- Slides: 12
Why is karyotype?
Karyotype - The characterization of the chromosomal complement of an individual or a species, including number, form, and size of the chromosomes. - A photomicrograph of chromosomes arranged according to a standard classification. - The complete set of chromosomes that constitutes the entire genome of a species.
Karyotype - A karyotype is a man-made arrangement of all the chromosomes of a cell. - the chromosomes are arranged and displayed (often on a photo) in a standard format known as an idiogram: in pairs, ordered by size and position of centromere for chromosomes of the same size. - karyotypes are used to study chromosomal aberrations, and may be used to determine other macroscopically visible aspects of an individual's genotype, such as sex. - in order to be able to see the chromosomes and determine their size and internal pattern, they are chemically stained (chromosome banding). - the study of whole sets of chromosomes is known as karyology.
Making Karyotype - karyotypes are arranged with the short arm of the chromosome on top, and the long arm on the bottom. They are labelled as p (for petite, or short) and q (for queue, or long) respectively. - chromosomes are arranged and numbered by size, from largest to smallest. - use centromere position and banding pattern (if there is) as guides. p q
Centromere Position - each chromosome has two arms, labeled p and q. They can be connected in either metacentric, submetacentric, acrocentric or telocentric manner. - if both arms are equal in length, the chromosome is said to be metacentric. - if arms' lengths are unequal, the chromosome is said to be submetacentric. - if p arm is so short that is hard to observe, but still present, then the chromosome is acrocentric. There are five acrocentric chromosomes in the human genome: 13, 14, 15, 21 and 22. - a telocentric chromosome's centromere is located at the terminal end of the chromosome. Humans do not possess any telocentric chromosomes.
Karyotype Metaphase spread of barley chromosomes with karyotype (idiogram) displayed.
Human chromosomes are divided into 7 groups & sex chromosomes A: 1 -3 Large metacentric 1, 2 or submetacentric B: 4, 5 Large submetacentric, all similar C: 6 -12, X Medium sized, submetacentric - difficult D: 13 -15 medium-sized acrocentric plus satellites E: 16 -18 short metacentric 16 or submetacentric 17, 18 F: 19 -20 Short metacentrics G: 21, 22, Y Short acrocentrics with satellites. Y no satellites.
Chromosomes (G-banded) for normal male individual
Chromosome (G-banded) Spread (47, XY, +21, Trisomy 21)
Idiogram (G-banding) of Human Chromosomes (47, XY, +21, Trisomy 21)
ASSIGNMENT Prepare an idiogram from the chromosome spread below. Submit the assignment by 7 August, 2008. Male individual with 47 chromosomes