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) 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 ) . 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 )

Trisomy (XXY) male Klinefelter Syndrome Monosomy (X) female Turner Syndrome

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