The document discusses key concepts in genetics and DNA structure. It defines genes as segments of DNA that carry hereditary information coded in nucleotide sequences. Chromosomes are DNA molecules packaged into structures in cell nuclei that contain genetic material. DNA has a double helix structure formed by pairing of nucleotides containing nitrogenous bases. The base pairing rule dictates that adenine pairs with thymine and guanine pairs with cytosine. Gene sequences on DNA encode unique proteins that determine an organism's traits.

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