L05-Heredity Genetics.pdf

Siblings Twins Siblings Itahi Uchiha (left)...

Siblings Twins Siblings Itahi Uchiha (left) Sasuke Uchiha (right) Chinky-Minky photo is a screen grab from a YouTube video of Sony TV network Uchiha photos are from the respective Wikipedia pages https://www.crictracker.com/hardik-krunal-pandya-take-inspiration-from-pathan-brothers/#google_vignette https://www.youtube.com/watch?v=Mehz7tCxjSE § Heredity - blending hypothesis, particulate hypothesis § Mendel’s work, observations, and inferences § Practical applications: blood group, enhancing crop yield (potato, rice) § Organism: any one of us, causative agent of sore throat, dog, coconut tree, etc. § Instruction manual: genetic material A self-driven program! Drives the development of the organism Controls the functioning of the organism Software makes its own hardware J. Craig Venter § DNA is the genetic material of all known organisms on planet Earth Exception: some viruses § How did we arrive at this conclusion? Through a set of highly innovative experiments Mendel with his fellow monks Chapter 14 in Campbell Biology, 10th ed.  ? Instruction manual of life? http://clipart-library.com/clipart/558290.htm  Purple flowers White flowers Phenotype of flowers (observable property) § An organism’s full hereditary information § Now we know this to be the genome, consisting of DNA Purple flowers White flowers Phenotype of flowers (observable property) § A trait is a specific characteristic of an individual § Traits can be qualitative (such as eye colour) or quantitative (such as height or blood pressure) § A given trait is part of an individual’s overall phenotype https://www.genome.gov/genetics-glossary/Trait § Heritable traits were the most obvious visible manifestations before we knew about DNA § Heritable traits are phenotypic characters that are passed on from parents to offspring Eye color, hair color, propensity to get cancer,... https://www.genome.gov/genetics-glossary/Trait Blending hypothesis - similar to a color palette Color mixing Parents Son/daughter https://www.collinsdictionary.com/dictionary/english/palette § Mendel’s choice of experimental system: pea plants He was an avid gardener and mathematician https://en.wikipedia.org/wiki/Pea Figure 14.1 in Campbell Biology, 10th ed. § Available in many variations § A short generation time § Produce large number of offspring in each mating § Cross pollination is easy Well separated pollen producing and egg bearing organs § Examples of characters Flower color Seed color Seed shape Pod shape Table 14.1 in Campbell Biology, 10th ed. § Purple and white color are traits Variants of flower color § Yellow and green color are traits Variants of seed color Table 14.1 in Campbell Biology, 10th ed. Gregor Mendel chose characters that show distinct alternate forms Table 14.1 in Campbell Biology, 10th ed. Pollination between flowers of the same plant Pollination between flowers of different plants (of the same species) https://www.britannica.com/science/self-pollination Technique 1 Carpel: ovule and seed producing reproductive organ in flowering plants 2 (like female). Stamens Stamen: pollen-producing reproductive organ of a flower (like male). Parental generation Pea flowers have both! (P) Carpel 1: Remove the stamens of purple flowers so they cannot pollinate 3 2 & 3: Pollinate a purple flower carpel with the stamens of a white 4 flower 4: The fertilized purple flower will give rise to seeds which can be Results planted 5 First filial generation 5: Observe the offspring for the trait (purple, white or pinkish flowers?) offspring (F1) Figure 14.2 in Campbell Biology, 10th ed. Plant yielding Plant yielding purple flowers purple flowers X Plant yielding purple flowers Mendel made sure to choose only true breeding varieties before starting the experiments Plant yielding Plant yielding purple flowers purple flowers Plant yielding purple flowers X Plant yielding Back cross purple flowers Mendel made sure to choose only true breeding varieties before starting the experiments  P Generation (true-breeding parents) Purple White flowers flowers Figure 14.3 in Campbell Biology, 10th ed.  P Generation (true-breeding parents) Purple White flowers flowers F1 Generation (hybrids) All plants had purple flowers § No blending! § F1 are all purple! § Where did the white go? Table 14.1 in Campbell Biology, 10th ed. § Follow traits for at least the P, F1, and F2 generations Stopping experiments with the F1 generation → basic pattern of inheritance would have eluded Mendel Campbell Biology, 10th ed. p269  P Generation (true-breeding parents) Purple White flowers flowers F = filial (child) F1 Generation (hybrids) All plants had purple flowers Self- or cross-pollination (among the F1 generation) F2 Generation 705 purple-flowered 224 white-flowered plants plants Table 14.1 in Campbell Biology, 10th ed.  § F2 has white flowers that were missing in F1 § Purple flowers are in larger numbers § White flowers are fewer F2 Generation Recessive trait Dominant trait 705 purple-flowered 224 white-flowered plants plants Table 14.1 in Campbell Biology, 10th ed. § Follow traits for at least the P, F1, and F2 generations Stopping experiments with the F1 generation → basic pattern of inheritance would have eluded Mendel § Quantitative analysis of the F2 plants from thousands of genetic crosses Campbell Biology, 10th ed. p269 Table 14.1 in Campbell Biology, 10th ed. Table 14.1 in Campbell Biology, 10th ed. § Quantitative analysis of the F2 plants from thousands of genetic crosses § Deduce two fundamental principles of heredity: Law of segregation Law of independent assortment Campbell Biology, 10th ed. p269 Inheritance of each trait is determined by "units" or "factors" that are passed on to descendants unchanged Individual inherits one such unit from each parent for each trait Law of segregation Two units for each heritable trait separate from each other during gamete formation and end up in different gametes Campbell Biology, 10th ed. p269  PP Purple 1 (homozygous) Pp 3 Purple (heterozygous) Ratio 3:1 Ratio 1:2:1 Pp 2 Purple (heterozygous) pp 1 White 1 (homozygous) Figure 14.6 in Campbell Biology, 10th ed.  PP (homozygous) 1 § Flower color is purple even if one of the two units if P Pp (heterozygous) Dominant trait Ratio 1:2:1 Pp 2 § Flower color is white only when both units are p (heterozygous) Recessive trait pp (homozygous) 1 Figure 14.6 in Campbell Biology, 10th ed.  Genetic makeup P generation Purple PP Gametes Appearance (true breeding) p P White pp Table 14.1 in Campbell Biology, 10th ed.  Genetic makeup P generation Purple PP Gametes Appearance (true breeding) p P White pp F1 generation Genetic makeup Gametes Purple Pp Appearance P p Figure 14.5 in Campbell Biology, 10th ed. F2 Generation 705 purple-flowered 224 white-flowered plants plants Figure 14.5 in Campbell Biology, 10th ed.  F1 generation Gametes P p Sperm from F1 (Pp) Egg from F1 (Pp) P p Genetic makeup P PP Pp Purple PP, Pp p Appearance F2 generation Pp pp White pp 3 : 1 Figure 14.5 in Campbell Biology, 10th ed. There are two units for each character During gamete formation, each pair of units for a character segregates independently of two units for other characters § Inheritance of each trait is determined by "units" § An individual inherits one such unit from each parent for each trait § A trait may not show up in an individual but can still be passed on to the next generation § These are not consistent with the blending hypothesis of heredity § Particulate hypothesis: genetic material must be in the form of discrete units § The “particulate” hypothesis is the idea that parents pass on discrete heritable units § Gregor Mendel documented a particulate mechanism through his experiments with garden peas  § An organism’s collection of heritable units is like a deck of cards; not a pail of paint. § Like playing cards, these units can be shuffled and passed along, generation after generation, in undiluted form. https://www.thoughtco.com/standard-deck-of-cards-3126599 https://www.freepik.com/premium-vector/illustration-theme-big-colored-set-different-types-plastic-buckets-various-size- pails-paint-bucket-consisting-collection-accessory-paint-from-pail-wall-pail-by-paint-as-bucket-water_61470516.htm Campbell Biology, 10th ed., p267  Laws of probability govern Mendelian inheritance Rr Rr Segregation of Sperm Segregation of alleles into eggs alleles into sperm 1 2 R 1 2 r R R 1 2 R R r 1 1 4 4 Eggs r r 1 r R r 2 1 1 4 4 Figure 14.9 in Campbell Biology, 10th ed.  Which of these two is dominant?! Attached earlobe Free earlobe Figure 14.15b in Campbell Biology, 10th ed. § Phenylketonuria § Hemophilia § Sickle cell disease § Beta-thalassemia §... https://www.ncbi.nlm.nih.gov/omim § More than two allelic forms exist for most genes in a population § Example: allelic forms of a gene that determines our blood group (a) The three alleles for the ABO blood groups and their carbohydrates Allele IA IB i Carbohydrate A B none Figure 14.11 in Campbell Biology, 10th ed. (b) Blood group genotypes and phenotypes Genotype IAIA or IAi IBIB or IBi IAIB ii Red blood cell appearance Phenotype A B AB O (blood group) Figure 14.15b in Campbell Biology, 10th ed.  Walther Flemming Used a staining technique to visualize chromatin (DNA + proteins that together constitute chromosomes) https://en.wikipedia.org/wiki/Walther_Flemming  Homologous Gene location (locus) chromosomes Figure 14.4 in Campbell Biology, 10th ed.  “unit” for purple flower C T A A A T C G G T G A T T T A G C C A Homologous Gene location (locus) chromosomes Figure 14.4 in Campbell Biology, 10th ed.  “unit” for purple flower Active enzyme C T A A A T C G G T Enzyme for the synthesis of purple pigment G A T T T A G C C A Homologous Gene location (locus) chromosomes Figure 14.4 in Campbell Biology, 10th ed.  Homologous Gene location (locus) chromosomes A T A A A T C G G T Inactive enzyme T A T T T A G C C A “unit” for white flower Figure 14.4 in Campbell Biology, 10th ed.  “unit” for purple flower Active enzyme C T A A A T C G G T Enzyme for the synthesis of purple pigment G A T T T A G C C A Homologous One functional Gene location (locus) chromosomes allele suffices A T A A A T C G G T Inactive enzyme T A T T T A G C C A “unit” for white flower Figure 14.4 in Campbell Biology, 10th ed. § Genetic screening and counselling § Ability to diagnose (early) and treat diseases, among other things, has increased life expectancy Even agricultural productivity has to increase Food security: agricultural produce, animal farming, etc. § Example of enhancing crop yield Prof. Rajesh Patkar’s lab – higher yield of potato per acre + higher (∼1.5 times) protein content per kg of potato Flood-affected (10-day submergence) Rice fields of Arun Kumar Singh at village Khuruhuja, District Chandoli, UP, India Swarna + SUB1 Swarna  § Genetic crossing – rice Tolerant to being submerged Intolerant to submergence “Scuba” – hybrid variety § Scuba rice has been adopted by farmers in Bangladesh and India Huge impact on livelihood https://explorebiology.org/collections/genetics/plant-genetics-and-the-future-of-food § Inheritance of traits was known for several generations § Gregor Mendel’s seminal work – innovative in several ways Choice of pea plant and traits Starting from true breeding varieties Following up to the 2nd generation Working with a large sample size, quantitation § Heritable traits are passed on via two units