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(1) Suppose you are a behavioralpsychologist and are asked to determine to what extent intelligence(IQ) is heritable or multifactorial. That is, how much is inheritedversus how much IQ results from environmental influences? How willyou proceed with such a study (hint:you can take as long as you need – even a career if necessary)?

This study will involve 12 setsof identical twins separated at birth. The twins would need to beisolated and raised in different environments. Since the twins havethe same heritable genes, any future differences in intelligencewould prove the impact of environmental influences. Standardized IQtests could be given to each twin pair at progressive five-yearintervals. These tests would help to highlight any differences inintelligence over time. Increasing differences in the test scoreswould prove that intelligence is multifactorial and can be influencedby the environment (Lewis, 2014).

(2) Explain how nondisjunctionhappens and why it is so dangerous or fatal to a developing fetus.What causes Down`s syndrome and why is it one of only two survivablenondisjunction events?

Nondisjunction occurs when twohomologous chromosomes fail to separate. This leads to thedevelopment of abnormal gametes. For a developing fetus,nondisjunction could be fatal due to the imbalance in the number ofchromosomes. Down’s syndrome is caused by a genetic disorder calledtrisomy. In particular, the disorder affects chromosome 21 (Cummings,2014). There are two survivable nondisjunction events. The firstoccurs due to meiosis I. In this case, all gametes are usuallyaffected thereby causing two gametes to have an extra chromosome.Another pair of gametes misses a chromosome. In the second scenario,meiosis II causes only half of the gametes to undergo nondisjunction.Therefore, only one gamete acquires an extra chromosome while anothermisses a chromosome (Cummings, 2014). Down’s syndrome occurs in thelatter case.

(3) What is the relationshipbetween the BRCA1/BRCA2 mutations and breast cancer? If a woman hasone of these mutations, should she opt for preventative (early)mastectomy? Provide an assessment based on your knowledge of thesituation.

BRCA1/BRCA2 are known as tumorsuppressor genes. Mutations that occur in these genes have beenlinked to hereditary ovarian and breast cancer (Cummings, 2014).Since some mutations may be harmless, a woman with one of thesemutations should first undergo assessment. If the infection is indeedharmful and her family history has a case of cancer, then the womanmay opt for preventive mastectomy.

(4) List the 5 importantcharacteristics that signal that a genetic trait is multifactorialand heritable (heritability less than &lt 1.0).

The five characteristics are asfollows:

  • If the trait is continuous such that the characters vary along a continuum

  • If the trait is heavily influenced by the environment

  • If the trait is determined by more than two genes

  • If the addictive genes contribute to the trait without dominance

  • If the trait is markedly different between people of the same genotype, such as identical twins (Lewis, 2014).

(5) Should insurance companies begiven access to a prospective client`s whole genome sequence? Why orwhy not? What information could the insurance agent glean from suchdata?

Insurance companies should haveaccess to whole genome sequences so that they can attain higheraccuracy in calculating the level of premiums. Hedging risk isthereby lessened since adverse selection is eliminated. Insuranceagents would estimate the possible diseases and lifespan of anindividual from this data (Lewis, 2014).

(6) A family has four boys andhas opted to try one more time for a daughter. A friend of thefamily has told them that since they have had so many boys alreadythat there would be only a 1/16 (0.5×0.5×0.5×0.5) chance of having aboy again but a 15/16 chance of having a daughter now. Is this areasonable or correct assessment? Please provide your own analysis ofthis situation.

The assessment is bothunreasonable and incorrect. Every childbearing event presents a 1/2(0.5) chance of having either a girl or a boy. Previous outputs donot influence the sperm output at the fifth attempt. Conception is amutually exclusive event owing to the proportions of X and Ychromosomes present in the sperm (Cummings, 2014). Nevertheless, itcan be said that the family has a 1/16 chance of having a family offive boys.

(7) A family pedigree for atrait shows a fatal disorder cropping up in members of a family inboth sexes and in every generation, but, surprisingly, it also showsthat unrelated husbands and wives marrying into this family are alsoequally prone to dying of this disorder. What are 2 possibleinterpretations of this observation concerning the origins andetiology of this deadly disorder?

The first possible interpretationhas to implicate the environment in which the family lives. The factthat people with different genetics also get infected shows thatenvironmental factors may be triggering the disorder. The secondpossible interpretation is that the disorder could be communicable(Lewis, 2014). Therefore, any who come into close and persistentcontact with the family automatically become infected.

(8) What is the probability thatthe offspring of a homozygous dominant individual and a homozygousrecessive individual will exhibit the dominant phenotype? Explainyour answer.

The probability of such offspringdisplaying the dominant phenotype is 1. This is because thehomozygous dominant individual always passes on the dominant genes totheir offspring (Lewis, 2014). Since the dominant gene always coversthe recessive gene, all offspring will exhibit the dominantphenotype.

(9) What is Huntington’sdisease? How is it inherited? Why do you suppose that the longer theCAG repeat mutation is in the diseases gene, the more severe thedisease and the earlier the onset of the disease?

Huntington’s disease is anincurable brain disorder that affects muscle coordination, behavior,and cognition. The disease is manifested by a rash or involuntarymovements. Huntington`s disease is inherited owing to a dominantmutation on the autosomal fourth pair of chromosomes (Cummings,2014). Only one-half of the defective gene from either parent causesthe disease. A normal individual has less than 36 repeats of thetrinucleotide CAG. The decay rate of the neurons increases with thenumber of CAG repeats beyond 36 (Cummings, 2014). This causes notonly heightened severity but also earlier onset of Huntington`sdisease.

(10) In a well-constructed shortparagraph, discuss some of the legal and ethical issues surroundinggenetic testing and other modern human genetic advances.

Genetic testing has helpedscientists to identify and treat many disorders that were previouslyunknown. However, genetic testing and other advances have raised somelegal and ethical issues. For example, the issue of privacy has beenwidely discussed. For example, genetic testing uses privateinformation to highlight compatibility between organ donors andrecipients (Wexler, 2014). Genetic testing has also been accused ofundermining the sanctity of life. The value of human life is loweredwhenever genetic testing causes fundamental change in genotype.Furthermore, genetic testing also lessens the natural impact of theenvironment in determining phenotype (Wexler, 2014).


Cummings, M. R. (2014). Humanheredity: Principles &amp issues.Belmont, CA: Cengage Learning.

Lewis, R. (2014). Humangenetics. New York,NY: McGraw-Hill.

Wexler, B. (2014). Geneticsand genetic engineering.Detroit, Michigan: Gale Cengage Learning.