Flow of genetic information. Multiple extracellular signals activate intracellular signal cascades that result in altered regulation of gene expression through the interaction of transcription factors with regulatory regions of genes. RNA polymerase transcribes DNA into RNA that is processed to mRNA by excision of intronic sequences. The mRNA is translated into a polypeptide chain to form the mature protein after undergoing posttranslational processing. HAT, histone acetyl transferase; CBP, CREB-binding protein; CREB, cyclic AMP response element–binding protein; CRE, cyclic AMP responsive element; CoA, Co activator; TAF, TBP-associated factors; GTF, general transcription factors; TBP, TATA-binding protein; TATA, TATA box; RE, response. | Chapter 062. Principles of Human Genetics Part 4 Figure 62-2 Flow of genetic information. Multiple extracellular signals activate intracellular signal cascades that result in altered regulation of gene expression through the interaction of transcription factors with regulatory regions of genes. RNA polymerase transcribes DNA into RNA that is processed to mRNA by excision of intronic sequences. The mRNA is translated into a polypeptide chain to form the mature protein after undergoing posttranslational processing. HAT histone acetyl transferase CBP CREB-binding protein CREB cyclic AMP response element-binding protein CRE cyclic AMP responsive element CoA Co activator TAF TBP-associated factors GTF general transcription factors TBP TATA-binding protein TATA TATA box RE response element NH2 aminoterminus COOH carboxyterminus. The presence of four different bases provides surprising genetic diversity. In the protein-coding regions of genes the DNA bases are arranged into codons a triplet of bases that specifies a particular amino acid. It is possible to arrange the four bases into 64 different triplet codons 43 . Each codon specifies 1 of the 20 different amino acids or a regulatory signal such as initiation and stop of translation. Because there are more codons than amino acids the genetic code is degenerate that is most amino acids can be specified by several different codons. By arranging the codons in different combinations and in various lengths it is possible to generate the tremendous diversity of primary protein structure. Replication of DNA and Mitosis Genetic information in DNA is transmitted to daughter cells under two different circumstances 1 somatic cells divide by mitosis allowing the diploid 2n genome to replicate itself completely in conjunction with cell division and 2 germ cells sperm and ova undergo meiosis a process that enables the reduction of the diploid 2n set of chromosomes to the haploid state 1 n Chap. 63 . Prior to mitosis cells exit the .
