QUESTION IMAGE
Question
cell division
the diagram below shows stages of cell division during asexual reproduction in an amoeba, a unicellular organism. scientists have found that binary fission in an amoeba is controlled. scientists believe that the transition from stage 2 to shape 3 is slowed by proteins. the additional time seems to help the amoeba change coding errors caused during dna replication.
cell division in an amoeba
stage 1
specialized proteins speed up change
amoeba
stage 2
specialized proteins show unknown change
question 18.
how does the chromosome number of the amoeba in shape 1 compare to amoeba a in shape 3?
a. four times the number of chromosomes
b. twice the number of chromosomes
c. same number of chromosomes
d. half the number of chromosomes
The problem is about cell division (asexual reproduction) in an amoeba. In asexual reproduction (like binary fission in amoeba), DNA replication occurs, doubling the chromosome number temporarily before division. Shape 2 likely represents the stage after DNA replication (so chromosome number is doubled from shape 1), and shape 3 would be after division? Wait, no—wait, the question is about shape 3 compared to shape 1. Wait, no, the question is: "How does the chromosome number of the amoeba in shape 1 compare to amoeba A in shape 3?" Wait, the diagram: Stage 1 (shape 1) is the amoeba before division, then shape 2 is during DNA replication (chromosomes double), then shape 3—wait, the final shapes are two amoebas (amoeba A and another). Wait, asexual reproduction (binary fission) in amoeba: DNA replicates (so chromosome number doubles in the cell), then the cell divides into two daughter cells, each with the same number as the original (shape 1) after replication? Wait, no. Wait, original cell (shape 1) has, say, N chromosomes. DNA replication makes it 2N. Then cell divides into two cells, each with N chromosomes. Wait, but the question is comparing shape 1 (original) to amoeba A in shape 3 (daughter cell). Wait, maybe I misread. Wait, the problem says "the transition from shape 2 to shape 3 is slowed by proteins... help the amoeba change coding errors during DNA replication." Wait, no—wait, the key is asexual reproduction (binary fission) in amoeba. In binary fission, the parent cell (shape 1) undergoes DNA replication (so chromosome number doubles in the cell, shape 2), then divides into two daughter cells (shape 3: two amoebas). Each daughter cell (amoeba A in shape 3) will have the same number of chromosomes as the parent cell (shape 1) because after replication (2N) and division, each daughter gets N (same as original). Wait, no—wait, no: DNA replication is S phase, making 2N, then mitosis (or binary fission) divides the cell into two, each with N? No, wait, in mitosis, the daughter cells have the same number as the parent (after replication, the cell has 2N, then divides into two cells each with N? No, no—wait, no: the parent cell (diploid, 2N) replicates DNA to 4N? No, no, amoeba is a unicellular eukaryote? Wait, no, amoeba is a unicellular organism, and in asexual reproduction (binary fission), the process is similar to mitosis. Wait, the parent cell (shape 1) has a certain number of chromosomes. During DNA replication (shape 2), the chromosomes duplicate, so the cell has twice the number. Then, when it divides into two daughter cells (shape 3: two amoebas), each daughter cell (amoeba A) will have the same number of chromosomes as the original parent cell (shape 1). Wait, no—wait, no: if the parent has N chromosomes, after replication it's 2N, then division into two cells, each with N. Wait, that would mean the daughter cell (amoeba A in shape 3) has half the number? No, that can't be. Wait, maybe I got it wrong. Wait, the question is: "How does the chromosome number of the amoeba in shape 1 compare to amoeba A in shape 3?" Wait, shape 1 is the original amoeba (before division). Shape 3 is after division, two amoebas. So in asexual reproduction (binary fission), the parent cell divides into two daughter cells, each genetically identical to the parent. So the chromosome number of the daughter cell (amoeba A in shape 3) is the same as the parent (shape 1). Wait, but that would be option C: same number. Wait, but let's think again. Wait, the diagram: Stage 1 (shape 1) is one amoeba. Then shape 2 is the amoeba with two nuclei? Wait,…
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C. same number of chromosomes