{"id":1363,"date":"2020-08-06T22:29:17","date_gmt":"2020-08-06T22:29:17","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/theory-questions-and-answers\/theory-questions-and-answers-vi\/"},"modified":"2021-05-17T12:24:57","modified_gmt":"2021-05-17T10:24:57","slug":"theory-questions-and-answers-vi","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/theory-questions-and-answers\/theory-questions-and-answers-vi\/","title":{"rendered":"Theory Questions and Answers VI"},"content":{"rendered":"\n

Questions<\/h3>\n<\/span>\n\n\n

Scroll down for answers!<\/em><\/p>\n\n\n\n

  1. Define the term \u2018anticipation\u2019 in disease. Give two examples of diseases that express this phenomenon?\u00a0<\/li>
  2. Why are beta-thalassemia patients not discovered\u00a0at birth?<\/li>
  3. How is the Bombay blood group formed? What antigens are present in the serum of a person with this blood type?<\/li>
  4. What other mutations apart from the LDL receptor mutation are responsible for Familial Hypercholesterolemia? How is this disease inherited?<\/li>
  5. In Africa, about 97% of the population is Rh+. How many per cent of the population is a heterozygote?<\/li>
  6. A heterozygous pea plant with round and yellow seed is crossed with a homozygous recessive pea plant with elongated and green seeds. Draw up the cross and state the phenotypic ratio of the F1 generation.<\/li>
  7. A heterozygous pea plant with round and yellow seed is crossed with a homozygous recessive pea plant with elongated and green seeds. The F1 generation was crossed with each other; based on and the following ratios, what is the distance between the genes? Are the genes linked?
    1. Round and yellow: 415\u00a0<\/li>
    2. Round and green: 42\u00a0<\/li>
    3. Elongated and yellow: 50\u00a0<\/li>
    4. Elongated and green: 360\u00a0\u00a0\u00a0<\/li><\/ol><\/li>
    5. In a population of 30000 people, 10000 of them have the O blood group. If 6000 of them are heterozygous for blood group A, calculate the allelic frequencies of the ABO genes.<\/li>
    6. A woman with haplotypes A1, A4, B5, B20 who has a child with haplotypes A2, A4, B5, B27 takes a DNA test to determine the paternity of her child. Which of these two men is most likely the father of the child? The possible fathers with their haplotypes are listed as follows:
      1. Uriel: A8, A17, B8, B27<\/li>
      2. Gideon: A2, A5, B27, B29. <\/li><\/ol><\/li><\/ol>\n\n\n<\/span>\n

        Answers<\/h3>\n<\/span>\n\n\n
        1. Anticipation is when a genetic disorder is passed on to the next generation with an earlier age of onset and an increase in the severity of symptoms. It is observed in diseases with dynamic mutations such as Fragile X syndrome and Huntington’s disease.<\/li>
        2. Beta thalassemia is not noticed at birth but only after a few months, because the fetus has two gamma chains and needs time to switch them for the beta chains. This is when the disease becomes evident, as the switch from the delta chain to beta chain is impaired.<\/li>
        3. The Bombay blood group is formed when the H gene is absent i.e genotype is __hh. In this case, the H precursor antigen is not made and neither the A nor B antigens are made. The antibodies present in the serum are Anti-A, anti-B and anti-H.<\/li>
        4. Mutations in Apolipoprotein B-100 and adaptin protein can also lead to FH. It is inherited in an autosomal dominant way.<\/li>
        5. Rhesus factor is an autosomal dominantly inherited trait.<\/li><\/ol>\n\n\n\n

          This means that Rh+ people are both the heterozygotes and homozygous dominants.<\/p>\n\n\n\n

          • So p2<\/sup>+2pq=0.97\u00a0 and q2=0.03.<\/li>
          • Therefore, q=\u221a0.03= 0.1732.<\/li>
          • And if p+q=1, then p=1-q=1-0.1732=0.8268.<\/li>
          • So the population of heterozygotes is 2pq= 2\u00d70.8268\u00d70.1732=0.2864.<\/li>
          • 28.64% of the population is a heterozygote<\/li><\/ul>\n\n\n\n

            6. Since the heterozygous plant expresses round shape and yellow colour, we can conclude that the round shape is dominant to the elongated shape, and the yellow colour is dominant to the green colour.<\/p>\n\n\n\n

            • Parental Phenotypes: Round and Yellow \u00d7 Elongated and Green<\/li>
            • Parental Genotypes: RrYy \u00d7 rryy<\/li>
            • Gametes: (RY)(Ry)(rY)(ry) \u00d7 (ry)<\/li><\/ul>\n\n\n\n
               <\/td>(ry)<\/td> <\/td><\/tr>
              (RY)<\/td>RrYy<\/td> <\/td><\/tr>
              (Ry)<\/td>Rryy<\/td> <\/td><\/tr>
              (rY)<\/td>rrYy<\/td> <\/td><\/tr>
              (ry)<\/td>rryy<\/td> <\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

              Phenotypic ratio of F1 =\u00a0Round and Yellow : Round and Green: Elongated and Yellow : Elongated and Green = 1:1:1:1<\/p>\n\n\n\n

              7. Distance between genes (cM) = (number of recombinant offspring \u00f7 total number of offspring) \u00d7 100%<\/strong><\/p>\n\n\n\n

              The round-yellow and elongated-green are the parental offspring(offspring with parental phenotype) while round-green and elongated-yellow are the recombinant offspring(offspring with new phenotype)<\/p>\n\n\n\n

              So distance = (92 \u00f7 867) \u00d7 100% = 10.6% = 10.6cM<\/p>\n\n\n\n

              Since the distance is less than 50cM, the genes are linked. <\/p>\n\n\n\n

              This also explains why the number of recombinant offspring is so low; genes that are linked\/too close to each other, have a lower probability of recombination.<\/p>\n\n\n\n

              8. <\/p>\n\n\n\n

              • IA<\/sup>= p<\/li>
              • IB<\/sup>= r<\/li>
              • i= q<\/li>
              • q2<\/sup>= 10000\u00f730000= 0.33 so q=\u221a0.33 = 0.5773<\/li>
              • 2pq= 6000\u00f730000(…heterozygous for A is IA<\/sup>i…) = 0.2<\/li>
              • p=0.1732<\/li>
              • p+r+q=1<\/strong><\/li>
              • r=1-p-q= 1-0.1732-0.5773= 0.2495<\/li><\/ul>\n\n\n\n

                9. Haplotypes are gene sequences that are inherited in blocks. Since the mother passed down A4, B5 to her child, we know that these two are on the same chromosome and A1, B20 are on her other chromosome. <\/p>\n\n\n\n

                Since the child inherited A4, B5 from the mother, A2, B27 came from the father. The man with this haplotype is Gideon and he will most likely be the father of the child.<\/p>\n<\/span>

                Questions<\/h3>

                Answers<\/h3><\/div>","protected":false},"excerpt":{"rendered":"

                Questions Scroll down for answers! Define the term \u2018anticipation\u2019 in disease. Give two examples of diseases that express this phenomenon?\u00a0 Why are beta-thalassemia patients not discovered\u00a0at birth? How is the Bombay blood group formed? What antigens are present in the serum of a person with this blood type? What other mutations apart from the LDL […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1357,"menu_order":5,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1363","page","type-page","status-publish","hentry"],"yoast_head":"\nTheory Questions and Answers VI – Meddists<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/theory-questions-and-answers\/theory-questions-and-answers-vi\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"4 minutes\" \/>\n<script type=\"application\/ld+json\" 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