Study question 12

Which of the following are true statements about DNA replication? Check all that apply.

-DNA replication occurs during Interphase of the cell cycle. -During DNA replication, chromosomes composed of one chromatid are transformed into chromosomes composed of two chromatids. -During DNA replication, chromosomes composed of one molecule of DNA are transformed into chromosomes composed of two molecules of DNA.

The bracketed two part structure joined at the circle region represents which of the following? Check all that apply.

-One double stranded chromosome composed of two chromatids. -Two molecules of DNA; each molecule representing one chromatid

The nucleus of each of the two stomach cells produced at the end of the M (mitotic) stage of the cell cycle will contain ____ chromosomes which is the ____ chromosome number.

8,2N

The diagrams below represent the chromosomes within the stomach cells of the Cockroach. Which diagram shows the correct representation and arrangement of the chromosomes during metaphase of mitosis? The circle represents the cell membrane.

A

The diagrams below represent the chromosomes within the stomach cells of the Cockroach. Which diagram shows the correct representation and arrangement of the chromosomes at the completion of mitotic cell division (i.e., after mitosis and cytokinesis)? The circle represents the nucleus of each new daughter cell.

E

Label #1 represents the molecule ______. Spelling must be correct to receive credit

Guanine

within which organelle in a eukaryotic cell does DNA replication occur?

Nucleus

During mitotic cell division, if a cockroach intestinal cell undergoes mitosis but not cytokinesis, what will result?

One cell with two nuclei (

What are growth factors and what is there function in the control of the cell cycle?

Proteins released by certain non-dividing body cells (1/4 pt.) • That stimulate other cells to divide (1/4 pt.)

Explain why it is essential that the cells lining the Cockroach's stomach are able to carry out mitotic cell division (mitosis + cytokinesis).

The cells lining the intestine are constantly being lost due to natural cell death. Cell death results from a number of factors including mechanical abrasion as the food passes through the stomach. (1/4 pt.) These cells must be replaced by the process of mitotic cell division. (1/4 pt.)

Label #2 represents the molecule ______. Spelling must be correct to receive credit.

Thymine

Label #3 represents

a nitrogen base

The chromatids of double stranded chromosomes are pulled apart.

anaphase

The arrow in Diagram C represents the ______ region. Spelling must be correct to receive credit.

centromere

The gray compound enclosed by the circle represents a monomer of DNA called a (an) _____________.

nucleotide

A complete set of chromosomes composed of one chromatid (single-stranded chromosomes) is found at EACH pole of the dividing cell.

telophase

Chromosomes composed of two chromatids (double stranded chromosomes) line up at the equator of the cell.

telophase

Cytokinesis is completed at the end of this stage.

telophase

At which checkpoint does the cell check to determine if it has reached an optimum size for the cycle to continue?

G1

How many homologous pairs of chromosomes are found in the leaf cells?

14

Based on the above karyotype, the 2N chromosome number of Barley is _________.

7

During sexual reproduction in Barley, reproductive cells called spores are produced by meiosis within the anthers of the flowers. These spores eventually develop into pollen grains that contain non-motile sperm. What is the N chromosome of the spores?

7

What distinguishes a benign tumor from a malignant tumor?

Benign tumor = mass of "abnormal" cells which do not invade other tissues (metastasize) (1/4 pt.) Malignant tumor = mass of abnormal cells which divide uncontrollably and invade other tissues (metastasize) (1/4 pt.)

The epithelial cells lining the intestine of an earthworm go through a cell cycle similar to that of epithelial cells lining the human stomach. Answer questions 4 - 11 based on this information. For each event, choose the stage of the cell cycle in which it occurs. Check all that apply. -Most cells double in size.

G1

The length of this stage often determines the length of the entire cell cycle.

G1

New cell organelles are synthesized. Check all that apply.

G1 S G2

At which checkpoint does the cell check to determine if DNA replication has occurred normally for the cycle to continue?

G2

DNA is replicated.

G2

At which checkpoint does the cell check to determine if the chromosomes have attached properly to the spindle microtubules and the cell is ready to enter anaphase of mitosis for the cycle to continue?

M

Chromosomes composed of two chromatids become chromosomes composed of one chromatid.

M

Cytokinesis occurs.

M

Double stranded chromosomes attach to the microtubules of the spindle.

M

Chromosomes composed of one chromatid become chromosomes composed of two chromatids.

S

Describe what is occurring in EACH of the three steps (separated by the red arrows) of DNA replication shown in the diagram. You should refer to each of the steps as step A (furthest to the left), step B (middle diagram) and step C (furthest to the left).

Stage 1 Starting with a single stranded chromosome composed of 1 chromatid = 1 molecule DNA (1/4 pt.) Stage II • Hydrogen bonds between the nitrogen bases of the nucleotides of the original DNA molecule break (1/4 pt.) and each half of the original DNA molecule separates. (1/4 pt.) • Nucleotides in the nucleoplasm, pair with the nucleotides of the original DNA molecule (1/4 pt. Stage III Results in the production of 1 double stranded chromosome composed of 2 molecules of DNA = 2 chromatids (1/4 pt.)

Label #4 represents which two molecules?

The monosaccharide deoxyribose and a phosphate functional group

Each of the two chains of molecules (colored blue) represents a template strand of the original DNA molecule. Why is it referred to as the template strand?

The template "strand" of a DNA molecule refers to the polynucleotide strand (sides of the ladder) of DNA (1/4 pt.) to which the complementary nitrogen bases attach during DNA replication

Diagram A (at the far left) represents which of the following? Check all that apply.

one molecule of DNA a chomosome composed of one chromatid two polynucleotide chains held together by weak hydrogen bonds

Chromatin fibers become tightly coiled to form discrete chromosomes.

prophase

The nuclear envelope disappears.

prophase

The spindle apparatus is formed.

prophase

Briefly explain how the process of cytokinesis in the stomach cell of a Cockroach would differ from cytokinesis in an actively dividing root cell of a Barley plant.

• Cytokinesis in a dividing plant cell occurs by the growth of a cell plate (membranous sac containing pectin) (1/4 pt.) that grows outward from the cell center (1/4 pt.) and fuses with the cell membrane of the parent cell. • Cytokinesis in a dividing animal cell (e.g. dragonfly intestine cell) occurs by pinching in of the cell membrane (½ pt.) caused by contracting belt of microfilaments.

At which checkpoint does the cell check to determine if the chemical structure of the chromosomal DNA has not been damaged?

G1

At which checkpoint does the cell check to determine if the nutrient supply is adequate for the cycle to continue?

G1