Discuss how the advent of recombinant DNA technology improved upon historical genetics research methods and
revolutionized genetic mapping techniques. What will be an ideal response?
ANSWER: Mutations play a central role in genetics. Historically, transmission of mutant alleles from
generation to generation was studied to discover the basic principles of genetics. In addition,
geneticists used induced and spontaneous mutations in laboratory organisms to dissect
biological processes such as metabolism, cell structure, and development. Gradually,
mutational analysis became the method of choice for establishing how many genes are
contained in an organism’s genome. While this approach worked well for experimental
organisms, human genetics grew very slowly because of its reliance on indirect and
inferential methods for collecting and analyzing information about the inheritance of genes in
our species. Although analysis of mutants is a useful tool in genetics, the other side of
mutations is that they are responsible for many inherited disorders in humans. If we hope to
learn how many genetic disorders humans can have and how to develop treatments for those
diseases, we need to know how many genes are in our genome, know where they are located
on our chromosomes, and have ways of establishing their functions. Genetic mapping is one
step to accomplish these goals. In human genetics, this approach began in the 1930s, when
Julia Bell and J. B. S. Haldane used pedigree analysis to show that the genes for hemophilia
(MIM 306700) and color blindness are both on the X chromosome.
Beginning in 1980, geneticists began mapping DNA sequences to specific human
chromosomes. Most often, those sequences weren’t genes but simply markers that detected
differences in restriction-enzyme cutting sites or differences in the number of repeated DNA
sequences in a cluster. However, once these markers were assigned to chromosomes, they
became valuable tools in linkage studies.
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a. 6 b. 7 c. 12 d. 13 e. 19
Most vegetable oils are:
a. liquid at room temperature and saturated b. unsaturated and solid at room temperature c. found only in animals d. complex carbohydrates e. liquid at room temperature and unsaturated
Homeotic genes
a. code for homeodomains. b. code for regulatory proteins. c. are a class of master genes. d. affect transcription. e. are all of these.
Males are more often affected by sex-linked traits than females because
A) males are hemizygous for the X chromosome. B) male hormones such as testosterone often exacerbate the effects of mutations on the X chromosome. C) female hormones such as estrogen often compensate for the effects of mutations on the X. D) X chromosomes in males generally have more mutations than X chromosomes in females. E) mutations on the Y chromosome often exacerbate the effects of X-linked mutations.