BIO 325 - Fall 2009 - Sample questions

BIO 325 - Fall 2009 - Sample questions - GENETICS (BIO 325)...

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GENETICS (BIO 325) Fall 2009 Sample questions __________________________________________________________________________________ 1. In Mendel’s experiments, dihybrids with round seed shape and yellow seed color were crossed with each other. Using the symbols R for the round seed shape allele, r for the wrinkled seed shape allele, Y for the yellow seed color allele and y for the green seed color allele, mention the proportion of plants with the following genotypes obtained from this cross: (a) R/r; Y/y (b) R/R; Y/y (c) R/r; y/y (d) r/r; y/y 2. The allele c causes albinism in mice ( C causes mice to be black). If the cross C/c x c/c is made, and there are 10 progeny, what is the probability that all the progeny will be black? 3. A couple without an ancestral history of Tay-Sachs disease (an autosomal recessive) have two normal children and an infant affected with Tay-Sachs. The sister of the husband wants to marry the brother of the wife; in such a mating, what would be the probability of their first child having Tay-Sachs disease? 4. Phenylketonuria (PKU) is a rare, human hereditary disease resulting from the inability of the body to process phenylalanine. PKU is manifested in early infancy and, if it remains untreated, generally leads to mental retardation. PKU is caused by an autosomal recessive allele with simple Mendelian inheritance. A couple intends to have children but consults a genetic counselor because the man has a sister with PKU and the woman has a brother with PKU. There are no other known cases in their families. They ask the genetic counselor to determine the probability that their first child will have PKU. What is this probability? 5. Shown below is human chromosome 5 with its banding pattern. (a) Is this chromosome a metacentric, submetacentric or a telocentric chromosome?
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(b) Identify the following regions on this chromosome: - the centromere - the telomeres 6. A rare inherited human condition (MOPD II) is observed in the following three families. Individuals marked with a / represent deceased individuals; those marked with an asterisk were used for linkage analysis in identifying the gene; where a number is written inside a symbol, it represents the number of siblings. From the following choices, select the most likely mode of inheritance of the human condition observed in these three families (the condition is common to all these families). (a) Autosomal recessive (b) Autosomal dominant (c) X-linked recessive (d) X-linked dominant (e) Mitochondrial 7. The occurrence of a disease is shown in the following pedigree. 2
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What is the most likely mode of inheritance of this disease? (a) Autosomal recessive (b) Autosomal dominant (c) X-linked recessive (d) X-linked dominant (e) Mitochondrial 8. Identify the most likely mode of inheritance (Autosomal recessive; Autosomal dominant; X- linked recessive; X-linked dominant; Y-linked; Mitochondrial) in the following pedigrees: (i) (ii) 3
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9. A diploid plant has a chromosome content of 2n = 4. Each diploid cell has one long pair and
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BIO 325 - Fall 2009 - Sample questions - GENETICS (BIO 325)...

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