Bio exam 3
A cell in G0 has two chromosomes as shown. This cell enters the cell cycle and is dividing normally until it fails the spindle checkpoint but divides anyway. The images below show the chromosomes of one daughter cell after cell division is complete.
Claim: Image C Evidence: This image shows replicated chromosome after cell division. Reasoning: The spindle checkpoint pauses the separation of chromatids until all chromosomes are attached on both sides at the centromere (at kinetochores) to spindle fibers before proceeding. This ensures that chromosomes are evenly pulled apart and daughter cells have the same number of chromosomes. In this case, there should be one of each type of chromosome. Because Image C shows a daughter cell with a replicated chromosome, it was not pulled apart in anaphase and shows the error of the spindle checkpoint.
Imagine a cell is going through S phase and a significant error takes place so one sister chromosome is not completely copied. At the end of prophase, the cell has the chromosomes represented here. If this cell completes mitosis and cytokinesis, will the two daughter cells have identical genetic information? Choose a claim: The daughter cells will have identical genetic information after mitosis and cytokinesis, or the daughter cells will not have identical genetic information after mitosis and cytokinesis.
The daughter cells will not have identical genetic information after mitosis. Normally, sister chromatids have identical genetic information. However, on the lower chromosome in the figure, one of the sister chromatids is missing gene Z and therefore missing part of the information. During mitosis, attachment of spindle fibers to the kinetochore of each sister chromatid and separation of the sister chromatids, which normally have identical genetic information, leads to daughter cells with identical genetic information. However, in these cells one of the daughter cells will not get gene Z. Since one of the sister chromatids is missing a gene which is part of the genetic information, mitosis will not produce daughter cells with identical genetic information.
In the process of replication, a short RNA primer (short sequence in red color and italicized) is added to the DNA template (black) to allow DNA polymerase to synthesize DNA using the DNA template.
Claim: The next DNA nucleotides are 5'-GTCGA-3' Support from diagram: The left side of the RNA primer is the 3' end because the RNA runs antiparallel to the template DNA. The corresponding template DNA sequence is 3'-CAGCT-5' Reasoning: New nucleotides are added to the 3' of the RNA primer. Since base pairing occurs antiparallel, the DNA template is read 3' to 5' as the new DNA strand is made 5' to 3'. DNA nucleotides base-pair with the DNA template in the following manner: A with T, T and A, G with C, C with G. Linking: Because the DNA template is 3'-CAGCT-5' and the DNA is built 5' to 3', the next nucleotides of the DNA strand are 5'-GTCGA-3'.
Make a claim about which image (A, B, C, or D) best depicts how this ligand generates the cellular response. Provide support from the chemical structure of the ligand and the cell drawings. In your reasoning, address: The properties of this ligand (polar or nonpolar and how you know) Where the receptor for this ligand is likely located (cell-surface or intracellular and how you know) How the ligand leads to the cellular response (what steps occur in the cell to change gene expression)
Claim: image A Support: polar ligand and cell surface receptorReasoningThe ligand contains more polar covalent bonds (carboxyl, amino) than nonpolar so it is overall polar. This means it cannot cross the cell membrane and would have to interact with a receptor on the cell surface. As a result, when the receptor is activated, the receptor would need to activate other signal transduction proteins inside the cell to cause a change in gene expression. Because image A shows the ligand binding to a cell surface receptor and signal transduction occurring inside the cell, this shows how the cellular response is generated.
