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 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 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 #5 #6 #7 #8 Amino Acid #6 Glutamic Acid

The “Mutated” Situation (HbS allele) DNA: GGA CAC CTC TTT Codon #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 normal sickle-cell trait 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 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 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) million people in the world 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: accessed May 5, 2009.

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: of-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

Source: US National Institutes of Health - National Institute of Allergy and Infectious Diseases [Public domain], ; downloaded 24 Nov Mechanism by which HIV attaches to and is absorbed into a CD4+ cell