Anthro 1 Spring 24 DNA PDF

The Biological Basis of Life – genes and DNA (deoxyribonucleic acid)  DNA Structure and Function  DNA Replication  Protein Synthesis  Exemplifies how the complexity and diversity of life is generated from a simple set of building blocks! Reasons to study genetics in this class: Understand how va...

The Biological Basis of Life – genes and DNA (deoxyribonucleic acid)  DNA Structure and Function  DNA Replication  Protein Synthesis  Exemplifies how the complexity and diversity of life is generated from a simple set of building blocks! Reasons to study genetics in this class: Understand how variation and inheritance works – Natural Selection Understand how DNA can inform on our ancient past – phylogenetic relationships between us and ancient creatures Are genes like a blueprint for the phenotype? A better analogy is that the genes are like a recipe A set of instructions guiding a multi-step process The Cell Prokaryotes – single-celled organisms, no nucleus Eukaryotes – cell that possesses a wellorganized nucleus Plasma membrane Cytoplasm Nucleus Organelles *mitochondria *ribosomes Nuclear DNA Mitochondrial DNA Eukaryotic Cell Prokaryotic cell Genes: … are segments of a molecule called DNA DNA Functions: 1. Storage of genetic information 2. Self-duplication & inheritance. 3. Expression of the genetic message: DNA’s major function is to code for proteins. DNA Structure I - Double helix formed by two chains of nucleotides Nucleotides: – Sugar—Deoxyribose – Phosphate Group – Nitrogenous Bases: Adenine, Thymine Cytosine and Guanine  DNA is composed of 2 chains of nucleotides that form a double helix shape.  The two strands are antiparallel.  The backbone of the DNA molecule is composed of alternating phosphate groups and sugars  The order of the bases in the DNA chain – in triplet, acts as a code (or language) that governs your growth, development and body maintenance. The complimentary nitrogenous bases form hydrogen bonds between the strands (rungs of the ladder) A is complimentary to T and G is complimentary to C. DNA Model DNA Replication – in the nucleus DNA separated into two ‘daughter’ strands Each acts as a template for formation of new DNA molecule “semiconservative” Replication fork Enzymes: – Helicase – Polymerase Free-floating nucleotides DNA replication animation DNA The Secret of Life - PBS Protein Synthesis  One of the primary functions of DNA  Transcription  Translation  RNA  Proteins  Structural components of tissues  Enzymes  Hormones  Ribonucleic acid  Composed of chains of amino acids (Polypeptide)  Amino acids are coded for by triplets of DNA – three sequential nucleotides Hemoglobin Molecule Transcription – 1 st step in the making of a protein – RNA makes a copy of the gene  Unzipping of DNA helix  Synthesize RNA copy of DNA  3 types—mRNA, tRNA, rRNA  Different sugar - Ribose  Uracil replaces Thymine  Single stranded helix Three base codon corresponds to DNA triplet = codes for amino acids The Genetic Code – amino acids Posttranscriptional processing Introns – noncoding sequences Exons – coding sequences What are introns…junk? 3 billion bases – only 2% contained within exons What are introns for? – Remnants of old genetic sequences preserved during evolution? – Sources of gene regulation – Sources of variation Translation – making proteins Occurs in cytoplasm of cell mRNA carries information from DNA - codons Ribosomes – reads the mRNA “message” tRNA – carry amino acids that correspond to the mRNA “message” Transcription and translation animation Youtube – DNA the Secret of Life, PBS SO… A gene is a segment of DNA that codes for a protein A DNA triplet codes for amino acid RNA makes copy of DNA and forms chains of amino acids Chains of amino acids form proteins DNA Code Mechanisms to protect against mistakes, but… – …what happens if there is a mistake? mutations, can be disastrous for the organism OR can be new source of beneficial traits…or BOTH! The Genetic Code – amino acids Mutations A permanent change in the nucleotide sequence in the DNA – Based on location - Somatic cell vs. germ-line – Based on length of sequence effected Gene-level vs. chromosomal mutations Mutations Types of mutations: Base substitutions (point mutation) – Missense – Nonsense – Silent Insertions and deletions What causes mutations Spontaneous mutations – by chance, mistakes – May occur in some regions at predictable rates! Induced mutations - exposure to harmful chemicals, radiation, etc. Sickle cell anemia Autosomal recessive disorder of hemoglobin Hemoglobin is a protein responsible for binding oxygen in red blood cells Point Mutation - Sickle Cell trait Pleiotrophic traits: 1 gene affects many traits Example: Sickle Cell Anemia 1 gene, 2 alleles Genotype Phenotype AA normal aa sickle cell anemia – early death Aa slight anemia Normal RBC Sickled RBC High frequency distribution of sickle cell allele Why so high? Malaria hypothesis Malaria is caused by single celled protozoan Plasmodium falciparum: Vector (agent of transmission) : Anopheles mosquito Genotype Fitness AA lower (many die of malaria) aa Zero, (all die of sickle cell anemia before reproductive age) Aa higher (only slight cases of malaria and sickle cell anemia) Balanced polymorphism: Natural selection favors heterozygous genotype because those individuals have greatest fitness. Both alleles maintained because heterozygous individuals have greatest fitness = heterozygote advantage Biocultural Evolution Sickle cell anemia illustrates the important evolutionary interaction between culture and environment in human evolution