Download Deoxyribonucleic Acid

DNA, Proteins, and Ways We Are Different
Biological Anthropology
Remember these guys?
Let’s take a look!
A chromosome contains genes
and genes contain…
Deoxyribonucleic Acid
• Present in all living
organisms
• Amount varies from
organism to organism
• Species can read each
others’ DNA
DNA
• Sugar-phosphate
backbone”
• Bases are “rungs”
adenine = thymine
cytosine = guanine
Genome
the total DNA/genes of a species
• Homo sapiens
– app. 3,000,000,000 DNA bases
– 35,000 – 40,000 genes
• Honeybee – 300,000,000 DNA bases
• Fruit fly – 13,600 genes
• Bacteria – a few hundred to a few thousand genes
DNA Replication
• Produces two identical
strands from one
original strand
• Each side of the original
is a template for making
a new copy of its
complement
But what are genes used for?
Protein Synthesis
• A two stage process
– Transcription
– Translation
• Our players:
–
–
–
–
Messenger RNA (mRNA) – the locks
Transfer RNA (tRNA) – the keys
Ribosome (“locksmith)
Amino Acids
Protein Synthesis
•
1: Transcription
messenger RNA (mRNA) copy of gene is made
•
mRNA copy leaves nucleus and goes to cytoplasm
Protein Synthesis
2: Translation
• mRNA copy is “read” by ribosomes
• Ribosomes match tRNA to codons on mRNA
Proteins: the End Result
• One gene codes for
one protein
• Differences
between individuals
due (in part) to
differences in their
proteins
Protein Synthesis,
once again…
• A two stage process
1) transcription
2) translation
• The process whereby the DNA message is
converted into a protein product
for more information…
Web sites
http://www.dnalc.org/resources/
Key words
• DNA replication
http://en.wikipedia.org/wiki/
• Protein synthesis
http://www.johnkyrk.com/
• DNA translation
http://www.youtube.com/
• Transcription
Evolution defined
drum roll please…
A change in allele frequency from one
generation to another
This means that…
the unit of selection is the individual
while
the unit of evolution is the population
Some Examples of Variation in
Our Blood Cells
Let’s Start with the Outside…
ABO Blood Group
Alleles
A
B
O
codominant
recessive
Genotype
AA, AO
BB, BO
OO
AB
Phenotype
A
B
O
AB
ABO Differences
Rh (Rhesus) Blood Group
Alleles
Genotype
Phenotype
D
dominant
DD, Dd
Rh+
d
recessive
dd
Rh-
Maternal/Infant Rh Incompatibility
Let’s Go Inside…
The Classic Example
Red-Blood Cell Sickling
and Malaria
Red Blood Cells
App. 30 trillion RBC in the human body
you are both destroying (and making) new
red blood cells at a rate of around 2.7 million
cells per second.
Every red blood cell contains
about 270 million hemoglobin
molecules, each one capable of
carrying four oxygen molecules
Beta Hemoglobin
• Protein consists of 146 amino acids
• Gene consists of 438 bases (146 X 3)
• Protein comes in two forms
Two Forms of Beta Hemoglobin
• Normal Hemoglobin (A)
• Mutated Hemoglobin (S)
The “Normal” Situation
(HbA allele)
DNA:
GGA CTC CTC TTT
Codon
Amino Acid #6
#5
#6
#7
Glutamic Acid
#8
The “Mutated” Situation
(HbS allele)
DNA:
GGA CAC CTC TTT
Codon
Amino Acid #6
#5
#6
Valine
#7
#8
The Difference is in Codon #6
Normal allele: CTC Normal A.A.: Glutamic Acid
Mutated allele: CAC Substituted A.A.: Valine
Everything else is the same:
145 identical amino acids
437 identical DNA bases
Sickle-Cell
Alleles
Genotype
Phenotype
HbA
codominant
HbA HbA
normal
HbS
codominant
HbA HbS
sickle-cell trait
HbS HbS
sickle-cell anemia
Red Blood Cells
‘donut’ shaped
sickle shaped
A simple mutation with multiple effects
Sickle-Cell in the U.S.
• Sickle cell anemia is the
most common inherited
blood disorder in the US
• About 8% of African
Americans are carriers
of sickle cell disease
• More than 70,000 people
have sickle cell disease
• Two million people have
sickle cell trait
• Sickle cell disease occurs
in 1 in every 500 African
Americans
• Approximately 1 in 12
African Americans has
sickle cell trait
Heterozygote Advantage
What possible advantage
could sickle-cell offer?
Malaria
• Infectious disease
caused by
• Falciparum
plasmodium
• Mosquito is carrier
Malaria
• perhaps the most deadly organism in
the world (to humans)
• 300-500 million people in the world
• 1-1.5 million people die each year
Malaria
• Parasite infects blood
• Part of life cycle
occurs in red blood
cells
• Population
continuously infected
Distribution of Malaria
Distribution
of the HbS
allele
The Connection
• Heterozygote has greatest fitness in
malarial environment
• Both high in frequency
ABO Differences
Viruses
• Not alive
• Require host cell to
reproduce
• Symptoms and
effects relate to which
host cells are used
Viruses
• Viruses use the cells
genetic machinery to
make new copies
Influenza A Virus
•Highly variable surface
structures
•Mutates readily
•Avoidance behaviors
frequent handwashing
covering coughs
having ill persons stay home,
(except to seek medical care)
minimize contact with others in
the household who may be ill with
swine-origin influenza virus.
Model of the influenza A virus showing HA and NA receptors
projecting from the surface of the virus.
Source: http://www.udel.edu/chem/white/C647/FluVirus.GIF;
accessed May 5, 2009.
H1N1 Virus
H1N1 Virus
A “triple reassortment” virus
consisting of human, avian, and
swine influenzas
Virus strains 90% identical to H1N1
have been circulating in swine for
approximately 10 years
Combination of viral strains thought
to have arisen when live pigs were
transported between North America
and Eurasia
Source:
http://www.gate2biotech.com/originsof-the-swine-flu-virus/; accessed on
24 Nov. 2009
HIV Virus
• The hosts of HIV are
CD4 (aka T4 or T-helper)
cells
• These cells are part of the
body’s immune system
• Infection can lead to AIDS
From HIV to AIDS
• HIV+
– exposure to virus and
antibody production
• CD4 (t-cell) count
drops after infection,
rebounds, then
diminishes
• ≤ 200 = “AIDS”
– Acquired Immune
Deficiency Syndrome
Mechanism by which HIV attaches to and is absorbed into a CD4+ cell
Source: US National Institutes of Health - National Institute of Allergy and Infectious Diseases [Public domain],
https://commons.wikimedia.org/wiki/File%3AHIV_attachment.gif ; downloaded 24 Nov. 2015