Chapter 14 Part II Chapter 14 Part II Chromosomes and Genes 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.
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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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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.
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
2 Codominance: pattern of inheritance in which both alleles of a gene are expressed- Ex: A person with AB blood
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
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
D. Pleiotropy
D. Pleiotropy
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
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
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
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.
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
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