Discuss the tools used to see if human behavior has a genetic component, and give two examples of either normal or
abnormal behavior that appears to have a genetic component. What will be an ideal response?
ANSWER: Several models for genetic effects on behavior have been proposed. The simplest model is a
single gene with a dominant or recessive pattern of inheritance that affects a well-defined
behavior. Several genetic disorders with behavioral components—Huntington disease, Lesch-
Nyhan syndrome, fragile-X syndrome, and others—are described by such a model. The
simplest multiple gene model is a polygenic additive model in which two or more genes
contribute equally to the phenotype. Other models include situations where one or more
genes have a major effect and other genes make smaller contributions to the phenotype, or
where two or more gene variants must occur together to produce the behavioral phenotype. In
each of these models, the environment can affect the phenotype significantly, and the study
of behavior must take this into account. To assess the role of the environment in the
phenotype, geneticists use heritability and other methods to measure the genetic and
environmental contributions to a trait. Increasingly, genomic methods are being used to study
behavior. Genome-wide association studies (GWAS) search for an association between a
behavioral trait and combinations of single nucleotide polymorphism (SNP) markers called
haplotypes. Using GWAS, scientists are able to scan thousands of genomes or tens of
thousands of genomes to see whether a specific haplotype is found significantly more often in
people with a particular behavior (schizophrenia, for example) than in the general population.
If so then a gene associated with this behavior may be in the same chromosome region as the
SNPs. This chromosome region can be studied in detail, searching for genes that may
contribute to the behavior being studied. Other genomic techniques, including exome
sequencing and epigenetic analysis, are helping unravel the complex genetic basis of human
behavior.
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Answer the following statements true (T) or false (F)
1. Flowers, fruits, and endosperm are defining characteristics of the angiosperms. 2. Lignophytes are seed plants that have become extinct whereas spermatophytes are those that are still living. 3. Terminal complexes in the cellular membranes of plants produce cellulose and are known as rosettes. 4. The K/T event was the transition of plants from water to land. 5. Pteridophytes and seed plants collectively are known as euphyllophytes.
DNA replication occurs
a. between the gap phases of interphase. b. immediately before prophase of mitosis. c. during prophase of mitosis. d. during prophase of meiosis. e. at any time during cell division.
Which time period would hold the record of the oldest fossils of multicellular animals, found in mountainous areas of
South Australia, and parts of Canada and China? a. Edicarian b. Devonian c. Cambrian d. Cretaceous e. Ordovician
An Enzyme is considered ______ because of its ability to recognize the shape of a particular molecule.
Fill in the blank(s) with the appropriate word(s).