Basic Genetics Concepts, Mendelian Inheritance & Engineering - PDF

1 GENETICS What is genetics? Genetics is the study of heredity -- the process in which a parent passes certain genes onto their children.” What does that mean? Children inherit their biological parents’ genes that express specific traits, such as some physical characteristics, natura...

1 GENETICS What is genetics? Genetics is the study of heredity -- the process in which a parent passes certain genes onto their children.” What does that mean? Children inherit their biological parents’ genes that express specific traits, such as some physical characteristics, natural talents, and genetic disorders. 2 Match the genetic terms to their corresponding parts of the illustration. o base pair o cell o chromosome o DNA (Deoxyribonucleic Acid) o genes o nucleus Illustration Source: Talking Glossary of Genetic Terms http://www.genome.gov/ glossary/ 3  4 Illustration Source: Talking Glossary of Genetic Terms http://www.genome.gov/ glossary/  HEREDITY describes how some traits are _________ passed from parents to their children. The traits are expressed by ______, GENES which are small sections of DNA that are coded for specific traits. Genes are found on ________________. CHROMOSOMES Humans have _______ TWO sets of _____ 23 chromosomes— _____ ONE set from each parent. 5 Within 15 minutes, use online resources or reference books to: a. Look up the definitions of the given words. b. Rewrite the definitions in your own words and note them in your notebook. 1. genes 2. Genome 3. Chromosomes 4. DNA 5. locus 6. allele 7. dominant 8. recessive 9. homozygous 10.heterozygous 11.genotype 12. phenotype 6 13.Mendelian Inheritance MENDELIAN INHERITANCE A trait may not be observable, but its gene can be passed to the next generation. § Each person has 2 copies of every gene—one copy from mom and a second copy from dad. These copies may come in different variations, known as alleles, that express different traits. 7 Mendel's garden on the abbey grounds where experiments in pea genetics were done. Why peas? Flower structure pollination and fertilization the offspring of peas n Law of Segregation n Only one characteristic can be found in a gamete n Ex. Blue eyes vs. brown eyes (can only have one of them) n Law of Independent Assortment n For two characteristics, the genes are inherited independently of one another n Also called the "Inheritance Law“ n Ex. If you had the genotype AaBb you would make four kinds of gametes: they would contain the combinations of either AB , Ab , aB or ab. n Law of Dominance- When an organism has two different alleles for a trait (is a hybrid or heterozygous), the allele that is expressed is the dominant one Ex. Blue eyes vs. Brown eyes (Bb- brown is expressed therefore it is dominant) n Punnett Square n Grid used for organizing genetic info and making predictions n When studying the inheritance of only one trait, called a monohybrid cross n For the first examples, we will only be testing the complete dominance condition (where one allele completely dominates over the other) 1. Determine parent genotypes (big letter for dominant, little letter for recessive) 2. Segregate alleles and place alleles of each parent on top and side of four-squared grid (mom’s on one side and dad’s on the other) 3. Combine parent alleles inside boxes (letters inside boxes show POSSIBLE genotypes of offspring- not ACTUAL) 4. Determine phenotypic ratio and possible genotypes in the following format: n Fraction, probability statement, phenotype (genotype) n Ex. ¾ cbetb (Could Be Expected To Be) purple (PP, Pp) ¼ cbetb white (pp) n MUST BE LIKE THIS EVERY TIME!!!! Yy x Yy Y = yellow, y = green Ss x ss S = smooth, s = rough n Purple flowers are dominant over white flowers in pea plants. Cross a heterozygous purple plant with a white plant. n Parent genotypes? n Pp n pp n Like tossing two coins at once (outcome of one doesn’t affect outcome of the other) n Involves two separate traits n How many letters will we use this time? n 2 different ones!! n Called a dihybrid cross n Figure out all possible allele combinations n Place combinations for both male and female on top and side of 16 square Punnett n Combine parent alleles inside boxes n Determine phenotypic ratios (no need to go through and do genotypes) n AaBb ―> n AB, Ab, aB, ab n AABB ―> n AB, AB, AB, AB (or just AB) n aabb ―> n ab, ab, ab, ab (or just ab) n AAbb ―> n Ab, Ab, Ab, Ab (or just Ab) n aaBB ―> n aB, aB, aB, aB (or just aB) n Aabb ―> n Ab, Ab, ab, ab (or just Ab, ab) n aaBb ―> n aB, aB, ab, ab (or just aB, ab) n RrYy x RrYy n R = round, r = wrinkled n Y = yellow, y = green 1. Figure out allele combinations n 1st plant? § RY, Ry, rY, ry n 2nd plant? § RY, Ry, rY, ry 2. Place on top and side of Punnett square/Fill in boxes 3. Figure out phenotypic ratios For example, two alleles in the gene for freckles are inherited from mom and dad: o allele from mom = has freckles F o allele from dad = no freckles f Child has the inherited gene pair of alleles, Ff (F allele from mom and f allele from dad). Child’s allele : Ff Child’s genotype: Ff Child’s phenotype: has freckles 29 n It’s not all as simple as I’ve made it out to be! n Not all traits are completely dominant n Several other patterns of inheritance n Incomplete dominance n Codominance n Sex-linked n Polygenic traits n Multiple alleles n Pleiotropy n Pattern of inheritance in which heterozygous offspring show a phenotype between the phenotypes of the parents (somewhere in the middle) n Neither allele expressed fully n Ex. Flower color in snapdragons n Red flower + white flower = pink flower n Ex. Cow color n Red (brown) bull + white cow = roan (pink) cow n Knowing that four o’clock flowers show a pattern of incomplete dominance, create a Punnett showing a cross of a two pink four o’clocks (r= red, w= white). n Pattern of inheritance where both alleles in the heterozygous offspring are fully expressed n Ex. Human blood type n Type = Phenotype, Letters = genotype n Type A: AA, AO (homo and heterozygous) n Type B: BB, BO (homo and heterozygous) n Type AB: AB (Only heterozygous) n Type O: OO (Only homozygous) n Knowing that blood type shows a pattern of codominance, cross a person with type O blood and one with type AB blood. n Phenotypic expression of an allele that is dependent on the gender of the individual n Carried on either sex chromosome (X or Y) n Remember: Men = XY, Woman = XX n Many more genes carried on the X chromosome, so many more X-linked traits than Y-linked traits n Ex. Hemophilia, color-blindness n If have one healthy X, it dominates over the infected X (in females) n If have only one infected X, Y can’t dominate over it n Knowing that color blindness is a sex- linked trait, cross a carrier female with a non-infected male and determine the probability of this couple having a color blind child. n Single gene affects more than one trait n Ex. Sickle cell disease, Marfan’s syndrome n One trait controlled by two or more genes n Ex. Human skin colors § Epistasis occurs when one gene masks or modifies the effect of another gene. The interaction can either enhance, suppress, or completely override the expression of a gene. § It involves interactions between genes at different loci. § Ex. Albino n More than two alleles for the same gene n Ex. Human blood type (phenotypes produced by 3 different alleles) SEATWORK #1  Scenario: In mice, the allele for black fur (B) is dominant over the allele for white fur (b). The allele for long tails (L) is dominant over the allele for short tails (l). A heterozygous black, heterozygous long-tailed mouse (BbLl) is crossed with a homozygous white, homozygous short-tailed mouse (bbll). Tasks: 1.Simplify the Problem to Focus on Each Trait: 1. Use a monohybrid Punnett square to predict fur color (B vs. b). 2. Use a monohybrid Punnett square to predict tail length (L vs. l). 2.Determine: 1. Genotypic ratio for each trait. 2. Phenotypic ratio for each trait. 3.Answer these questions: 1. What percentage of the offspring will have black fur? 2. What percentage will have long tails?  Scenario: In squash, the allele for yellow fruit color (Y) is dominant over green fruit color (y), and the allele for smooth skin (S) is dominant over rough skin (s). A plant heterozygous for both traits (YySs) is crossed with a plant that is homozygous recessive for both traits (yyss). Tasks: 1.List all possible gametes for each parent. 1. Heterozygous plant (YySs): 2. Homozygous recessive plant (yyss): 2.Create a dihybrid Punnett square for the cross. 3.Determine: 1. The phenotypic ratio of the offspring. 2. The genotypic ratio of the offspring. 4.Answer these questions: 1. How many offspring will have yellow and smooth fruits? 2. How many offspring will have green and rough fruits? 3. What percentage of the offspring will have yellow fruits with rough skin?  Scenario: In cattle, coat color shows codominance. The allele for red coat color (R) and the allele for white coat color (W) result in roan coat (RW) when both are present. This is combined with a separate trait for horn presence, where the allele for horns (H) is dominant over the allele for no horns (h). Cross a roan, horned cow (RWHh) with a white, no-horned cow (WW hh). Tasks: 1.List all possible gametes for each parent. 2.Create a dihybrid Punnett square. 3.Determine: 1. Genotypic ratio. 2. Phenotypic ratio. 4.Answer these questions: 1. How many offspring will have roan coats with horns? 2. What percentage of offspring will have white coats without horns? 3. How many offspring will have red coats with horns? Scenario: The ABO blood group is determined by a single gene with three alleles: IAIA: Produces A antigen (dominant). IBIB: Produces B antigen (dominant). ii: Produces no antigen (recessive). A person with blood type AA (genotype IAiIAi) is crossed with a person with blood type BB (genotype Ibi IBi). Tasks: 1.Create a Punnett square to predict the blood types of the offspring. 2.Determine: 1. The genotypic ratio. 2. The phenotypic ratio. 3.Answer these questions: 1. What are the possible blood types of the offspring? 2. What percentage of the offspring will have blood type ABAB? 3. What percentage will have blood type OO? Pedigree A chart of a family’s history in regard to a particular genetic trait Males are squares Females are circles Shading represents individuals expressing disorder Half shade represent a carrier Horizontal line between circle and square is a union Vertical line down represents children of that union Counselor may already know pattern of inheritance and then can predict chance that a child born to a couple would have the abnormal phenotype Have a look at the pedigree above? What does this tell you about the disease? Well the first and most obvious thing is that this disease is caused by a recessive allele, h. If you see two people who don’t have the disease producing one or more children who do, then this must be a genetic disease caused by a recessive allele. In the top generation, parents 1 and 2 do not have the disease, but they have three children 2,3,4 one of whom has the disease. What does this tell us about the genotype of parents 1 and 2 in generation I? Well if neither have the disease and they have a child who does, both 1 and 2 in the top generation must be heterozygous – Hh Anyone with the disease must be homozygous recessive hh. Have a look at generation II in the diagram above? The man, number 2, who is a sufferer and so genotype hh marries woman 1 who does not have the disease. They produce 4 children, three with the disease and one without. What must the genotype of the woman 1 be? Well she must be heterozygous Hh. How do we know? What children would she produce if she were a homozygous HH woman? A pedigree caused by a dominant allele would look very different. Every sufferer would have at least one parent who also suffers from the disease. Two sufferers producing some children who do not have the disease is indicative of a disease caused by a dominant allele. If we use the symbol P for the dominant allele that causes the disease, and p for the recessive allele that is “normal”, work out the genotypes of all 12 people on the diagram above. (5-10 minutes) A) Is the trait dominant or recessive? B) What are the most probable genotyped of I-1 and I-2? C) What is the probability that II-2 is Dd? D) What is the probability that II-1 and II-2 will have another normal offspring A) Look at the family of IV-9 and IV-10. If the trait is dominant, is it possible for them to have an affected offspring? B) If the trait is recessive, is it also possible for IV-9 and IV-10 to have an unaffected offspring? C) Based on your answers for a) and b), is the trait dominant or recessive? D) Give the Genotypes of the following 1. IV-9 2. IV-10 3. V-1 4. I-1 5. I-2 1.Pp 2.Pp 3.pp 4.Pp 5.PP or Pp 6.PP or Pp 7.pp 8.pp 9.Pp 10.pp 11.pp 12.pp Lec-8-DNA-Recombination.pdf GENETIC ENGINEERING WHAT IS THE DIFFERENCE BETWEEN THE MICE IN THESE TWO GROUPS? WHAT IS GENETIC ENGINEERING? Genetic engineering is the direct modification of an organism’s genome, which is the list of specific traits (genes) stored in the DNA. Changing the genome enables engineers to give desirable properties to different organisms. Organisms created by genetic engineering are called genetically modified organisms (GMOs).  HISTORY OF GMO DEVELOPMENT 1973: created first genetically modified bacteria 1974: created GM mice 1982: first commercial development of GMOs (insulin-producing bacteria) 1994: began to sell genetically modified food 2003: began to sell GMOs as pets (Glofish)  WHAT IS THE GMO PROCESS? § All genetic changes affect the protein synthesis of the organism. § By changing which proteins are produced, genetic engineers can affect the overall traits of the organism. § Genetic modification can be completed by a number of different methods: q Inserting new genetic material randomly or in targeted locations q Direct replacement of genes (recombination) q Removal of genes q Mutation of existing genes  GMO BACTERIA Bacteria are the most common GMOs because their simple structure permits easy manipulation of their DNA. One of the most interesting uses for genetically modified bacteria is the production of hydrocarbons (plastics and fuels) usually only found in fossil fuels. § Cyanobacteria have been modified to produce plastic (polyethylene) and fuel (butanol) as byproducts of photosynthesis § E. Coli bacteria have been modified to produce diesel fuel  ENGINEERING PLANTS How might genetic engineering modify plants to solve everyday problems? (Consider world hunger, weather problems, insecticide pollution…)  GENETICALLY MODIFIED CROPS GMO crop production in the US (2010): § 93% of soybeans § 93% of cotton § 86% of corn § 95% of sugar beets Example: § One common modified crop is Bt-corn. § A gene from the Bt bacteria is added so the corn produces a protein that is poisonous to certain insects but not humans.  Banana Vaccines Modified virus injected in sapling tree causes the bananas to contain virus proteins Venomous Cabbage Scorpion genes added to the cabbage prevent insects from eating it OTHER REASONS TO GENETICALLY MODIFY CROPS § Insect resistant § Herbicide resistant § Drought/freeze resistant § Disease resistant § Higher yield § Faster growth § Improved nutrition § Longer shelf life  ENGINEERING ANIMALS Could genetic engineering be used to modify any animals to solve problems?  BIOLUMINESCENT ANIMALS Uses: § Protein tracking § Disease detection using bioluminescent imaging (BLI) to identify different types of cells § Novelty pets (Glofish are available now)  Fast-Growing Salmon Genes from two other fish cause this salmon to continually produce growth hormones Less Smelly Cows Modifying bacteria responsible for methane production in cattle results in 25% less-flatulent cows  COULD SPIDERMAN BE REAL? Web-Producing Goats Spider genes in goats enable the production of spider silk in goat milk  GMO CONCERNS What are some concerns regarding genetically modified foods and animals? § Risk to human health; unsafe to eat § Harm to the environment and wildlife § Increased pesticide and herbicide use § Farmers’ health § Seed and pollen drift § Creation of herbicide-resistant super weeds § What about genetic engineering in humans? Nearly 50 countries around the world, including Australia, Japan and all of the countries in the European Union, have enacted significant restrictions or full bans on the production and sale of genetically modified organism food products, and 64 countries now have GMO labeling requirements.