The document discusses the characteristics and functions of genes. It defines a gene as a segment of DNA or chromosome that carries coded information for a specific function. Genes are the basic unit of heredity and can undergo processes like crossing over and mutation. Each gene provides instructions to make a specific protein. Genes control inheritance, cell division, development, metabolism, and variation between individuals. The different types of genes include housekeeping genes, inducible genes, and regulatory genes.

1. PRESENTATION
ON
CHARACTERISTICS AND
FUNCTIONS OF GENE
BY: MEENAKSHI P. DHYANI
NURSING LECT. (CHN)

2. INTRODUCTION
The term „Gene‟ was introduced in 1909. Prior to
him Mendel had used the word factor for a
specific, distinct, particular unit of inheritance
that takes part in expression of a trait.
Morgon’s work suggested gene to be the shortest
segment of chromosome, which can be separated
through crossing over, can undergo mutation and
influence expression of one or more traits.

4. DEFINITION
 Presently, a gene is defined as a unit of
inheritance composed of a segment of DNA or
chromosome situated at a specific locus
(gene/locus), which carries coded information
associated with a specific function & can
undergo crossing over as well as mutation.

5. CHARACTERISTICS/FEATURES OF GENES
 Specific Features of Genes:-
 The term gene is often used to refer genetic material on a
chromosome that code for a trait. E.g. one person has a gene for
hair colour.
 It is a unit of recombination or capable of undergoing crossover.
 A unit of genetic material, which can undergo mutation.
 A unit of hereditary connected with somatic structure or function
that leads to a phenotype expression.
 A gene is the basic physical & functional unit of hereditary.

6. HOMOLOGOUS PAIR OF CHROMOSOMES

7. CONT……
 Gene which are made up of DNA, act as RNA instructor to make molecules
called proteins.
 Every person has two copies of each gene, one inherited from each
parent. Most genes are the same in all people, but a small number of
genes less than (1% of the total) are slightly different between people.
Alleles are forms of the same gene with small differences in their
sequence of DNA bases. These small differences contribute to each
person‟s unique physical features.
 The physical development & phenotype of a person can be thought of as a
product of genes interacting with each other & with environment.
 Total set of genes in a person are known as Genome.

8. CONT…..
 Gene is basically an instruction for human body, each gene
has a specific purpose & very single function of the human
body is coded in one or more genes.
 A person’s unique genetic constitutes called the Genotype
are made up of about 30,000 to 40,000 genes
 A person’s phenotype, the observable characteristics of his
or her genotype includes the physical appearance & other
biological, physiological & molecular traits.

9. STRUCTURE OF GENE

11. FUNCTIONS OF GENE
 Genes are components of genetic material & are thus
unit of inheritance.
 They control the morphology or phenotype of
individual.
 Replication of genes is essential for cell division.
 Genes carry the hereditary information from one
generation to next.
 They control the structure & metabolism of the body.
 Reshuffling of genes at the time of sexual reproduction
produce variation.

12. CONT……
 Different linkages are produced due to crossing over.
 Genes undergo mutation & change their expression.
 New genes are consequently new traits develop due to
reshuffling of different parts of genes.
 Genes change their expression due to position effect.
 Differentiation or formation of different type of cells,
tissues & organs in various parts of the body is
controlled by expression of others.
 Development or production of different stages in the
life history is controlled by genes.

13. TYPES OF GENES
 House Keeping Genes (Constitutive Genes):They are those genes which
are constantly expressing themselves in a cell because their products are
required for the normal cellular activities, e.g., genes for glycolysis, ATP-
ase.
 Non-constitutive Genes (Luxury Genes):The genes are not always
expressing themselves in a cell. They are switched on or off according to
the requirement of cellular activities.
 Inducible Genes:The genes are switched on in response to the presence
of a chemical substance or inducer which is required for the functioning
of the product of gene activity.
 Repressible Genes:They are those genes which continue to express
themselves till a chemical (often an end product) inhibits or represses
their activity. Inhibition by an end product is known as feedback
repression.
 Multigenes (Multiple Gene Family):It is a group of similar or nearly
similar genes for meeting requirement of time and tissue specific
products,

14. CONT……
 Repeated Genes: The genes occur in multiple copies because their products
are required in larger quantity.
 Single Copy Genes: The genes are present in single copies (occasionally 2—3
times), e.g., protein coding genes. They form 60—70% of the functional
genes. Duplications, mutations and exon reshuffling can form new genes.
 Pseudogenes: They are genes which have homology to functional genes but
are unable to produce functional products due to intervening nonsense
codons, insertions, deletions and inactivation of promoter regions, e.g.,
several of snRNA genes.
 Processed Genes: They are eukaryotic genes which lack introns. Processed
genes have been formed probably due to reverse transcription or
retroviruses. Processed genes are generally non-functional as they lack
promoters.
 Transposons (Jumping Genes): They are segments of DNA that can jump or
move from one place in the genome to another.

15. CONT…..
Overlapping Genes: Genes those overlap other genes.
Structural Genes: Structural genes are those genes
which have encoded information for the synthesis of
chemical substances required for cellular machinery.
Regulatory Genes (Regulatory Sequences): Regulatory
genes do not transcribe RNAs for controlling structure
and functioning of the cells.
 Tissue Specific Genes: They are genes which are
expressed only in certain specific tissues and not in
others.
Mitochondrial gene: Genes present in the human
mitochondria.