introduction on DNA structure ands functions of DNA

1. Reduyan Hasan
Lecturer
DyNC

2. Introduction
 During mid 19th Century, Gregor Mendel observed that
certain
 features pass from parents to their children/offspring.
 A child usually looks like their parents and is due to
inheritance of
 certain characteristics from parents to children .
 This transmission of characteristics from parents to
children is
 known as heredity.
 The basic unit of heredity is gene, which consist of portion
of DNA
 molecules.
 The term gene was coined by Johannsen in 1909.

3. Genetics
 Genetics is the study which
deals with the science of genes,
 heredity and its variations in
living organism.
 Gregor Mendel is the father of
Genetics
 The term Genetics was coined
by William Bateson

4. Gene
 Gene is defined as a segment of DNA
(Deoxyribonucleic Acid)
 which carries the genetic information.
 Gene is the basic physical and functional unit of
heredity
 DNA has also segment which do not contain
gene.
 The human genome contains about 30000 —
40000 genes and each
 gene varies in size,

5. Gene Definition
A gene is defined as the fundamental unit of heredity. It is a
segment of DNA that has information coded in it in the form
of a nucleotide sequence. It has the ability to undergo
mutation and crossing over.

6. Chromosomes
 Chromosomes are thread-like structures located inside the
nucleus
 of animal and plant cells. Each chromosome is made of protein
and
 a single molecule of deoxyribonucleic acid (DNA).
 Passed from parents to offspring, DNA contains the specific
 instructions that make each type of living creature unique.
 The term chromosome comes from the Greek words for color
 (chroma) and body (soma). Scientists gave this name to
 chromosomes because they are cell structures, or bodies, that are
 strongly stained by some colorful dyes used in research.

7. Chromosome Definition
A chromosome is a DNA molecule that consists of a part or all
of the genetic material of an organism. The chromosome is
present in the nucleus of each cell, and it is packaged into
thread-like structures.

8. Nucleic acids
 Nucleic acids are the macromolecules present
in all living cell.
 Nucleic Acids are of two types —
 DNA (Deoxyribonucleic Acid)
 RNA (Ribonucleic Acid)

10. DNA stands for
Deoxyribonucleic acid

12. DNA Structure
 DNA consists of two molecules that are arranged
into a ladder-like structure called a Double
Helix.
 A molecule of DNA is made up of millions of
tiny subunits called Nucleotides.
 Each nucleotide consists of:
1. Phosphate group
2. Pentose sugar
3. Nitrogenous base

13. Nucleotides
Phosphate
Pentose
Sugar
Nitrogenous
Base

14. Nucleotides
 The phosphate and sugar form the backbone
of the DNA molecule, whereas the bases form
the “rungs”.
 There are four types of nitrogenous bases.

15. Nucleotides
A
Adenine
T
Thymine
G
Guanine
C
Cytosine

16. Nucleotides
 Each base will only bond with one other
specific base.
 Adenine (A)
 Thymine (T)
 Cytosine (C)
 Guanine (G)
Form a base pair.
Form a base pair.

17. Base-Pair Rule
Adenine <==> Thymine
Guanine <==> Cytosine
The sides of the DNA
ladder are phosphate &
sugar held together
by hydrogen bonds

18. Importance of DNA

19. DNA Structure
 Because of this complementary base pairing,
the order of the bases in one strand
determines the order of the bases in the other
strand.

20. G
G
A
T
T
A
A
C
T
G
C
A
T
C

21. Base Pair Rule
One side: A T A T C A T G C G G G
Other side:

22. DNA Structure
 To crack the genetic code found in DNA we
need to look at the sequence of bases.
 The bases are arranged in triplets called
codons.
A G G - C T C - A A G - T C C - T A G
T C C - G A G - T T C - A G G - A T C

23. DNA Structure
 A gene is a section of DNA that codes for a
protein.
 Each unique gene has a unique sequence of
bases.
 This unique sequence of bases will code for the
production of a unique protein.
 It is these proteins and combination of proteins
that give us a unique phenotype.

24. How the Code Works
The combination of A,T,G,C determines what
traits you might have, for ex.
C A T C A T = purple hair
T A C T A C = yellow hair

25. Think of the bases of DNA like
letters.
Letters form words....
Words form sentences....
*endless
combinations