m4 - ebnalfady

[ArchivalUser]

4. A newborn baby has a sibling with sickle cell anemia (141900) and is at risk for the disease. The appropriate diagnostic test for sickle cell anemia in this baby will include
a. DNA amplification
b. Hemoglobin antibodies
c. DNA restriction
d. Red cell counting
e. DNA fingerprinting

[ArchivalUser]

aa

[ArchivalUser]

DNA amplification =what?

[ArchivalUser]

DNA amplification=pcr in this qs
.) Sufficient DNA for analysis can be obtained by ampli¬fication of leukocyte DNA using the polymerase chain reaction (PCR).

Short segments of DNA (oligonucleotide primers) are designed to be com¬plementary to areas flanking the DNA region of interest”in this case, the portion of the β-globin gene that may harbor the sickle cell anemia (141900) mutation. Some 20 to 30 cycles of cooling (to anneal the primers), synthesis (with heat-stable DNA polymerase), and heating (to melt the DNA and allow the next cycle) can amplify the targeted DNA seg¬ment over 1 million-fold. Hybridization in duplicate to allele-specific oligonucleotides (ASOs; one ASO for the hemoglobin A mutation, one ASO for the S mutation) can establish the diagnosis of normal (AA alleles), sickle trait (AS alleles), or sickle cell anemia (SS alleles). Newborns have fetal hemoglobin (α- and γ-globin) with little expression of hemoglobin A (α- and β-globin genes) until 3 to 6 months of life, so testing for anemia or for abnormal hemoglobin with antibodies would not be helpful.
DNA polymorphisms (nucleotide sequence variations) occur approxi¬mately once per 200 to 500 base pairs (bp) of human DNA. If the sequence variation affects the recognition site for a restriction endonuclease, the altered segment sizes produced by endonuclease digestion allow detection of the sequence change [restriction fragment length polymorphism (RFLP)]. If the nucleotide change causing the RFLP is adjacent to (linked with) or coincident with a disease mutation, then one size variant of the RFLP may be diagnostic. However, mutations of known sequence (such as that for sickle cell anemia) are better detected by PCR and ASOs. The use of several highly variable RFLPs produces a pattern of restriction fragments that is highly distinctive for each individual (DNA fingerprinting) but not diagnostic for a particular disease.

[ArchivalUser]

the answer in some qss may put PCR INSTEAD OF DNA amplification

[ArchivalUser]

thanks bro, for q&A with explanations

[ArchivalUser]

thanks