From DNA to Protein - Gene Expression: RNA and Protein RNA transcripts DNA molecule Figure 14.6 Typically, many RNA polymerases simultaneously transcribe the same gene, producing a conglomerate structure often called a “Christmas tree” after its shape. Here, three genes next to one another on the same chromosome are being transcribed. Figure It Out: Are the polymerases transcribing this DNA molecule moving from left to right or from right to left? Answer: Left to right Fig. 14-6, p. 219

Chapter 10 Opener Many of the differences in the body structures of males and females can ultimately be traced to the activity of a single gene.

Link Between DNA and Protein

How does information get from nucleus to cytoplasm?

RNA RNA differs structurally from DNA RNA is single stranded RNA uses the sugar ribose RNA uses the nitrogenous base uracil (U) instead of thymine (T)

RNA Intermediaries 3 types of RNA involved in protein synthesis Messenger RNA (mRNA) carries DNA gene information to the ribosome Transfer RNA (tRNA) brings amino acids to the ribosome Ribosomal RNA (rRNA) part of the structure of ribosomes

Transcription and Translation

FIGURE 10-3 Genetic information flows from DNA to RNA to protein (a) During transcription, the nucleotide sequence in a gene specifies the nucleotide sequence in a complementary RNA molecule. For protein-encoding genes, the product is an mRNA molecule that exits from the nucleus and enters the cytoplasm. (b) During translation, the sequence in an mRNA molecule specifies the amino acid sequence in a protein.

The Genetic Code Base sequence in a DNA gene dictates the sequence and type of amino acids in translation Bases in mRNA are read by the ribosome in triplets called codons

Table 10-3 The Genetic Code (Codons of mRNA)

Transcription Transcription of a DNA gene into RNA has three stages Initiation Elongation Termination

FIGURE 10-4a Transcription is the synthesis of RNA from instructions in DNA A gene is a segment of a chromosome's DNA. One of the DNA strands will serve as the template for the synthesis of an RNA molecule with bases complementary to the bases in the DNA strand.

FIGURE 10-4b Transcription is the synthesis of RNA from instructions in DNA A gene is a segment of a chromosome's DNA. One of the DNA strands will serve as the template for the synthesis of an RNA molecule with bases complementary to the bases in the DNA strand.

FIGURE 10-4c Transcription is the synthesis of RNA from instructions in DNA A gene is a segment of a chromosome's DNA. One of the DNA strands will serve as the template for the synthesis of an RNA molecule with bases complementary to the bases in the DNA strand.

FIGURE 10-4d Transcription is the synthesis of RNA from instructions in DNA A gene is a segment of a chromosome's DNA. One of the DNA strands will serve as the template for the synthesis of an RNA molecule with bases complementary to the bases in the DNA strand.

mRNA Messenger RNA (mRNA) serves as the complementary copy of a DNA gene that is read by a ribosome

mRNA - Prokaryotes FIGURE 10-6a Messenger RNA synthesis in prokaryotic cells (a) In prokaryotes, many or all of the genes for a complete metabolic pathway lie side by side on the chromosome.

FIGURE 10-6 Messenger RNA synthesis in prokaryotic cells (b) Transcription and translation are simultaneous in prokaryotes. In this colorized electron micrograph, RNA polymerase (not visible at this magnification) travels from left to right on a strand of DNA (blue). As it synthesizes a messenger RNA molecule (red), ribosomes (dark polygons) bind to the mRNA and immediately begin synthesizing a protein (not visible).

mRNA – Eukaryotes

FIGURE 10-7a Messenger RNA synthesis in eukaryotic cells

FIGURE 10-7b Messenger RNA synthesis in eukaryotic cells

mRNA – Alternate Splicing

Ribosomes Ribosomes are large complexes of proteins and rRNA genome.imim.es

Ribosomes

Transfer RNAs Transfer RNAs hook up to and bring amino acids to the ribosome There is at least one type of tRNA assigned to carry each of the twenty different amino acids

Transfer RNAs Each tRNA has 3 exposed bases called an anticodon The bases of the tRNA anticodon pair with an mRNA codon within a ribosome binding site odec.ca

Translation Has 3 steps: Initiation Elongation of the protein chain termination

FIGURE 10-8a Translation is the process of protein synthesis Protein synthesis, or translation, decodes the base sequence of an mRNA into the amino acid sequence of a protein.

FIGURE 10-8b Translation is the process of protein synthesis Protein synthesis, or translation, decodes the base sequence of an mRNA into the amino acid sequence of a protein.

FIGURE 10-8c Translation is the process of protein synthesis Protein synthesis, or translation, decodes the base sequence of an mRNA into the amino acid sequence of a protein.

FIGURE 10-8d Translation is the process of protein synthesis Protein synthesis, or translation, decodes the base sequence of an mRNA into the amino acid sequence of a protein.

FIGURE 10-8e Translation is the process of protein synthesis Protein synthesis, or translation, decodes the base sequence of an mRNA into the amino acid sequence of a protein.

FIGURE 10-8f Translation is the process of protein synthesis Protein synthesis, or translation, decodes the base sequence of an mRNA into the amino acid sequence of a protein.

FIGURE 10-8g Translation is the process of protein synthesis Protein synthesis, or translation, decodes the base sequence of an mRNA into the amino acid sequence of a protein.

FIGURE 10-8h Translation is the process of protein synthesis Protein synthesis, or translation, decodes the base sequence of an mRNA into the amino acid sequence of a protein.

FIGURE 10-8i Translation is the process of protein synthesis Protein synthesis, or translation, decodes the base sequence of an mRNA into the amino acid sequence of a protein.

FIGURE 10-9 Complementary base pairing is critical to decode genetic information (a) DNA contains two strands: the template strand is used by RNA polymerase to synthesize an RNA molecule. (b) Bases in the template strand of DNA are transcribed into a complementary mRNA. Codons are sequences of three bases that specify an amino acid or a stop during protein synthesis. (c) Unless it is a stop codon, each mRNA codon forms base pairs with the anticodon of a tRNA molecule that carries a specific amino acid. (d) The amino acids borne by the tRNAs are joined together to form a protein.

The End