name a disorder karyotype analysis, pick and explain a disorder associated with a variation in chromosome number type of variation in chromosome number. causes of variation. phenotypic symptoms of disorder. name a disorder.
Genetic Variation
Genetic variation refers to the variation in the genome sequences between individual organisms of a species. Individual differences or population differences can both be referred to as genetic variations. It is primarily caused by mutation, but other factors such as genetic drift and sexual reproduction also play a major role.
Quantitative Genetics
Quantitative genetics is the part of genetics that deals with the continuous trait, where the expression of various genes influences the phenotypes. Thus genes are expressed together to produce a trait with continuous variability. This is unlike the classical traits or qualitative traits, where each trait is controlled by the expression of a single or very few genes to produce a discontinuous variation.
name a disorder karyotype analysis, pick and explain a disorder associated with a variation in chromosome number
type of variation in chromosome number.
causes of variation.
name a disorder.
The example of disorder that can be taken in the current scenario which results from variation in chromosome number is Down's syndrome or 21st Trisomy.
Down's syndrome occurs due to an error that occurs during separation of the sister chromatids from chromosomes during meiosis or reduction division at the 21st chromosomal position. Since the separation does not take place, one of the two cells possesses more than the actual desired karyotype which is present in the meiotic cells (which usually possesses either 21+XX or 21+XY). Due to the nondisjunction of the 21st chromosome, one of the cells contains (22+XX or 22+XY) +1 chromosome which results in 47 chromosomes during fusion of sperm and ova. That is why this chromosomal aberration is known as 21st Trisomy, as 21st chromosome does not separate into two sister chromatids and leads to formation of 3 copies of the 21st chromosome (or trisomy) ar the 21st position of the newly formed zygote.
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