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DNA: Chargaff's Rules, Structure, Replication, and Base Pairing, Study notes of Genetics

Chargaff's rules, the structure of dna, nucleotides, dna replication, complementary base pairing, and the components of dna. Learn about chargaff's discoveries regarding the nitrogen bases in dna, the double helix structure, and the importance of complementary base pairing in maintaining the dna molecule's shape.

What you will learn

  • How does complementary base pairing maintain the double helix shape of DNA?
  • What is the structure of the DNA molecule?
  • What are Chargaff's rules?

Typology: Study notes

2021/2022

Uploaded on 09/27/2022

hayley
hayley 🇺🇸

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1. What are Chargaff’s rules?
Studied DNA from many different species
Interested in the four different nitrogen bases of DNA: adenine (A), guanine (G), cytosine (C), and thymine (T)
Discovered concentrations of the four bases differed from one species to another
Observed within each species -- concentration of adenine (about the same) concentration of thymine.
-- concentrations of guanine and cytosine (about the same)
2. Identify the structure of the DNA molecule. What are nucleotides?
A Nucleic Acid macromolecule (Textbook page 171)
Double helix shape of two polynucleotide chains of DNA
Made from nucleotide monomers with 3 parts:
3. What makes up a nucleotide?
phosphate group
sugar “deoxyribose”
nitrogen-containing base (A,C, G, or T) (Held together with H-bonding)
Adenine & Guanine 2-ring; Thymine & Cytosine 1-ring
(Knowing structure helps in better understanding function)
4. Why is DNA replication said to be semi-conservative?
The two daughter molecules contain one strand from the parent molecule and one new strand that is complementary to it…
ie, half of the parent DNA molecule is conserved in each of the two daughter DNA molecules.
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1. What are Chargaff’s rules?

● Studied DNA from many different species

● Interested in the four different nitrogen bases of DNA: adenine (A), guanine (G), cytosine (C), and thymine (T)

● Discovered concentrations of the four bases differed from one species to another

● Observed within each species -- concentration of adenine (about the same) concentration of thymine.

-- concentrations of guanine and cytosine (about the same)

2. Identify the structure of the DNA molecule. What are nucleotides?

● A Nucleic Acid macromolecule (Textbook page 171)

● Double helix shape of two polynucleotide chains of DNA

● Made from nucleotide monomers with 3 parts:

3. What makes up a nucleotide?

● phosphate group

● sugar “deoxyribose”

● nitrogen-containing base (A,C, G, or T) (Held together with H-bonding)

Adenine & Guanine 2-ring; Thymine & Cytosine 1-ring

(Knowing structure helps in better understanding function)

4. Why is DNA replication said to be semi-conservative?

The two daughter molecules contain one strand from the parent molecule and one new strand that is complementary to it…

ie, half of the parent DNA molecule is conserved in each of the two daughter DNA molecules.

5. Create a diagram that shows how DNA replication occurs.

6. What is complementary base pairing?

Adenine - Thymine and Guanine - Cytosine

7. Explain why complementary base pairing is necessary to maintain the double helix shape of the

DNA molecule.

The one-ring molecule binds with a two-ring molecule ... the distance between the two chains is constant to maintains the

uniform shape of the DNA double helix

Note: specific sequence of A, T, C, and G nucleotides within an organism's DNA is unique to that individual, and it is this sequence that controls not only the operations within a particular cell, but within the organism as a whole.

scientist Rosalind Franklin used a process called X-ray diffraction to capture images of DNA molecules. Dr. Franklin interpreted the black lines in photos as representing distances between the nucleotides that were arranged in a spiral shape called a helix.

Watson and Crick : DNA actually takes the form of a double helix , a ladder-like structure that is twisted along its entire length (Figure 6). Franklin, Watson, and Crick all published articles describing their related findings in the same issue of Nature in 1953.

One Human:

100 trillion cells DNA in each cell nearly two meters long