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Mendelian Genetics Gregor Mendel ~ Father of modern genetics. Mendel was an Austrian monk and mathematician. One of his assignments in the monastery.

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Presentation on theme: "Mendelian Genetics Gregor Mendel ~ Father of modern genetics. Mendel was an Austrian monk and mathematician. One of his assignments in the monastery."— Presentation transcript:

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2 Mendelian Genetics

3 Gregor Mendel ~ Father of modern genetics. Mendel was an Austrian monk and mathematician. One of his assignments in the monastery was to tend the garden. Pea Plants Traits Self-pollination ~ purebred Cross-pollination ~ hybrid

4 Genes and Dominance Gene Allele Dominant Recessive Phenotype Genotype Homozygous Heterozygous Holt-Oram Syndrome Marfan’s syndrome

5 Segregation The separation of alleles on different chromosomes during meiosis. Each allele ends up in a different egg or sperm cell. Tt TTtt Diploid mother cell Haploid daughter cells

6 Fertilization Fertilization: The union of an ovum and a sperm cell. Zygote: The first new diploid cell of an individual made by fertilization.

7 Mendel’s Laws of Heredity Law of Segregation (1 st Law) ~ Alleles for the same gene are separated during meiosis when the chromosomes separate. Law of Independent Assortment (2 nd Law) ~ Genes on different, nonhomologous chromosomes assort independently during meiosis. (They are “shuffled” like cards.) Assortment occurs during meiosis. Principle of Dominance ~ Some traits are dominant, and some are recessive. Dominant traits will always be expressed when they are present.

8 Punnett Square ~ A device that is used to predict the possible gene combinations for a trait that two parents can pass to their offspring. Monohybrid cross ~ A cross of two parents to evaluate what happens with one set of alleles. In other words, seeing how one gene will be passed to offspring.

9 Purebred Parents: TT x TT P 1 Cross TT x tt F 1 Cross Tt x Tt Phenotypic Ratios: Show the ratio of the different possible phenotypes of offspring. Genotypic Ratios: Show the ratio of the different possible genotypes of offspring. Probabilities: Show the percentages of chance for each type of phenotype or genotype Tall vs. Short Pea Plants

10 Actual vs. Hypothetical A couple has a 50% chance of having a girl every time they have a baby. They have four children, and all are girls. What is the hypothetical number of girls and boys? What is the actual number of girls and boys?

11 Dihybrid Cross ~ Crossing the genes for two different traits at the same time. 9:3:3:1 ~ The phenotype ratio if both parents are heterozygous for both traits. TtYy x TtYy

12 Build-a-Baby Eyes –Cyclops dominant (E) –Binocular recessive (e) Appendages –Flippers dominant (A) –Legs recessive (a) Color –Green dominant (C) –Blue recessive (c) Body –Round dominant (B) –Pear-shaped recessive (b) Hair –Curly dominant (Z) –Bald recessive (z) Heads –One head dominant (H) –Two heads recessive (h) Use the penny to decide the genotype of your baby for each trait. Heads – dominant, Tails – recessive. Make a text box showing the different genotypes for your baby, then draw the baby according to what phenotypes he or she would show.

13 Dihybrid Cross ~ Crossing the genes for two different traits at the same time. 9:3:3:1 ~ The phenotype ratio if both parents are heterozygous for both traits. Tall, green father: Ttyy Short, yellow mother: ttYY

14 Linked Genes ~ Genes for different traits that are on the same chromosome, so they are passed on to offspring together.

15 Multiple Alleles There are more than two possible genes that can be inherited for a trait. Examples –Flower color –Blood type

16 Incomplete Dominance ~ Describes genes that are neither dominant or recessive. The traits show as a “mixed” phenotype. r ~ red allele y ~ yellow allele w ~ white allele rr ~ red flower yy ~ yellow flower ww ~ white flower ry ~ orange flower rw ~ pink flower

17 Co-dominance ~ Traits that have more than one dominant allele. Some traits have more than one possible dominant or recessive gene. For instance, blood type! Blood type is determined by proteins on the surface of your red blood cells.proteins Type ADominant Type BDominant Type ABCo-Dominant Type ORecessive

18 Co-dominance

19 Cows

20 Dihybrid Cross TYTytYty TYTTYYTTYyTtYy TyTTYyTTyyTtYyTtyy tYTtYYttYYttYy tyTtyy T = tall pea plant t = short pea plant Y= yellow pea pods y = green pea pods Fill in the missing offspring genotypes. What is the phenotype ratio for the offspring? What must the genotypes of the two parents be?

21 Bellwork: Do a dihybrid cross for the following, then show the genotypic and phenotypic ratios for the offspring. Pansy color is incompletely dominant. Broad leaves are dominant over narrow leaves. An orange pansy with broad leaves ryBb A red pansy with broad leaves rrBb Do a dyhbrid cross for a mother who is AB+ and her husband who is B-. Here are their genotypes: Mother: I A I B RrFather: I B irr What are the phenotype and genotype ratios for their potential children?


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