Presentation on theme: "Chapter 14 Part II Chromosomes and Genes"— Presentation transcript:
1 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.
2 12-1 Mendelism and the Genotype Incomplete Dominance and CodominanceIncomplete Dominance: offspring show traits intermediate between 2 parental phenotypes.Red x white = pinkOne allele only partially dominant to partner
3 Codominance: pattern of inheritance in which both alleles of a gene are expressed Ex: A person with AB blood
4 12-1 Mendelism and the Genotype Genes that interactMore than one pair of genes may interact to produce the phenotype
5 EpistasisEpistasis: absence of expected phenotype as a result of masking expression of one gene pair by the expression of another gene pair.Homozygous recessive masks effect of dominant allele at another locus.Ex: albino animals (aa) for melanin production prevent expression of hair and eye color
8 Multiple AlleleThere may be more than 2 alleles for one locus, but each individual inherits only two allelesEx: Blood Type ABO gives 4 possible phenotypes: A, B, AB, O
9 Polygenic Inheritance Polygenic Inheritance: occurs when a trait is controlled by several diff. Allelic pairs at diff. lociEx: Seed color and skin color
10 12-1 Mendelism and the Genotype Environment and PhenotypeBoth temperature and environment affect phenotypeex: plants like primrose and animals like Siamese cats and Himalayan rabbits
11 12-2 Mendelism and Chromosomes Chromosomal Theory of InheritanceBoth chromo’s and alleles are paired in diploid cellsChromo’s and alleles of each pair separate during meiosis so gametes have 1/2.Chromo’s and alleles separate individually; gametes contain all combinations.Fertilization restores diploid chromo # and pairs alleles.
12 Sex ChromosomesAutosomes - non-sex chromo’s that are the same # and kind in between sexesSex Chromosomes determine if the individual is male or femaleMales produce X-containing or Y-containing gametes, males determine sexX-linked Gene is any gene located on X chromosome
13 12-2 Mendelism and Chromosomes Sex-Linked ProblemsX-linked alleles are designed as superscript to X chromosomeHeterozygous females are carriers; they do not show the trait but can pass it on.Males are never carriers but express the one allele on the X chromosomeOne form of color-blindness is X-linked
14 12-3 Chromosomal Mutations Changes in Chromo #Monosomy: indiv. only has one particular type of chromosomeTrisomyNondisjunction: failurePolyploidy: offspring end up with more than two complete sets of chromo’s.
15 Changes in Chromosomal Structure Environmental FactorsInversionTranslocationDeletionDuplication