* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download File - Groby Bio Page
Gene therapy of the human retina wikipedia , lookup
Gene therapy wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
Gene nomenclature wikipedia , lookup
Nutriepigenomics wikipedia , lookup
Medical genetics wikipedia , lookup
Transgenerational epigenetic inheritance wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Genomic imprinting wikipedia , lookup
Gene expression programming wikipedia , lookup
Genetic engineering wikipedia , lookup
Pharmacogenomics wikipedia , lookup
History of genetic engineering wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Genome (book) wikipedia , lookup
Population genetics wikipedia , lookup
Quantitative trait locus wikipedia , lookup
X-inactivation wikipedia , lookup
Designer baby wikipedia , lookup
Genetic drift wikipedia , lookup
Microevolution wikipedia , lookup
Theoretical genetics SA Definitions Homework Gene - A unit or section of DNA that is inherited and encodes a particular protein Allele - The form of a gene, in a diploid organism there will always be a pair of alleles for each gene – one from each parent Locus - The location of a gene on a chromosome – the position is the locus (plural loci) Phenotype - The appearance of a characteristic. How a genetic factor manifests itself e.g. eye colour, disease Genotype - The genetic factors that determine a characteristic. The combination of alleles that an organism possesses for a gene Definitions When one trait appears and the other does not it is said to be Dominant - ‘dominant’ over the other Recessive - When two copies of the allele are needed for the trait to appear Codominant - When both characteristics appear together in the heterozygote e.g. AB blood group Homozygous Heterozygous - when the alleles of a particular gene are identical. when the alleles of a particular gene are different. Diploid - a term applied to cells in which the nucleus contains 2 sets of chromosomes. Haploid - a term referring to cells that contain only a single copy of each chromosome eg the sex cells or gametes New Definition 2 or more genes that are located on the same chromosome and are Linkage - normally inherited together Theoretical genetics Learning objectives Success criteria Understand the basics of Explain the terms allele, theoretical genetics locus, phenotype, genotype, dominant, codominant and recessive Use genetic diagrams to solve problems Inheritance Gregor Mendel (often called the father of genetics). He investigated inheritance by crossing varieties of pea plants that had different characteristics. Monohybrid crosses – involving one gene (same as GCSE!) GCSE Recap Drawing monohybrid crosses Predicting Outcomes of Genetic Crosses Some characteristics are determined by only two genes (one from the mother, one from the father). Draw a genetic diagram to predict the outcome Boy or Girl? Monohybrid Cross Male: XY Female: XX This means sperm produced will either have the X gene or the Y gene Eggs produce will all have the X gene Possible Eggs Possible sperm GCSE Task Have a go at, at least one question per section, remember to write down the question number so you can SA Answers 1. T T t 2. TT Tt T t t t Tt Tt 3. Tt tt T T T t 4. Tt Tt T TT Tt t T t TT Tt t Tt tt Tt tt Answers 5. q Q q 6. Q q Qq qq q 7. Qq qq Q Q QQ QQ Qq Qq q q Q Q Qq Qq Qq Qq q Q q Q QQ Qq 8. Qq qq 9. R Answers R r 10. R R r RR Rr Rr rr Answer = 25% R r RR Rr RR Rr Answer = 0% 11. r R r 12. Rr Rr rr rr Answer = 50% r R R r r Rr Rr Rr Rr Answer = 0% 13. A a Answers a a 14. Aa aa Aa aa Answer = 50% A a a 15. A Aa Aa Aa Aa Answer = 0% B B b 16. BB Bb Bb bb Answer = 25% B B B b B BB BB BB BB Answer = 0% 17. B B Answers B b 19. BB BB Bb Bb Answer = 100% 18. Someone who has a faulty and a working allele, they do not have the disease. B B b 20. b BB Bb Bb bb Answer = 25% B b b B Bb Bb Bb Bb Answer = 100% A Level: Monohybrid Crosses Looking at one characteristic Shows what the offspring genotypes could be This first generation is known as F1 Crossing this first generation for the second generation would be known as F2 Steps to take when drawing a monohybrid cross 1. Choose one letter to represent N normal wings n – vestigial wings Parents genotypes NN Gametes N Genotypes for F2 generation NN Normal Ratio of F2 generation n Nn N Gametes nn N Genotypes for F1 generation Nn Phenotypes x Nn n Nn Normal 3 : 1 n N Nn n Nn Normal nn dominant and recessive alleles 2. Work out what the parental genotypes are and then what gametes they might produce 3. Work out what the offspring could be (All heterozygous Nn) 4. Look at what the phenotypes are in the F1 generation (All normal) 5. Second cross of offspring 6. Show gametes of F1 generation 7. Work out what the offspring could be 8. Look at what the phenotypes are in the F2 generation 9. Work out ratios Vestigial Same thing using punnett squares 1. Choose one letter to represent N normal wings n – vestigial wings Parents genotypes Gametes Genotypes for F1 generation Genotypes for F2 Generation Ratio of F2 generation NN N x nn N n N N n Nn Nn n Nn Nn N n N NN Nn n Nn 3 : 1 nn n dominant and recessive alleles 2. Work out what the parental genotypes are and then what gametes they might produce 3. Using a punnett square work out what the offspring of the F1 generation could be (All heterozygous Nn) 4. Look at what the phenotypes are in the F1 generation (All normal) 5. Second cross of offspring 6. Using a punnett square work out what the offspring of the F2 generation could be 7. Look at what the phenotypes are in the F2 generation 8. Work out ratios Exam question 1.The ability to taste the chemical PTC is determined by a single gene in humans with the ability to taste given by the dominant allele T and inability to taste by the recessive allele t. Suppose two heterozygous tasters (Tt) have a large family. a. Predict the proportion of their children who will be tasters and non-tasters. Use a Punnett square to illustrate how you make these predictions. b. What is the likelihood that their first child will be a taster? c. What is the likelihood that their fourth child will be a taster? 1.The ability to taste the chemical PTC is determined by a single gene in humans with the ability to taste given by the dominant allele T and inability to taste by the recessive allele t. Suppose two heterozygous tasters (Tt) have a large family. a. Predict the proportion of their children who will be tasters and nontasters. Use a Punnett square to illustrate how you make these predictions. Heterozygous tasters Tt X Tt T t T t TT Tt Tt tt 75 % Taster and 25% non-tasters b. What is the likelihood that their first child will be a taster? 75 % c. What is the likelihood that their fourth child will be a taster? 75% EXAM QUESTION Q2. In certain trees, smooth bark is dominant over wrinkled. a. Cross two trees that are heterozygous for smooth bark. b. If there are 100 offspring produced, how many will have wrinkled bark. Trees : Allele Key B = Smooth and b = wrinkled Heterozygote X Heterozygote Phenotype: Smooth X Smooth Genotype: Bb X Bb Offspring Genotype: Phenotype Ratio: B b B BB Bb b Bb bb BB :2Bb : bb 3 Smooth: 1 Wrinkled offspring : 75 Smooth : 25 Wrinkled Monohybrid Crosses – try these situations. What will the offspring be? Outline parental genotype, F1 genotype and phenotype Unattached and attached ear lobes. Unattached is dominant. Heterozygous female and homozygous recessive male. 2. Tall and short plants. Tall is dominant. Homozygous dominant female and heterozygous male. 1. Monohybrid Crosses – try these situations. What will the offspring be? Unattached and attached ear lobes. Unattached is dominant. Heterozygous female and homozygous recessive male. Parental Genotype: Ll x ll F1 Genotype: Ll or ll F1: Phenotype L l l Ll ll 50% Unattached l Ll ll 50% Attached Tall and short plants. Tall is dominant. Homozygous dominant female and heterozygous male. Parental Genotype: PPxPp P P F1 Genotype: PP or Pp P PP PP F1: Phenotype p Pp Pp 100% Tall GOLDEN RULES Homozygous dominant x homozygous recessive = all heterozygous. Heterozygous x heterozygous = 3 : 1 ratio Heterozygous x homozygous recessive (test cross) = 1 : 1 Codominance What is codominance? When both alleles are present they both affect the phenotype (equally dominant) For example: A & B in blood typing Snapdragon Flowers An example of codominance: both alleles are expressed in the phenotype when the plant is heterozygous Alleles code for red or white When one of each allele is present then the flower is pink Snapdragon Flowers – more detail Homozygous Red The 2 alleles for red flowers code for an enzyme which catalyses red pigment formation, hence the flowers are red Homozygous White The 2 alleles for white flowers do not code for the enzyme, so no pigment is produced, hence the flowers are white Heterozygous The one red allele codes for some pigment, but only enough to make the flower pink, not red Codominance: Punnet Squares Do not use one upper and one lower case letter, as we are not talking about recessive and dominant alleles Use 2 different letters Snapdragon Flowers Red flowers = CRCR White flowers = CWCW Pink flowers = CRCW TASK: Draw a punnett square for crossing a red flower with a white flower. Once you find out the F1 generation, draw a punnett square for crossing 2 of these plants to find out the F2 generation Codominance: F1 Generation Crossing a red flower with a white flower Male gametes Female gametes CR CR CW CRCW CRCW CW CRCW CRCW All offspring are pink Codominance: F2 Generation Female gametes Crossing the F1 to find the F2 (Crossing 2 pink flowers) Male gametes CR CW CR CRCR CRCW CW CRCW CWCW Offspring = 50% pink, 25% red, 25% white Homework Research and prepare a leaflet on sickle cell anaemia. It should include Causes at the genetic level Affect on protein structure Codominance Symptoms Worldwide distribution The link to malaria