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Chapter 11

Chapter 11. Introduction to Genetics. IV. MEIOSIS. Mendel’s principles require 2 things-1)each organism inherits a single copy for every gene from each parent.

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Chapter 11

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  1. Chapter 11 Introduction to Genetics

  2. IV. MEIOSIS • Mendel’s principles require 2 things-1)each organism inherits a single copy for every gene from each parent. • 2)When an organism produces its own gametes,those 2 sets of genes must be separated from each other so that each gamete has only 1 set.

  3. Interest Grabber Analyzing Inheritance Section 11-1 • Offspring resemble their parents. Offspring inherit genes for characteristics from their parents. To learn about inheritance, scientists have experimented with breeding various plants and animals. • In each experiment shown in the table on the next slide, two pea plants with different characteristics were bred. Then, the offspring produced were bred to produce a second generation of offspring. Consider the data and answer the questions that follow.

  4. I. The work of Gregor Mendel • _____________________=The scientific study of heredity. genetics

  5. Interest Grabber continued Section 11-1 Parents Long stems  short stems Red flowers  white flowers Green pods  yellow pods Round seeds  wrinkled seeds Yellow seeds  green seeds First Generation All long All red All green All round All yellow Second Generation 787 long: 277 short 705 red: 224 white 428 green: 152 yellow 5474 round: 1850 wrinkled 6022 yellow: 2001 green • 1. In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics? • 2. How do the characteristics of the second generation compare to the characteristics of the first generation?

  6. A. Gregor Mendel’s Peas • Austrian monk whose statistical work w/ pea plants yielded a greater understanding of biological inheritance • He knew each flower produces pollen,containing the male reproductive cells-sperm and female portion produces egg cells.During sexual reproduction,male and female cell join in ________-making a new cell that develops into an embryo • Pea plants self-pollinating fertilization

  7. identical • He started w/ true-breeding plants-meaning that if they are allowed to self-pollinate,they make offspring _________ to themselves. • 1 group ____ plants • 1 group ______ • 1 made only ______ seed • 1 made ______ seeds tall short green yellow

  8. Mendel wanted to produce seeds from male and female reproductive cells from 2 different plants,preventing self-pollination by cross-pollination,with 2 different plants as parents….This allowed him to cross- breed characteristics

  9. B. Genes and Dominance Traits • Mendel studied different characteristics. • These characteristics are called ______________-such as seed or flower color or height in humans • Studied 7 traits-see p.264-and he studied the offspring • The offspring are called F1(“first filial”…Filius and filia are Latin words for son and daughter) • __________________are the offspring of crosses of parents w/different traits. • Mendel expected characteristics to blend-like red+white=pink-This was not the outcome hybrids

  10. 2 conclusions: • 1) biological inheritance is determined by factors carried by one generation to another.we now call these chemical factors that determine traits___________________. • Different forms of a gene are called ___________________ genes alleles

  11. 2) The Principle of Dominance states some alleles are ________________and some are recessive • Alleles occur in pairs and only one allele w/ a certain trait needs to be present for a _________________trait • 2 alleles of that trait must be present for _______________traits. • Tall plants were dominant and short recessive. dominant dominant recessive

  12. Figure 11-3 Mendel’s Seven F1 Crosses on Pea Plants Section 11-1 Seed Shape Seed Color Seed Coat Color Pod Shape Pod Color Flower Position Plant Height Round Yellow Gray Smooth Green Axial Tall Wrinkled Green White Constricted Yellow Terminal Short Round Yellow Gray Smooth Green Axial Tall

  13. Principlesof Dominance Section 11-1 P Generation F1 Generation F2 Generation Tall Short Tall Tall Tall Tall Tall Short

  14. Principles of Dominance Section 11-1 P Generation F1 Generation F2 Generation Tall Short Tall Tall Tall Tall Tall Short

  15. Principles of Dominance Section 11-1 P Generation F1 Generation F2 Generation Tall Short Tall Tall Tall Tall Tall Short

  16. Interest Grabber Tossing Coins Section 11-2 • If you toss a coin, what is the probability of getting heads? Tails? If you toss a coin 10 times, how many heads and how many tails would you expect to get? Working with a partner, have one person toss a coin • ten times while the other person tallies the results on a sheet of paper. Then, switch tasks to produce a separate tally of the second set of 10 tosses.

  17. 1. Assuming that you expect 5 heads and 5 tails in 10 tosses, how do the results of your tosses compare? How about the results of your partner’s tosses? How close was each set of results to what was expected? 2. Add your results to those of your partner to produce a total of 20 tosses. Assuming that you expect 10 heads and 10 tails in 20 tosses, how close are these results to what was expected? 3. If you compiled the results for the whole class, what results would you expect? 4. How do the expected results differ from the observed results?

  18. C. Segregation • Mendel wondered if the recessive alleles had disappeared or were they still present in the F1 plants .He allowed all 7 kinds of F1 hybrids to produce an F2 generation by self-pollination

  19. F1 cross-recessive traits reappeared(~ ¼ F2 showed recessive trait) • Mendel said the alleles for tall and short segregated(separated) during formation of sex cells • Each gamete (Sex cell) carries a single copy of each gene • F1 produces 2 types of gametes-one has short allele and one has tall allele. • ______________letter stands for dominant allele and lower case letter for __________________.example:Tt T stands for tall and lower case for short. recessive big

  20. Probability and Punnett Squares • Likelihood for occurrence for a particular event is __________________________ • PAST OUTCOMES DO NOT AFFECT FUTURE OUTCOMES • Probability is used to determine genetic occurrences using a diagram called a ___________________-which can predict and compare genetic variations that will result from a cross. probability Punnett square

  21. homozygous • ____________________means the organism has the same 2 alleles for a trait---TT—also called true-breeding • _______________means the organism has 2 different alleles for a certain trait---Tt-also called hybrid. • ______________is the observed physical trait----example:tallness or shortness • ________________=genetic makeup or actual alleles----example:TT or Tt heterozygous genotype phenotype

  22. Tt X Tt Cross Section 11-2

  23. Tt X Tt Cross Section 11-2

  24. T t T t Tt TT tT tt 1 Genotypes:___TT__Tt_____tt Phenotypes:____tall _____short 2 1 3 1 Punnett squares

  25. Each offspring will have the same probability of a genotype and phenotype because each is ____________or a single occurrence • Larger the # of offspring ,the closer to_________________ • predicted ratio. segregated

  26. III.Mendelian Genetics • Mendel wondered if the segregation of one pr of alleles affected another(?) • A) Independent Assortment • To answer his questions ,he performed a ______________. • 1)Two-Factor Cross F1 • Crossed truebreeders w/ only round yellow peas (genotype RRYY) x plants w/wrinkled green peas(rryy) • Offspring were round yellow,establishing the dominance of RRYY • Resulting genotype RrYy 2 factor cross experiment

  27. rryy x RRYY

  28. 2) The Two factor Cross:F2 • All F1 plants were ______.He wanted to see how the alleles will segregate when F1’s are crossed w/ each other to make an F2 generation • F2 produced 556 seeds-315 round 7 yellow and 32 were wrinkled and green • ______seeds had a combination…Therefore seed shape separated separately from color. • This is known as ______________________-genes segregate independently during formation of gametes.This accounts for much of the variation in color The Principle of Independent Assortment Heterogeneous for seed shape and color 209

  29. Summaryof Mendel’s Principles • Inheritance of biological characteristics is controlled by genes from the parents • When there are 2 or more alleles of a gene,then one is dominant and one is recessive • Most sexually reproducing organisms have 2 adults w/ 2 copies of each gene-one from each parent. • Alleles usually segregate independently.

  30. C.Beyond Dominant and Recessive alleles • Exceptions to the rules • Majority of genes have more than 2 alleles. • Some are neither dominant nor recessive and multiple genes and alleles or genes control traits • 1 ) Incomplete dominance-one allele is not completely dominant over another one

  31. 2) ____________-both alleles contribute to the phenotype—example –in chickens the allele for black feathers is codominant with white---this results in __________offspring • 3) _______________-more than 2 possible alleles exist in a population(not in one organism-example-rabbits have 1 gene for coat color,but 4 possible alleles for that gene….also an example is genes for human blood type • 4)_____________-traits controlled by 2 or more genes’ INTERACTION-4 different genes cover probably control human skin color MULTIPLE ALLELES CODOMINANCE SPECKLED POLYGENIC TRAITS

  32. Applying Mendel’s principles • _____________________started using fruit flies to study genetics-______________________________________They are easy to study because they produce many offspring quickly….Mendelian genetics applied to them MORGAN Drosophilia melanogaster

  33. E. Genetics and the Environment • Traits not determined solely by genes • Traits determined by ____________________________ Interaction of the genes and the environment they are in.

  34. IV. MEIOSIS • Mendel’s principles require 2 things-1)each organism inherits a single copy for every gene from each parent. • When an organism produces its own gametes,those 2 sets of genes must be separated from each other so that each gamete has only 1 set

  35. Chromosome # • The sets of chromosomes will be homologous,meaning that one from male corresponds w/ one from female • A cell w/ both sets of homologous chromosomes is _______________,meaning 2 sets(2N)---For Drosophilia,2N=8-2 complete sets of chromosomes and 2 complete sets of genes. • Gametes,however contain a __________________#-1 set of chromosomes-for Drosophilia N=4. haploid diploid

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