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 process1) 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/

http://en.wikipedia.org/wiki/

http://www.johnkyrk.com/

http://www.youtube.com/

Key words

• DNA replication

• Protein synthesis

• DNA translation

• Transcription

Evolution defined

A change in allele frequency from one generation to another

drum roll please…

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

Genotype

AA, AO

BB, BO

OO

AB

Phenotype

A

B

O

AB

Alleles

A

B

O

codominant

recessive

ABO Differences

Rh (Rhesus) Blood Group

Genotype

DD, Dd

dd

Phenotype

Rh+

Rh-

Alleles

D

d

dominant

recessive

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 bodyyou 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 TTTCodon #5 #6 #7 #8

Amino Acid #6 Glutamic Acid

The “Mutated” Situation(HbS allele)

DNA: GGA CAC CTC TTTCodon #5 #6 #7 #8

Amino Acid #6 Valine

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

Genotype

HbA HbA

HbA HbS

HbS HbS

Phenotype

Alleles

HbA

HbS

codominant

codominant

normal

sickle-cell trait

sickle-cell anemia

Red Blood Cells

‘donut’ shapedsickle 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

• More than 70,000 people have sickle cell disease

• Sickle cell disease occurs in 1 in every 500 African Americans

• About 8% of African Americans are carriers of sickle cell disease

• Two million people have sickle cell trait

• Approximately 1 in 12 African Americans has sickle cell trait

Heterozygote Advantage

What possible advantagecould 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/origins-of-the-swine-flu-virus/; accessed on 24 Nov. 2009

HIV Virus

• The hosts of HIV areCD4 (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

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

Mechanism by which HIV attaches to and is absorbed into a CD4+ cell