GENERAL GENETIC

Lab 10

Chromosomal Aberration

Mutation

Definition :, (genetics) any event that changes genetic structure; any alteration in

the inherited nucleic acid (DNA) sequence of the genotype of an organism that can

alter the amino acid sequence of the protein encoded by the gene .

- Mutations are caused by radiation ,viruses and mutagenic chemicals

, as well as errors that occur during : meiosis or DNA replication .

- Variations can be caused by mutation.

Mutations causing variation can arise in 2 ways :

1- Numerical abnormalities in chromosomes

2- Structural abnormalities in chromosomes

A- Numerical abnormalities in chromosomes ( Aneu-ploidy)

Example:

1- Monosomy : ( 45 chromosome)

Turner Syndrome : have only one sex chromosome (X) and affects

in female ( growth – shorter than normal - sexual development -

ovaries fail ) .

2- Trisomy :

1-Klinefelter Syndrome :( 47 chromosome)

have one extra sex X chromosome (XXY) and affects in male

( hypogonadism and sterility)

2 - Down Syndrome : (Trisomy 21)

have 3 copies of chromosome 21 ,

Disorder: (Mongolism – week in the bone and muscles – Bore in

heart – heavy tongue )

Definition : This occurs when individual is missing either a chromosome from a pair

( monosomy) or has more than two chromosome of a pair

( Trisomy , Tetrasomy ) .

Klinefelter SyndromeMonosomy (X) female Turner Syndrome

Trisomy (XXY) male

B- Structural abnormalities in chromosomes Type of :

1- Mitotic stopping ( C – metaphase )

Cause : using carcinogenic material ( Cholchisene ) that cause DNA

duplicating without dividing in the cell because of the inhibition in the

formation of spindles in metaphase

Result : stopping dividing and chromosomal high coiling without facing the

poles .

2-Ring Chromosome : that happen in 2 ways

1- Cause : when the end of the short and long arms

breaks

Result : The 2 end stick to each other , thus resulting

in loss of information

2- Cause : when the 2 ends of the short and long

arms stick together usually without loss of material

Result : That ring can cause problems when the cell

divides and can cause problems for the individual .

3- chromosome fragments

Cause : Separation of pieces from the main chromosome .

Result : these pieces remind independent without engagement with another

chromosome and it lost because it does not has a centromer .

4- Bridges ( Di-centric chromosomes)

Cause : Physical breakage of the DNA molecule in sister chromatid which produce

“sticky ends” before replication

Result : make a bridge between the 2 chromosomal sets in anaphase .

6- Sticky chromosomes

chromosome are overlapping , unclear and sticky .

6- Tri-poles

Cause : Partial suppression in spindle formation activity .

Result : pulled in different ways in anaphase .

7- Multi-nucleated

Cause : Failure in the formation of the central plate .

Result : the cell appear with two or more nuclei .

A- Multi-nucleated

B,G, J - Fragment

H, I, J : Bridges

C- metaphase

Ring Chromosomes

Genetic Pedigree