# Test Prep for AP® Courses

33.

Which statement cannot be inferred from the karyotype shown?

1. The cell contains DNA.
2. The cell contains 46 chromosomes.
3. The cell is diploid.
4. The cell is prokaryotic.
34.
Explain how DNA, which in humans measures approximately two meters, can fit inside a human cell that is about $10μm$. Discuss how the organization of the genetic material in eukaryotes differs from prokaryotes.
1. The DNA is found wrapped around histones to form nucleosomes, which further compact and ultimately form linear chromosomes. The prokaryotic genome is found as a loop and in eukaryotes as a double-stranded linear structure.
2. The DNA is wrapped around the nucleosomes to show a compact structure. The eukaryotes show a loop structure and prokaryotes show a double-stranded linear genome.
3. The genetic material shows ringed heterochromatin structure. The prokaryotes show multiple loops, and eukaryotes show a condensed chromatin.
4. The genetic material is wrapped around histones. The prokaryotes have a condensed structure in nucleoids, but eukaryotes have double-stranded linear structure.
35.

Which statement about structure 1 on the karyotype is NOT true?

Which of the following statements about structure 1 on the karyotype is not true?

1. Structure 1 consists of homologous chromosomes.
2. The two parts of structure 1 will have genes in different loci.
3. The two parts of structure 1 originate from different parents.
4. The two parts of structure 1 will have slightly different sequences of nucleotides.
36.

Based on the karyotype provided, the nondisjunction of which chromosome causes Down syndrome?

1. chromosome 21
2. chromosome 22
3. X chromosome
4. Y chromosome
37.
Describe the sequence of mitotic cell cycle for one pair of chromosome that is undergoing normal mitotic division.
1. anaphase - metaphase - prophase - cytokinesis
2. anaphase - prophase - metaphase - cytokinesis
3. prophase - anaphase - metaphase - cytokinesis
4. prophase - metaphase - anaphase - cytokinesis
38.

In a study on cell division, researchers culture synchronously dividing human cells with thymidine, which causes the cells to arrest at the G1 boundary. The cells are then placed in medium lacking thymidine, which releases the block, and the cells begin to divide again. Starting with Sample A and ending with Sample D, the DNA content of the cells is measured at different times after thymidine is removed. Results for four samples (A–D) are shown in the graph.

Figure 10.18

Which sample presents the expected results for cells in S phase?

1. sample A
2. sample B
3. sample C
4. sample D
39.
Li-Fraumeni syndrome (LFS1) is a rare hereditary disorder that leads to a predisposition to cancer. This hereditary disorder is linked to mutations in the tumor suppressor gene encoding the transcription factor p53. p53 acts at the $G1$ checkpoint. If damaged DNA is detected, p53 halts the cell cycle. As p53 levels rise, the production of p21 is triggered. p21 enforces the halt in the cell cycle. A variant of Li-Fraumeni, called LFS2, is thought to occur due to a mutation of the CHK2 gene, which is also a tumor suppressor gene. CHK2 regulates the action of p53. Which of the following cascades is most likely to occur in a normal cell that does not contain the LFS mutation?
1. cell cycle progression
2. p53
3. p21
4. CHK2
1. p53
2. p21
3. CHK2
4. cell cycle progression
1. p21
2. p53
3. CHK2
4. cell cycle progression
1. CHK2
2. p53
3. p21
4. cell cycle progression
40.
Figure 10.20

The insulin growth factor (IGF-1) promotes cell proliferation as shown in the diagram. The expression of which protein in the diagram is controlled through negative feedback?

1. active Cdk4
2. cyclin D1
3. cyclin D1/Cdk4 complex
4. IGF-1
41.

Explain why p53, p21, and CHK2 are considered tumor suppressor genes, not proto-oncogenes. Give an example of a proto-oncogene.

1. p53, p21, and CHK2 suppress the proteins that regulate the cell cycle, whereas proto-oncogenes, like phosphorylated Rb, help in cell cycle progression.
2. p53, p21, and CHK2 are negative cell cycle regulators, whereas Cdks are proto-oncogenes, which could cause cancer when mutated.
3. p53, p21, and CHK2 suppress the proteins that regulate the cell cycle, whereas Rb is considered a protooncogene, as it is the most primitive.
4. The three proteins help stop the formation of tumors, whereas Cdk’s are called proto-oncogenes because they are the most primitive of all.