2. TABLE OF CONTENT
• Article no : 01. Deletion
• 1. Definition…………………………….
• 2. Causes ………………………………….
• 3. How deletions occurs……………..
• 4. Type of deletions……………………
• 5. Effects of deletions…………………
3. DEFINE OF DELETION
• Deletion is loss of part of chromosome.
• Basically deletion is type of genetic mutation that
involves the removal of part of genetic material.
• It involves the loss of one or more nucleotides from
segment of DNA.
4. CAUSES OF DELETION
• ➤ Losses from translocation
• ➤ Crossover within an inversion
• ➤ Unequal crossing over
• ➤ Breaking without rejoining
5. OCCURRENCE OF DELETION
• How basically deletion occurs?
• A deletion mutation occurs when part of a DNA
molecule is not copied during DNA replication. This
uncopied part can be as small as a single nucleotide or
as much as an entire chromosome. The loss of this DNA
during replication can lead to a genetic disease.
6. • Continue
Some chromosomes have fragile spots where breaks occur, which result in the
deletion of a part of the chromosome. The breaks can be induced by heat, viruses,
radiation, or chemical reactions. When a chromosome breaks, if a part of it is
deleted or lost, the missing piece of chromosome is referred to as a deletion or a
deficiency.
For example
Example of deletion mutation is DiGeorge syndrome. DiGeorge syndrome is a
disorder caused due to the deletion of a small segment of chromosome 22.
Chromosome 22
7. TYPES OF DELETION
• There are two types of deletions
• ➤ Interstitial deletions
• ➤ Terminal deletions
• 1. Interstitial deletions
• In this type of deletion internal part of chromosome is missig.
• • The chromosome has broken in two places and the broken ends have fused,
leaving out the deleted segment.
8. • 2.Terminal deletion.
• In this type the deletion occurs towards the end of chromosome
• • In this case there is only single break and the homologous chromosome fail to
rejoin it means tip of chromosome is lost
9. EFFECTS OF DELETION
• Small deletions are not fatal but large mutations are usually fatal. Some deletions
lead to human disorders.
• ➤ Homozygous deletions are lethal. They cause abnormal developments.
• ➤ In some deletions number of base pair is not equally divisible by three it cause
frame shift mutation. Thus all of codons coming after the deletion are read
incorrectly during translation that produces a severely altered and non functional
protein.
• ➤ Deletions cause male infertility and two thirds of cause Duchenne muscular
dystrophy.(. It is the most common hereditary neuromuscular disease which is
caused by genetic mutation in one of mother’s X chromosome.)
