AP Biology : AP Biology

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #303 : Cellular Biology

In preparation for cellular division, the cell must first duplicate its chromosomes. Each duplicated chromosome consists of two __________.

Possible Answers:

centromeres

chromatins

homologous chromosomes

sister chromatids

duplicates

Correct answer:

sister chromatids

Explanation:

Sister chromatids are two identical copies of the same chromosome. They are attached to each other at a region called the centromere. Homologous chromosomes are not identical. Rather, they are chromosomes that look alike, and have the same genes at the same loci, but not necessarily the same versions of those genes. For example, we all have two copies of chromosome number 1. Assume eye color is coded on this chromosome. One copy may have the brown allele, while the other copy might have the green allele. Both chromosomes have loci that code for eye color, but they are not identical since one came from each parent.

Example Question #304 : Cellular Biology

What is the purpose of chromatin?

Possible Answers:

To maintain structure of the chromosome and assist in controlling the activity of the genes

To maintain structure of the chromosome only

To hold the sister chromatids together

To assist in controlling the activity of the genes only

Correct answer:

To maintain structure of the chromosome and assist in controlling the activity of the genes

Explanation:

Chromatin serves as a scaffold for DNA and helps regulate gene activity. Chromatin can be condensed, as euchromatin, or loosely packed, as heterochromatin. The compactness of chromatin determines its level of activity. When it is loosely packed, it can be acted upon by DNA replication and/or transcription enzymes, and those genes may be expressed. Centromeres hold sister chromatids together.  

Example Question #41 : Understanding Mitosis

Which of the following is not a phase of mitosis?

Possible Answers:

Prometaphase

Telophase

Anaphase II

Prophase

Correct answer:

Anaphase II

Explanation:

The five phases of mitosis are prophase, prometaphase, metaphase, anaphase, and telophase in that order. Since mitosis involves the production of two genetically identical diploid daughter cells from one parent cell, there is only one cell division. Thus, all phases that dictate a Roman numeral refer to meiosis, which involves the production of four nonidentical haploid daughter cells from one parent cell as the result of two cell divisions. During anaphase II of meiosis, the sister chromatids are pulled to opposite poles of the cell, and the second round of cytokinesis begins.

Example Question #42 : Understanding Mitosis

During what phase do a cell's chromosomes duplicate?

Possible Answers:

G2 phase

G1 phase

S phase

Mitosis

Correct answer:

S phase

Explanation:

During interphase the cell grows and duplicates its chromosomes in preparation for mitosis. Specifically, cell growth begins in G2 phase of interphase and chromosomal duplication (DNA replication) occurs in S phase. The cell continues to grow in G2 phase, and proofreads the DNA that was just replicated in S phase to make sure there are no errors, preventing mutations from being passed to daughter cells.  

Example Question #81 : Cellular Division

Kinetochores fibers form in which phase of mitosis?

Possible Answers:

Prometaphase

Anaphase

Prophase

Metaphase

Correct answer:

Prometaphase

Explanation:

Kinetochore fibers allow the microtubules from the spindle apparatus to attach to the chromatids. Kinetochores are formed in prometaphase. These will help move the chromosomes in preparation for metaphase, when the chromosomes will need to be lined up on the metaphase plate. 

Example Question #43 : Understanding Mitosis

When the chromosomes align themselves along a plane that is equidistant between the two poles of the cell, which phase of mitosis is the cell in?

Possible Answers:

Prophase

Metaphase

Anaphase

Telophase

Correct answer:

Metaphase

Explanation:

The plane along which the chromosomes align is called the metaphase plate and this event occurs during metaphase. At this point, the sister chromatids are ready to be pulled apart during anaphase. Ultimately, the products of mitosis are two identical (since sister chromatids are identical) diploid daughter cells. 

Example Question #83 : Cellular Division

Nuclear envelopes develop around newly formed nuclei in what stage of mitosis?

Possible Answers:

Metaphase

Prophase

Telophase

Anaphase

Correct answer:

Telophase

Explanation:

Once the soon-to-be daughter DNA has reached opposite poles of the cell, new nuclear envelopes form around them during telophase. Also, in telophase, the spindle apparatus breaks down and the DNA begins to condense. Remember that telophase is essentially the opposite of prophase.  

Example Question #44 : Understanding Mitosis

The cleavage furrow develops via __________.

Possible Answers:

telophase

anaphase

cytokinesis

prophase

Correct answer:

cytokinesis

Explanation:

The cleavage furrow is the start of physical cell splitting, occurs during telophase, and is called cytokinesis. The cleavage furrow is mediated by motor proteins such as actin and myosin. They tighten a "ring" around the cell until it pinches off into two daughter cells. Note that plant cells also exhibit cytokinesis, but they do so without the formation of a cleavage furrow. Rather, they form a cell plate, which is made of the same material as their cell wall, cellulose.

Example Question #313 : Cellular Biology

In which phase of mitosis do the sister chromatids first separate?  

Possible Answers:

Anaphase

Metaphase

Telophase

Prophase

Correct answer:

Anaphase

Explanation:

Separation of the sister chromatids by the microtubules pulling them to opposite poles occurs in anaphase. Also, during late anaphase, cytokinesis begins. This is the process of the cell dividing, since the nucleus has already divided (karyokinesis).

Example Question #45 : Understanding Mitosis

In which phase of mitosis do the chromatin fibers become tightly coiled, the nuclei disappear, and the mitotic spindle begins to form?

Possible Answers:

Anaphase

Telophase

Prophase

Metaphase

Correct answer:

Prophase

Explanation:

All these events occur in prophase, the first stage of mitosis. Metaphase involves the duplicated chromosomes being aligned along the metaphase plate, with each pair of sister chromatids attached to spindle fibers. During anaphase, the sister chromatids are pulled apart to opposite poles of the cell. Telophase is essentially the opposite of prophase: the DNA decondenses, the nuclear envelope begins to reform, and the mitotic spindle begins to disappear.   

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