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Chapter 14 Part II Chromosomes and Genes Incomplete dominance, codominance, multiple alleles, epistasis, polygenic inheritance, the chromosomal theory.

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Presentation on theme: "Chapter 14 Part II Chromosomes and Genes Incomplete dominance, codominance, multiple alleles, epistasis, polygenic inheritance, the chromosomal theory."— Presentation transcript:

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2 Chapter 14 Part II Chromosomes and Genes Incomplete dominance, codominance, multiple alleles, epistasis, polygenic inheritance, the chromosomal theory of inheritance, sex chromosomes, linked genes, and chromosomal mutations are covered in this chapter.

3 12-1 Mendelism and the Genotype A Incomplete Dominance and Codominance 1Incomplete Dominance: offspring show traits intermediate between 2 parental phenotypes. -Red x white = pink -One allele only partially dominant to partner

4 2Codominance: pattern of inheritance in which both alleles of a gene are expressed -Ex: A person with AB blood

5 12-1 Mendelism and the Genotype B Genes that interact 1More than one pair of genes may interact to produce the phenotype

6 C Epistasis 1Epistasis: absence of expected phenotype as a result of masking expression of one gene pair by the expression of another gene pair. aHomozygous recessive masks effect of dominant allele at another locus. bEx: albino animals (aa) for melanin production prevent expression of hair and eye color

7 D. Pleiotropy

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9 E Multiple Allele aThere may be more than 2 alleles for one locus, but each individual inherits only two alleles bEx: Blood Type ABO gives 4 possible phenotypes: A, B, AB, O

10 F Polygenic Inheritance aPolygenic Inheritance: occurs when a trait is controlled by several diff. Allelic pairs at diff. loci bEx: Seed color and skin color

11 12-1 Mendelism and the Genotype G Environment and Phenotype aBoth temperature and environment affect phenotype bex: plants like primrose and animals like Siamese cats and Himalayan rabbits

12 12-2 Mendelism and Chromosomes A Chromosomal Theory of Inheritance 1Both chromos and alleles are paired in diploid cells 2Chromos and alleles of each pair separate during meiosis so gametes have 1/2. 3Chromos and alleles separate individually; gametes contain all combinations. 4Fertilization restores diploid chromo # and pairs alleles.

13 BSex Chromosomes 1Autosomes - non-sex chromos that are the same # and kind in between sexes 2Sex Chromosomes determine if the individual is male or female 3Males produce X- containing or Y-containing gametes, males determine sex 4X-linked Gene is any gene located on X chromosome

14 12-2 Mendelism and Chromosomes CSex-Linked Problems 1X-linked alleles are designed as superscript to X chromosome 2Heterozygous females are carriers; they do not show the trait but can pass it on. 3Males are never carriers but express the one allele on the X chromosome 4One form of color-blindness is X-linked

15 12-3 Chromosomal Mutations AChanges in Chromo # 1Monosomy: indiv. only has one particular type of chromosome 2Trisomy 3Nondisjunction: failure 4Polyploidy: offspring end up with more than two complete sets of chromos.

16 Changes in Chromosomal Structure A Environmental Factors 1Inversion 2Translocation 3Deletion 4Duplication


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