If a woman hears her baby cry, she may experience milk ejection from the nipples even before the baby is placed to the breast. What is the explanation for this?

TLS Online TPP Program

#Question id: 16133

#Unit 14. Methods in Biology

You are running a human assisted reproduction clinic and providing state-of-the-art genetic diagnostic services. A married couple who already had a child with cystic fibrosis approach you because they wish to have another child, but only if they can be assured that the child will not have cystic fibrosis. You genotype the woman and discover that she is a heterozygote for Del508, the most common mutation causing cystic fibrosis. You suggest that the couple consider first polar body testing, in which several unfertilized oocytes (each with its first polar body) are retrieved from the woman, the first polar bodies are removed, and PCR tests are conducted on DNA from each of the first polar bodies. The couple agrees, and you obtain the following results:

 

Given the couple's desire to have a child without cystic fibrosis, which oocytes would you employ in vitro fertilization?

TLS Online TPP Program

#Question id: 16134

#Unit 14. Methods in Biology

You obtain 6 BACs (of known order, as shown below) and 7 STSs (of unknown order) that derive from a region of mouse chromosome 16 whose genomic sequence has not yet been finished.   

 

By PCR (using 20-bp primers at either end of each STS), you test each of the 6 BACs for the presence (+) or absence (-) of each of the 7 STSs. You obtain the following results:

 

You determine the DNA sequences of PCR products obtained at STS5 using BACs B, C, D, E, and F as PCR templates. The DNA sequences of PCR products obtained using BACs B and C are identical, but they differ by several nucleotide substitutions from the DNA sequences of PCR products obtained using BACs E and F. Oddly, PCR product obtained using BAC D appears to be a mixture of two sequences – one corresponding to the BAC B/ BAC C sequence and the other corresponding to the BAC E/ BAC F sequence. Briefly account for these findings, and explain how a single PCR assay could amplify two different sequences.

TLS Online TPP Program

#Question id: 16135

#Unit 14. Methods in Biology

You obtain 6 BACs (of known order, as shown below) and 7 STSs (of unknown order) that derive from a region of mouse chromosome 16 whose genomic sequence has not yet been finished.   

 

By PCR (using 20-bp primers at either end of each STS), you test each of the 6 BACs for the presence (+) or absence (-) of each of the 7 STSs. You obtain the following results:

 

Would you expect the DNA sequence of PCR product obtained at STS5 using mouse genomic DNA as template to more closely resemble that obtained using BAC B, BAC D, or BAC F? Briefly explain your answer.

TLS Online TPP Program

#Question id: 16136

#Unit 14. Methods in Biology

You obtain 6 BACs (of known order, as shown below) and 7 STSs (of unknown order) that derive from a region of mouse chromosome 16 whose genomic sequence has not yet been finished.   

 

By PCR (using 20-bp primers at either end of each STS), you test each of the 6 BACs for the presence (+) or absence (-) of each of the 7 STSs. You obtain the following results:

 

Is there a second STS at which you would like to sequence PCR products obtained using BACs as templates? If so, which BACs would you test in this way, and what sequencing results might you predict for each of the BACs tested?

TLS Online TPP Program

#Question id: 16137

#Unit 14. Methods in Biology

You obtain 6 BACs (of known order, as shown below) and 7 STSs (of unknown order) that derive from a region of mouse chromosome 16 whose genomic sequence has not yet been finished.   

 

By PCR (using 20-bp primers at either end of each STS), you test each of the 6 BACs for the presence (+) or absence (-) of each of the 7 STSs. You obtain the following results:

 

How would you use the sequence information presented in to design two new STSs (with new PCR primer pairs) to replace STS5? (Call the new ones STS51 and STS52. STS51 should be present (+) in BAC B, and STS52 should be present (+) in BAC F.)

TLS Online TPP Program

#Question id: 16138

#Unit 14. Methods in Biology

You obtain 6 BACs (of known order, as shown below) and 7 STSs (of unknown order) that derive from a region of mouse chromosome 16 whose genomic sequence has not yet been finished.   

 

By PCR (using 20-bp primers at either end of each STS), you test each of the 6 BACs for the presence (+) or absence (-) of each of the 7 STSs. You obtain the following results:

 

Would you expect STS51 and STS52 to be present in BAC D?