1. VII RNA and Protein Synthesis

2. Genes, segment of DNA, are coded DNA instructions that control the production of proteins.
Genetic messages can be decoded and used in protein synthesis by copying part of the nucleotide sequence from DNA into mRNA.
mRNA contains coded information for making proteins.

3. The Structure of RNA
There are three main differences between RNA and DNA:
The sugar in RNA is ribose instead of deoxyribose.
RNA is generally single-stranded.
RNA contains uracil in place of thymine.

4. Types of RNA
There are three main types of RNA:
messenger RNA
ribosomal RNA
transfer RNA

5. Types of RNA
The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA.
Messenger RNA (mRNA) carries copies of instructions for assembling amino acids into proteins.

6. Ribosomes are made up of proteins and ribosomal RNA (rRNA).
The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA. Ribosomal RNA is combined with proteins to form ribosomes.
Ribosomes are made up of proteins and ribosomal RNA (rRNA).

7. Amino acid
The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA.
Transfer RNA
During protein construction, transfer RNA (tRNA) transfers each amino acid to the ribosome.

8. Protein Synthesis DNA molecule DNA strand (template) 3¢ 5¢
TRANSCRIPTION
mRNA 5¢ 3¢
Codon
TRANSLATION
Protein
Amino acid

9. Transcription DNA is copied in the form of RNA
This first process is called transcription.
The process begins at a section of DNA called a promoter.

10. RNA
RNA polymerase
DNA
During transcription, RNA polymerase uses one strand of DNA as a template to assemble nucleotides into a strand of RNA.

11. RNA Editing
Some DNA within a gene is not needed to produce a protein. These areas are called introns.
The DNA sequences that code for proteins are called exons.

12. The introns are cut out of RNA molecules.
Exon
Intron
DNA
The introns are cut out of RNA molecules.
The exons are the spliced together to form mRNA.
Pre-mRNA
mRNA
Many RNA molecules have sections, called introns, edited out of them before they become functional. The remaining pieces, called exons, are spliced together. Then, a cap and tail are added to form the final RNA molecule.
Cap
Tail

13. The Genetic Code
The genetic code is the “language” of mRNA instructions.
The code is written using four “letters” (the bases: A, U, C, and G).

14. A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid.
A codon is a group of three nucleotides on messenger RNA that specify a particular amino acid.

15. The Genetic Code
The genetic code shows the amino acid to which each of the 64 possible codons corresponds. To decode a codon, start at the middle of the circle and move outward.

16. Translation
Translation is the decoding of an mRNA message into a polypeptide chain (protein) on ribosomes.
During translation, the cell uses information from messenger RNA to produce proteins.
Nucleus
mRNA

17. The ribosome binds new tRNA molecules and amino acids as it moves along the mRNA and the anticodons of tRNA match the mRNA codons.
Lysine
Phenylalanine
tRNA
Methionine
Ribosome
During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process.
mRNA
Start codon

18. Protein Synthesis Translation direction Lysine tRNA mRNA Ribosome
During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process.
mRNA
Translation direction
Ribosome

19. The process continues until the ribosome reaches a stop codon.
Polypeptide
Ribosome
tRNA
During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process.
mRNA

20. Amino acids within a polypeptide
Codon
Codon
Codon
DNA
mRNA
Protein
Single strand of DNA
Codon
Codon
Codon
mRNA
This diagram illustrates how information for specifying the traits of an organism is carried in DNA. The sequence of bases in DNA is used as a template for mRNA. The codons of mRNA specify the sequence of amino acids in a protein, and proteins play a key role in producing an organism’s traits.
Alanine
Arginine
Leucine
Amino acids within a polypeptide

21. END OF SECTION