Human Genetics and How Much Do Our Genes Influence Our Political Beliefs - Assignment Example

Assignment 2: Human Genetics Details: al Affiliation: Assignment 2: Human Genetics QA. For each of questions 1‑5, select the most appropriate response, and explain your choice. (3 marks each; total = 15 marks) 1 Mitochondrial inheritance is maternal. sex-limited. sex-influenced. genomic. rare. Explain: It is the maternal inheritance of mitochondrial DNA that enables genealogical researchers to trace an individual’s lineage (Lewis, 2008). 2 An individual who has ____________ is male. a. development of the Müllerian ducts b. an MSY region c. an SRY gene and no testes d. indifferent gonads e. degradation of the Wolffian ducts Explain: The male-specific region of the Y chromosome [MSY] differentiates and is responsible for the male sex determination (Lewis, 2008). 3 A normal female human is expected to have a. a mosaic phenotype. b. X-inactivation of both X chromosomes in a somatic cell. c. traits associated with the SRY transcription factor. d. one Barr body in each somatic cell. e. two of the above. Explain: Named after Murray Barr, the brain behind its discovery, a Barr body describes the embryogenesis of female mammals, where all but one of the multiple X-chromosomes is rendered inactive in a process known as lionization, thus the barr body in each somatic cell of a female human (Lewis, 2008). 4 Which of the embryo possibilities described below would most likely result in repeated miscarriages? a. heterozygous for a lethal allele b. homoplasmy for a normal allele c. homozygous for lethal alleles d. lack of penetrance for a lethal allele e. heteroplasmy Explain: Mitochondria provide energy for all cellular processes within the body. As alluded to above, mitochondria is maternally inherited, and so are the defects of mtDNA. Thousands of mutant and normal mtDNA both coexist in individuals with mtDNA disorders, and their very degree of coexistence [heteroplasmy] determines the severity of the disorder (Lewis, 2008). Accordingly, the accumulation of mutant mtDNA in the reproductive tissues appears to underlie/impair fetal viability, thus, increasing chances of having recurrent miscarriages. 5 Genomic imprinting is an example of a. heterogeneity. b. epistasis. c. pleiotropy. d. an epigenetic effect. e. a phenocopy. Explain: for the behavior of imprinted genes does not depend on just the DNA sequence, but on a host of epigenetic factors. QB. Match each descriptor or example in the right-hand column to the best term in the left-hand column. Use only one descriptor per term and one term per descriptor. (10 marks) 6 Term Descriptor/example 1. __c__ linkage disequilibrium a/3. refers to male mammals 2. ___d_ sex-limited trait b/6. inherited together 3. __a__ heterogametic c/1. difference in expression due to internal environment 4. __j__ heritability d/2. caused by restrictions to crossing over 5. _h___ hemizygous e/8. additive effects of two or more genes 6. ___b_ haplotype f/7. dosage compensation 7. __f__ sex-influenced trait g/10. discrete expression 8. __e__ polygenic h/5. males expressing an X-linked recessive trait 9. __i__ qualitative trait i/9. testicular cancer 10. __g__ X-inactivation j/4. variation in phenotype due to genetic variation 7 An organism has 16 chromosomes in its somatic cells. Determine the number of gametes with different chromosome compositions that it can potentially create. Explain your answer. Ignore the allelic variation created by crossing over. (3 m) 2n=16 ----- n=16/2 = 8 gametes. Gametes and/or sex cells have one chromosome from each autosome pair and one sex chromosome. 8 In the following pedigrees, the disorders or traits presented follow simple patterns of Mendelian inheritance. For each trait, determine the most probable mode of inheritance, stating whether the trait is due to an autosomal or X-linked gene, and a dominant or recessive allele. In each case, indicate and explain the evidence for each pattern, giving at least one statement and example from the pedigree to defend each part of your analysis. Then, providing a legend for your symbols, assign genotypes to the specified individuals. (15 marks) a. Provide genotypes for individuals II-5 : Normal male [XNY]; the resultant trait is autosomal; not all the daughters are affected and that the affected male parent has sired an affected child. III-6 : Normal female [XNXN]; the resultant trait is X-linked; the trait is acquired from normal parents. III-11 : Colour blind Man [Xn Y]; the resultant trait is also X-linked; the trait is acquired from a carrier male parent and a colour blind female. b. Provide genotypes for individuals I-5 : Not applicable II-5 : Normal color vision [man] [XNY] III-3 : Color blind woman [XnXn] IV-3 : Carrier woman [XnXN] 9 Achondroplasia is an autosomal dominant disorder associated with a gene on chromosome 4. Sickle cell anaemia is due to a gene on chromosome 11. A man and a woman with achondroplasia, who each had a normal parent, are carriers for sickle cell anaemia. a. Give the genotypes of these individuals; provide a legend for your symbols. (2 marks) Man [♀] HbA Hbs Woman [♂] HbA Hbs b. Construct a Punnett square to determine the possible types of offspring these two people could have together. (4 marks) Man ♂ ♀ HbA HbS HbA HbA HbA HbA Hbs HbS HbA Hbs Hbs Hbs c. Summarize the Punnett square to list the genotypes and their ratio. (2 marks) HbA HbA, HbA Hbs, HbA Hbs, HbS Hbs d. List the possible phenotypes and the expected proportions of these phenotypes. (2 marks) 3 Normal individuals/offsprings and 1 sickle celled individuals [3:1] e. What is the name for this type of cross? (1 mark) Incomplete dominance/cordominance f. If these genes had been on the same chromosome, would you expect the same results for potential offspring? Why or why not? (4 marks) The result wouldn’t change; we are dealing with the same type of chromosome [X] that exists in both sexes. 10 A woman is heterozygous for three X-linked loci: AaBbDd. She has seven sons with the following genotypes: (7 marks) two are X ABd Y three are X abD Y one is X ABD Y one is X Abd Y a. What is the most likely combination of alleles on each of the mother’s X chromosomes? ABD; abd are the result of genetic recombination. b. Which of the seven sons is/are the result of recombination? Between which genes did the crossover occur in the mother’s oocyte to create each recombinant X? The three with XabDY and the last one with XAbdY; the genes of the mother are not fully expressed in these individuals’ genetic formation. c. List the other possible recombinant genotypes that have not appeared in these sons. XabDY and XabDY 11 Based on the simplified two-gene model for eye colour, explain using genotypes how two blue-eyed parents could produce a brown-eyed child. (4 marks) Man ♂ ♀ B/G B/g b/G b/g B/G BB/GG BB/Gg Bb/GG Bb/Gg B/g BB/Gg BB/gg Bb/Gg Bb/gg b/G Bb/GG Bb/Gg bb/GG Bb/Gg b/g Bg/Gg Bb/gg bb/Gb bb/gg Every individual has two copies of each of the genes in their system, one from each parent. The color of the human eye color is determined by at least three hereditable genes. However, only two are well understood. A gene often has two alleles: a dominant one that confers eye color (B for blue eye color) and a recessive one which gives rise to the brown eye color. A brown eyed dad and a green eyed mom may be carriers of the recessive gene of eye color, and thus be able to pass down brown eye genes to their children. As alluded to in the diagram above, both parents are carriers of the brown eyes genes. There is, thus, a slim chance that brown eyed child [bb/gg] being born in the family. 12 In what ways is genomic imprinting similar to X-inactivation? In what ways is it different? (6 marks) Similarities Both lead to monoallelic expression [without altering the genetic sequence]; that is genomic imprinting and X-inactivation share certain physical properties such as DNA hypermethylation, altered replication timing and histone hypo-acetylation both involve gene silencing; X-inactivation turns off entire chromosome, while imprinting turns off specific genes. Since no changes occur in the coding sequence of the DNA, it is believed that it is possible to reverse abnormal X-inactivation or abnormal genomic imprinting, and in effect, reactivate the relevant genes and ameliorate the disease phenotype in question. Differences Genomic imprinting is dependent on the parent-of origin; X-inactivation is, however, usually random. Imprinting is specific with regards to regions of a given chromosome [not chromosome-wide]; Xinactivation on the other hand involves nearly an entire chromosome. There is clear binding of nontranslated RNA in X-inactivation; such is not evident in genomic imprinting. X inactivation turns off/silences entire chromosome involved, whereas imprinting turns off only specific regions of a gene (Lewis, 2008). 13 In a twin study of 1000 MZ pairs, 625 pairs were found to have both twins with the same form of a given trait. In a study of 1000 DZ twins, 426 pairs were found to have both twins with the same form of that trait. (5 marks) a. What parameter can be calculated from this data? Percentage/degree of identity in the genome of twins b. Calculate it for MZ twins and DZ twins, showing your calculations. MZ = [625/1000]*100 = 62.5% DZ = [426/1000]*100 = 42.6%. c. What does this parameter tell us about this trait? Monozygotic twins develop from a single zygote splitting into two embryos, thus, the higher similarity in almost every trait, including the sex and/or their genome. Fraternal or dizygotic (DZ) twins, on the other hand, result from the fertilization of two eggs implanted in the uterus at the same time. Unlike MZ twins, DZ twins have extremely slim chance of having the same chromosome profile, thus the percentage above. 14 Choose a current newspaper article (no older than two years before the start of your course contract) that describes a genetic study.* Summarize the information presented in the article in paragraph form. Your article should have enough information to address all or nearly all of the following points in your summary. Include any other information relevant to your studies in this course, as provided in the article. (20 marks) In his article titled ‘How much do our genes influence our political beliefs?’, Thomas Edsall (2014) gets down to explore not only the subject of gene inheritance, but in a unique area of study, politics, coming out with baffling revelations that have more than drawn criticisms almost in equal measure. Like any other ordinary individual, Edsall begins his article by questioning the relations between the two, and gives a prospective answer sought after almost unconsciously by alluding to a biologically supported evidence indicating that it is and will always remain a tall order to bridge the cultural differences on both sides of the political divide; differences expressed in terms of distinct attitudes, beliefs and sentiments that more than give meaning and order, and so the rules governing behavior within a political system and/or process. Utilizing a wide range of tests to compare views on political, social, ideological and economic issues in their study titled “Obedience to traditional Authority: A heritable factor underlying authoritarianism, conservatism and religiousness,” Ludeke, Bouchard, and Johnson (2013) demonstrates, as expressed by Edsall in the article, that identical (monozygotic) twins share a greater degree of commonality in their thoughts compared to those of fraternal (dizygotic) twins. With the same observations are two political science students, Amanda Friesen and Aleksander Ksiazkiewicz, who confirms the existence of a common genetic factor underlying political views, the importance of traditional values and religious principles in the study. Notably, 19 presidential elections since 1940 in the United States bears the relative stability of opinions of voters, with winners receiving less than 53 percent of the total vote count; a pointer to the fact that attitudes over gay marriage, abortion among other reproductive technologies, single parenthood, religion and authority, and a host of traditional values are but partly heritable. Edsall concludes that it defeats logic to reject studies that more than illuminated understanding of the human system, particularly with regards to self-governance. Reference Lewis, R. (2008). Human Genetics: Concepts and Applications (8th ed.). New York, NY: McGraw-Hill. Edsall, T. B. (2014, July 8). How much do our genes influence our political beliefs? New York Times. Retrieved from http://www.nytimes.com/2014/07/09/opinion/thomas-edsall-how-much-do-our-genes-influence-our-political-beliefs.html Read More