother s body
Germ line cell
Heritability in
Single-celled Organisms
X-ray radiation
causes a
mutation in this
parental gene
(green)
x&
Somatic and germ line are the
same, so all mutations in
parent will be passed to
offspring; that is, all mutations
are heritable
Evolution
•  Heritable alleles are passed from parent to
offspring over generations.
•  Evolution is change in allele frequencies in
a population over generations.
•  Natural Selection is one type of evolution
(there are 4…)
Definitions and Types of Evolution
•  There are 4 causes of changes in the allele
frequencies in a population over time:
–  (1) Migration of individuals in or out of a population can cause the
allele frequencies to change (e.g., a bunch of red eyed people join
our population in the next generation)
–  (2) Mutations can cause allele frequencies to change (e.g., one
person s child happens to be born with a mutated allele that
produces purple eyes)
–  (3) Genetic drift occurs when a random event NOT related to
one s alleles alters the allele frequencies in a population (e.g., the
5 blue eyed people in our population happen to fall off a cliff,
erasing all blue genes from the subsequent generation—and
having blue eyes had NOTHING to do with falling)
–  (4) Natural selection…
Natural Selection
•  Natural selection is change in allele
frequencies in a population over
generations due to the causal effects
alleles have on reproduction
•  Natural Selection is nonrandom,
differential propagation of alleles
Natural Selection
•  If reproducing entities exist, if variations are heritable, and if
variations have reproductive consequences, then over time,
the entire population will come to possess the reproductively
superior variation
–  *note that for multicelled organisms, these variations are in the germ
line of cells
•  In terms of genetics: Over generations, alleles that build
proteins that promote their own reproduction relative to the
rest of the alleles in the population will reproduce more than
the population’s alleles that build proteins that hinder their
own reproduction.
•  The best-reproducing genes, and the traits they build,
reproduce best.
•  Simple, and NOT circular, as time only goes in one direction.
The Modern
Evolutionary Synthesis
•  A union of ideas from different branches in biology that provides a
logical account of the physical process of evolution; links are made
over time with regard to:
–  1850s-1890s: Darwin s ideas
–  Early 1900s: Mendel s (earlier) work was rediscovered and
incorporated
–  Starting in 1920s: work by population geneticists Haldane, Wright,
Morgan, and others
–  Further advances in the understanding of DNA (Watson, Crick, and
Franklin) in mid 1900s
–  In later 1900s: ideas elaborated by Hamilton, Maynard-Smith, and
Williams
–  Also in late 1900s; ideas about genes, evolution, and adaptations—and
particularly their roles in human life—were popularized by Dawkins,
challenged by Gould, etc.
•  Today, the synthesis is accepted by most working biologists