Upload
cassidy-quincy
View
218
Download
2
Tags:
Embed Size (px)
Citation preview
Chromosomal Disorders
Chromosomal disorders
Having mild to severe (fatal) mental and/or physical deformities due to:
1.Adding or deleting part of a chromosome
1.Having extra or missing chromosomes
How do these disorders happen?
Mistakes before and during
Parents never have the disorders! Can happen to anyone. Family history does not matter!
Must follow:
*Replication rules: Make an exact copy of the DNA with A-T and G-C
*Law of segregation: homologous chromosomes must separate into different gametes
*Crossing over- homologous chromosomes exchange pieces DNA
meiosis!!!
TelophaseII
AnaphaseII
MetaphaseII
ProphaseII
AnaphaseI
MetaphaseI
TelophaseI
Starting cell Interphase
Meiosis
ProphaseI
The cell grows bigger and a copy of each chromosome is made
Interphase
Chromosomes condense and crossing-overoccurs
ProphaseI
The homologous pairs line up in the middle
MetaphaseI
The homologous pairs are pulled away to opposite sides
AnaphaseI
Cell has split in two
TelophaseI
New spindle fibers begin to form
ProphaseII
Chromosomes line up in the middle
MetaphaseII
Sister chromatids are pulled apart
AnaphaseII
Each cell separates leaving 4 unidentical haploid cells
TelophaseII
How do these disorders happen?
1. Adding or deleting part of a chromosome
Causes:
Mistakes during DNA replication Or
Mistakes during Crossing over
How do these disorders happen?
2. Having extra or missing chromosomes
Causes:
Nondisjunction: homologous chromosomes pairs or sister
chromatids do not separate during
meiosis.
This leads to gametes (sperm or egg) that contain more or less than 23 chromosomes
Common Chromosomal Disorders
Down Syndrome = an extra 21st chromosome
Turners Syndrome = Missing X or Y chormosome
Klinefelters Syndrome =having extra X chromosomes XXY or XXXY