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Lesson Outline Introduction Concept 1: Sexually reproducing organisms make sex cells or gametes. Concept 2: Genes are stable, passed on in sex cells and control traits Concept 3: Genes are a part of the chromosome and are found in pairs in somatic cells. Concept 4: Genes can change on occasion and the alternative version or allele may control the trait Concept 5: Individuals can be homozygous or heterozygous. Concept 6: Gene pairs associate and then separate during gamete formation Concept 7: Gametes combine at random to form the individuals in the next generation. Concept 8: One allele can be dominant over another or show a lack of dominance. Concept 9: The segregation of genes allows geneticists to make predictions. Concept 10: Segregation can be predicted based on independent assortment.

Just the facts Rate Me 1 2 3 4 5 Concept 3: Genes are a part of the chromosome and are found in pairs in somatic cells. The idea that the genes which control a specific trait are found in pairs in somatic cells was proposed by a geneticist who never saw a gene. Gregor Mendel didn’t even know about chromosomes when he proposed this idea. He observed a pattern of inheritance in pea plants that could be explained by this idea. Now we know that genes are in pairs in somatic cells because the chromosomes are in pairs. A cell will have two of each kind of chromosomes (with the exception of sex chromosomes in one of the sexes) and therefore two of each of the genes found on those chromosomes. Fig. 6: Genes are in pairs in somatic cells because chromosomes are in pairs. The paired chromosomes seperate during gametes formation. Comments Be the first to write a comment... Add Comment

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This project was supported in part by the National Research Initiative Competitive Grants CAP project 2011-68002-30029 from the USDA National Institute of Food and Agriculture, adminstered by the University of California-Davis and by the National Science Foundation (NSF), Division of Undergraduate Education, National SMETE Digital Library Program, Award #0938034, administered by the University of Nebraska. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the USDA or NSF.
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