DNA Worksheet Name: ____________________________ Due Date: _____________ Period: ____

PURPOSEAnalyze the structure of DNA.

BACKGROUND INFORMATIONDNA, the genetic material of organisms, is composed of four kinds of nucleotides. A DNA molecule consists of two strands of nucleotides with sugars and phosphates on the outside and bases paired by hydrogen bonding on the inside. The paired strands form a twisted–ladder or spiral staircase shape called a double helix. Adenine nucleotides always pair with thymine nucleotides and guanine nucleotides always pair with cytosine nucleotides.

MATERIALSColored pencils (green, yellow, blue, orange, red and purple)

PROCEDURE1. Read the directions. 2. Label the DNA molecule, using the existing labels as a guide.3. Color the DNA molecule according to the instructions.4. Answer the Data Analysis questions below after you have labeled and colored your DNA molecule.

DATA ANALYSIS1. Describe the structure of a nucleotide.____________________________________________________________

___________________________________________________________________________________________

2. How do nitrogen bases bond with each other?______________________________________________________

___________________________________________________________________________________________

3. Explain why the structure of a DNA molecule is often described as a twisted-ladder.___________________________________________________________________________________________________________________

4. What is the importance of the sequence of nucleotides in genetic information?___________________________

___________________________________________________________________________________________

5. Why does DNA need to replicate? ________________________________________________________________ ____________________________________________________________________________________________

6. The sequence of nitrogenous bases on one strand of a DNA molecule is GGCAGTTCATGC. What would be the sequence of bases on the complementary strand? _________________________________________________

7. If there are only 4 nucleotide types in DNA, how can all living things be so different?__________________________________________________________________________________________________________________

___________________________________________________________________________________________

8. DNA is like a spiral staircase. The sides are made up of alternating sugar and phosphate compounds.

Label the sugar and phosphate compounds.They alternate all the way down the molecule.

Color the sugars – red and the phosphates - purple.

The stair steps are made of four chemical bases.They are:

Guanine Cytosine Thymine Adenine

Guanine and cytosine always lock together.

Thymine and adenine always lock together.

Label the empty bases.

Color the bases as follows:Guanine - greenCytosine - yellowThymine - orangeAdenine - blue

SUGAR THYMINE

PHOSPHATE

CYTOSINE

PHOSPHATE

SUGAR

THYMINE

PHOSPHATE

CYTOSINE

SUGAR

9. In relation to the pictures below: Explain three main steps in the process of DNA replication. Name the enzymes that go with each step

10. In which direction are new nucleotides added during replication?____________________________________________________________________________________________________________________________________

11. What is the difference between and leading and lagging strand?___________________________________________________________________________________________________________________________________________________________________________________________________________________________________

12. What are Okazaki fragments? Why are they needed?____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Concepts DNA is composed of nucleotides and is shaped like a double helix, with strands running antiparallel Bases always form complementary base pairs (adenine with thymine and cytosine with guanine) Complementary base pairing enables DNA to replicate, or copy itself DNA replication involves three steps and each step uses a specific enzyme There is a leading strand and a lagging strand for each replication fork The lagging strand is made from Okazaki fragments

13. Complete the following strand of DNA by placing the letter of the correct nitrogenous base on the line provided

5’ C C A G T A G T T 3’

a.

b.

c.

a)____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________b)____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________c)____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

14. If the DNA molecule above were the parent strand of DNA, when the strands are split for replication, which strand would be the template for the leading strand and why?

15. Label the picture of DNA replication.

__________________ is the enzyme that opens the DNA strand

is the new piece of DNA that continuously adds nucleotides during replication.

is the new piece of DNA that takes longer to make because it is going in the opposite direction of the replication fork.

_________________ is the place where DNA is opening.

is the enzyme that adds new nucleotides during replication.

Okasaki fragments are joined into a single strand by an enzyme called ________________

16. Using your class power point notes, label and color the Cell Cycle. Don’t forget to label the arrow!

G1 S G2 M C

Explain what is happening during each phase.

G1 Phase = _________________________________________________________________ _________________________________________________________________

S Phase = __________________________________________________________________ __________________________________________________________________

G2 Phase =__________________________________________________________________ __________________________________________________________________

M (Mitosis) Phase = __________________________________________________________ __________________________________________________________

C (Cytokinesis) Phase = _______________________________________________________ _______________________________________________________

STAGES OF MITOSIS

Interphase

Cell Division

17. Figure A shows 6 diagrams made during the cell cycle in an animal cell. Instructions:a) Use the word bank provided to label the phases shown.b) Number the pictures in order from 1 to 6. c) Repeat the process for Figure B which shows 6 diagrams made during the cell cycle in a plant cell.d) How is mitosis different in plant cells compared to in animal cells?

__________________________________________________________________________________________________________________________________________________________

Word Bank:anaphasecytokinesisinterphasemetaphaseprophasetelophase

Matching:

Match the questions below with the proper answers that follow them. Write the correct CAPITAL letter in the blank.

_______ 18. What is mitosis?

_______ 19. In order, what are the four main stages of mitosis?

_______ 20. What is the name of the stage a cell goes through just prior to mitosis?

_______ 21. What is the main event of interphase?

_______ 22. What are two important events of prophase?

_______ 23. What is the main event of metaphase?

_______ 24. What structure is involved in moving chromosomes during mitosis?

_______ 25. What is the main event of anaphase?

_______ 26. What are two important events of telophase?

_______ 27. At the completion of mitosis when the cell divides, what name is given to the two new cells?

_______ 28. You began life as a one-celled structure called a zygote. What process then

took place over and over to build a body containing billions of cells?

A. The chromosomes in the nucleus of the cell make identical copies of themselves

B. The chromosomes move toward and line up along the center of the cell, called the equator.

C. The nuclear membrane disappears and the chromosomes become distinct.

D. MitosisE. New nuclear membranes form around each of

the two sets of chromosomes, and the cell divides into two daughter cells.

F. Prophase, metaphase, anaphase, and telophaseG. Daughter cellsH. MicrotubulesI. Division of the nucleus of the cell (usually

followed by division of the cell itself)J. The microtubules pull one set of chromosomes to

one side of the cell and an identical set to the opposite side of the cell

K. Interphase

Understanding Cancer

Most healthy cells of the body grow, divide a certain number of times, age, and die. Sometimes, this orderly process is disrupted when cells lose the ability to limit and direct their growth. Cells may divide too often and produce an excess of cells, called a tumor. A tumor can be benign or malignant. Benign tumors do not spread to other parts of the body, and can usually be surgically removed. A malignant tumor—cancer—invades and destroys nearby healthy tissues and organs. Cancerous tumors can metastasize, that is, can spread to other parts of the body and form new tumors. There are probably at least 100 different kinds of cancer; with each one affecting different kinds of cells and having different characteristics.

Cancer cells do not respond normally to the chemical signals that regulate the cell cycle. In some cancer cells, the way cell division signals are transmitted to the nucleus is abnormal. In other cancer cells, the entire cell cycle control system may be abnormal. If cancer cells stop dividing, they do so at random points in the cell cycle rather than at the normal checkpoints. When cultured in the laboratory with adequate nutrients, cancer cells can divide indefinitely and are referred to as “immortal”. Most mammalian cells grown in culture divide only 20 to 50 times before they stop dividing, age and die. How Cancer Begins

Changes in the genes that influence the cell cycle can cause the transformation of a normal cell into a cancer cell. There are two types of these genes. The first type codes for proteins that stimulate cell division. Genes of this type are normally turned off in cells that are not dividing. This type of gene can be converted to an oncogene, that is, a “cancer gene,” by mutation.

One common oncogene, a gene called ras, is present in mutated form in about 30 percent of human cancers and in some forms of leukemia.

The second type of gene associated with cancer is a tumor suppressor gene. Tumor suppressor genes code for proteins that normally restrain cell division. In many cancers, tumor suppressor genes have been inactivated by mutation. An inherited mutation in one copy of a tumor-suppressor gene results in higher risk of cancer. However, cancer does not occur unless and until the remaining, healthy copy of the gene is also inactivated by mutation. If a person is born with two normal copies of a tumor suppressor gene, both must be inactivated before cancer can develop.

Almost 50 percent of human cancers are associated with a mutation in the tumor suppressor gene p53. These cancers include many breast, colon, lung, prostate, and skin cancers. The protein produced by the p53 gene normally acts as an emergency brake in the cell cycle. The p53 protein also induces the death of damaged cells. To perform these functions, p53 proteins must bind to DNA. Mutant p53 protein cannot bind to DNA, thus cell division occurs unchecked.

Mutations that result in cancer, whether they involve oncogenes or tumor suppressor genes, can occur spontaneously. Mutations can also be induced by factors in the environment, such as X-rays and ultraviolet radiation, cigarette smoke, asbestos, and even by the human papilloma virus and the hepatitis B virus. Surviving Cancer

In the United States, about one of every five deaths—more than half a million each year—are caused by cancer. Only heart disease kills more people. The

number of new cancer cases and the number of cancer deaths for every 100,000 persons have decreased over the past 10 years. The death rates for children and adults under the age of 50 have decreased dramatically.

Some kinds of cancer kill more people than others. Lung cancer is the number one cancer killer. Colorectal cancer, breast cancer, and prostate cancer are the next most common. Cancer survival is measured by the percentage of cancer patients who survive a specific number of years. Five-year cancer survival rates for common cancers are shown in the table [below].

Cancer survival is influenced by the type of cancer and by the stage at which a cancer is diagnosed. For example, the 5-year survival rate for colorectal cancer diagnosed in its first stage is 96 percent. When diagnosed in its fourth and most advanced stage, however, the 5-year survival rate is only 5 percent. Cancer screenings and early detection of cancers, such as those of the breast and colon, greatly increase a person’s chances of surviving cancer.

Name: _________________________________ Period: ______ Due Date: _______

Cancer Survival RatesCancer Site 5-year Survival Rate (%)

Questions:29. What is a tumor? What is the difference between a benign tumor

and a malignant tumor?

30. What are the two types of cancer-causing genes that are discussed? Which one is turned off when it causes cancer? Which one is turned on when it causes cancer?

31. Name 4 environmental factors that can cause cancer.

32. The article says that cancer is the second leading cause of death. According to the article, what is the leading cause of death?

33. According to the 5-year survival rate chart, if 100 people got pancreatic cancer, how many will still be alive after 5 years? If 100 people got breast cancer, how many would be alive after 5 years?

34. Describe the common duties of an oncologist.

Prostate 98Breast 88

Colorectal 63Leukemia 47

Brain 32Lung 15

Pancreas 4All cancers 64

Career – Cancer Treatment: Profile Oncologist

Oncologists are cancer specialists—physicians who care for people who have been diagnosed with cancer.

Job DescriptionOncologists may begin to treat a patient soon after he or she is diagnosed with cancer. Oncologists work cooperatively with surgeons, radiologists, and other physicians to devise the best combination of treatments for the particular patient and cancer being treated. Oncologists may manage radiation treatment and/or chemotherapy, as well as other types of cancer therapy.

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