chap 2 genetics problems

chap 2 genetics problems - Section 2.03 Answers to End of...

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Section 2.03 Answers to End of Chapter Problems Answers to Chapter Concept Problems 1) Definitions a) A gene cluster is a collection of genes that are physically located close to each other on a chromosome and which have a related function. The globin gene cluster in humans is an example. b) Heterozygous advantage indicates that the heterozygous genotype is more fit (reproduces more successfully, has a selective advantage ) than either homozygous genotype. For example, β A β S is more fit than β A β A or β S β S in an environment where malaria is prevalent. c) Dominant refers to a trait (phenotype) observed in a homozygote that is also observed in a heterozygote created by mating the dominant homozygote to a homozygote expressing a different, recessive trait. For convenience, the allele that corresponds to the dominant trait is also referred to as dominant (although, strictly speaking, this is not correct usage of “dominant ”). For example, normal (healthy) is dominant to sickle cell anemia, and the β A allele is said to be dominant to β S . d) An intron is an internal segment of the transcribed region of a gene that is removed from the pre-mRNA by a process called splicing. Introns are found in most eukaryotic protein coding genes and their pre-messenger mRNAs. For example, the human β -globin gene and pre-mRNA have two introns. e) The hemoglobin tetramer is a molecule composed of two α -globin polypeptides and two β -globin polypeptides, each of which contains a heme group. The hemoglobin tetramer is also simply called, hemoglobin. f) Hereditary anemia refers to all forms of anemia (abnormally low numbers of red blood cells) that are due to inheritance of a particular allele of a gene (and therefore are genetic). Sickle cell anemia is an example of a hereditary anemia . g) An exon is a segment of the transcribed region of a gene that is not removed from the pre-mRNA by splicing. Every intron is flanked by exons . For example, the human β - globin gene and pre-mRNA have three exons .
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h) Heterozygous refers to genotypes in which the alleles at a genetic locus differ. For example, β A β S , β A β E , and β A β C are three examples of heterozygous genotypes. i) Recessive refers to a trait (phenotype) observed in a homozygote but absent from the heterozygote created by mating the recessive homozygote to a homozygote expressing a different, dominant trait. For convenience, the allele that corresponds to the recessive trait is also referred to as recessive , although this is not true, strictly speaking. For example, sickle cell anemia is recessive to normal (healthy), and the β S allele is said to be recessive to β A . j) The term molecular disease is essentially synonymous to the term genetic disease, but is used to emphasize that the genetic disease is understood at the molecular level. For example, sickle cell anemia was the first genetic disease to be christened as a molecular disease when it was discovered that the sickle cell mutation changed the sequence of the β
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chap 2 genetics problems - Section 2.03 Answers to End of...

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