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  1. CH11

  2. Fig. 1. Difference between the outcomes from blending and from particulate inheritance. In post-Mendelian terms, we assume a single diallelic locus, and hence three diploid genotypes (AA, blue; Aa, green; aa, yellow). Under particulate inheritance, the population's variability is preserved from generation to generation. In contrast, the conventional wisdom of Darwin's day saw offspring inherit a blend of parents' characteristics, here represented as the average of the two parental shadings. The result is that the variability diminishes in successive generations (the variance is halved each generation if mating is at random) SCIENCE MAGAZINE B. MAY

  3. Why are peas so great to work with? 1 2 3 4 5 Technique Figure 11.2 Parental generation (P) Stamens Carpel Results First filial generation offspring (F1)

  4. Figure 11.4 • Review of terms…. • What is a locus? What are alleles? • Is this individual with these chromosomes in their cells homozygous or heterozygous? • What is the genotype? • If purple flower allele is dominant, what is the phenotype? Allele for purple flowers Pair of homologous chromosomes Locus for flower-color gene Allele for white flowers

  5. Figure 11.3-3 Experiment P Generation (true-breeding parents) Purple flowers White flowers F1 Generation (hybrids) All plants had purple flowers What So all F1 are Pp What are the genotypes of the gametes of these Pp plants? Self- or cross-pollination F2 Generation 224 white-flowered plants 705 purple-flowered plants

  6. Figure 11.6 Phenotype Genotype PP (homozygous) Purple 1 Pp (heterozygous) 3 Purple 2 Pp (heterozygous) Purple pp (homozygous) White 1 1 Ratio 1:2:1 Ratio 3:1

  7. Figure 11.3-3 Experiment P Generation (true-breeding parents) Purple flowers White flowers F1 Generation (hybrids) All plants had purple flowers Self- or cross-pollination F2 Generation 224 white-flowered plants 705 purple-flowered plants

  8. Imagine crossing a pea heterozygous at the loci for flower color (white versus purple) and seed color (yellow versus green) with a second pea homozygous for flower color (white) and seed color (yellow). What types of gametes will the first pea produce? • two gamete types: white/white and purple/purple • two gamete types: white/yellow and purple/green • four gamete types: white/yellow, white/green, purple/yellow, and purple/green • four gamete types: white/purple, yellow/green, white/white, and purple/purple • one gamete type: white/purple/yellow/green

  9. Imagine crossing a pea heterozygous at the loci for flower color (white versus purple) and seed color (yellow versus green) with a second pea homozygous for flower color (white) and seed color (yellow). What types of gametes will the first pea produce? two gamete types: white/white and purple/purple two gamete types: white/yellow and purple/green four gamete types: white/yellow, white/green, purple/yellow, and purple/green four gamete types: white/purple, yellow/green, white/white, and purple/purple one gamete type: white/purple/yellow/green For this cross assume white is dominant and yellow is dominant…. What different offspring will you get????

  10. Figure 11.8 316 916 316 116 Experiment YYRR yyrr P Generation Gametes yr YR F1 Generation YyRr Hypothesis of dependent assortment Hypothesis of independent assortment Predictions Sperm or Predicted offspring in F2 generation ¼ ¼ ¼ ¼ yr YR Yr yR Sperm ½ ½ YR yr ¼ YR YYRR YYRr YyRR YyRr ½ YR YYRR YyRr ¼ Yr Eggs YYRr YYrr YyRr Yyrr Eggs ½ yr yyrr YyRr ¼ yR YyRR YyRr yyRR yyRr ¾ ¼ ¼ yr Phenotypic ratio 3:1 YyRr Yyrr yyRr yyrr Phenotypic ratio 9:3:3:1 Results Phenotypic ratio approximately 9:3:3:1 315 108 101 32

  11. Twins…EACH of you should respond to each question on paper after you have a discussion in your group about your response! 1. Why are twins raised in different households considered so valuable to biologists? 2. What is heritability? (they talk about height in this article)

  12. FYI these graphs are not a result of twin analyses but are a result of studying inheritance through regression statistics. 3. Which graphs show hi, medium and low heritability? 4. What might a graph with the actual heritability of height look like? Draw one!

  13. 5. If heritability is high like .8 does that mean the environment is not important? 6. Why do we freak out when we learn the heritability of IQ is something like .75? Historical connections? 7. What are we learning from situations where identical twins differ in specific substantial ways despite being raised in the same household? (autism example) 8. So what is epigenetics? 9. There are several analogies towards the end of the article-what were they?

  14. http://erinjenne.blogspot.com/2011_02_01_archive.html

  15. Figure 11.10-2 P Generation Red CRCR White CWCW Gametes CR CW Pink CRCW F1 Generation ½ ½ Gametes CR CW Today…..What is this called? Is this blending inheritance???

  16. Albinism in humans occurs when both alleles at a locus produce defective enzymes in the biochemical pathway leading to melanin. Given that heterozygotes are normally pigmented, which of the following statements is/are correct? One normal allele produces as much melanin as two normal alleles. Each defective allele produces a little bit of melanin. Two normal alleles are needed for normal melanin production. The two alleles are codominant. The amount of sunlight will not affect skin color of heterozygotes.

  17. Imagine a locus with four different alleles for fur color in an animal. The alleles are named Da, Db, Dc, and Dd. If you crossed two heterozygotes, DaDb and DcDd, what genotype proportions would you expect in the offspring? 25% DaDc, 25% DaDd, 25% DbDc, 25% DbDd 50% DaDb, 50% DcDd 25% DaDa, 25% DbDb, 25% DcDc, 25% DdDdDcDd 50% DaDc, 50% DbDd 25% DaDb, 25% DcDd, 25% DcDc, 25% DdDd

  18. When a disease is said to have a multifactorial basis, it means that both genetic and environmental factors contribute to the disease. it is caused by a gene with a large number of alleles. it affects a large number of people. it has many different symptoms. it tends to skip a generation.

  19. Figure 11.12 What is this called???? What is going on???? BbEe BbEe Sperm ¼ ¼ ¼ ¼ bE Be be BE Eggs ¼ BE BbEe BBEE BbEE BBEe ¼ bE BbEe bbEe BbEE bbEE ¼ Be BBEe BbEe BBee Bbee ¼ be bbee BbEe bbEe Bbee 9 : 3 : 4

  20. Figure 11.13 1 64 20 64 15 64 15 64 1 8 1 64 6 64 6 64 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 8 1 64 AaBbCc AaBbCc Sperm Eggs Phenotypes: Number of dark-skin alleles: 0 4 3 6 1 2 5