ps6s - MIT Department of Biology 7.014 Introductory...

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MIT Department of Biology 7.014 Introductory Biology, Spring 2004 7.014 Problem Set 6 Solutions Question 1 a) Define the following terms: Dominant – In genetics, the ability of one allelic form of a gene to determine the phenotype of a heterozygous individual, in which the homologous chromosomes carries both it and a different (recessive) allele. Recessive – In genetics, an allele that does not determine phenotype in the presence of a dominant allele. Phenotype – The observable properties of an individual resulting from both genetic and environmental factors. Genotype – An exact description of the genetic constitution of an individual, either with respect to a single trait or with respect to a larger set of traits. Alleles – The alternate forms of a genetic character found at a given locus on a chromosome. Homozygous – In a diploid organism, having identical alleles of a given gene on both homologous chromosomes. An individual may be a homozygote with respect to one gene and a heterozygote with respect to another. Heterozygous – Of a diploid organism having different alleles of a given gene on the pair of homologues carrying that gene. Mendel’s First Law – Law of Segregation - In genetics, the separation of alleles, or of homologous chromosomes, from one another during meiosis so that each of the haploid daughter nuclei produced by meiosis contains one or the other member of the pair found in the diploid mother cell, but never both. Mendel’s Second Law – Law of Independent Assortment - During meiosis, the random separation of genes carried on nonhomologous chromosomes. Sex-Linked – The pattern of inheritance characteristic of genes located on the sex chromosomes of organisms having a chromosomal mechanism for sex determination. Haploid – Having a chromosome complement consisting of just one copy of each chromosome; designated 1n or n. Diploid – Having a chromosome complement consisting of two copies (homologues) of each chromosome. Designated 2n. 1
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Question 1, continued b) One summer, you decide to become an UROP student for a professor who studies the genetics of corn, Zea mays . When you cross the following a true-breeding strain of corn with purpled, smooth kernels to a true-breeding strain of corn with yellow, wrinkled kernels you find that the F 1 progeny all have purple, smooth kernels. You then cross two F 1 progeny and see the following in the F 2 generation. P 0 Phenotype AABB aabb P 0 Genotypes** Purple, Smooth Kernels Yellow, Wrinkled Kernels F 1 Phenotype AaBb F 2 Genotype** Purple, Smooth Kernels F 2 Phenotypes* # of F 2 Progeny Yellow, Wrinkled Kernels 56,251 Yellow, Smooth Kernels 167,879 Purple, Smooth Kernels 508,746 Purple, Wrinkled Kernels 170,435 F 2 Genotypes** aabb (1) aaBb, aaBB (3) AaBb, AABB, AaBB, AABb (9) Aabb, AAbb (3) i) Does the pattern above indicate a Mendelian method of inheritance for the traits of kernel color and kernel texture? Explain. The pattern above corroborates with a Mendelian mode of inheritance: (1) The breeding of two
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This note was uploaded on 05/02/2009 for the course BIOL 7.014 taught by Professor Walker during the Spring '05 term at MIT.

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ps6s - MIT Department of Biology 7.014 Introductory...

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