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Please help on #13-19Medical Science DQs.docx

Medical Science DQs.docx

Genetics DQs: Objectives 1-8, Nussbaum Chapters 2-4
1. Describe the organization of the human chromosome by graphically representing how the following
items are related in a hierarchical fashion: chromosome, base pair, nucleosome, kilobase pair,
intron, gene, exon, chromatin, codon, nucleotide, promoter.
2. At a certain locus, a person has two alleles A and a.
a. What alleles will be present in this person’s gametes?
b. (1) When do A and a segregate if there is no crossing over between the locus and the
centromere of the chromosome? (2) if there is a single crossover between the locus and the
centromere?
3. Disregarding crossing over, which increases the amount of genetic variability, estimate the
probability that all your chromosomes have come to you from your father’s mother and your
mother’s mother. Would you be male or female?
4. Would a chromosome abnormality of equal size on chromosome 18 or 19 be expected to have
greater clinical impact? On chromosome 21 or 22?
5. Describe how mutation in each of the following might be expected to alter or interfere with normal
gene function and thus cause human disease: promoter, initiator codon, splice sites at intron-exon
junctions, one base pair deletion in the coding sequence, stop codon.
6. Most of the human genome consists of sequences that are not transcribed and do not directly
encode gene products. For each of the following, consider ways in which these genome elements
might contribute to human disease: introns, Alu or LINE repetitive sequences, locus control regions,
pseudogenes.
7. Contrast the mechanisms and consequences of RNA splicing and somatic rearrangement.
8. Consider different ways in which mutations or variation in the following might lead to human
disease: epigenetic modifications, DNA methylation, miRNA genes, lncRNA genes.
9. Consider the mechanisms/consequences of genomic imprinting and X chromosome inactivation.
10. Polymorphism can arise from a variety of mechanisms, with different consequences. Describe and
contrast the types of polymorphism that can have the following effects:
a. A change in dosage of a gene or genes
b. A change in the sequence of multiple amino acids in the product of a protein-coding gene
c. A change in the final structure of an RNA produced from a gene
d. A change in the order of genes in a region of a chromosome
e. No obvious effect
11. Which of the following types of polymorphism would be most effective for distinguishing two
individuals from the general population: a SNP, a simple indel, or a microsatellite? Explain your
reasoning.
12. What is the main cause of numerical chromosome abnormalities in humans?
13. Compare/contrast genetic imprinting and uniparental disomy as it relates to BWS. Describe the
mechanism by which uniparental disomy can even occur. In addition to mutations in the genes
implicated in BWS, discuss how a mutation in the imprinting locus control region could cause BWS.
How might imprinting explain the phenotypes associated with triploidy?
Uniparental disomy is defined as the presence of a disomic cell line containing two chromosomes,
or portions thereof, that are inherited from only one parent.
Imprinting involves the introduction of epigenetic marks in the germline of one parent, but not the
other, at specific locations in the genome.
14. Although it is always a severe disease, the severity of sickle cell disease is determined partially by
the haplotype on which the mutation occurs. How could the haplotype affect disease severity?
Describe penetrance and how this affects disease severity using another congenital genomic
disorder as an example. Sickle cell provides an example of heterozygote survival advantage. What
is this and what other disorders can you think of that express this same advantage? What is the
rationale for hypothesizing a heterozygote advantage for those diseases?
15. Gene therapy can be used for several blood disorders including sickle cell and thalasemmias. What
is gene therapy and what are the difficulties with gene therapy for these (and most) disorders? Genetics DQs: Objectives 1-8, Nussbaum Chapters 2-4
16. Case: A 2300-gm male infant was born at 37 weeks’ gestational age to a 25-year-old mother. This
was her sixth pregnancy; she had had two previous
children and three spontaneous abortions. At birth,
multiple congenital anomalies were noted, including
bilateral cleft
lip
and
palate,
microcephaly,
polydactyly, low-set abnormally shaped ears, and
undescended testes. Cytogenetic evaluation of the
infant showed 46,XY,+13,der(13;14)(q10;q10).
a. What is the most probable diagnosis?
b. Is cytogenetic confirmation (karyotyping) of
such a typical phenotype necessary? Explain.
c. This is the child’s karyotype (right), identify
the problem. Is this a balanced or unbalanced
karyotype? What possible karyotype(s) does
the mother possess (assuming she is phenotypically normal)? What were the theoretically
possible gametes she formed?
d. Would you expect infants with his karyotype to be phenotypically different from infants with
47,XY,+13? Explain.
e. If this infant has inherited his robertsonian translocation from one of his parents, what
significance does this have for the parents’ reproductive future? Describe a possible
mechanism by which this infant obtained this mutation if it was not inherit.
f. Identify the problem (karyotype, right). How
would you denote this karyotype? What is the
mechanism
(process)
that
results
in
karyotypes such as this one? What is the most
common causative factor associated with this
type of karyotype? g. Is this individual phenotypically normal
(karyotype, right)? Describe the mechanism
that can cause this individual to produce an
infant such as in the case above. Are the
cytogenetically abnormal babies resulting from
this karyotype associated with advanced
maternal age (>34 years)?
17. You send a blood sample of a dymorphic infant to the
lab and the child’s karyotype reads: 46,XY,del(18)
(q12).
a. What does this mean?
b. You decide to sample blood from each parent. Why?
c. The father’s karyotype reads: 46,XX,t(7;18)(q35;q12). What does this mean? Sketch the
father’s karyotype. When did the father’s mutation happen? What are the likely gametes he
can produce? Genetics DQs: Objectives 1-8, Nussbaum Chapters 2-4
18. Is the following phenotype normal or abnormal? What is the prognosis for the gametes?
a. 47,XX,+13
b. 46,XY,del(band 4)
c. 46,XX,inv(3)(p25;q21)
d. 47,XX,+15(centromere 15)
19. Briefly describe the genetic abnormality and clinical presentation of the following diseases:
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
p. Down syndrome
Chronic myelogenous leukemia
Sickle cell anemia
Alzheimer’s disease
Familial hyperlipidemia
Cystic fibrosis
Hemophilia
Marfan’s syndrome
Phenylketonuria
Tay Sachs Disease
Fragile X
Turner’s Syndrome
Kleinfelter’s Syndrome
Huntington’s Disease
Duchenne’s muscular dystrophy
Prader Willi: Chromosome 15 from mother is copied onto the father.

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