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1 Mendelelian Genetics I CAN: TELL THE ROLE OF MEIOSIS IN GENETIC VARIABILITY.
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Gregor Mendel (1822-1884) Studied the inheritance of traits in pea plants Developed the laws of genetics aka “Father of Genetics”
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Mendel stated that physical traits are inherited as “particles” Mendel did not know that the “particles” were actually GENES Particulate Inheritance
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Genetic Terminology Trait - any characteristic that can be passed from parent to offspring Heredity - passing of traits from parent to offspring Genetics - study of heredity
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Punnett Square A diagram used to show the probability of a trait being present in offspring.
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“Genes” Alleles - two forms of a gene (dominant & recessive) Dominant - stronger of two genes. Expressed in a cross; represented by a capital letter (R) Recessive - gene that shows up less often in a cross; is dominated or overpowered by the dominant gene; represented by a lowercase letter (r)
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More Terminology Genotype – genetic makeup or gene combination for a trait (e.g. RR, Rr, rr) Phenotype - the physical feature resulting from a genotype (e.g. red, white)
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Genotypes Homozygous genotype - gene combination where both alleles are alike (e.g. RR or rr); also called pure bred Homozygous genotype - gene combination where both alleles are alike (e.g. RR or rr); also called pure bred Heterozygous genotype - gene combination where the alleles are different (e.g. Rr); also called hybrid
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9 Mendel’s Laws
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Law of Dominance Some alleles are dominant and some are recessive.Some alleles are dominant and some are recessive. When combined in a hybrid, the dominant overpowers the recessive.Like RrWhen combined in a hybrid, the dominant overpowers the recessive.Like Rr The dominant form of the trait ALWAYS shows in the phenotype if ONE dominant gene is present.The dominant form of the trait ALWAYS shows in the phenotype if ONE dominant gene is present.
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Law of Dominance T = tall (dominant) t = short (recessive) TT – tall Tt – tall tt - short R = round (dominant) r = wrinkled (recessive) RR – round Rr – round rr - wrinkled Y = yellow (dominant) y = green (recessive) YY – YY – Yy – Yy – yy - yy - P = purple (dominant) p = white (recessive) PP – PP – Pp – Pp – pp - pp -
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Law of Segregation During meiosis, the two alleles responsible for a trait separate from each other. (when the homologous chromosomes separate) Alleles for a trait are "recombined" at fertilization Study diagram!!!
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Law of Segregation
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Let’s Practice Using SpongeBob!!! Assignments For Today!! Begin Spongebob Practice Sheet Watch Video to Better Understand How to use Punnett Squares. Watch Video to Better Understand How to use Punnett Squares. Practice Doing Punnett Squares – Spongebob Worksheet. Complete Lecture Quiz Paper Pet Genetics Power Notes
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Male Gametes Male Parent MEIOSIsMEIOSIs Meiosis Female Parent Female Gametes
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GENOTYPE vs. PHENOTYPE B – brown eyes (dominant) b – blue eyes (recessive) What are the possible genotypes for brown eyes? What are the possible genotypes for blue eyes? W – widow’s peak ( ? ) w – no widow’s peak ( ? ) Possible genotypes for having a widow’s peak: Possible genotypes for not having a widow’s peak:
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HETEROZYGOUS vs. HOMOZYGOUS F – free earlobe (dominant) f – attached earlobe (recessive) FF – homozygous Ff – ff - H – hitchhiker’s thumb ( ? ) h – no hitchhiker’s thumb ( ? ) HH – hh – Hh -
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PUNNETT SQUARES
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Trait: Seed Shape Alleles: R – Roundr – Wrinkled Cross: Homozygous Round seeds x Heterozygous Round seeds Genotype: Phenotype Genotypic Ratio: Phenotype: Genotypic Ratio: Phenotypic Ratio:
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Male Gametes Male Parent MEIOSIsMEIOSIs Meiosis Female Parent Female Gametes
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Male Gametes Male Parent MEIOSIsMEIOSIs Meiosis Female Parent Female Gametes
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ALLELE KEY TRAITDOMINANT (ALLELE)RECESSIVE (ALLELE) 1. 1 1. 2 1. 3 1. 4 1. 5 1. 6 1. 7 1. 8 1. 9 1. 10
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TRAITS FOR THE MALE… TRAITGENOTYPEPHENOTYPE 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
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TRAITS FOR THE FEMALE… TRAITGENOTYPEPHENOTYPE 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
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Male Gametes Male Parent MEIOSIsMEIOSIs Meiosis Female Parent Female Gametes Complete at least 2 Punnett Squares Using Parents Genotypes…Show the Percents.
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Last Part of Project Pick a DIPLOID # for your ORGANISMS and Draw a Karotype like the one on page 168 Be sure the last pair gives THE sex of each organism. Lastly, write or type a one page paper that explains the following: ITS NICHE (TOTAL WAY OF LIFE TYPE OF REPRODUCTION, ADAPTATIONS) DIET (CARNIVORE, HERBIVORE OR OMNIVORE) HABITAT..(NAME THE BIOME ) DESCRIBE THE CLIMATE YOUR HYPOTHESIS ABOUT HOW IT WENT EXTINCT ANY OTHER INTERESTING BIOLOGY STUFF YOU WOULD LIKE TO ADD TO SHOW THE TEACHER YOU ARE LEARNING
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Types of Genetic Crosses Punnett Square - cross involving a single trait e.g. flower color AKA Monohybrid cross Dihybrid cross - cross involving two traits e.g. flower color & plant height
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▪ Examines the cross of 2 different traits Y = Yellow (dominant) y = green (recessive) R = Round (dominant) r = wrinkled (recessive) Cross 2 heterozygous yellow, heterozygous round plants: what are the genotypes? Seed color Seed shape
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Law of Independent Assortment Alleles for different traits are distributed to the gametes independently of one another. This law can be illustrated using dihybrid crosses.
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Y = Yellow y = green R = Round r = wrinkled YyRr YyRr
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Summary of Mendel’s laws LAW PARENT CROSS OFFSPRING DOMINANCE TT x tt tall x short Tt 100% tall SEGREGATION Tt x Tt tall x tall 75% tall 25% short INDEPENDENT ASSORTMENT RrGg x RrGg round & green x round & green 9/16 round seeds & green pods 3/16 round seeds & yellow pods 3/16 wrinkled seeds & green pods 1/16 wrinkled seeds & yellow pods
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Non-Mendelian Inheritance
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Incomplete Dominance One trait is not dominant over the other. The offspring’s trait is a MIXTURE of the 2 parents. +
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Codominance One trait is not dominant over the other. BOTH alleles are expressed in the offspring. + = WWBB WB
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+ = Homozygous Red Roan Homozygous White
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Human Blood type AA or AO BB or BO AB OO
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EXIT TICKET……. COMPLETE ALL PARTS OF THE MONSTERS GENETICS WORKSHEET BE SURE TO DRAW AND COLOR MIKE… YOU WILL NEED GREEN AND YELLOW
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GENETICS WITH A SMILE EACH PARENT CREATE YOUR OWN BABY BASED ON IT’S TRAITS.. INCLUDE THE FOLLOWING ON YOUR BABY’S PICTURE: – BABY’S NAME & PARENT’S NAME – BIRTHDAY – CUTE HAIR BOW IF A GIRL! – NICE NECK-TIE IF A BOY!
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SEX LINKED TRAITS ▪ Genes located on sex chromosomes are called sex-linked genes. ▪ Y chromosome genes in mammals are responsible for male characteristics. ▪ X chromosome genes in mammals affect many traits.
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SEX LINKED TRAITS * Most sex linked (X-linked) disorders are recessive and show up only in males. * Females are carriers of sex linked disorders
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POLYGENETIC TRAIT ▪ Trait produced by 2 or more genes that interact ▪ Human skin color ▪ Human eye color Order of dominance: brown > green > blue.
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PEDIGREES ▪ A pedigree is a chart for tracing genes in a family ▪ Trace phenotypes to infer the genotypes -Male carrier Autosomal genes: widow’s peak -Male without trait -Male with trait -Female without trait -Female with trait -Female carrier -Male carrier
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Sex Linked genes: colorblindness M – normal color vision m - colorblind -Male without trait -Male with trait -Female without trait -Female with trait -Female carrier -Male carrier
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