Question

how do mutations affect the proteins produced by the cell and how it can lead to premature birth of infants?

Answer 1

Any change in DNA which affects the phenotype of an organism is referred to as mutation. If such changes occur in germline cell of an individual and a transfer to next generation then they affect the phenotype of the offspring as well.

Mutations are of two types and result in the production of abnormal mutation.

1. Chromosomal mutations - this mutation affect the chromosome totally. It either results in loss of a chromosome (aneuploidy) or gain of a chromosome (euploidy). The common chromosomal mutations are trisomy (down syndrome), tetrasomy, nullisomy, disomy.

2. Gene mutations - these mutations do not affect the chromosome totally, instead they affect only one gene or more than one genes located on a chromosome.

They are of two types point mutation and frameshift mutation.

Point mutation is exchange in only one nucleotide. They are commonly called as substitution mutation.

It includes,

Missense mutation in which mutation in nucleotide occurs in such a way that it changed it amino acid being encoded by the codon.

Nonsense mutation in which mutation in nucleotide occurs in such a way that it codes for a stop codon and results in the formation of a truncated peptide.

Silent mutation in which the nucleotides changes in such a way that the amino acid does not change.

Frameshift mutations are those which completely change the Amino acid sequence of the given protein. They are commonly called as indel mutations.

They include insertion mutation which is addition of a nucleotide and deletion mutation which is removal of a nucleotide.

Mutation occuring in the germline cell of an individual get passed onto their gamete cell and therefore the new individual so formed is affected by that mutation.

Any change in gene will ultimately change either the structure of protein or amount of protein being encoded or formation of a truncated peptide or even loss of the protein completely.

These mutation occurs during formation of gamete cell which occur by the process of meiosis. Probable reasons that lead to mutation during meiosis are -

1. Failure of separation of homologous chromosome during anaphase 1

2. Failure of separation of divided chromosomes during telophase 1 ( also called as nondisjunction of chromosome)

3. Failure of separation of of sister chromatids during anaphase 2

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