DNA Proteins and Ways We Are Different Biological
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
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
Protein Synthesis • A two stage process – Transcription – Translation • Our players: – – Messenger RNA (m. RNA) – the locks Transfer RNA (t. RNA) – the keys Ribosome (“locksmith”) Amino Acids
Protein Synthesis • 1: Transcription messenger RNA (m. RNA) copy of gene is made • m. RNA copy leaves nucleus and goes to cytoplasm
Protein Synthesis 2: Translation • m. RNA copy is “read” by ribosomes • Ribosomes match t. RNA to codons on m. RNA
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
So… If we change the DNA message?
We change the protein!
Evolution defined drum roll please… A change in allele frequency from one generation to another
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 D dominant DD, Dd d recessive dd Phenotype Rh+ 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 (Hb. A allele) DNA: GGA CTC TTT Codon #5 #6 #7 #8 Amino Acid #6 Glutamic Acid
The “Mutated” Situation (Hb. S 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 Alleles Genotype Phenotype Hb. A codominant Hb. A normal Hb. S codominant Hb. A Hb. S sickle-cell trait Hb. S 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 Hb. S 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 üfrequent handwashing ücovering coughs ühaving ill persons stay home, (except to seek medical care) üminimize 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/C 647/Flu. Virus. GIF; accessed May 5, 2009.
H 1 N 1 Virus
H 1 N 1 Virus A “triple reassortment” virus consisting of human, avian, and swine influenzas Virus strains 90% identical to H 1 N 1 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. gate 2 biotech. com/originsof-the-swine-flu-virus/; accessed on 24 Nov. 2009
HIV Virus • The hosts of HIV are CD 4 (aka T 4 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 • CD 4 (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 CD 4+ cell Source: US National Institutes of Health - National Institute of Allergy and Infectious Diseases [Public domain], https: //commons. wikimedia. org/wiki/File%3 AHIV_attachment. gif ; downloaded 24 Nov. 2015
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