Biology Name _____KEY___________________________CP 2012-13

DNA Structure and Replication

Homework Packet

Sections 12.1, 12.2 and 12.3 in your textbook will help you to complete the worksheets attached. Use the Internet as an additional resource if needed!

Record of Incomplete Homework for this Unit:

Record the following information for every assignment not completed on time.Use the choices below the table.

Homework # Date Assigned I did not complete this HW because:

A. I did not record it in my planner/ I did not check the class websiteB. I did not understand the material and have arranged to see the teacher for helpC. I did not understand the material and did not see the teacher for helpD. I forgot/ I just didn’t do itE. OTHER: Please explain any extraordinary circumstances

HW #1 DNA, Chromosomes and Chromatin

1) What do the letters ‘DNA’ stand for? __deoxyribonucleic acid__________________

2) Circle the letter of the following statements which are true.

a) DNA is composed of chromosomes.

b) Chromosomes are composed of DNA.

c) DNA is composed of chromatin.

d) Chromatin is composed of DNA.

e) Chromosomes and chromatin are composed of the same DNA.

f) DNA is composed of nucleotides.

g) Nucleotides are composed of DNA.

3) You have a gene that codes for blue eyes on your chromosome. Will it also be on your chromatin? Explain.

____Yes. Chromosomes are simply the condensed form of the same genome (collectively, all the genes of an organism ).___________________________________________________________________________________

_____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

4) Fill in the following concept chart. Use the following terms: guanine, thymine, cytosine, adenine, nucleic acid, nitrogen base, deoxyribose sugar, nucleotides and phosphate group. DNA is a Nucleic Acid

which is made up of

Nucleotides

which are made up of 3 parts

deoxyribose sugar Phosphate group Nitrogen Basewhich can be one of 4 types: adenine, guanine, cytosine, thymine

HW #2 DNA Structure 1) Why isn’t DNA found in the nucleus of prokaryotic cells? _prokaryotic cells do not have a nucleus__

2) Which of the following would NOT be a function of a gene? (check all that apply)______a) Providing the code for the cell to build an insulin protein molecule.______b) Providing the code for building an amylase enzyme molecule.______c) Carrying the hereditary code for the color of your eyes to your offspring.______d) Provide the code for building and iron (Fe) atom.______e) Carrying the hereditary code for some types of cancer.

3) Fill in the blank:a) A unit of hereditary or genetic information is called a ______gene_______.

b) Many genes make up a strand of __________DNA_______________________.

c) DNA looks like a ________________double helix_________________.

d) The simple units that make up DNA are called __nucelotides_________.

4) Use the word bank below. Which of the following

nucleotide

phosphate group

deoxyribose sugar

nitrogen base

adenine

guanine

cytosine

thymine

DNA

a) make up a DNA nucleotide? _____phosphate group, nitrogen base, deoxyribose sugar__________

b) are nitrogen bases? ___cytosine, adenine, thymine, and guanine________

c) are the same in every DNA nucleotide?___phosphate group and deoxyribose sugar________________

d) vary from one DNA nucleotide to the next? ___nitrogen base__________________

e) have a double ring structure? ____adenine and guanine (purines)___________________________

f) arepyrimidines? _____cytosine and thymine_________________________________

g) pair with cytosine? ______guanine_______ adenine? ____thymine__________________

h) Which nucleotide forms a complimentary pair with thymine? adenine________________

5) What is the difference between a chromosome and a chromatin? (Check all that apply)______a) A chromosome has different DNA than the chromatin.______b) The chromatin is made of shorter pieces of DNA than the chromosome.______c) The chromosome is condensed and duplicated DNA.______d) The chromatin is less condensed so that the DNA code can be “read” during protein synthesis.______e) The chromosome has a different sequence of nitrogen bases than the chromatin.

6) The system of base pairing in which the same nitrogen bases pair with each other is called______a) sequence pairing _______c) complimentary base pairing______b) component pairing _______d) A-T and C-G pairing

7) If one strand of DNA has the following nitrogen base sequence what is the nitrogen base sequence of it’s complimentary mRNA strand?

DNA Strand I T - A - C - G - C - A - A - T - A - C - G - G - A - C - T

DNA Strand IIA -T- G- C -G -T - T -A -T - G -C -C - T - G -A

HW #3 DNA Structure and Function

Complete the following questions.1. The structure of DNA was discovered by _Watson and Crick_____ and __Wilkins and Franklin________2. What is the monomer or simplest unit of a DNA molecule? _nucleotide_________________________3. What three parts make up this monomer unit? __phosphate group, nitrogen base, deoxyribose sugar_______4. Describe the shape of a molecule of DNA. ___double helix or twisted ladder_______________________5. In DNA, purines only pair with _____pyrimidines______________________6. What is the complimentary nucleotide for an adenine DNA nucleotide? __thymine_______________7. What is the complimentary nucleotide for a guanine nucleotide? ____cytosine__________________8. T F Purines have a double ring structure of carbons and nitrogen. (Correct the statement if false.)9. What type of bonds hold the two strands of DNA together? __hydrogen_____________________10. Does each cell in an organism have the same DNA? ____Yes___________11. Conundrums: Circle the correct statement in each sentence.

a. Is DNA made up of nucleotides or are nucleotides made up of DNA? b. Are genes made up of chromosomes or are chromosomes made up of genes?

Study the following strands of DNA. Use your observations to answer the following questions.

1 2 3 4

12. In the figures above, what do the letters A, C, G and T stand for? ____A= adenine, C=cytosine, G=guanine, T=thymine___________________________________________________________________

13. Count the numbers of each nucleotide in figure 1: _____3__ A, _____3__ T, _____2__C, ____2___G.

14. In figure 2, the number of adenine nucleotides is equal to the number of _____thymine_______ nucleotides.

15. In figure 2, the number of cytosine nucleotides is equal to the number of _____guanine______ nucleotides.

16. What pattern have you observed about the nucleotide structure of DNA? ___adenine pairs with thymine and guanine pairs with cytosine so that the number of each nucleotide is equal to the number of its base pair.

17. What two molecules make up the side chains in the DNA molecule? __sugar____ and __phosphate___

HW #4 The Structure of DNA

Read Section 12.2 in your textbook and answer the following questions.

For Questions 1–5, complete each statement by writing in the correct word or words.

1. The building blocks (monomers) of DNA are nucleotides .

2. Nucleotides in DNA are made of three basic components: a sugar called deoxyribose,a phosphate ,and a nitrogenous base .

3. DNA contains four kinds of nitrogenous bases: adenine, guanine, thymine, andcytosine.

4. "DNA" stands for: deoxyribonucleic acid

5. The two strands of a DNA molecule are held together by _hydrogen_____ bonds between complementary nitrogenous bases.

Three scientists who worked to solve the structure of DNA were Rosalind Franklin, James Watson, and Francis Crick. Franklin found clues. These clues helped Watson and Crick explain the structure and properties of DNA.

6. Complete the Venn diagram using letters to identify phrases from the list below.

a. first built a three-dimensional model of DNA Watson and Crickb. helped determine the shape of a DNA moleculeBothc. first photographed DNA using X-ray diffraction Franklind. showed that DNA is a double helix Bothe. studied DNA’s structure and properties Both

7. Complete the table by estimating the percentages of each based on Chargaff’s rules.

DNA sample Percent of adenine

Percent of thymine

Percent of guanine

Percent of cytosine

1 31.5 31.5 18.5 18.5

2 30 30 20 20

3 33 33 17 17

The Double-Helix ModelFor Questions 8–13, on the lines provided, label the parts of the DNA molecule that correspond to the numbers in the diagram.

8. hydrogen bonds

9. nucleotide

10. nitrogen base

11. deoxyribose sugar

12. phosphate group

13. base pair

14. The drawing below shows half of a DNA molecule. Write the missing letters to complete each complementary base pair (the first two have been done for you).

Given strand top to bottom: C-A-G-G-C-C-T-A-C Complementary top to bottom: G-T-C-C-G-G-A-T-G

15. Circle the correct answers. What two parts do all DNA nucleotides have in common?guanine deoxyribose phosphate group

16. In DNA, each nucleotide is connected to the next nucleotide. The connection is found between

A. sugar of one nucleotide and phosphate of anotherB. base of one nucleotide and sugar of anotherC. phosphate groups of two nucleotides

17. ____________ True or False: All cells contain DNA.

18. In DNA, which nucleotide is always paired with thymine? adenine

19. In DNA, which nucleotide is always paired with guanine?cytosine

20. DNA is an important molecule in each cell because it contains the codes that give the cell the instructions for building ________proteins__________________.

HW #5 DNA ReplicationLogin to your account at www.biology.com. Click "Explore", then click "Unit 4: Genetics", then click "Chapter 12: DNA", then click "12.3: DNA Replication". Go through the slides of the LESSON OVERVIEW. After viewing, you can click "Home" and go back to browse 12.2 in your online textbook.

Copying the Code1. Why are the strands of a DNA molecule said to be complementary?

Each strand of the double helix contains all the information needed to reconstruct the other half by the mechanism of base pairing; because each strand can be used to produce the opposite strand they are said to be complementary.

2. What is the first step in eukaryotic DNA replication?The two strands of the double helix unzip, or separate, to form two replication forks. Helicase= enzyme needed

3. If the base sequence on a separated DNA strand is CGTAGG, what will the base sequence on its complementary strand be?GCATCC

4. What enzyme joins individual nucleotides to produce the new strand of DNA?DNA Polymerase

5. What enzyme makes it less likely that DNA will be lost from telomeres during replication?Telomerase

6. How does this enzyme work?Telomerase works by adding short, repeating sequences of DNA to the telomeres, ensuring that important genes

near the telomeres are copied completely, and not lost during the process of replication .

7. What is a replication fork?The point at which the complementary strands are separated, or “unzipped”.

8. Does DNA replication take place in the same direction along both strands of the DNA molecule that is being replicated? Explain your answer. (Hint: Look at the illustration of DNA replication in your textbook.)No. DNA replication takes place in opposite directions. DNA polymerase can only follow the strand in one

direction along the sugar phosphate backbone.

9. In which type of cell is DNA circular? circle one.

prokaryotic eukaryotic

10. In which type of cell does replication begin at several points? circle one.prokaryotic eukaryotic

11.Label the diagram below with the following terms using the pictures in your text as a guide. Some terms are listed twice because you need to label both sides of the diagram.

HINT: There is an excellent animation of this - after you go through the slides of the Lesson Overview, click the "Activities" tab and then click "Interactive Art" to see the steps of DNA replication in action.

a. Nitrogenous bases

b. Replication fork

c. DNA polymerase

d. Original strand

e. Direction of Replication

f. Replication fork

g. Original strand

h. New strand

i. DNA polymerase

j. Direction of Replication

k. New strand

12. Is DNA replication always a foolproof process? Explain your answer.No. While DNA polymerase does have a proofreading function that ensures almost perfect copies, errors are

made. These errors are mutations, which may be helpful, harmful, or have no effect at all.

Nitrogenous bases

Replication ForkOriginal Strand

DNA polymerase

New strand

DNA polymerase

Original Strand

Replication Fork

New strand

Direction of replication

Direction of replication