1. 13.1: RNA & Transcription

2. DNA DNA contains genes (sequences of nucleotide bases)
These genes code for proteins
Proteins are used to build cells and do much of the work inside cells

3. Genes & Proteins
Proteins are made of amino acids linked together by peptide bonds
20 different amino acids exist
long chains of amino acids
are known as
polypeptides

4. DNA is found inside the nucleus
Proteins, however, are made in the cytoplasm of cells by organelles called ribosomes

5. DNA‘s code must be copied and taken to the cytoplasm
In the cytoplasm, this code must be read so amino acids can be assembled to make proteins
This process is accomplished by RNA (ribonucleic acid)

6. RNA Differs from DNA RNA has a sugar ribose, not deoxyribose
RNA contains the base uracil (U), not thymine (T)
RNA molecule is single-stranded, not double-stranded

7. Like DNA, RNA is a polymer of nucleotides
Like DNA, RNA is a polymer of nucleotides. In an RNA nucleotide, the sugar ribose is attached to a phosphate molecule and to a base, either G, U, A, or C. Notice that in RNA, the base uracil replaces thymine as one of the pyrimidine bases. RNA is single-stranded, whereas DNA is double-stranded.

8. Types of RNA

9. messenger RNA (mRNA): carries information from DNA to the ribosomes
ribosomal RNA (rRNA) and other proteins make up ribosomes
transfer RNA (tRNA) molecules transfer each amino acid to the ribosome as it builds the protein

10. DNA  RNA  Protein Eukaryotic Cell DNA Pre-mRNA mRNA Ribosome Protein
Nuclear
membrane
Transcription
RNA Processing
Translation
DNA
Pre-mRNA
mRNA
Ribosome
Protein
Eukaryotic Cell 10

11. Transcription & Translation
Protein synthesis is the process of making a protein by taking the DNA instructions in the nucleus to the ribosome where the protein is put together
This process is accomplished in two phases:
Transcription & Translation

12. Messenger RNA (mRNA) long straight chain of nucleotides
made in the nucleus
copies DNA & leaves through nuclear pores
contains the nitrogen bases A, G, C, U (no T)

13. Transcription process of copying the sequence of one strand of DNA
uses the enzyme RNA polymerase
RNA polymerase binds to the gene’s promoter then unwinds & separates the DNA

14. RNA polymerase then uses one strand of DNA as a template to add nucleotides into a complementary strand of pre-mRNA

15. mRNA replaces T with U (uracil) making it clear to the cell that the mRNA is a copy

16. Editing Pre-mRNA
After the DNA is transcribed into pre-mRNA, editing must be done to the nucleotide chain to make the mRNA functional
Introns, non-functional segments of DNA, are snipped out of the chain by an enzyme

17. Exons, segments of DNA that code for proteins, are then “spliced” back together before the mRNA leaves the nucleus.

18. Once the mRNA strand is functional, it leaves through nuclear pores into the cytoplasm