DNA Replication - DOC

Report as inappropriate Your report has been received

Shared by: lst6KUYi

Tags

Stats

views:: 30
posted:: 6/15/2012
language:: English
pages:: 6

Public Domain

Document Sample

Biology (Science II)

Unit VI: Genetics

Time Frame: 2 weeks

Competencies

1. Understand the chromosomal basis of inheritance and the role of DNA as the
blueprint of life
1.1 Explain the chromosomal basis of inheritance
1.2 Give the importance of DNA in the transmission of traits

2. Understand the fundamental role of chromosomes and genes in hereditary variations
2.1 Discuss the relationship of chromosomes and genes
2.2 Understand the different chromosomal aberrations

Lesson 1: DNA Structure

I. Subject Matter: DNA Structure

Time Frame: 1 period

References:

Suggested Textbook:

University of the Philippines National Institute for Science and Mathematics Education
Development. (In Press). Sourcebook on practical work for teachers: High school
biology. (Vol. 3). Quezon City: Galvez, E.R., Catalan, M.H.dH., Lebig, L.D.,
Orbita, P.J.S.

II. Objectives:

1. Identify the molecules which make up DNA
2. Use models to construct a molecule of DNA

III. Materials:

For Student Activity

Paper nucleotides
Scissors
Crayons

208 BSE-Department of Education
IV. Lesson Proper:

A. Recall

What are some reasons that cause organisms to adapt to their environment?

B. Motivation

Building a house usually requires a blueprint, or a plan of the structure of the
house to determine how it will look like after construction. People involved in the
construction refer to this blueprint from time to time.

All organisms also have blueprints that contain information that will determine their
physical and chemical characteristics. This blueprint is deoxyribonucleic acid
(DNA).

You will perform an activity that will help you understand some important concepts
in DNA structure.

C. Activity

Photocopy enough copies of paper models for the whole class.
Assign students to color and cut out the paper models a day before the activity.

D. Postlaboratory Discussion

Answers to Developmental Questions.

Question 1. What are the two common parts of a nucleotide?
Answer: sugar and phosphate

Question 2. What is the one part of a nucleotide that differs among the other
different nucleotides?
Answer: base

Question 3. List the four different kinds of nitrogen bases.
Answer: adenine, guanine, cytosine, thymine

Question 4. What is the pairing arrangement of nitrogen bases?
Answer: Adenine pairs with thymine and guanine pairs with cytosine

Question 5. Are there always going to be an equal number of adenine and
thymine nucleotides in a molecule? Why?
Answer: Yes. Adenine can only pair with thymine because of their chemical
structures.

BSE-Department of Education 209
Question 6. Are there always going to be an equal number of guanine and
cytosine nucleotides in a molecule? Why?
Answer: Yes. Guanine can only pair with cytosine because of their chemical
structures.

Question 7. The sides (or “uprights”) of the ladder are made up of alternating
___________ and _________ molecules. The steps (or “rungs”) of
the ladder are made of ____________ held together by hydrogen
bonds.
Answer: sugar and phosphate; nitrogen bases

E. Generalization

1. DNA contains the information needed to form and control the physical
makeup and chemical processes of an organism.
2. DNA is a double-stranded helix made up of repeating units of nucleotides.
3. A nucleotide is composed of the following: sugar and phosphate molecules,
and a nitrogenous base. The base can either be adenine, guanine, thymine
and cytosine.
4. Adenine and thymine, cytosine and guanine are said to be complementary
bases. Because of their chemical structures, adenine can only bond with
thymine and cytosine can only bond with guanine.

F. Valuing or Application

The discovery of the DNA structure was only the beginning of understanding the
human genome. The basic techniques in the study of the genetic material are
now being used in the mapping of the human genome.

G. Assessment

One chain of a DNA molecule has the nucleotide sequence C, C, G, C, T. What is
the sequence of the nucleotides on its partner chain?

Answer: G, G, C, G, A

V. Agreement

Read on the process of DNA replication.

210 BSE-Department of Education
Activity 1. Investigating DNA Structure

Deoxyribonucleic acid is the blueprint of life. It contains the information needed to form the
physical makeup and control the chemical processes of every part of an organism. DNA is
composed of repeating nucleotides. In this activity, the DNA structure will be investigated
through the use of paper nucleotides.

Objectives

1. To identify the molecules which make up DNA
2. To use models to construct a molecule of DNA

Materials

Paper nucleotides
Scissors
Crayons

Procedure

1. Color and cut out the nucleotides.
2. Examine the nucleotides.

Question 1. What are the two common parts of a nucleotide?
__________________________________________________________
__________________________________________________________

Question 2. What is the one part of a nucleotide that differs among the other different
nucleotides?
__________________________________________________________
__________________________________________________________

Question 3. List the four different kinds of nitrogen bases.
__________________________________________________________
__________________________________________________________

A molecule of deoxyribose joins with phosphate and any one of the four bases to form
a chemical compound called a nucleotide. A nucleotide is named for the base that
joins with the deoxyribose. For example, if guanine attaches to deoxyribose, the
molecule is called a guanine nucleotide.

3. Manipulate and fit nucleotides together to form a row in the following sequence from
top to bottom:

TAC CAG CGG CGT GCC ACT

Let this arrangement represent the left half of the DNA molecule.

BSE-Department of Education 211
4. Complete the right side of the DNA molecule by matching the bases of other
nucleotides. It may be necessary to turn molecules upside down in order to join certain
base combinations. The ends of each base will allow only a specifically-shaped
matching new base to fit exactly.

Question 4. What is the pairing arrangement of nitrogen bases?
_________ pairs with ________ and ____________ pairs with
__________.

Question 5. Are there always going to be an equal number of adenine and thymine
nucleotides in a molecule? Why?
__________________________________________________________
__________________________________________________________

Question 6. Are there always going to be an equal number of guanine and cytosine
nucleotides in a molecule? Why?
__________________________________________________________
__________________________________________________________

5. The structure of DNA is actually in a double helix arrangement.

Question 7. The sides (or “uprights”) of the ladder are made up of alternating
___________ and _________ molecules. The steps (or “rungs”) of the
ladder are made up of ____________ held together by hydrogen bonds.

Source:

University of the Philippines National Institute for Science and Mathematics Education
Development. In Press. Sourcebook on Practical Work for Teachers: High school
biology. (Vol. 3). Quezon City: Author.

212 BSE-Department of Education
G
C

Deoxyribose Deoxyribose
(sugar) (sugar)
phosphate phosphate

A T

Deoxyribose
Deoxyribose (sugar)
(sugar) phosphate
phosphate

DNA nucleotides

BSE-Department of Education 213