 Journal: Where is DNA found inside a cell?

 Usually DNA inside the nucleus is wrapped around proteins to form an ‘X’ shape  These ‘X’ shaped coils of DNA are called chromosomes

 Why is DNA coiled up and not just a big clump in the nucleus?

 P arm: Short arm of the chromosome  Q arm: Long arm of the chromosome  Centromere: midpoint where the two sides of the ‘X’ cross

 Two identical halves of a single replicated chromosome  Contain the same DNA on each half

 The same for each cell in the body, except sex cells which only have half a set of chromosomes.  Each individual has the same number of chromosomes their entire life  The number of chromosomes is the same across an entire species.

OrganismChromosome numbers Human46 Chimpanzee48 House Mouse40 Corn20

 Autosomes  22 pairs  Contain all other traits  Sex Chromosomes  One pair  Determines your gender

 Chromosomes can be identified by their:  Size  Shape  Gene Banding Pattern

 An organized arrangement of a person’s chromosomes.  Allows you to determine gender and chromosomal abnormalities.

 Female: XXMale: XY

 If the number of chromosomes in a karyotype does not equal 46, then a chromosomal abnormality has occurred.  Differences in chromosome number causes disease.

 Trisomy 21 also known as Down’s Syndrome  Extra chromosome #21

 Trisomy 18 also known as Edward’s Syndrome  Extra chromosome #18  Results in heart and mental defects and overlapping fingers

 Turner’s Syndrome: XO  Females with underdeveloped ovaries  Typically have short stature

 Klinefelter’s Syndrome – XXY  Males with little body hair present.  Typically tall.  Some development of breast tissue normally seen in females.