*Note that lectures began the 21st of February. The week after exam 1 we watched a movie on Tuesday, and the following Thursday class was cancelled. 2/21/12GENES Introduction to Genetics- There are approximately 25,000 genes in the human body. - Genes are stretches of DNA that work together to perform specialized functions- To better understand genes, we need to discuss DNA- DNA is a chemical code that allows us to form, develop, and live (human functioning)- DNA is stored in the nucleus of every cell except for red blood cells. -Information encoded into DNA determines virtually every observable and many unobservable human characteristic.-People vary because their DNA varies-Every person has their own unique sequence of DNA (Except for MZ twins)-Each person's arrangement of genes is referred to as a genotype. Structure of DNA-Two fibers twisted around each other to form a double helix-Each fiber is referred to as a polynucleotide-Along the backbone of each polynucleotide is a sequence of nucleotides (also called bases)4 different types of basesA: AdenineT: ThymineC: CytosineG: Guanine-These four bases (nucleotides) make up the genetic alphabet. -AT always go together CG always go togetherHow are the two polynucleotides held together? -Through the bonding of bases.-Specifically, A pairs with T and G pairs with C and vice versa. -These bonds hold these two strands of DNA together. Ordering of Base Pairs -The ordering of base pairs is very important-Very Small divergences can alter drastically what we are studying-Humans and chimpanzees share over 96% of their DNAIntro to DNA-Humans share approximately 99.9% of their DNA-.1 percent of DNA is responsible for many of the changes among the human population. At various segments along DNA, contiguous base pairs work together.-These base pairs, working together, are called genes. ATCCAGGGTTAGAAT^ Thats just the front side the bottom would be redundant to write bc A would know would match up with T .. etc.-In reality, genes are made up of 1000 or more base pairs. What do Genes do?-They code for the production of proteins-Proteins are essential to life-Structural Proteins: Hair, tendons, fingernails, etc.-Functional Proteins: Coordinate actions and activities of the body. Intro to Genetics-Genes are configured on threadlike structures called chromosomes.-The human body contains 23 pairs of chromosomes; one pair from mom one from dad.-Females have two X chromosomes and males have an X and a Y chromosome. -Every person has two copies of most genes. One from mom one from dad.-The two copies make up the entire gene.-Each copy is referred to as an allele. -2 alleles = 1 gene. -We shouldn't talk about “gene for this, gene for that” what varies is the ALLELE-For most genes, only one allele exists in the population. -But for a small fraction of genes, there are at least two alleles that are in existence. -These genes are referred to as polymorphisms-Why?- Example with height Intro to Genetics-How do Genes Vary?1) Single nucleotide polymorphismsACGAGGAACCAGTTAACGAGCACCAGTTA2/23/12 & 2/28/2012Intro to Genetics-Variable number of tandem repeats (VCNTRs)-Different polymorphisms can affect the functioning of the human body-Same as STRs except more nucleotides are repeated (hundreds)-Short term tandem repeats (STRs)TAGGAATTATTATTATTATTATAGGAATTATTATTA- Genotype- each person’s unique sequence of DNA- Phenotype- measurable human characteristics- E.g., personal traits, behaviorsHow do genes affect phenotypes?- One gene, one disorder (OGOD)-Polygenic effects- Pleiotropic effectsOGOD- Single gene single phenotype-No single gene determine your behavior- This is false and one gene cannot dictate someone’s behaviorPolygenic effects- Many genes Single phenotypePleiotropic effect- one gene multiple phenotypesGenes and the environment- Genes and the environment often combine to create different behaviors and different personality traits- Not nature vs. nurture, but nature and nurture- Referred to as gene- environment interplayTwo main types of gene- environment interplay1. Gene X environment interactions (GxE)2. Gene X environment correlations (rGE)Gene X Environment Interaction- Genetic effects are only visible in certain environments- Two people in the same environment , may interpret it and react to it differently because of their unique genotypes- Ex: two siblings in the same environment that turn out to be very differentGxEs- GxEs can explain why children in the same family turn out differently- We filter and experience things differently- GxEs can explain why rehabilitation efforts work for some people but not for others- GxEs can explain why the environment does not have same effect on all people- Remember Caspi et al ‘s article - They found that the certain gene only had an effect in certain environment- This is a classic example of GxE- A growing empirical evidence has revealed the importance of GxEs in the etiology of crimeand delinquency- We often see that an environment is related to a person’s behaviors or their personality traits rGEs- RGEs refers to the close association between genes and the environmentPassive rGEs- Children receive two elements from their parents : genes and an environment- Passively receive both from their parents- The environment is largely a reflection of their parents genetic propensities- Previous example with IQ3/1/12Evocative RGE's -People elicit certain responses from their environment based, in large part, on their genotype.Engage in “niche-picking” Example: thrill seeking and skydiving ; delinquent peers. -What accounts for variation in our environment? We choose them. Ex. Some people are thrill seekers. Some people jump off airplanes. Which genes may relate to antisocial behavior?-Genes responsible for the production, transportation, and breaking down of neurotransmitters are the most promising.What are neurotransmitters?-Chemical messengers that allow for communication between neurons. Neurotransmitters-billion of neurons in the human brain-thousands of connections for each neuron. -Space between neurons -synaptic cleft or synapseNeurotransmittersNeurotransmitters are released from one neuron where they cross the synaptic cleft and relay the message to the adjacent neuron.Synapse– See Diagram of a Synapse* Two Processes: Reuptake and EnzymesNeurotransmitters-If either of these two processes malfunctions, then changes in emotions, temperament, and behaviors can occur.-In addition, certain medications