Mitosis and Meiosis

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SAT Subject Test in Biology › Mitosis and Meiosis

Questions 1 - 6
1

Each of the following is a step in mitosis EXCEPT __________.

homologous pairs separate and are pulled toward opposite poles of the cell

chromosomes condense

sister chromatids separate and are pulled toward opposite poles of the cell

the cytoplasm divides into two daughter cells

spindle fibers shorten

Explanation

There are no homologous pairs in mitosis. Mitosis has sister chromatids that separate and result in two identical daughter cells. Meiosis has homologous pairs because it occurs in sex cells and has one chromosome from the father and the other from the mother. These chromosomes pair up in Metaphase I and then separate in Anaphase I. Mitosis occurs in somatic cells so there is only one chromosome made up of two sister chromatids that separate during Anaphase.

2

During which phase of meiosis does crossing over occur?

Prophase I

Metaphase I

Prophase II

Anaphase I

Anaphase II

Explanation

Crossing over occurs during Prophase I. During Prophase I, chromatin condenses and homologous chromosomes come together to form a tetrad. At this point, sometimes pieces of the chromatids within the chromosomes break off and exchange DNA. This process is known as "crossing over." This cannot occur in Prophase II because there are no homologous chromosomes in this stage, and therefore there isn't any different DNA to exchange.

3

1. Chromosomes begin to condense

2. Centrioles separate and begin to form a mitotic spindle as they move towards opposite sides of the cell

3. The nucleolus breaks down

During which phase of cell division do the given processes occur?

Prophase

Interphase

Telophase

Metaphase

Anaphase

Explanation

During prophase, the cell will begin to condense its chromosomes to prepare for separation during anaphase. The pair of centrioles in the cell will also separate and begin to move towards opposite ends of the cell, while remaining attached to each chromosome by a microtubule. These fibers form the mitotic spindle, which organizes and repositions the chromosomes during cell division. During this phase, the nuclear envelope and nucleolus also break down and disappear.

4

During which of the following phases of the cell cycle do chromosomes align in the middle of the cell?

Metaphase

S

G2

Telophase

Anaphase

Explanation

The correct answer is "metaphase." The chromosomes are each attached to spindle fibers at the centromere. When the chromosomes align along the middle of the cell (often called the "metaphase plate"), the cell is in metaphase. Metaphase occurs after prophase (during which the cell grows and replicates its DNA) but before anaphase (when the chromosomes are pulled by spindle fibers to opposite ends of the cell).

5

A new organism from Mars has been discovered, and its genome has . Although these organisms are fluorescent green, their cells undergo meiosis and mitosis in the exact same way that human cells do.

After one of these cells undergoes meiosis, how many chromosomes will it have?

Explanation

A somatic (body) cell is always diploid, meaning that it has chromosomes. When a cell undergoes meiosis, the number of chromosomes in each daughter cell will be half the number in the original parent cell. Each daughter cell produced from meiosis will be haploid, meaning that it will have chromosomes.

6

A new organism from Mars has been discovered, and its genome has . Although these organisms are fluorescent green, their cells undergo meiosis and mitosis in the exact same way that human cells do.

After one of these cells undergoes mitosis, how many chromosomes will it have?

Explanation

A somatic (body) cell is always diploid, meaning that it has chromosomes. When a cell undergoes mitosis, the number of chromosomes in each daughter cell is the same as the number of chromosomes in the original parent cell. Each daughter cell produced from mitosis is diploid, meaning that it will have (in this case ) chromosomes.

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