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?
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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In seedcracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch
population? A) disruptive selection B) directional selection C) stabilizing selection D) No selection would operate because the population is in Hardy-Weinberg equilibrium.
One primary oocyte will form
(a) one ovum. (b) four ova. (c) up to three polar bodies. (d) both a and c.
Molecular oxygen (O2), which is required for the production of ATP by mitochondria, must pass through at least three membranes to get to the enzymes where it is used
O2 is also produced in chloroplasts and must pass through at least four membranes to be released from the plant. How does O2 move across biological membranes? A. There are numerous protein transporters that allow O2 to travel across membranes. B. O2 is nonpolar, and very small, so it can diffuse across the membrane. C. O2 undergoes a chemical reaction that binds it to other substances that are transported across the membranes. D. O2 is hydrophilic and travels with water across the membranes.
Genetic drift has an especially significant effect in what kind of populations?
A. populations that are large B. populations that are small C. populations with high genetic variability D. populations that are in Hardy-Weinberg equilibrium E. populations that are migrating