Chromosomal Variations, Continuous and Discontinuous Variations, Genotypic & Phenotypic Variations. Hardy-Weinberg law of random mating, Recombination technology It also explains the main points for a variation.

2. MUHAMMAD MUBASHIR ALI
BBOF19E001
PRESENTATION TOPIC:
VARIATIONS
SBMITTED TO:
DR. HAFIZ MUHAMMAD WARIS
PLANT SYSTEMATICS

3. VARIATIONS

4. VARIATIONS
The term “variation” refers to
observable differences within a
species. In biology, any
difference between cells,
individual organisms or groups
of organisms of any species.

5. TYPES OF VARIATIONS
B. PHENOTYPIC VARIATIONS
A. GENOTYPIC VARIATIONS
A. GENOTYPIC VARIATIONS
The variations that are caused by differences in number
or structure of chromosomes or by the differences in
the genes carried by the chromosomes.

6. Genotypic variations comes in many different forms. Different
hair color, eye color and skin color and many other examples
come in this type of variations.

7. FACTORS OF GENOTYPIC
VARIATIONS
PANMIXIA
RANDOM
FERTILIZATION
RECOMBINATION MUTATION

8. PANMIXIA
Panmixia is also called as random
mating which refers to mating in a
population that occur in proportion to
their genotypic frequencies. Because of
this the potential mates have an equal
chance of being selected.

9. THE HARDY-WEINBERG LAW OF RANDOM
MATING:
If a large, random-mating population that is not affected by the
evolutionary processes of mutation, migration, or selection, both
the allele frequencies and the genotype frequencies are constant
from generation to generation. The population is in a state of
equilibrium.
As an example, consider a diploid pathogen such as an oomycete
that has two alleles at an isozyme locus. If the frequency of the fast
allele (F) is 0.40 and the frequency of the slow alleles (S) is 0.60,
then the expected frequencies of the genotypes FF, FS, and SS
would be 0.16, 0.48, and 0.36, respectively.

10. RANDOM FERTILIZATION
When a male gamete and a female gamete finally meet, each is the
result of an immense number of genetic possibilities created
during independent assortment and crossing over.
We can calculate the possible number of random combinations of
chromosomes in each gamete (sperm/egg) using the equation:
Number of possible combinations = 2n
Human diploid cells have 23 pairs of chromosomes. Here n = 23
which will make 8,388,608 genetically unique gametes.

11. RECOMBINATION
“Recombination is a process by which pieces of DNA are
broken and recombined to produce new combinations of
alleles.”
This recombination process creates genetic diversity at the level
of genes that reflects differences in the DNA sequences of
different organisms.
Genetic recombination occurs due to crossing over during the cell
division in cell.

12. CROSSING OVER:
“Crossing over is the swapping of genetic material that
occurs in the germ line.”
• In humans, there are over 8 million configurations in which
the chromosomes can line up during metaphase I of meiosis.
• It is the specific process of meiosis, resulting in four
unique haploid cells, that results in these many combinations.
• Together with random fertilization , more possibilities for
genetic variation exist between any two people than the
number of individuals alive today.

13. • A sperm cell , with over 8 million chromosome
combinations, fertilizes an egg cell , which also has over
8 million chromosome combinations.
• That is over 64 trillion unique combinations, not counting
the unique combinations produced by crossing-over.

14. MUTATION
A mutation is a change in a DNA sequence. Mutations can
result from DNA copying mistakes made during cell division,
exposure to ionizing radiation, exposure to chemicals called
mutagens, or infection by viruses.
Germ line mutations:
A gene change in reproductive cell (eggs & sperm) and can be
passed on to offspring. For example cancer and cystic fibrosis.
Somatic mutations:
A mutation that occurs in the body cells after the embryo has
begun to form. Cancer is an example of this mutation type.

15. TYPES OF MUTATIONS
Chromosomal
Alterations
Point Mutations
Frameshift
Mutations

16. CHROMOSOMAL
ALTERATIONS
Chromosomal alterations are mutations
that change chromosome structure.
They occur when a section of a
chromosome breaks off and rejoins
incorrectly or does not rejoin at all.

17. POINT MUTATIONS
A point mutation is a change in a single nucleotide in DNA. This
type of mutation is usually less serious than a chromosomal
alteration. An example of a point mutation is a mutation that changes
the codon UUU(Phenylalanine) to the codon UCU(Serine).

18. FRAMESHIFT MUTATIONS
A frameshift mutation is a deletion or insertion of one or more
nucleotides that changes the reading frame of the base sequence.
Deletions remove nucleotides, and insertions add nucleotides.
Consider the following sequence of bases in RNA:
Now, assume an insertion occurs in this sequence. Let’s say
an A nucleotide is inserted after the start codon AUG:
AUG-AAU-ACG-GCU = start-asparagine-threonine-alanine
AUG-AAA-UAC-GGC-U = start-lysine-tyrosine-glycine

19. AFFECT OF INSERTION
This insertion changes the reading frame and thus
all of the codons that follow it. As this example
shows, a frameshift mutation can dramatically
change how the codons in mRNA are read. This
can have a drastic effect on the protein product.

20. PHENOTYPIC VARIATIONS
“Phenotypic variation, then, is the variability in phenotypes that
exists in a population.”
Phenotypes are traits or characteristics of an organism that we can
observe, such as size, color, shape, capabilities, behaviors, etc.
Not all phenotypes can actually be seen. For example, blood types are
phenotypes that we can only observe using laboratory techniques.
Phenotypes can be caused by genes, environmental factors, or a
combination of both.

21. TYPES OF PHENOTYPE
VARIATIONS
CONTINUOUS
VARIATIONS
DISCONTINUOUS
VARIATIONS

22. CONTINUOUS VARIATIONS
When a characteristic or phenotype normally exists in a range or
gradient, it varies continuously, such as height and skin color. In
between the shortest person in the world and the tallest person in
the world, any height is possible, not just four feet, five feet, or six
feet.

23. GRAPHICAL REPESENTATION OF
CONTINUOUS VARIATIONS

24. DISCONTINUOUS VARIATIONS
"A characteristic of any species with only a limited number of
possible values shows discontinuous variation.”
These phenotypes exist only at discrete intervals, like 'black and
white' differences.
For example, you can have blood type A, B, AB, or O, but there aren't
any intermediate blood types in between.
Another example is the ability to roll your tongue. Either you can or
you can't, so this phenotype varies discontinuously.

25. GRAPHICAL REPESENTATION OF
DISCONTINUOUS VARIATIONS

26. THANK YOU