chapter 14 part ii chromosomes and genes incomplete dominance, codominance, multiple alleles,...
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Chapter 14 Part II Chromosomes Chapter 14 Part II Chromosomes and Genesand 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.
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12-1 Mendelism and the Genotype12-1 Mendelism and the Genotype
A Incomplete Dominance and Codominance
1 Incomplete Dominance: offspring show traits intermediate between 2 parental phenotypes.- Red x white = pink- One allele only partially
dominant to partner
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2 Codominance: pattern of inheritance in which both alleles of a gene are expressed- Ex: A person with AB blood
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12-1 Mendelism and the Genotype12-1 Mendelism and the Genotype
B Genes that interact
1 More than one pair of genes may interact to produce the phenotype
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C Epistasis1 Epistasis: absence of expected phenotype as a
result of masking expression of one gene pair by the expression of another gene pair.
a Homozygous recessive masks effect of dominant allele at another locus.
b Ex: albino animals (aa) for melanin production prevent expression of hair and eye color
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D. Pleiotropy
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D. Pleiotropy
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E Multiple Allele
a There may be more than 2 alleles for one locus, but each individual inherits only two alleles
b Ex: Blood Type ABO gives 4 possible phenotypes: A, B, AB, O
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F Polygenic Inheritance
a Polygenic Inheritance: occurs when a trait is controlled by several diff. Allelic pairs at diff. loci
b Ex: Seed color and skin color
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12-1 Mendelism and the 12-1 Mendelism and the GenotypeGenotype
G Environment and Phenotype
a Both temperature and environment affect phenotype
b ex: plants like primrose and animals like Siamese cats and Himalayan rabbits
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12-2 Mendelism and 12-2 Mendelism and ChromosomesChromosomes
A Chromosomal Theory of Inheritance
1 Both chromo’s and alleles are paired in diploid cells
2 Chromo’s and alleles of each pair separate during meiosis so gametes have 1/2.
3 Chromo’s and alleles separate individually; gametes contain all combinations.
4 Fertilization restores diploid chromo # and pairs alleles.
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B Sex Chromosomes1 Autosomes - non-sex chromo’s that
are the same # and kind in between sexes
2 Sex Chromosomes determine if the individual is male or female
3 Males produce X-containing or Y-containing gametes, males determine sex
4 X-linked Gene is any gene located on X chromosome
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12-2 Mendelism and 12-2 Mendelism and ChromosomesChromosomes
C Sex-Linked Problems
1 X-linked alleles are designed as superscript to X chromosome
2 Heterozygous females are carriers; they do not show the trait but can pass it on.
3 Males are never carriers but express the one allele on the X chromosome
4 One form of color-blindness is X-linked
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12-3 Chromosomal Mutations12-3 Chromosomal Mutations
AChanges in Chromo #
1 Monosomy: indiv. only has one particular type of chromosome
2 Trisomy
3 Nondisjunction: failure
4 Polyploidy: offspring end up with more than two complete sets of chromo’s.
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Changes in Chromosomal Changes in Chromosomal StructureStructure
A Environmental Factors
1 Inversion
2 Translocation
3 Deletion
4 Duplication