GENE CHROMOSOMES PPT

1. GENE , CHROMOSOMES,
PRACTICAL APPLICATIONS IN NURSING, DNA
PRESENTEDBY:
RITIKARANA
MSC NSG
NEUROSCIENCES

2. GENE

3. INTRODUCTION
 The term “gene” derived from German word “gen”
meaning “begetting” ,Greek word “genos” meaning
“race”, “offspring”.
 The classical principles of genetics were deduced by
Gregor Mendel in 1865 on the basis of breeding
experiments with peas.
 He assumed that each trait is determined by a pair of
inherited ‘factors’ which are now called gene.
 In 1909 Wilhelm Johannsen coined the term ‘GENE’.

4. DEFINITION
 A gene is defined as the fundamental, physical, and
functional unit of heredity.
 A gene is a specific sequence of DNA containing genetic
information required to make a specific protein.

5. BASIC TERMS
• GENETICS:- “Genetics is the study of heredity, the process in which a
parent passes certain genes onto their children.
• DOMINANT GENE:- Dominant gene has capability to express itself in
phenotype of and individual even in presence of alternative allele form.
• RECESSIVE GENE:- A recessive gene is a gene whose effects are
masked in the presence of a dominant gene.

6. CONT……
• ALLELE:- An allele is two alternative form
of a gene.
• GENOTYPE:- It represents the genetic
makeup of an organism. It represents tallness
& dwarfness.
• PHENOTYPE: It express morphological or
physiological character of an individual.

7. GENE TYPES
1. Basic genes: These are the fundamental genes that bring
about expression of particular character.
2. Lethal genes: These bring about the death their
possessor.
3. Multiple gene: When two or more pairs of independent
genes act together to produce a single phenotypic trait.
4. Cumulative gene: Some genes have additive effects on
the action of other genes. These are called cumulative
genes.
5. Pleiotropic genes: The genes which produce changes in
more than one character is called pleiotropic gene.

8. 6. Modifying gene: The gene which cannot
produce a character by itself but interacts with
other to produce a modified effect is called
modifier gene.
7.Inhibitory gene: The gene which suppresses or
inhibits the expression of another gene is called
inhibitory gene.

9. GENE ACTION
1. Supplementary gene action (9:3:4):- In supplementary gene interaction, the
dominant allele of one of two gene governing a character produces
phenotypic effect.
 However dominant allele of the other gene does not produce a phenotypic
effect on its own.
 But when it is present with dominant allele of the first gene it modifies the
phenotypic effect produced by that gene.

10. 2. Complementary gene action (9:7): Complementary gene interaction.
 If both gene loci have homozygous alleles and both of them produce
identical phenotypes the F2 ratio become 9:7 instead 9:3:3:1.
 In such case, the genotype aaBB, aaBb, Aabb, aabb produce one
phenotype.
 Both dominant alleles when present together each other are called
complementary genes and produce a different phenotype.

11. 3.Inhibitory gene action (13:3):
• When dominant allele of one gene locus (B) in homozygous (BB) and
heterozygous (Bb) condition produce the same phenotype the F2 ratio
becomes 13:3 instead of 9:3:3:1.
• While homozygous recessive (bb) condition produces different
phenotype.

12. 5. Duplicate gene interaction (15:1):
 When dominant allele of both gene loci produce the same phenotype
without cumulative effect.
 In that case the ratio becomes 15:1 instead of 9:3:3:1.
 Duplicate gene interaction occurs in shepherds purse plant

13. 6. Masking gene action (12:3:1): When out of two genes, the dominant allele
(e.g., A) of one gene masked the activity of allele of another gene (e.g., B).
 Then A gene locus is said to epistatic to the B gene locus.
 Dominant allele A express itself only in the presence of either B or b so such
type of epistatic is know as dominant epistatic.
 The allele of hypostatic locus express only when the allele of epistatic locus
present in homozygous recessive condition

14. 7. Polymeric gene action (9:6:1):
 Polymeric gene interaction is the combination of two dominant
alleles that intensifies the phenotype or creates a median variation.
 Each dominant allele produces a physical trait different from the
combined dominant alleles.
 Therefore, this creates three phenotypes for only two dominant
alleles.

15. GENE CONCEPT
CLASSICAL CONCEPT OF GENE:
 Introduced by Sutton (1902) and was elaborated by Morgan (1913),Bidge
(1923), Muller (1927) and others which outlined as follows:
 Genes are discrete particles inherited in Mendel experiment that occupies a
definite locus in chromosome and responsible for expression of specific
phenotypic character.
 Number of genes in each organism is more than the number of chromosomes.
 Hence, several genes are located on each chromosome
 Genes are arranged in a single linear order like beads on a string.

16.  Each gene occupies specific position called locus. If the position of gene
changes, character changes. Genes can be transmitted from parent to off
springs.
 Genes may exist in several alternate formed called alleles.
 Genes are capable of combined together or can be replicated during a cell
division.
 Genes may under for sudden changes in position and composition called
mutation.
 Genes are capable of self-duplication producing their own exact copies.

17. MODERN GENE CONCEPT
 S. Benzer (1957) coined different terms for different nature of gene and
genetic material in relation to the chromosome on the basis of genetic
phenomena to which they involve.
 Genes as unit of transmission or cistron.
 Genes as unit of recombination or recon.
 Gene as unit of mutation or muton.
 Genes as unit of transmission or cistron.

18.  The part of DNA specifying a single polypeptide chain is termed
as cistron.
 A cistron can have 100 nucleotide pairs in length to
30,000nucleotide pairs.
 It transmits characters from one generation to other as unit of
transmission.
 Genes as unit of recombination or recon.
 The smallest segment of DNA capable of being separated and
exchange with other chromosome is called recon.
 A recon consists of not more than two pairs of nucleotides.

19. GENE STRUCTURE

21. CHROMOSOME

22. INTRODUCTION
 Chromosomes were first described by Strausberger in 1875.
 The term “Chromosome”, however was first used by
Waldeyer in 1888.
 They were given the name chromosome (Chromo = colour;
Soma = body) due to their marked affinity for basic dyes.
 Their number can be counted easily only during mitotic
metaphase.
 Genes, the unit of inheritance are located on the chromosomes
of the gametes.

23. DEFINITION
 In the nucleus of each cell, the DNA molecule
is packaged into thread-like structures called
chromosomes.

24. CHEMICAL COMPOSITION
 Thin chromatin threads called Chromatin Fibers.
 Interphase chromatin -30 - 40% DNA, 50 - 65% protein and 1-
10% RNA.
 Metaphase chromosomes- 15 - 20% DNA, 10 - 15% RNA and 65 -
75 % protein.
 DNA- nucleotide & primary protein-histones.

25. CHROMOSOMAL STRUCTURE

26. CHROMOSOMAL STRUCTURE
• BASED ON NUMBER OF CHROMOSOMES:

28. CHROMOSOME NUMBER
 Each species has a definite and generally, a constant somatic and gamete
chromosome number.
 Somatic chromosome number is number of chromosomes found in somatic,
more meristematic, tissues of species and represented by 2n.
 Two copies of each chromosome are ordinarily identical in morphology, gene
content,order are known as homologus chromosomes.
 Gametic chromosome number is half of somatic number and represented by n
which denotes number of chromosomes found in gametes of number.
 Two or more rounds of successive DNA replication without an intervening
called endoreduplication.

29. CHROMOSOME SIZE
 Chromosome size is measured at mitotic metaphase generally measured in
length and diameter.
 Plants usually have longer Chromosome than animals.
 Plant Chromosomes are generally 0.8-7µm in length where as animal
chromosomes are 0.5-4µm in length.
 Chromosomes size varies from species to species.

30. CHROMOSOME SHAPE
 Shape of chromosome is generally determined by the position of
centromere .
 Chromosomes generally exits in three different shapes, viz., rod
shape, J shape and V shape.

31. FUNCTIONS
 Carry the genetic material from one generation to another.
 Act as a guiding force in the growth, reproduction, repair and regeneration
process, which is important for their survival.
 Protect the DNA from getting tangled and damaged.
 Histone and non-histone proteins help in the regulation of gene expression.
 Spindle fibres attached to the centromere help in the movement of the
chromosome during cell division.
 Each chromosome contains thousands of genes that precisely code for multiple
proteins present in the body.

32. PRACTICAL APPLICATIONS OF GENE
IN NURSING

33. DEFINITION
GENETIC NURSING: Genetics nursing is a nursing specialty that focuses on
providing genetic healthcare to patients.
GENETIC NURSE: A genetics nurse is a licensed professional nurse with
special education and training in genetics.

34. APPLICATIONS
 There is a vital recognition of the need to enhance education of nurses regarding genetics.
 There have been several attempts to mandate a minimal amount of information related to
genetics in curricula.
 There are several opportunities for doctoral program research in nursing genetics.
 Nurses should be aware of when/where to incorporate genetics into practice.
 Genetic counselling may be appropriate in many settings. OBG nursing and pediatric nurses
look at genetic anomalies in infants and may be part of genetic screening.
 Cancer nurses should be aware of latest data related to testing for genetic markers.

35.  Cardiac specialists and community nurses should be aware of genetic predictors
of Coronary Heart Disease.
 Significant research into genetics has been conduced by nurses and it is a
priority area identified by studies include:
 Biologic factors in prevention of type 2 diabetes
 Weight management in women Genetics and renal function.
 Cystic fibrosis management.
 Primary prevention in patients with family history of Coronary Heart Disease.

36. DNA
(DEOXYRIBOSE NUCLEIC
ACID)

37. INTRODUCTION
 In 1869, Miescher discovered "nuclein"
(DNA) in the cells from pus & later he
separated it into a protein and an acid
molecule. It came to known as nucleic acid
after 1874. 
 In 1926, Levene proposed “Tetra nucleotide
theory”.
 Rosalind Franklin used X-ray crystallography
to visualize the structure of DNA.
 James D. Watson and Francis Crick, co-

38. CONT…….
 DNA Stands for “DeoxyriboNucleic Acid”. 
 Term DNA was given by Zaccharis .
 DNA is biopolymer consist of nucleotide as monomeric unit.
 DNA is found in the cells of all living things. 
 DNA contains all of the genetic information that makes you who
you are and every  individual organism has unique DNA.

39. DEFINITION
 DNA, or deoxyribonucleic acid, is the hereditary material in humans
and almost all other organisms.

40. DNA COMPOSITION
 Made up of molecules called nucleotides.
 Each molecule contains a phosphate group , a sugar group and a
nitrogen base.
 These nitrogen bases are:
 adenine(A),
 guanine(G),
 thymine (T)
 cytosine(C).

41. DNA STRUCTURE
 DNA structure was described by James
Watson and Francis Crick in 1953.
 Honoured Nobel prize with in 1962.
 According to them, DNA is double helical
structure in which two parallel chains are
joined together by regular cross bars.

43. EXPERIMENT TO PROVE DNA AS A
GENETIC MATERIAL
1. GRIFTH
EXPERIMENT

44. 2. HERSHEY AND CHASE EXPERIMENT:

45. DNA REPLICATION
• ENZYMES :
DNA HELICASE
DNA PRIMASE.
PRIMERS
DNA POLYMERASE
TOPOISOMERASE/DNA GYRASE.
EXONUCLEASES.
DNA LIGASE.

46. STEPS
• INITIATION.
• PRIMER BINDING.
• ELONGATION.
• TERMINATION.

47. DNA FUNCTION
 DNA enables the cell to maintain, grow and divide by directing the
synthesis of structural proteins.
 carries hereditary characters from parents to young ones
 DNA controls cellular metabolism through the transcription of
selective RNAs.
 DNA brings about the differentiation of cells during development.
 Gene Therapy.
 DNA Fingerprinting

48. CONCLUSION
 Chromosomes play an important role and act as a guiding force in the
growth, reproduction, repair and regeneration process, which is important for
their survival.
 Genetic counselling may be appropriate in many settings. OBG nursing and
pediatric nurses look at genetic anomalies in infants and may be part of
genetic screening.
 Cancer nurses should be aware of latest data related to testing for genetic
markers.
 Cardiac specialists and community nurses should be aware of genetic
predictors of Coronary Heart Disease.
 Significant research into genetics has been conduced by nurses.