Chapter Four - Six, Fifteen

Chapter Four - Six, Fifteen - I Sociology and Anthropology...

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Sociology and Anthropology 252: Chapters 4-6, 15 Outlines 1. Chapter Four: Genetics – From Genotype to Phenotype 1. From Genotype to Phenotype 1. Austrian scientist Gregor Mendel (1822-1884) had a sense of how genes worked almost 90 years before Watson and Crick figured out the structure and function of DNA. He made inferences about how genes worked based on observations of how specific traits of plants and animals were passed down generationally. 2. DNA functions include replication and protein synthesis. 1. Structural Genes: contain information to make proteins. These genes are surrounded by regulatory regions – sequences of bases that are important in initiating, promoting, or terminating transcription. 1. If these regulatory regions are altered or missing, the expression of the gene can be affected. 2. There must also be regulatory genes that further guide the expression of structural genes. 1. Structural genes may be quite similar across different (but related) species, so regulatory genes are critical in determining the form an organism, or species, takes. 3. Genotype and Phenotype: The genotype is the set of specific genes (alleles) an organism carries; it is the genetic constitution of that organism. The phenotype is the observable physical feature of an organism that is under some form of genetic control or influence. Direct Relationship: the observed phenotype is a direct product of the underlying alleles. In other situations, the genotype interacts with factors in the environment to produce a phenotype. In phenotypes that are the result of complex gene-environment interactions, it can be difficult to figure out the contributions each makes to the observable variation. 1. The ABO Blood Type System: illustrates a straightforward relationship between genotype and phenotype. Refers to a protein found on the surface of red blood cells, which is coded for by a gene located on chromosome 9. This gene has three alleles: A, B, and O. A and B stand for two variations of the protein, and O stands for the absence of the protein. 1. Because we are diploid organisms, we have two copies of each gene, one on each chromosome. If an individual has the same allele on each chromosome they are homozygous. If the alleles are different, they are heterozygous. 1. Phenotypic expression of the alleles for a gene depends on whether the genotype is heterozygous or homozygous. 2. An allele that must be present on both chromosomes to be expressed (homozygous) is a recessive allele. O is the recessive allele: in order for it to be expressed, one must be homozygous O. 3. An allele that must be present at only one chromosomal locus to be expressed is dominant. Both A and B are dominant to O and co-dominant with each other: only one copy is needed. 4.
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Chapter Four - Six, Fifteen - I Sociology and Anthropology...

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