From DNA to Evolution: Genetics and Natural Selection

Genetics - All organisms have a set of instructions that determine their characteristics - The instructions are called genes and are passed on to offspring from the parent Organism(s) - The instructions are organized into a code that is called DNA - The DNA molecule makes up an organism’s genes - DNA consists of segments called genes - The DNA is organized into structures called chromosomes that we find in the nucleus of A cell - DNA is made up of deoxyribose sugar molecules, phosphate molecules and nitrogenous Bases - The nitrogenous bases are the components that make up the DNA code - There are four nitrogenous bases in DNA: adenine, thymine, guanine, and cytosine - Abbreviated A, T, G, C - When DNAA replicates it unzips and new nitrogenous bases are added - The bases that will be added are known based on the rule of complementary base Pairing - If one strand is ATCGTGCA - Then the other is TAGCACGT Protein Synthesis - The proteins that make us up are created by instructions from our DNA - The DNA creates instructions in the form of mRNA

- The mRNA is sent to the ribosomes to build the proteins out of amino acids Mutations - A change in an individual’s DNA is called a mutation - Mutations will lead to a change in the proteins that are synthesized - Example: Sickle Cell Anemia Human Genome Project - During the 1990’s there was a major push to determine the entire sequence of Human DNA - This was called the Human Genome Project which was completed in 2003 - The hope was to learn all the genes and to be able to pinpoint characteristics and Problems Epigenetics - Researchers learned that the code was only part of the equation - Genes could be turned on or off which made understanding the characteristics we see Even more complicated - The study of gene expression is called epigenetics - Researchers study the changes in the epigenome - While the genetic code is important, the epigenome can change the traits - DNA is wrapped around proteins called histones - Two major factors in how lightly the DNA is wrapped around the histones are Methyl tags and acetyl tags - More methyl tags will silence the gene

- More acetyl tags will make the gene active Methylation - Although methylation always silences genes, some genes are good, and some are bad so We cannot say it is always a positive or always a negative thing - Methyl tags connect to cytosine typically in locations where the sequence contains a Cytosine and a guanine next to each other Acetylation - Less methyl tags will mean more acetyl tags that will connect to the tail of the histone And unwind the DNA to make genes more active What Influences the Epigenome? - Inheritance - The Environment Genetics to Consider - DNA replication - Protein Synthesis - Mendelian Genetics - Non-Mendelian Genetics - Epigenetics Evolution - Evolution is the change in a species over a long period of time - When we say a species has evolved, we mean that its entire population has changes in Some way not just an individual

Natural Selection - Refers to the way that nature influences the survival and extinction of different species - The environment is the key factor Phylogenetic Trees - Phylogenetic trees are constructed to show the evolutionary relationships between Species