CH 1 STUDY QUESTIONS

1. How does classical conditioning described by Pavlov differ from operant conditioning described by Skinner? (pages 2/3)

-Classical conditioning is a form of associative learning in which a subject learns the relationship between two stimuli, or between a stimuli and a behavior. Pavlov studied and analyzed dog’s salivary secretions in response to food. He found he could elicit this salivation response reliable by administering a distinct auditory or visual stimulus that would signal anticipation of a subsequent food reward. Pavlov called with conditional reflexes, but if now known as classical conditioning or associative learning.

-Operant conditioning is a type of learning in which behavior is strengthened if it is reinforced, and weakened if it is punished. Operant conditioning results in behavior modification through positive reinforcement. Skinner’s favorite animal was a pigeon and skinner reasoned that when a hungry pigeon would receive a food reward, it might associate the food with the execution of a particular behavior and would repeat that behavior.

2. What contributions did Lorenz and von Frisch make to understanding social behavior? (Pages 4/5)

-Lorenz formulated the idea of fixed action patterns of instinctive behaviors. Such stereotyped behaviors are set in motion by an innate releasing mechanism, which elicits a fixed sequence of behavioral events. (i.e. courtship and mating rituals, nest building for birds, ect) Lorenz also popularized the notion of imprinting, in which animal learns the characteristics of its parents.

-Karl von Frisch dedicated much of his life to the study of bees. In doing so, completed experiments that studied both the sensitivity of honeybees to colors, ultraviolet, and polarized light, along with another experiment that discovered how communications might occur, and lastly discovered that when a bee located a food source in the vicinity of the hive it would perform a flight pattern, which he described as a “round dance”. In doing these elegant experiments, he was able to further explain a complex social communication system that elicits distinct behavioral patterns.

3. What contribution did Tinbergen make to define the modern field of ethology? (Page 5)

-Ethology: The study of behavior. Tinbergen formulated a set of critical questions that should be addressed to the study of any behavior, and that relate respectively to function, causation, development, and evolution of the behavior: what is the impact of the behavior on the animal’s survival and reproduction; what stimuli elicit the behavior, and how can these behavioral responses be modified by learning; how do behaviors change with age and to what extent are early critical periods essential for development of the behavior; and how do similar behaviors compare between related species and how have they arisen in the course of evolution? These are the questions that poignantly define the field of ethology.

4. Describe the conceptual differences between the evolutionary theories of Lamarck and Darwin. (Pages 5-7)

-Jean-Baptiste Lamarck proposed that beneficial changed acquired during an organism’s lifetime could be passed on to its progeny and that over successive generations this process would alter the organism’s characteristics. This theory of inheritance of acquired traits invoked a teleological process of evolution (i.e. a process that saw design or purpose in nature). For example, according to Lamarck, giraffes would stretch their necks to be better able to reach increasingly higher foliage and this change would be transmitted to their progeny. The theory of evolution discredited this idea.

-Charles Darwin studied under John Stevens Henslow and took a five-year voyage to explore the South American coast. During this expedition, Darwin noted that distinct species of mocking birds, tortoises, and finches inhabited different islands in the Galapagos Islands. The fauna of the Galapagos Islands became the cornerstone of evidence for his theory of evolution, especially the fourteen species of finches that displayed distinctly different beak morphologies, functionally adapted to their different food sources—insects, grubs, leaves, seeds, or fruit – and which have since become known as “Darwin’s finches”. In subsequent years he would develop his theory that species evolve as a consequence of natural selection that that favors survival and procreation of the best-adapted individuals. Also known as survival of the fittest.

5. Explain why Mendel was able to derive his fundamental rules for inheritance, whereas Galton fell short of making the same discoveries. (Pages 9-11)

-Gregor Mendel preformed experiments that would lay the foundation for the science of genetics. Mendel began his famous experiments on garden peas, which he cultivated in the small monastery garden. He was able to examine only distinctive physical traits that could be categorically classified. He therefore selected seven characteristics, which stand out clearly and definitely in the plant. These were round or wrinkled seed, yellow or green seeds, inflated or wrinkled seedpods, green or yellow seedpods, purple or white flowers, purple or white flowers, flowers along the stem or at the tip, and tall or dwarf plants. Mendel observed that these traits are passed from parents to their offspring according to set ratios. He reasoned that individual’s posses two sets of factors that underlie each of these traits, one form each parent. He found that a particular characteristic was sometimes expressed (dominate) and some concealed (recessive). Further scientists created the terms gene, genotype, and phenotype to explain Mendel’s findings.

-Galton did not come to these same results as Mendel after doing experiments and mathematical equations because Mendel had deliberately chosen categorical traits, whereas Galton examined continuous traits that were complex and arose from multiple interacting genes. His statistical analyses laid the foundation for the field that would become known as quantitative genetics.

6. What is eugenics? Why did it appear a reasonable concept in the early days of the history of genetics, and why has it fallen into disrepute? (Page 10-11)

-Galton became convinced that the human population could be improved by encouraging marriages between “appropriate” individuals. He advocated that incentives should be provided for early marriages between members of higher social rank. The notion that government interference in direction human reproduction to improve society was acceptable became known as eugenics, a term Galton invented. As the notion of eugenics is based on subjective judgments of what constitutes a better individual, and since eugenics principles have been used to justify genocide. For example, by the Nazi during the Holocaust, the concept of eugenics fell into disrepute during the second half of the twentieth century, and is not widely regarded as unethical and scientifically flawed.

7. What is the fundamental contribution of the modern evolutionary synthesis as formulated by Dobzhansky? (Page 13)

- The major concept that emerged from the modern evolutionary synthesis was that genes provide the units for natural selection, and that changes in allele frequencies represent the mechanism for evolution. This was clearly formulated by Theodosium Dobzhansky. Dobzhansky defined evolution as “a change in the frequency of an allele within a gene pool.” This concept became a central tenet of population genetics, a science that arose as a result of the modern evolutionary synthesis.

8. What is Haldane’s rule? (Page 13-14)

-When one sex is absent, rare, or sterile, in the F1 offspring of two different animal races, that sex is the heterozygous (heterogametic) sex. Haldane’s rule has implications for speciation because if a sex-linked gene necessary for fertility or viable in two subspecies is absent from the homologous chromosome and not transmitted to offspring with the heterozygous sex, fertility and viability of the F1 hybrids will be reduces.

9. What was the early evidence that DNA represents the genetic material? (page 14)

- One of the greatest discoveries in modern science was the elucidation of the structure of DNA. Some of the earliest evidence began when a few scientists could show that they could transform an inactive strain of Streptococcus pneumoniae into a virulent strain by incorporating DNA isolated from virulent bacteria into the inactive strain. Also a couple other scientists showed that when bacteria are infected with bacteriophage T2, it is the viral DNA and not its protein that is injected into the bacteria and directs viral replication.

10. What critical pieces of information enabled Watson and Crick to develop their model for the structure of DNA? (Page 14-15)

-James Watson and Francis Crick discovered the structure of DNA in 1952. They had first arrived at the wrong conclusion with believing that DNA had a triple helix with base pairs on the outside. However, after being shown an X-ray photograph taken by Rosalind Franklin, who was performing comprehensive X-ray diffraction studies on DNA, Watson and Crick learned their mistakes. Photograph 51 provided the last bit of information needed by Watson and Crick to derive their model for the structure of DNA. Previously, Erwin Chargaff had reported that the molar concentration of adenine always equaled that of thymidine, and that the amount of guanine always equaled that of cytosine. Watson had noticed that the sized of the A-T and G-C base pairs were similar in size. These facts, together with the X-ray diffraction pattern in Franklin’s photograph, allowed Watson and Crick to describe a model in which A-T and G-D base pairs were located on the inside of a double helix, with the phosphate backbone exposed on the outside.

11. What is the central dogma? (Page 15)

-The notion that proteins are encoded by an mRNA that is synthesized from a DNA template became known as the central dogma in molecular biology. The central dogma has largely help up, although it was modified in 1971 by Howard Temin who showed that RNA viruses can direct the synthesis of DNA from an RNA template, an exception to the central dogma.

12. What were some of the major contributions made to behavior genetics by Thomas Hunt Morgan? -Thomas Hunt Morgan worked with Drosophila and identified many mutant genes. He discovered a fly that had white eyes instead of the standard red eyes and named it “white”, starting the pattern of naming mutant drosophila for their mutations. He noticed that when he crossed the white eye males with red eye females all of the offspring had red eyes indicating that it was recessive. When he crossed the offspring the white eyes reappeared but only in males, indicating that the trait was sex linked. He postulated that genes were carried on chromosomes. He deduced that the amount of crossing over between adjacent genes differs, and that crossover frequency could be used as a measure of the distance separating genes.

13. Describe the contributions of S. Benzer and J. Hirsch of behavior genetics. (Page 18)

-J. Hirsch performed experiments in behavioral genetics on geotaxis in Drosophila. Flies are positively geotactic, that is, they move upwards against the force of gravity. Hirsch constructed a vertical maze, in which he could introduce flies on one side in the center of the maze and watch them move toward a light source at the other side of the maze. These experiments tactic lines that have been propagated for decades, and still exist today.

-S. Benzer conducted behavioral genetics experiments on circadian activity of Drosophila. Flies, like other animals, show periods of activity and inactivity that are governed by an endogenous clock entrained to the daily light-dark cycle. Using a photoelectric monitoring device, Benzer monitored activity of flies during the day and night. These experiments were critical to developing the field of chronobiology, the study of biological clocks.

Chapter 2 1. What are the values of the equilibrium potentials for sodium and potassium in neurons under physiological conditions?
Sodium- +60mV Potassium- -90mV

2. What will be the equilibrium potential for calcium when the extracellular concentration of calcium is 1.25mM and the intracellular calcium concentration is 100nM, under conditions in which calcium is the only permeant ion?

3. Explain the ionic mechanisms that give rise to an action potential.
A change in voltage that depolarizes the cell opens the voltage gated sodium channels and the flow of sodium through these channels leads to further depolarization, which promotes the opening of more sodium channels. Once the potassium channels begin the open the sodium channels close and remain closed for a period called the refractory period. Then the cell repolarizes as potassium leaves the cell and then potassium channels will close and the sodium channels will reset.

4. Explain why action potentials cannot spontaneously reverse direction as they travel along the axon.
Due to the refractory period in which all of the sodium channels are closed, the action potential is unable to reverse and go the other direction.

5. Explain why the action potential is an all or none event, and why the postsynaptic potential is a graded potential. Why is it essential that the action potential is an all or none event and the postsynaptic potential a graded event?
Action potentials are all or none in the manner that the stimulation must pass threshold in order for the current to be passed. The smaller the intensity(frequency) of the stimulation, the smaller distance the action potential would be able to travel. Postsynaptic potentials are graded events, meaning that the number of ions that flow in the postsynaptic cell depends on the number of receptors that are activated which is proportional to the amount of NT released from the presynaptic terminal.

6. An electrophysiologist records currents from an axon at different voltage steps under voltage clamp conditions. What will he observe: (1) if he removes extracellular sodium (2) in the presence of tetrodoxin; and (3) in the presence of tetraethylammoinium
(1) If there is no extracellular sodium, the cell will be unable to depolarize and the action potential will never pass threshold, and never occur
(2) TTX blocks voltage gated Na+ channels, so once again the sodium channels would never be able to open and depolarize the cell, failing to cause an action potential
(3) TEA blocks some voltage gated K+ channels, so the cell may have trouble repolarizing and remain in a constant state of depolarization

7. The issue of whether synaptic transmission was electric or chemical was hotly debated in the 1950s. Sir Bernard Katz was a protagonist of the chemical synaptic transmission theory, and provided strong evidence for chemical synaptic transmission through his observations of miniature endplate potentials. What properties of mepps provided support for the notion that release of NT is quantal?
They recorded from the muscle fiber of a frog and they observed that even when they didn’t stimulate the nerve, they were able to pick up on some small changes in the resting membrane potential. When they did stimulate the nerve, the muscle fiber would depolarize depending on the amount of stimulation.

8. Explain how alterations in the concentrations of cyclic nucleotides mediate phototransduction and olfactory transduction.
Phototransduction: Activated opsin activates a G protein coupled receptor “transducing” and the activated alpha subunit causes an activation of cyclic GMP phosphodiesterase that breaks down cycle GMP into 5’- GMP. In the dark cyclic GMP binds to ion channels in the rod’s plasma membrane. This binding is required for the channels to remain open. A lowering of intracellular cyclic GMP, as a result of activation of rhodopsin, results in closing of a fraction of these cyclic GMP activated ion channels
Olfactory: Binding of an odorant to a receptor results in activation of adenylyl cyclase via stimulatory G protein, Golf. Cyclic AMP then opens an ion channel in the ciliary plasma membrane, here the stimulus results in an opening of the channel. The Opening results in an influx of cations, calcium, which enters through the cyclic AMP gated channel, opens a chloride channel and efflux of chloride through this calcium activated chloride channel amplifies depolarizing generator current

9. Describe common aspects of the structure and signal transduction mechanisms of G protein coupled receptors.
GPCRs are composed of three subunits. Alpha, beta, and gamma. GDP is bound to the alpha subunit and when the ligand binds to the receptor, the GProtein complex dissociates into the alpha subunit and beta/gamma complex. The GDP is exchanged for GTP, and then an effector enzyme is activated and activates a secondary messenger. Alpha subunit slowly hydrolyzes the GTP, converting it to GDP and then it reassociates with the beta/gamma subunit,

Ch 3 STUDY QUESTIONS

1. Describe the relationship between dilatations in the rostral neural tube during early development and regions of the adult brain?

-In the rostral region of the neural tube three dilations appear, which form the primitive forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon). The prosencephalon further divides into the telencephalon and the diencephalon. The telencephalon gives rise to the two cerebral hemispheres (the cerebrum), which in humans become greatly enlarged, covering the rest of the brain and representing approximately 80% of the total mass of the adult human brain. The diencephalon forms the thalamus and hypothalamus. The mesencephalon develops into the midbrain. The rhombencephalon also divides into two parts: the metencephalon and the myelencephalon. The former givers rise to the pons and cerebellum, and the latter to the medulla oblongata, which is continuous with the spinal cord.

2. What is long-term potentiation and what role do calcium and nitric oxide play in this process?

-Long-term Potential (LTP) is a long-lasting increase in the strength of transmission at a synapse, as a result of repetitive or coincident stimulation. LTP may underlie learning and memory formation, and is especially well documented in an area of the mammalian brain know as the hippocampus, thought to be involved in the acquisition of memory.

-The influx of calcium through NMDA-type glutamate receptor channels mediates structural changes in the synapse that facilitate activation of this synapse in the future. This is thought to underlie the physiologically observes phenomenon of LTP: once a neural pathway is stimulated, it becomes easier to stimulate the same pathway subsequently.

-The short-lived free radical gas, nitric oxide (NO), plays an important role as neuromodulator in LTP. NO is synthesized from the amino acid arginine by nitric oxide synthetase, an enzyme that is regulated by calmodulin, a ubiquitous calcium-building protein. During LTP, calcium flowing into the postsynaptic cell activates the production of nitric oxide, which then diffuses back to the presynaptic terminal, where it activates the production of the second messenger cyclic guanosine 3.5-monophosphate (cycle GMP) by guanylyl cyclase. NO acts here as a retrograde neurotransmitter.

3. Describe evidence that supports the notion that the hippocampus is required for acquisition of memory, but not long-term storage of memory.

-The hippocampus is a part of the brain that plays a role in the acquisition of new memories. It is involved in transferring information form our short-term memory to our long-term memory.

-The hippocampus is an integral component of the limbic system. Information arrives from the entorhinal cortex (EC) to the dentate gyrus (DG) and CA3 pyramidal neurons. CA3 neurons also receive input from the dentate gyrus via mossy fibers (MF). CA3 neurons project to the ipsilateral and contralateral CA1 regions. CA1 neurons send axons to the subiculum (sb), from where output is returned to entorhinal cortex, completing a neural loop.

Hm had his hippocampus removed but he could still recall many of his memories. However, he could no longer form any short term memories. His IQ was still normal as was before the surgery.

4. Imagine that you discovered a nucleus in the hypothalamus that you suspect mediates grooming behavior in mice. What experiments would you perform to prove that neurons in this region indeed mediate this behavior?

-Hypothalamus is an area of the brain that regulates endocrine activity, as well as somatic functions, such as body temperature, sleep, and appetite.

5. A physiologist inserts an electrode into the brain of a monkey and when he passes current through this electrode, he observes that the monkey moves its left index finger. In what region of the brain is the electrode inserted?

-

6. There are at least three distinct neural tracts in the bran that utilize dopamine as neurotransmitter. Name them and explain the functions associated with each of them, indicating related diseases and their possible treatments.

-Dopamine is an important catecholamine neurotransmitter in the neural pathway in the brain that projects from the substantia nigra to the corpus striatum. This neural projection is important in the initiation of movement, and dopamine deficiencies in this pathway can result in Parkinson’s disease, characterized by rigidity, muscle tremors, and difficulty in initiating movements and speech. Dopamine is also implicated in schizophrenia and manic depression. These psychiatric disorders involve different dopaminergic projections, the mesocortical pathway, which projects from the ventral tegmentum in the midbrain to the frontal cortex, and the mesolimbic pathway, which connects the ventral tegmentum to the nucleus accumbens.

7. What are the functions of the central complex and the mushroom bodies in the insect brain?

-The central complex is a region in the insect brain associated with locomotion. The mushroom bodies are higher-ordered intergrative structures in the insect brain, chemosensory information is integrated by the mushroom bodies, and associative learning and memory formation. The central complex and the mushroom bodies are the most prominent structures in the central brain. Sensory-motor integration, which enables Drosophila to have a behavioral response to stimuli, depends on the central complex.

8. Describe the neural circuits that mediate withdrawal of the foot after accidentally stepping on a thumb tact.

The spinal cord reflex mediates immediate withdrawal. This inhibition is mediated via interneurons that release glycine as a NT. At the same time a “pain message” is being sent to the brain via ascending tracts.

9. Explain the concept of “receptive field”. Could different neurons have overlapping receptive fields?

-The receptive field is a segment of the environment or range of a stimulus spectrum that elicits activity in a particular neuron of a sensory pathway.

10. How would a typical ganglion cell respond to a spot of light that travels in a straight line across the center of its receptive field?

-One observes that in some cells, the spontaneous firing rate of action potentials is inhibited when the light hits the periphery of the receptive field. The opposite phenomenon is also observed. “ON center” and “OFF center”.

Ch 4 STUDY QUESTIONS

1. Discuss the advantages and disadvantages of field studies on behavior compared to studies conducted in the laboratory.

-Field studies have the advantage in that analyses can be conducted under ecologically relevant conditions. Although DNA analysis from samples gathered in the fields can be used to determine kinship relations during long term studies of groups of wild animals, gaining insights into the underlying genetic and neurobiological principles that give rise to behaviors requires experimental manipulations, which in most cases are only feasible in the laboratory.

-Laboratory studies are advantageous in that breeding, and thus the genetic background, and environmental conditions, can be controlled. Temperature, humidity, like/dark cycle, diet, social environment, and age can be controlled precisely. The behavioral repertoire and the range of variation observed in the field are generally broader than that observed under standard laboratory conditions. IN addition, laboratory experiments on behavior are plausible for a relatively limited number of species, generally designated as model organisms.

2. Describe at least three behavioral assays that use locomotion as a read-out.

-Spontaneous endogenous locomotor activity can be measured by recording revolutions of a running wheel placed in the animal’s cage during a fixed time period. Mice can run many kilometers a night on the running wheel. There is a variation in running activity among strains, and this variation has a genetic component. In addition to serving as an indication of locomotor ability, the running wheel can also be used to monitor general circadian activity.
-Locomotion in flies can be measured as spontaneous open field behavior, similar to open girl tests used with rodents. Circadian activity can be measured by placing a single sly in a narrow tube and recording movement each time it breaks an infra-red light or laser beam. Tapping a vial containing a single fly sharply against the bench can also induce locomotion, and measuring the amount of time the fly moves during a brief period following the mechanical disturbance. This locomotor reactivity is in essence a startle-response.
-Behaviors are shaped through the continuous sensory input and appropriate adjustments or motor output, and different behaviors may be interdependent.

3. Prepare a list of environmental conditions that can lead to changes in average behavioral phenotypes.

-The genes that give rise to the behavioral phenotype can be classified in two categories: genes that contribute to manifestation of the train; and a subset of these genes, which contribute to variation in the trait. Genes that contribute to the manifestation of a behavioral trait, but that do not vary in a population can be detected through mutagenesis approaches. Genes that give rise to phenotypic variation are the province of quantitative genetics, and their identification and estimates of their relative contributions to the observed phenotypic variance required statistical analyses.

4. Define the concepts “homozygous effect” and “heterozygous effect”. What is over dominance?

-The heterozygous effect is the mean value of the heterozygous genotype, expressed as a deviation from the mean of the two homozygotes at a particular locus.
-The homozygous effect is the difference in the phenotype between individuals with alternative homozygous genotypes at a particular locus.
-Over dominance is when the fitness of the heterozygote is greater than that of either homozygote.

5. What is epistasis? Construct reaction norms that illustrate additivity versus epistasis between two loci, A and B, each with two alleles.

-Epistasis is the making or modulations of the phenotypic effect of alleles at one gene by alleles of another gene through non-additive enhancer or suppressor effect.
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6. What is the difference between genotype-environment correlation and genotype-environmental interaction?

- Genotype-environment correlation is an association between genotype and environment that occurs if the environment an individual experiences depends on its genotype.
- Genotype-environmental interaction is the variation among genotypes in environmental plasticity.

7. What does the statement mean, “the phenotype is not fully penetrant?” What could be the reason for incomplete penetrace?

-Penetrance and expressivity are used to indicate that the relationship between genotype at a locus and the phenotype of the trait is not perfect. Penetrance refers to the proportion of the individual with a given genotype that display the phenotype associated with that genotype. Expressivity refers to quantitative variation in expression of a phenotype among individuals of the same genotype. In both cases, the cause of the phenomenon could be epistasis or environmental effects.

Chapter 7
1. Why are heritability estimates useful?
They are important for gene mapping studies, and they are also useful for human behavioral traits, such as cognitive disorders or addiction, as they can provide insights into what extent genetic components contribute to the likelihood that the disorder is transmissible from parent to offspring.

2. Explain how we can statistically quantify the resemblance between offspring and their parents.
We need to obtain quantitative measurements of our behavioral trait for one or both parents, and at least one of their offspring for many families in the population. We are looking for the mean value of the trait, or the average of both of the parents (mid parent value). We will then quantify the data using a regression of mean offspring phenotypic value on the parental phenotypic values. The regression is bop = (Covop/(sigma)^2. The Covop is the covariance of trait phenotypes between offspring and parents and (sigma)^2p is the variance of parent phenotypes. There are three possible offspring- parent regressions: regression of mean offspring phenotype on the female parent; the male parent; or the mid parent value. The higher the offspring coefficient , the greater the amount of genetic variance.

3. Explain how we can statistically quantify the resemblance between siblings.
There are two types of sibling (half and full). To quantify full siblings, we need to obtain measurements of the behavioral phenotype for at least one offspring in each of many families in the population, parents are not needed. For half siblings, we need to obtain measurements for at least one offspring in each of many half sibling families. Use ANOVA. The larger the covariance between the members of a full or half sibling family, the larger the fraction of the total variance that is attributed to differences between family means.

4. What causes genetic covariance between relatives?
Genetic covariance between relatives is the covariance of the genotypic values of the related individuals, or the amount by which breeding values and dominance deviations vary togetherin the two relatives being considered. This arises because two related individuals are more likely to share alleles than two unrelated individuals. 5. What causes environmental covariance between relatives?
If the common environmental circumstances are different for each family, the variance due to common environment will cause a greater similarity among members of a family and greater differences among families, than would be expected from the proportion of alleles that they share. This increases the phenotypic covariance between relatives.

6. Describe three ways in which heritability can be estimated. Which of these methods would you prefer to use and why?
We can estimate heritability from relatives, identical twins, and full siblings. I prefer to use full siblings because we have a long generation time and that means that measurements on parents aren’t always available, and some behavioral phenotypes change over time, or are expressed only late in life, so measurements at the same age are impossible.

7. Discuss potential sources of bias of hertitability estimates. What is the consequence of these potential biases?

8. Explain the concept of “realized heritability”.
Realized heritability is heritability estimated from the regression of offspring means on the mean of parents selected to have either high or low values of the behavioral trait.

9. In a population in which the heritability of a behaviorial trait is 0.45, what is: 1. The correlation among full siblings. 2. The regression of offspring on one parent? What assumptions have you made?

10. Imagine that you have conducted a study on alcohol drinking in humans by questioning fathers and their adult children about their alcohol consumption per week. You have data from over 500 families. You calculate the regression of mean alcohol intake of adult children and their fathers to be 0.35. What is your estimate of heritability of alcohol intake? Comment on the reliability of the estimate.

11. Imagine that you have conducted a study on schizophrenia in humans. You measure the correlation of pairs of monozygotic twins as 0.7, and of pairs of dizygotic twins as 0.3. all twin pairs were reared together in the same household. What is your estimate of heritability of schizophrenia? How is the estimate biased?

12. Why is it preferable when estimating heritability using a single parent- offspring design to compare fathers and their children, rather than mothers and their children?