Chapter 15

Chapter 15 - Chapter 15- Chromosomal Basis of Inheritance...

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Chapter 15- Chromosomal Basis of Inheritance Locating Genes on Chromosomes Genes or hereditary factors are located on chromosomes In this chapter, we describe the chromosomal basis for the transmission of genes from parents to offspring, along with some important exceptions 15.1 Mendelian inheritance has its physical basis in the behavior of chromosomes Choromosomes and genes are both present in pairs in diploid cells; homologous chromosomes separate and alleles segregate during the process of meiosis; and fertilization restores the paired condition for both chromosomes and genes Chromosome theory of inheritance - Mendelian genes have specific loci (positions) on chromosomes, and it is the chromosomes that undergo segregation and independent assortment Behavior of homologous chromosomes during meiosis can account for the segregation of the alleles at each genetic locus to different gametes Nonhomologous chromosomes can account for the independent assortment of the alleles for two or more genes located on different chromosomes Law of segregation- two alleles for each genes separate during gamete formation Ex: R and r segregate at anaphase I, yielding two types of daughter cells for this locus then each gamete gets one long chromosome with either the R or r allele . Next, fertilization recombines the R and r alleles at random Law of independent assortment- alleles of genes on nonhomologous chromosomes assort independently during gamete formation Ex: alleles during loci segregate in anaphase I, yielding four types of daughter cells depending on the chromosome arrangement at metaphase I. compare the arrangement of the R and r alleles relative to the Y and y in anaphase I. Each gamete gets a long and
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This note was uploaded on 04/09/2008 for the course BILD 1 taught by Professor Boulanger during the Fall '08 term at UCSD.

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Chapter 15 - Chapter 15- Chromosomal Basis of Inheritance...

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