most common gene or point mutations.They constitute a replacement of one nucleotide within another gene, the "wrong" nucleotide.This happens when, during the replication of DNA before cell division instead of complementary nitrogenous base (adenine - thymine, guanine - cytosine) nucleotide to "adjust" the wrong combination (eg, adenine - cytosine or thymine - guanine).So there are mutations that are passed to the next generation of cells, as in the case of sex cells - gametes - and then the next generation of organisms.In most cases, gene mutations lead to adverse effects, because "tainted" genes encode proteins with a distorted structure, which will not be able to perform their functions in the body.
When mutation affects sev
eral genes within a chromosome, a mutation called a chromosomal.This may be a gap between the end portion of chromosomes (loss), "cutting" middle fragment (deletion), doubling the area (duplication), the unfolding of the fragment to 180˚ (inversion).During translocation, which is also a type of chromosomal mutations, part of the chromosome is attached to another, non-homologous to it.
Why are there chromosome mutations
chromosomal mutations typically occur in the process of cell division.When unequal crossing over, for example, one of the homologous chromosomes may lose all or some of the genes and the other - to get "extra".
Which of chromosomal mutations are most dangerous
most dangerous of chromosomal mutation - a deletion and loss.The loss of the end portion of chromosome 21 is a person of acute leukemia - leukemia, which leads to death.Effects of deletions ranged from death and serious hereditary diseases to non-infringement in general (if the fragment is lost, not carrying information about the properties of the organism).
most "ambitious" are the genomic mutation in the genotype when there was no chromosome or vice versa there is excess.This can happen when the wrong divergence (or non-disjunction) of chromosomes during the formation of gametes in meiosis.For non-disjunction of chromosome 21 in the woman's egg in case of fertilization causes Down syndrome child.