Selective Heterozygous Advantage of Carriers of с.-23+1G>A Mutation in GJB2 Gene Causing Autosomal Recessive Deafness 1A.

We present the results of analysis of skin epidermis thickness in individuals with recessive mutation c.-23+1G>A in the GJB2 gene in comparison with individuals without this mutation living in Eastern Siberia (Yakut population). We examined 152 individuals with different genotypes by GJB2 gene mutation c.-23+1G>A. Homozygotes and heterozygotes by c.-23+1G>A have thicker epidermal layer (0.245 mm and 0.269 mm, respectively) in comparison with individuals without this mutation (0.193 mm) (p<0.05). The obtained data support the hypothesis about selective advantage of carriers of mutant GJB2 gene alleles and partly explain extremely high carrier frequency (10.3%) of c.-23+1G>A mutation in the GJB2 gene in Yakut population in Eastern Siberia.

[Palindromic and repetitive sequences in initiation sites of DNA replication in Tetrahymena]. / Palindromnye i povtoriaiushchiesia posledovatel'nosti nukleotidov v uchastkakh initsiatsii sinteza DNK u infuzorii Tetrahymena.

DNA replication was induced in Tetrahymena pyriformis cells at the stationary phase of culture growth by a series of heat shocks. The selective nature of this DNA synthesis was established. DNA was uniformly labelled with [3H]thymidine during the exponential phase of culture growth and with [14C]thymidine during the stationary phase. The renaturation kinetics of DNA samples was investigated by measuring the relations of 14C/3H radioactivity in the renatured and denatured DNA fractions after their separation on hydroxyapatite. The results were analysed by means of a computer program based on the experimentally found renaturation curve of T. pyriformis macronuclear DNA. Under conditions described palindromic and repetitive (which are repeated about 1000 times) nucleotide sequences are intensively replicated. It is assumed that synchronous activation of replicons occurs as a consequence of induction. It may well be that replication starts in the central parts of comparatively long palindromes, which are identical or very similar in their nucleotide sequences.