Pedigree charts and genetics testing

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Pedigree charts and genetics testing


Pedigree charts and genetics testing


Assignment 4 Pedigree charts and Genetic testing 1) Consider the pedigree chart ( provided in learning activity 1.4) showing the inheritance of hemophilia in the family and descendants of Queen Victoria. Queen Victoria’s third child, Alice, passed hemophilia on to the German and Russian imperial families.
Alice had six children, one of whom had hemophilia. Her only son., Fred , died at the age of three after a fall. Of her five daughters, two were carriers of the recessive gene.
One of those heterozygous daughters, Alix, married Tsar nikolas 11 of Russia. The recessive gene was thereby introduced into the Russian imperial family.
Alix and Nikolas had five children: Olga, Tatiane, Marie, Anastasia, and alexis. Alexis, their only son, was often in severe pain as a child because of the bleeding into joints that occurred. But alexis dis not die from hemophilia. At the age of 14 he was executed along with his four older sisters and his parents. None of his sisters had any children, so their genotypes are not known.
what is the probability that Anastasia was heterozygous for the hemophilia gene? What is the probability that she was homozygous recessive? What is the probability that she was homozygous dominant?
If had lived and had married and had children with a normal, purebred woman, what are the chances that his daughter would have hemophilia? What are the chances that his son would have hemophilia?
In 1995 a man by the name of Eugene Romanov claimed that he was a grandson of Nikolas II’s youngest daughter, Anastasia,whose body had never been recovered. He claimed to share both the last name,Romanov, and the disease of hemophilia with the royal Family’s lineage. He claimed that Anastasia was not executed but was raised by a farmer and late married and gave birth to a daughter, his mother. Assuming that Eugene’s argument was true, what were the likely genotypes of his mother and grandmother if neither had hemophilia? What were the likely genotypes of his father and grandfather if neither had the disease? Could Eugene’s argument be true? Why or why not? 2) The condition known as rickets in humans causes bones in its victims. To be abnormally soft. Rickets in children can cause bone deformities. Usually ,rickets is caused by a dietary lack of vitamin D, calcium, and phosphorus; rickets is, therefore, not usually a genetic condition. How ever one form known as vitamin D resistant rickets is caused by a dominant allele located on the X chromosome. The pedigree chart in figure 1.10 shows the inheritance of the genetic form of rickets through three generations of a family.

Figure 1.10 Pedigree chart: inheritance of Genetic form of rickets
⬜️Normal male
⬛️male with rickets
⚪️Normal female
⚫️Female with rickets
1 ⬜️. ⚫️2

P generation

F1 generation 3⬜️. ⚫️4. 5⬜️. 6⚪️. 7⬜️8⬛️. ⚪️9

F2 generation ⬜️. ⬛️. ⚫️. ⬜️. ⬜️. ⬜️

10. 11. 12. 13. 14. 15

a) What is the genotype of the parental female (#2) if R is the dominant rickets allele on the X chromosome? Explain your reasoning?

b) what is the genotype of the parental male (#1)? Explain your reasoning?

C) Explain why individual #8 has rickets, has three sons who so not who do not have rickets.

d) what is the genotype of individual #4? Explain your reasoning.

e) Individual #10 wonder why he does not have rickets, but his brother and sister both have the disease. Explain how this situation is possible.

3) Larry and his older brother, Harry, have just found out that their father has been diagnosed with Huntington disease. Larry is 22 years old and Harry is three years older than Larry. Huntington disease is an incurable disorder that causes a slow progressive deterioration of the brain, resulting in death. Symptoms appear in the affected individual between the ages of 30 and 50 and they do not improve. Huntington disease is an autosomal dominant disorder for which a genetic screening test has been developed. That test can reveal with 100 percent certainty whether or not the person will develop the disease. Larry is still single,but Harry is married and he and his wife are expecting their first child. In your opinion, should Larry have the screening test for Huntington disease? Why or why not? Should Harry have test done? Why or why not?

4) Cynthia is 42 years old and is pregnant with her third child. Routine genetic screening conducted 18 weeks into the pregnancy showed an abnormal result that may indicate that the baby has down syndrome. Cynthia is being encouraged to consider amniocentesis, which could either confirm down syndrome or yield normal result. Amniocentesis is not required in your opinion, should Cynthia proceed with amniocentesis? Why or why not? If she does agree to amniocentesis and the results indicate that the fetus does have Down syndrome, what should Cynthia do?

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