+VARIATION IN CHROMOSOME STRUCTURE PART 1+

NATURAL VARIATION IN CHROMOSOME STRUCTURE

• A cytogeneticist studies variations in chromosome structure and number.
• The chromosomes for a given species vary in both size and shape.
• Chromosomes are named according to the location of their centromere.
• Based on the location of the centromere, the chromosome is either called metacentric, submetacentric, acrocentric, or telocentric.

1. All chromosomes have long arm(q) and short arm(p).

• A karyotype is a micrograph that arranges the chromosomes with the short arm at the top and then in descending order by size.
• Cytogeneticists use stains to further identify the chromosomes.

1. The use of Giemsa stain produces a G banding pattern which is used as a standard identification pattern for chromosomes.
2. Banding patterns may also be used to identify changes in chromosome structure.
   

MUTATIONS AND CHROMOSOME STRUCTURE

• Changes in chromosome structure may either change:

1. Total amount of genetic material within the chromosome (increase or decrease).
2. Rearrange the genetic material within a chromosome or between 2 chromosomes.

• Changes to chromosome include:

1. Deficiencies and deletions = Changes the total genetic content (missing region) of the chromosome.
2. Duplications = Changes the total genetic content (repeating segment) of the chromosome.
3. Inversions = Changes the arrangement of the chromosome.
4. Translocations = May be either simple translocations or reciprocal translocations. These typically change both the arrangement of chromosome and total genetic content.