Human Genetics and Evolution Genetics and Inheritance Natural

Human Genetics and Evolution • • Genetics and Inheritance Natural Selection Historical Fact of Evolution Humans Today and Agriculture Larry M. Frolich, Ph. D. Biology Department, Yavapai College

DNA and GENETICS • Cells divide and pass on instructions coded in DNA of chromosomes • Each chromosome is a huge DNA molecule with coded information • DNA has dual role: – DNA replicates to pass on information – DNA is transcribed to make proteins that run cell metabolism Larry M. Frolich, Ph. D. Biology Department, Yavapai College

DNA and chromosomes • Long DNA molecules (millions of base pairs long) in nucleus are called chromosomes • Each chromosome is organized and packaged or wrapped up with proteins giving it a certain shape • In humans, 23 pairs of chromosomes – 1 of each pair from mother – 1 of each pair from father • Total view of all 23 pairs is called karyotype Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Chromosomes • Each chromosome is a single DNA molecule wrapped up within a special group of proteins giving it a particular shape Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Genes and Genome • Genome: – entire DNA of cell (all DNA molecules) – also includes DNA of mitochondria, chloroplasts in eukaryotes – Thought question: Are viruses, phages, transposons part of genome? • Gene: – Region along DNA molecule that codes for 1 protein – usually 1000's of base pairs long – E. coli lac operon is first gene whose regulation and function was understood at molecular level in coding of DNA Larry M. Frolich, Ph. D. Biology Department, Yavapai College

DNA is transcribed and translated to make proteins that run cell metabolism • DNA is transcribed to m. RNA • m. RNA is translated to amino acid sequence • Amino acid sequence folds up into protein • Proteins catalyze reactions of cell metabolism • This process is called “gene expression”—the information in one region of the DNA—a “gene” —is being expressed so that the cell’s metabolism can function Larry M. Frolich, Ph. D. Biology Department, Yavapai College

2 steps of gene expression 1. Transcription – DNA is read to make a m. RNA in the nucleus of our cells 2. Translation – Reading the m. RNA to make a protein in the cytoplasm Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Overview of transcription and translation REMEMBER: A particular region of DNA that has the code to make a particular protein is called a “gene. ” Larry M. Frolich, Ph. D. Biology Department, Yavapai College

DNA is also structured to replicate • DNA is “double helix”— two complementary strands wound in a spiral • Strands separate and DNA replicates by filling in other half of each separated strand • Famous Watson-Crick model (Nobel prize) Larry M. Frolich, Ph. D. Biology Department, Yavapai College

DNA replicates to pass on information (to daughter cells in mitosis) Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Changes in DNA sequence • Mutation—change in DNA sequence. • Example: Changes in DNA allow bacteria to resist effects of antibiotics • Mutation changes DNA sequence, which in turn changes protein sequence that codes for a specific protein in one of the many cell metabolic pathways Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Mutations can spread through a population • Mutation allows cell to survive in a new environment--in this case, in the presence of penicillin. This type of beneficial mutations can result in more individual cells that are resistant to penicillin and can thereby grow colonies • The offspring or daughter cells then continue to spread throughout the population, especially where penicillin is present. This is natural selection leading to evolutionary change!! We have seen it happen. . . in the laboratory. . . in the "wild. " • Fifty years, ago, almost no bacteria were resistant to penicillin. Today, some penicillin resistant cells are found in virtually all bacterial populations. Larry M. Frolich, Ph. D. Biology Department, Yavapai College

How does evolution happen? • Darwin’s great idea—natural selection • Just like “artificial selection” for agricultural breeds (in fact, is there any difference—what is “artificial” about human involvement? ) Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Inheritance and Natural Selection • Some combinations of alleles, produced during meiosis and fertilization might be more advantageous • This is what leads to natural selection. Individuals with more advantageous traits will survive to reproduce and pass on those traits. • Darwin realized that slow changes in inherited traits, due to natural selection produced the great evolutionary history of life. • Before his synthesis of all the evidence, no one could make sense of living systems. Now, “Nothing in Biology Makes Sense Except in the Light of Evolution” • --Theodosius Dobzhansky Larry M. Frolich, Ph. D. Biology Department, Yavapai College

The Classic Example—Sickle Cell Anemia Washington University Sickle Cell Webpage Natural Selection DNA point mutation Cell/Organism effects Heredity/Spread through population Species/Community Larry M. Frolich, Ph. D. interactions Biology Department, Yavapai College

Evidence for historical fact of evolution • Fossil record – Most rocks contain fossils – Long-term change in biological communities – Transitions: origin of mammals, origin of birds • Anatomical similarities • Shared embryological features • Shared biochemical and genetic features Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Humans are primates • Our closest living relatives are monkeys and apes • We share a common ancestor, most recently with apes, farther into deep time with monkeys and even farther in with lemurs and tarsurs • The living species are not our actual ancestors—we need the fossil record to see them Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Fossil record of primates evolutionarily close to humans • • • Mediocre to increasingly good human fossil record (see Smithsonian review article) Not all fossils on direct ancestral line to humans Larry M. Frolich, Ph. D. Past shows many different human and human-like species living at one time Biology Department, Yavapai College

Accident of history—one human species today • Good solid evidence that living humans form one single species—Homo sapiens – Ability to interbreed – Little anatomical difference among populations – Little biochemical difference among populations – DNA and protein analysis show recent single common ancestor within 1 million years, perhaps only 200, 000 years ago • But past was different (evolution is not planned!) – H. neanderthalis (200, 000 years ago) – H. floresiensis (12, 000 years ago) Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Homo floresiensis (12, 000 years ago, Pacific Island) Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Comparison Neanderthal and Modern human skulls Good evidence that Neanderthals buried dead, had religion, cultural practices, used tools Imagine a world where another sentient, culturally-driven primate lived! Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Humans today • Dominate planet • Ecologists have often focused on “wild” ecosystems • But most landscapes now have some human elements, usually very strong effects • Is this good or bad? And for whom? Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Development of agricultural systems were evolutionary events Larry M. Frolich, Ph. D. Biology Department, Yavapai College

Larry M. Frolich, Ph. D. Biology Department, Yavapai College