The polymerase chain reaction (PCR) is a powerful biological tool that allows the rapid amplification of any fragment of DNA without purification. In PCR, DNA primers are made to flank the specific DNA sequence to be amplified. These primers are then extended to the end of the DNA molecule with the use of a heat-resistant DNA polymerase. The newly synthesized DNA strand is then used as the template to undergo another round of replication.The 1st step in PCR is the melting of the target DNA into 2 single strands by heating the reaction mixture to approximately 94° C, and then rapidly cooling the mixture to allow annealing of the DNA primers to their specific locations. Once the primer has annealed, the temperature is elevated to 72° C to allow optimal activity of the DNA polymerase. The polymerase will continue to add nucleotides until the entire complimentary strand of the template is completed at which point the cycle is repeated (Figure 1) Figure 1One of the uses of PCR is sex determination, which requires amplification of intron 1 of the amelogenin gene. This gene found on the X-Y homologous chromosomes has a 184 base pair deletion on the Y homologue. Therefore, by amplifying intron 1 females can be distinguished from males by the fact that males will have 2 different sizes of the amplified DNA while females will only have 1 unique fragment size.The use of PCR for sex determination relies on the fact that:
Answer(s): B
According to the passage, sex determination can be determined by amplifying intron 1 of the amelogenin gene which is found on the sex chromosomes. Due to a deletion, intron 1 on the Y sex homologue is shorter than intron 1 on the X sex homolog. This difference in size can be used to distinguish between males and females because males have one X and one Y chromosome while females have two X chromosomes. Therefore, females will have only one uniform size of intron 1 which does not bear the deletion. In contrast, males will have 2 different sizes of intron 1 following its amplification. Hence, B. is the correct answer choice.
The polymerase chain reaction (PCR) is a powerful biological tool that allows the rapid amplification of any fragment of DNA without purification. In PCR, DNA primers are made to flank the specific DNA sequence to be amplified. These primers are then extended to the end of the DNA molecule with the use of a heat-resistant DNA polymerase. The newly synthesized DNA strand is then used as the template to undergo another round of replication.The 1st step in PCR is the melting of the target DNA into 2 single strands by heating the reaction mixture to approximately 94° C, and then rapidly cooling the mixture to allow annealing of the DNA primers to their specific locations. Once the primer has annealed, the temperature is elevated to 72° C to allow optimal activity of the DNA polymerase. The polymerase will continue to add nucleotides until the entire complimentary strand of the template is completed at which point the cycle is repeated (Figure 1)Figure 1One of the uses of PCR is sex determination, which requires amplification of intron 1 of the amelogenin gene. This gene found on the X-Y homologous chromosomes has a 184 base pair deletion on the Y homologue. Therefore, by amplifying intron 1 females can be distinguished from males by the fact that males will have 2 different sizes of the amplified DNA while females will only have 1 unique fragment size.What would PCR amplification of an individual's intron 1 of the amelogenin gene reveal if the individual were male?
Answer(s): D
A male individual, which contains one X and one Y chromosome, should have 2 types of intron 1. The passage states that intron 1 on the Y chromosome has a deletion which renders it smaller in length than the corresponding allele on the X chromosome, thereby providing males with 2 different size fragments. Females which have 2 X chromosomes will then have only 1 type of intron 1 of uniform size.
The polymerase chain reaction (PCR) is a powerful biological tool that allows the rapid amplification of any fragment of DNA without purification. In PCR, DNA primers are made to flank the specific DNA sequence to be amplified. These primers are then extended to the end of the DNA molecule with the use of a heat-resistant DNA polymerase. The newly synthesized DNA strand is then used as the template to undergo another round of replication.The 1st step in PCR is the melting of the target DNA into 2 single strands by heating the reaction mixture to approximately 94° C, and then rapidly cooling the mixture to allow annealing of the DNA primers to their specific locations. Once the primer has annealed, the temperature is elevated to 72° C to allow optimal activity of the DNA polymerase. The polymerase will continue to add nucleotides until the entire complimentary strand of the template is completed at which point the cycle is repeated (Figure 1)Figure 1One of the uses of PCR is sex determination, which requires amplification of intron 1 of the amelogenin gene. This gene found on the X-Y homologous chromosomes has a 184 base pair deletion on the Y homologue. Therefore, by amplifying intron 1 females can be distinguished from males by the fact that males will have 2 different sizes of the amplified DNA while females will only have 1 unique fragment size.Both copies of intron 1 of the amelogenin gene on the 2 sex chromosomes can be referred to as:
Answer(s): C
Alleles are two or more alternative forms of a gene that are found at the same place on homologous chromosomes. Since there is a 184 base pair deletion on the Y homologue and there is no deletion at the same position in the X homologue, intron 1 represents two different alleles of the same amelogenin gene.
Apoptosis is the process of programmed cell death that can occur in multicellular organisms. The proteins involved in apoptosis are associated with pathways for cell cycle arrest and DNA repair. These processes are mostly regulated through the interplay of various proteins involved in feedback loops including some of the ones shown in Figure 1.Feedback loops forming a regulatory network affecting apoptosis, cell cycle arrest and DNA repair.Figure 1:(Bioformatics Institute)According to Figure 1, CDK2 activity would most reasonably increase due to all of the following EXCEPT:
Notice the key in the figure which will allow us to follow each arrow that stimulates the next protein and each symbol for negative feedback which means there will be some downregulation (amount/concentration goes down). [Notice a key step in the diagram: p21 inhibits CDK2]Degradation of p21 implies that the concentration of p21 in its active form goes down. The diagram shows that p21 has a negative influence on CDK2. In other words, when p21 is high, CDK2 goes low. But in our instance, p21 is low (degraded) so this allows CDK2 to rise unchecked.High cyclin G concentrations: From the bottom of Figure 1, we can see that high cyclin G leads to high mdm2 and low p53 (notice carefully, when we leave mdm2, there is only one place to go in the diagram because all the other symbols are pointing to mdm2 and only one symbol is pointing away). Note that we used the most direct route to get to CDK2 as the question used the words "most reasonably". Low p53 means low p21 which we established will lead to a rise in CDK2.A mutation in the gene that produces PTEN: The great majority of mutations will result in an ineffective gene product or none at all. Thus we have a decrease in PTEN which will lead to a rise in PIP3 (if you are unsure, think of what happens if PTEN goes up, then PIP3 must go down because of the negative feedback symbol), rise in AKT, rise in mdm2, decrease in p53 which we already established means an eventual rise in CDK2.High p53 concentrations: clearly we get the opposite of the above, meaning a decrease in CDK2. High p53 stimulates p21 which has a negative feedback on CDK2.
The human kidney can be damaged from a number of causes resulting in a patient's inability to filter toxins (i.e. urea) from the body which could result in death. Complete kidney failure is usually first treated with dialysis which "cleans" the blood.Dialysis. The "dialyzer" is a glass container that has 3 main components: (1) blood percolating Figure 1:through to be cleaned; (2) a dividing membrane; and (3) the dialysate. The latter is liquid containing chemicals used to draw fluids and toxins out of the bloodstream and supply electrolytes and other chemicals to the bloodstream. (kidney.niddk.nih.gov)Considering the information provided, which of the following is NOT consistent with the process of dialysis?
On the Surface: Dialysis only refers to the transfer of the solute (diffusion), while the transfer of the solvent is called osmosis.Going Deeper: Diffusion is the movement of a substance down its concentration gradient (from a region of high concentration to one of lower concentration). This is the process that must be occurring in the dialyzer to remove toxins from the blood (because the dialysate, logically, would have no toxins so the toxins defuse out of the blood into the dialysate). Note that vital substances in the blood should be kept in the blood: options would include having a dialysate with the same concentration of those substances (so they don't diffuse out of the blood) or by adjusting the permeability of the membrane.Osmosis is the movement of a solvent across a semi-permeable membrane from a region of low solute concentration to a region of high solute concentration. In Biology and Biochemistry, that solvent is, of course, water. In this context, the easier way to imagine osmosis is that it is simply the diffusion of water across a semi- permeable membrane from a region of high water concentration (i.e. low solute concentration) to a region of low water concentration (i.e. high solute concentration).So, in summary, osmosis deals with how much water passes through the membrane, while dialysis deals with what type of solute (i.e., sodium, protein, glucose) passes through by simple diffusion.E. B. Notice the link between diffusion and osmosis and the Second Law of Thermodynamics (Physics). All spontaneous change leads to an increase in the entropy (randomness) of the universe. Of course, biological systems exist because processes which increase entropy can be coupled with processes which increase order, as long as the overall (net) entropy of the universe increases.
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