Unit 3: DNA & Heredity

Learning Objectives

• Determine the structure and functions of DNA;

• Determine the parts of Nucleotides and give samples of Nitrogenous Base;

• Pair the exact pairing of each nitrogenous bases and translate a sample codon.
  
  

What is DNA?

DNA stands for Deoxyribonucleic acid
-it is the genetic material that carries the instructions for building and maintaining living organisms. It is present in every cell of our bodies and plays a crucial role on how our bodies function.

What is DNA?

The kind of cell which is formed, (muscle, blood,

Nerve etc) and the kind of organism which is produced (buttercup,

giraffe, herring, human etc) is controlled by DNA

It controls all the chemical changes which take place in cells.

Structure of DNA

The structure of DNA resembles a twisted ladder, with the strands forming the sides and the rungs made of pairs of molecules called nucleotides.

Structure of Nucleotide

Each Nucleotide is made up of:
A sugar called deoxyribose
Phosphate group
Organic Base

DNA  usually consists of a double

strand of nucleotides. The sugar-phosphate chains are on the outside

and the strands are held together by chemical bonds between the bases. The paired strands are coiled into a spiral called DOUBLE HELIX.

There are four types of Nitrogenous Bases:

A= adenine
T= thymine
C=cytosine
G=guanine

A is paired with T

C is paired with G

Base Pair Rule
Adenine can bond only with Thymine

A-T or T-A (2 H bonds)

Cytosine can bond only with Guanine

C-G or G-C (3 H bonds)

Complementary Base Pairing in DNA

DNA Replication

The process by which DNA makes a copy of itself. In DNA replication enzymes work to unwind and separate the double helix and add complimentary nucleotides to the exposed strands.

DNA Replication

DNA replication is semi-conservative. When it makes a copy, one half of the old strand is ALWAYS kept in the new strand. This helps reduce the number of copy errors.

DNA Replication

DNA helicases—break H-bonds linking bases.

DNA polymerases—move along each of the strands, adding nucleotides, according to base pairing rules.

DNA Replication

The result is two exact copies of the original DNA

Each new double helix is composed of one original DNA strand and one new strand.

DNA Transcription

DNA Translation

DNA translation refers to the process of converting the genetic code stored in DNA into a functional protein. Proteins are essential for the structure, regulation, and function of cells. They play a vital role in various biological processes, including metabolism, cell signaling, and immune responses.

DNA Translation

In RNA, Uracil base is paired with adenine and replaces thymine during DNA transcription.


So, the new base pair in RNA is

A is paired with U (for uracil)
C is still paired with G

How to translate a Codon?

A codon is a trinucleotide sequence of DNA or RNA that corresponds to a specific amino acid.

How to translate a Codon?

How to translate a Codon?

To read a codon, we must refer to the genetic code chart. With this chart, we can determine which amino acid or signal each codon represents.


Let's take an example:

CAG = Gln (Glutamine)  

How to translate a Codon?

To read a codon, we must refer to the genetic code chart. With this chart, we can determine which amino acid or signal each codon represents.


Let's take an example:


AUG = Met (methionie)  

Summary

• DNA is the genetic material that carries the instructions for building and maintaining living organisms. It is present in every cell of our bodies and plays a crucial role in how our bodies function.

• DNA stands for

Deoxyribonucleic acid

Summary

• The structure of DNA resembles a twisted ladder, with the strands forming the sides and the rungs made of pairs of molecules called nucleotides. Each Nucleotide is made up of: A sugar called deoxyribose, Phosphate group and Organic Base.

• There are four types of Nitrogenous Bases:
  A= adenine
  T= thymine
  C=cytosine
  G=guanine

Summary

• The central dogma of biology is a fundamental concept that describes the flow of genetic information within cells. Replication ensures the accurate copying of DNA, transcription converts DNA into mRNA, and translation uses mRNA to synthesize proteins. This sequence of events allows living organisms to grow, develop, and function.

End of the Presentation