{"id":1362,"date":"2020-08-06T22:29:03","date_gmt":"2020-08-06T22:29:03","guid":{"rendered":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/theory-questions-and-answers\/theory-questions-and-answers-v\/"},"modified":"2021-05-19T10:36:57","modified_gmt":"2021-05-19T08:36:57","slug":"theory-questions-and-answers-v","status":"publish","type":"page","link":"https:\/\/meddists.com\/learn\/pre-clinical\/medical-genetics\/theory-questions-and-answers\/theory-questions-and-answers-v\/","title":{"rendered":"Theory Questions and Answers V"},"content":{"rendered":"\n

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

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

  1. A woman with blood group B has a sister with blood group A. Describe their genotypes and that of their parents if the parental blood groups are O and AB.<\/li>
  2. Explain the gain of function mutations. <\/li>
  3. What are cancer syndromes and what is their role in the development of cancers? Give two examples.<\/li>
  4. Explain the difference between driver and passenger mutations.<\/li>
  5. What is the function of the Anaphase Promoting Complex and at what stage of the cell cycle does it work?<\/li>
  6. What is the difference between caretaker genes and gatekeeper genes? Give an example for each.<\/li>
  7. <\/a>What pattern of inheritance is shown in the pedigree below(the image is inserted after question 10 at the bottom of the question section)? List four diseases that follow this same pattern.<\/li>
  8. Explain the difference between dominant epistasis and recessive epistasis.<\/li>
  9.  Two healthy parents have a healthy daughter and a son with Duchenne’s Muscular Dystrophy(DMD). What are the genotypes of all four people and what is the probability of the daughter to be a carrier?<\/li>
  10. Two healthy parents have a daughter with Phenylketonuria(PKU).<\/li><\/ol>\n\n\n\n

    They visit the doctor as they have some questions about future pregnancies. As the doctor, answer the following questions:<\/p>\n\n\n\n

    a. What is the probability of both parents to be carriers of the disease?<\/p>\n\n\n\n

    b. What is the probability that their second child will have PKU?<\/p>\n\n\n\n

    c. What is the probability that their second child will be a carrier of the disease?<\/p>\n\n\n\n

    d. They later have a second child, a son and he turns out to be healthy. What is the probability that the boy is a carrier of the disease?<\/p>\n\n\n\n

    e. If this couple should have three more children, what is the probability that none of them will have PKU?<\/p>\n\n\n\n

    \"\"
    IMAGE FOR QUESTION 7 <\/figcaption><\/figure>\n\n\n<\/span>\n

    Answers<\/h3>\n<\/span>\n\n\n
    1. If Parent 1 has blood group O, her genotype will be iiH_  and the genotype of parent 2 is IA<\/sup>IB<\/sup>H_. The genotype of the woman is IB<\/sup>iH_ and that of her sister is IA<\/sup>iH_. The girls receive the ‘i’ gene from parent 1 and the ‘I’ gene from parent 2.<\/li>
    2. These are mutations that cause the gene to be expressed more than normal, with a stronger activity or at the wrong time and location. It leads to the formation of an enzyme with a new, mutant phenotype that forms a new product.<\/li>
    3. Cancer syndromes are inherited disorders that increase the chances of a person to develop cancer. Examples are Fanconi anaemia and Bloom syndrome.<\/li>
    4. Driver mutations are those that happened before carcinogenesis and are the cause of the malignant transformation while Passenger mutations are those that appeared during the course of cancer and are as a result of the carcinogenic process.<\/li>
    5. The Anaphase Promoting Complex (APC) ensures that chromosomes are properly lined up at the equator before separating. It works at the metaphase-anaphase checkpoint.<\/li>
    6. Care-taker genes are those ensure that no carcinogenic mutations happen in the cells while gate-keeper genes are those that either halt the cell cycle or cause cell apoptosis once the carcinogenic mutations happen. They are both tumour suppressor genes. An example of a care-taker gene is BRCA1 and an example of a gate-keeper gene is Tp53.<\/li>
    7. It is an autosomal recessive inheritance pattern. Examples of disease that follow this pattern are Phenylketonuria, Tay-Sachs disease, Sickle cell anaemia and Cystic fibrosis.<\/li>
    8.  In dominant epistasis, the epistatic gene can only have an influence in the presence of a dominant allele i.e the gene can only be epistatic when it is expressed in a heterozygous or homozygous dominant manner while in recessive epistasis, the epistatic gene can only have an influence in the absence of the dominant allele i.e the gene can only be epistatic when expressed in a homozygous recessive manner.<\/li>
    9. DMD is an X-linked recessive disorder. This means that the genotype of the son is Xd<\/sup>Y. For the father to be healthy, his genotype has to be XD<\/sup>Y. Since the son received a mutant X chromosome from the mother, we can conclude that she is a heterozygote( she cannot be homozygous recessive because she is healthy). So the genotype of the mother is XD<\/sup>Xd<\/sup>. In this case, the daughter can either have a genotype of XD<\/sup>XD <\/sup>or XD<\/sup>Xd<\/sup>(she will receive XD <\/sup>from her father and can receive either XD <\/sup>or Xd <\/sup>from her mother). Therefore, she has a 50% chance to be a carrier(heterozygote) for DMD<\/li>
    10. a. PKU is an autosomal recessive disease. This means that for two healthy parents to have a child with PKU, both parents MUST be heterozygotes. Therefore, the probability of both parents to be carriers of PKU is 1.<\/li><\/ol>\n\n\n\n

      b. We will make a cross between the parents to figure this out<\/p>\n\n\n\n

      Parental phenotypes:             Healthy \u00d7 Healthy<\/p>\n\n\n\n

      Parental genotypes:                 Gg  \u00d7  Gg<\/p>\n\n\n\n

      Parental gametes:                    \u24bc\u24d6\u00d7\u24bc\u24d6<\/p>\n\n\n\n

       <\/td>\u24bc<\/td>\u24d6<\/td><\/tr>
      \u24bc<\/td>GG<\/td>Gg<\/td><\/tr>
      \u24d6<\/td>Gg<\/td>gg<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

      As seen here, one out of four children will have PKU. Therefore, the probability for the second child to have PKU  is \u00bc <\/p>\n\n\n\n

      c. As seen in the above cross, out of four children, two of them are carriers(heterozygotes). Therefore the probability of the second child to be a carrier is 2\/4=1\/2.<\/p>\n\n\n\n

      d. In this case, the probability will be 2\/3. This is different from the previous question in the sense that in the previous question, we did not know if the child was healthy or not so we took the chances out of ALL the children, so 2 out of 4. <\/p>\n\n\n\n

      In this question, we already know that the child is healthy and as seen from the Punnett’s square above, this already eliminates one possibility, leaving three healthy kids. So out of the 3 HEALTHY CHILDREN, two of them are heterozygotes.<\/p>\n\n\n\n

      e. Referring to Punnett’s square above, 3 out of four children will not have the disease and the probability that one child will not have the disease is 3\/4.<\/p>\n\n\n\n

      So the probability that none of the three children will have the disease is 3\/4 \u00d7 3\/4 \u00d7 3\/4 = 27\/64<\/p>\n\n\n\n

       We multiply all three because the events are independent events<\/p>\n<\/span>

      Questions<\/h3>

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

      Questions Scroll down for answers! A woman with blood group B has a sister with blood group A. Describe their genotypes and that of their parents if the parental blood groups are O and AB. Explain the gain of function mutations.  What are cancer syndromes and what is their role in the development of cancers? […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1357,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1362","page","type-page","status-publish","hentry"],"yoast_head":"\nTheory Questions and Answers V – 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-v\/\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"5 minutes\" \/>\n<script type=\"application\/ld+json\" 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