Chapter seventeen: from gene to protein

Q1: how does gene to protein?
A1: transcription and translation
Q2: what's the central dogma of life?
A2: From gene to protein; from genotype to phenotype
Q3: what does DNA make?
A3: mRNA

Five Facts:
1.transcription is the DNA directed synthesis of RNA
2. eukaryotic cells modify RNA after transcription
3. translation is the RNA directly synthesis of a polypeptide
4. point mutations can affect protein structure and function
5. while gene expression differs among the domains of life, th econcept of a gene is universal

Figure:
Translation is the process where the copied stretch of mRNA is translated into proteins.This occurs in ribosomes, either free floating in cells or bound to the endoplasmic reticulum.An enzyme called RNA polymerase catalyses the reaction. A tRNA triplet code lines up alongside the single stranded mRNA molecule. tRNA has an amino acid binding site attached, and the amino acid that binds is dependent on the codon of the tRNA molecule.When two amino acids are next to each other on the tRNA then a peptide bond forms between them and the first amino acid breaks free of the tRNA.

Summary:
Gene expression is the process by which DNA directs the synthesis of proteins. A, G, U, C are the nucleotides of RNA. An RNA molecule is a single strand.
Transcription begins with initiation, the RNA polymerase attaches to promoter regions on the DNA and begins to unzip the DNA in to two strands. A promoter region for mRNA transcriptions contains the sequence TATA box.Elongation occurs as the RNA polymerase unzips the DNA and assembles RNA nuceotides using one strand of the DNA as a template. As in DNA replication, elongation of the mRNA molecule occurs in the 5-3 direction. Termination occurs when the RNA polymerase reaches a special sequence of nucleotides that serve as a termination point. In eukaryotes, the termination region often contains the DNA sequence AAAAA.
Before a mRNA leaves nucleus, it undergoes two kinds of alternations. The first modification adds special nucleotude sequence to both ends of the mRNA. GTP is added to 5 end to form 5'cap. poly-A tail is added to 3 end. The tail provide stability and also appears to controlo the movement of the mRNA across the nuclear serve to regulate gene experssion. A transcribed DNA segmant contains teo kinds of sequences0exons, which are sequence that express a code for a polyprptide, and intons, intervening sequences that are noncoding. Before the RNA moves to the cytoplasm, snRNPs, delete out the introns and splce the exons.
A cell translations an mRNA binding message into protein using tRNA. After binding specific amino acidds, tRNA lines up via their anticodons at complementary codons on mRNA. Ribosomes help facilitate this coupling with binding sites for mRNA and tRNA. The formation of peptide bonds between amino acids is catalyzed by rRNA.

Videos:
http://www.youtube.com/watch?v=l96PKVfGh-0&feature=related