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Problem 1. You send a blood sample from a dysmorphic infant to the chromosome laboratory for analysis. The laboratory report states that the child’s karyotype is 46,XY,del(18)(q12). a. What does this karyotype mean?
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Problem 1 • You send a blood sample from a dysmorphic infant to the chromosome laboratory for analysis. The laboratory report states that the child’s karyotype is 46,XY,del(18)(q12). • a. What does this karyotype mean? • b. The laboratory asks for blood samples from the clinically normal parents for analysis. Why? • c. The laboratory reports the mother’s karyotype as 46, XX and the father’s karyotype as 46, XY,t(7;18)(q35;q12). What does the latter karyotype mean? Referring to the normal chromosome idiograms sketch the translocation chromosome or chromosomes in the father. Sketch these chromosomes in meiosis in the father. text problem 1 page 155
Answer Problem 1 • You send a blood sample from a dysmorphic infant to the chromosome laboratory for analysis. The laboratory report states that the child’s karyotype is 46,XY,del(18)(q12). • a. What does this karyotype mean? • The child has 46 chromosomes, male, with a deletion on the long arm of chromosome 18 from q12 onward • b. The laboratory asks for blood samples from the clinically normal parents for analysis. Why? • To determine whether the abnormality is de novo or inherited from a balanced carrier parent • c. The laboratory reports the mother’s karyotype as 46, XX and the father’s karyotype as 46, XY,t(7;18)(q35;q12). What does the latter karyotype mean? • 46 chromosome, male, only one normal 7 and 18, reciprocal translocation between 7 and 18 The regions after q35 on 7 and after q12 on18 have switch • Referring to the normal chromosome idiograms sketch the translocation chromosome or chromosomes in the father. Sketch these chromosomes in meiosis in the father. text problem 1 page 155
Answer Problem 1 • Referring to the normal chromosome idiograms sketch the translocation chromosome or chromosomes in the father in his son. Sketch these chromosomes in meiosis in the father. What kinds of gametes can he produce. 21 21 14 14 11.3 12 11.3 12 35 21 12 21 31 22 31 18 33 18 12 33 35 Translocation here 7 7 text problem 1 page 155
Answer Problem 1 • Referring to the normal chromosome idiograms sketch the translocation chromosome or chromosomes in the father in his son. Sketch these chromosomes in meiosis in the father. 35 33 31 21 12 14 21 11.3 12 11.3 21 12 14 21 33 31 22 Pairing at meiosis text problem 1 page 155
Problem 2 Note this could be a picture of a dicentric chromosome • Considering the chromosome spread to the right. • a. If this person was phenotypically normal and had 6 children how many would you expect to be phenotypically normal For this problem assume two separate chromosome in the picture
Answer Problem 2 • a. If this person was phenotypically normal and had 6 children how many would you expect to be phenotypically normal quadrivalent pair formed during meiosis One completely normal individual Two phenotypically normal individual Four affected individuals
Problem 3 • Considering the follow karotype. • a. Is this individual normal • b. What is his karyotype • c. If he is not what syndrome does he have. • d. What is one possible mechanism to explain this karotype
Answer Problem 3 • Considering the follow karotype. • a. Is this individual normal • No, this individual is not • One chromosome is larger • It appears to be an isochromosome of 21 • b. What is his karyotype • 46 XY t(q21q:q21) 46 chromosomes, male with translocation between the long are of chromosome 21 • c. If he is not what syndrome does he have. • This individual is essentially trisomy for 21 so he probably has Down Syndrome • d. What is one possible mechanism to explain this karotype • Appears to be an isochromosome of 21. Chromosome 21 is acrocentric with the short arm (p) mainly containing satellite DNA for ribosomal RNA. Chromosomes 13,14,15, and 22 have a similar structure. Loss of the short of 21 should cause little to no deleterious affects. The duplication of the long arm will result in trisomy 21. A similar event could occur in chromosome 13, 14, 15, and 22 however only 21 will produce a viable phenotype. Trisomy 13 is possible but most cases die in a month
Problem 4 • Consider the karyotype to the right. • a. What syndrome does the individual have? • b. List the average phenotypic features of a 13 year old individual • c. Would this individual be able to have normal childern
Answer Problem 4 • Consider the karyotype to the right. • a. What syndrome does the individual have? • This individual has turner syndrome. Probably due to monosomy of the X chromosome
Answer Problem 4 • b. List the average phenotypic features of a 13 year old individual • c. Would this individual be able to have normal childern • No improper development of the ovaries
Problem 5 • An individual presents with the following clinical signs • Infantile feeding difficulties, childhood hyperphagia and obesity, hypotonia, congnitive impairment, sterility, and dysmorphism. • What syndrome does this individual have? • Which of the karyotypes below is most consistent with the individuals syndrome. • What is one possible mechanism that may have caused this syndrome.
Answer Problem 5 • An individual presents with the following clinical signs • Infantile feeding difficulties, childhood hyperphagia and obesity, hypotonia, congnitive impairment, sterility, and dysmorphism. • What syndrome does this individual have? • This individual probably has Prader Willi syndrome • Which of the karyotypes below is most consistent with the individuals syndrome. • The karyotype with no chromosomal abnormalities Klinefelter Down Syndrome Appears Normal Turner Syndrome
Answer Problem 5 • What is one possible mechanism that may have caused this syndrome. • Because the karyotype is normal this disorder may have been caused by uniparental disomy. This is a type of nondisjunction.
