Genetics powerpoint slides

1. Chromosomal mutation
and Gene mutation
By: Qusainshahid
Msc final
2k19/MBOT/11

2. • Mutation caused by
1.physical agents: x-rays and uv lights.
2.chemical agents: nitrous acid
3.spontneous mutation: by unequalcrossing over.

3. 1.chromosomal mutation (Abberation)
• When a change occurs in the structure of chromosome, it is called chromosomal
abberetion.
• These can be visible in the structure of chromosomes.
• These changes are as follows:
STRUCTURAL CHANGES:
i. Deletion
ii. Duplication
iii. Translocation
iv. Inversion.
NUMERICAL CHANGES:
i. Aneuploidy
ii. Euploidy

4. 1. Deletion:
• When a small part of chromosome is separated, and
missed, it does not attached with the original
chromosome again.
• It is called deletion.
Effects of deletion:
• If deletion occurs in one chromosome of the
homologous pair, it is harmful and it occursin both
chromosomes of the pair, then death may occur.

5. 2.Duplication:
• When a part of chromosome is separated from a chromosome and
then it is attached with another chromosome
• The part of chromosome is present in excess to the normal
chromosome, it is called duplication.
• In this type of deletion, there is repetition of genes because these
are attached to the homologous genes
• It is called repeat duplication .
Effects of duplication:
• It causes abnormality in the structure and function of the body.
• The duplication also plays a very important role in evolution of
new genetic material and it can change the phenotype of the
organism.
• It may cause polyploidy.

6. 3.Translocation:
• When a part of chromosome is transferred to
a non-homologous chromosome, it is called
trasnlocation.
Effect of translocation:
• Due to translocation changes may be
produced in species and new specie may be
developed.

7. 4.Inversion:
• When a change occurs in the sequence of
genes within the chromosome,it is called
inversion.
• It involves no less or gain in the number of
gene but only in the rearrangementof genes
in a particular chromosome.
Effects of inversion:
• It does not cause a change in the phenotype,
but gene mutation may occur. Process of
crossing over is also reduced due to inversion.

8. Chromosomal number mutation
1.Aneuploidy:
• Aneuploidy is a type of mutation in the chromosome
number where in the ploidy (chromosome number) of
the new individual is different from its wild type. This is
typically a result of the nondisjunction of chromosomes
during mitosis or meiosis, hence producing offspring
with either extra or lost chromosomes.
• The naming of aneuploid conditions is generally based
on the number of chromosomes added or deleted. For
instance, a monosomic (2n -1) individual bears only one
copy of a chromosome, instead of having two.
• Other variations of aneuploidy
are trisomic (2n+1), nullisomic (2n-2), and disomic (n+1).

9. 2.Euploidy:
• Euploidy is a condition when a cell or an organism
has one or more than one complete set of
chromosomes.For example, when a humancell has
an extra set of 23 chromosomes, then it is
called euploid. In other words, euploidy occurs
whenever a cell has a multiple of the haploid number
of chromosomes. For example, a normal diploid
human cell would contain 46 chromosomes (2n).
However, if it happens to contain 69 chromosomes
(3n),then it would be considered euploid.
• The euploids may be of two types
1. Monoploid
2. polyploid

10. Human disease or defects due to abnormal
abnormal number of chromosomes
• About 95 percent of the time, Down's syndrome is caused by trisomy 21 — the
person has three copies of chromosome 21, instead of the usual two copies, in all
cells.This is caused by abnormal cell division during the development of the sperm
cell or the egg cell.
PHYSICAL SYMPTOMS: Common physical signs of Down's
syndrome include decreased or poor muscle tone. Short neck, with excess skin at the
back of the neck. Upward slanting eyes, often with a skin fold that comes out from
the upper eyelid and covers the inner corner of the eye.
Down's syndrome
2n+1:

11. Turner's syndrome
• This abnormal condition occurs due to monosomic
condition.
• Turner's syndrome, a condition that affects only
females, results when one of the X chromosomes (sex
chromosomes) is missing or partially missing.
• Turner's syndrome can cause a variety of medical and
developmental problems, including short height, failure
of the ovaries to develop and heart defects.
PHYSICAL SYMPTOMS: such persons are sterile, they have
short size, they have skin foldings on neck and shoulder,
swollen hands, may be color blind, they are mentally
normal with weak brain.

12. Klienfilter's syndrome
• Klinefeltersyndrome is a sex chromosome disorder in men
children that results from the presence of an extra X
chromosome in cells.
• It is caused by trisomic condition.
• They have XX andY chromosomes.
• Such persons are sexually immature, but they reach their adult
size.
• They are usually physically normal but may be mentally
retarded.
• Their ratio is 12 out of 10,000 births.
PHYSICALSYMPTOMS:
• In adult age the affected person contain mixed characters of
both male and female.
• Such persons are sterile. i.e. can not take part in reproduction.

13. Gene mutation
• A gene mutation is an alteration in the sequence of nucleotides in DNA,
• This change can effect a single nucteotide pair or a larger gene sequence in
a chromosome.

14. Point mutation
• Point mutation are the most common type of gene mutation
• Also known as base pair mutation
• Change in a single nucleotide base pair.
Point mutation can be categorized in three types:
➢Silence mutation
➢Missense mutation
➢Non sense mutation.

15. 1.Silent mutation
• The change in one codon for an amino acid into another codon for that
same amino acid.
• Also reffered as synonym mutation.
• ExampleGCA is changed to GAA.
Silent mutation

16. 2.Missense mutation
• The codon for one amino acid is changed
into a codon for another amino acid
• Missense mutation sometimes reffered as
non-synonymous mutation.

17. 3.Non sense mutation
• The codon for one amino acid
is changed into a translation
termination (stop) codon.
• Single base substitution that
become top codon.

18. Frame shift mutations
• A frameshift mutation is a type of mutation involving the
insertion or deletion of a nucleotide in which the number
of deleted base pairs is not divisible by three. If
a mutation disrupts this reading frame, then the entire
DNA sequence following the mutation will be read
incorrectly.
• Example:
Tay–Sachs disease is a genetic disorder that results in the
destruction of nerve cells in the brain and spinal cord.The
most common form is infantile Tay–Sachs disease which
becomes apparent around three to six months of age,
with the baby losing the ability to turn over, sit, or crawl.

19. 3.Base substitution mutation
• Base substitution is mutation in which one base pair is
replaced by another.
• It can be of two types
➢Transition mutation
➢Transverse mutation

20. Transition mutation
• A transition is the replacement of the base by other
base of the same chemical.
• Transitions are interchanges of two-ring purines (A
G) or of one-ring pyrimidines (CT): they therefore
involve bases of similar shape.

21. Transverse mutation
• Transversions are interchanges of purine for
pyrimidine bases, which therefore involve
exchange of one-ring and two-ring structures.
• A transversion is opposite, the replacement of
base from one chemical to another.

22. Disease DueTo Gene Mutation
Sickle cell anemia
• Some red blood cells become sickle-shaped and
these elongated cells get stuck in small blood
vessels so that parts of the body don't get the
oxygen they need. Sickle cell anemia is caused
by a single code letter change in the DNA. This in
turn alters one of the amino acids in the
hemoglobin protein.

23. Thank you