From which set of individuals could one properly conclude that the disease in th

Question

From which set of individuals could one properly conclude that the disease in this pedigree is not inherited in an X-linked recessive manner? In other words, which individuals are inconsistent with X-linked recessive inheritance? Choose the best option from those listed below.

A. 1, 2, 3, 5, 6, 7

B. 3, 4, 9, 10, 11, 12

C. 7, 8, 13, 14, 15, 16

Question:

From which set of individuals could one properly conclude that the disease in this pedigree is not inherited in an autosomal dominant manner? In other words, which individuals are inconsistent with autosomal dominant inheritance? Choose the best option from those listed below.

A. 1, 2, 3, 5, 6, 7

B. 3, 4, 9, 10, 11, 12

C. 7, 8, 13, 14, 15, 16

Question:

From which set of individuals could one properly conclude that the disease in this pedigree is not inherited in an autosomal recessive manner? In other words, which individuals are inconsistent with autosomal recessive inheritance? Choose the best option from those listed below.

A. 1, 2, 3, 5, 6, 7

B. 3, 4, 9, 10, 11, 12

C. 7, 8, 13, 14, 15, 16

Question:

Cystic fibrosis is inherited as an autosomal recessive trait. On average, about ¼ of the children from carrier parents are expected to have the disease. In one study, thousands of families with at least one confirmed case of cystic fibrosis were analyzed. About 1/3, not 1/4 of the children from carrier parents were found to have the disease. Explain why this discrepancy was seen.

Question:

What observation led Garrod to suspect that alkaptonuria was an inherited disease?

Explanation / Answer

In the first pedigree, it is B-3,4,9, 10, 11, 12.. This will be because, the no. 10 female is affected. If the trait had been inherited in a X-linked recessive manner, an unaffected female could have affected sons but not affected daughter (the father beimg normal).

In the second pedigree, it is B- 3,4,9, 10, 11, 12.. This will be because, the no. 11 male's parents are both unaffected, though he is affected by the trait. This should not happen in case of autosomal dominant inheritance.

In the third pedigree, it is C-7,8,13,14,15,16 because if the trait had been autosomal recessive, then the affected parents 7 and 8, bear both affected alleles This is true for both of the parents and in this case their all offsprings would have been affected, which is not the case. So, it is inconsistent.

Garrod is best known for his scientific study of inborn errors of metabolism. He developed an increasing interest in chemical pathology, and investigated urinechemistry as a reflection of systemic metabolism and disease. This research, combined with the new understanding of Mendelian inheritance, evolved from an investigation of a few families with an obscure and not very dangerous disease (alkaptonuria) to the realization that a whole territory of mysterious diseases might be understood as inherited disorders of metabolism.

In the 1890s he collaborated with Frederick Gowland Hopkins, a well-known and respected London physician and biochemist who studied the concept of how vitamins, then known as “accessory factors”, effect dietary health of patients. Under Hopkins’s influence and led by his own childhood fascination with color variations, he took particular notice of how the color of urine changed.

In 1897, a mother arrived at the Great Ormand Street Hospital with an infant and a diaper stained brownish-black. Dr. Garrod recorded the family history of the baby and kept tabs on the newborn’s growth over the years. He quickly began seeking other patients with the same disorder and found forty cases and read up on the disorder, the first instance of which was noted in 1822.

In 1900, the same mother became pregnant. Once the baby was born, Garrod had nurses closely inspecting the baby’s diaper. Sure enough, they noted the appearance of the black urine 52 hours after the baby was born. Garrod subsequently deduced that the condition, alkaptonuria, was innate. Looking at his records, Garrod noticed that alkaptonuria was more likely to occur in the children of first cousins.

Working with William Bateson, Garrod came to understand the pattern of alkaptonuria appearance in children based on Mendelian principles. Once he applied Mendel’s concepts to alkaptonuria, he published a paper in 1902 called “The Incidence of Alkaptonuria: A Study of Chemical Individuality”. In the paper, Garrod explains how he came to understand the condition and speculates as to its causes. He cites various case studies and compares alkaptonuria to albinism in how it's inherited.

The increased incidence of cydtc fibrosis, could be due to mutations in the adult in the respective gene. It could be that in carrier of cydtic fibrosis, mutation occurred in the normal allele. This would lead to the disease.

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