1. The Cell Cycle Interphase
Cell spends most of its life here (average mammalian cell, about 90% of life) G1
Cell double organelles
accumulates materials needed for DNA synthesis S
DNA replication occurs G2
Cell synthesizes the proteins needed for cell division
The Cell Cycle

2. Some cells—such as nerve and muscle cells—typically do not complete the cycle and are permanently in the G1 stage.
Embryonic cells spend very little time in G1 and complete the cell cycle in a few hours.
The Cell Cycle

4. RNA!

5. DNA vs. RNA P D T P R U Deoxyribose sugar Double stranded
Adenine, cytosine, guanine, thymine
Ribose sugar
Single stranded
Adenine, cytosine, guanine, uracil P D T P R U

6. RNA The other nucleic acid!! Once seen as merely a sidekick to DNA
What is it?
What does it do???
The other nucleic acid!! Once seen as merely a sidekick to DNA
Now known to perform multiple vital roles in the coding, decoding, regulation, and expression of genes

7. Types of RNA
Messenger RNA—mRNA—copies the genetic code & transfers it to the ribosomes
Transfer RNA—tRNA—transfers amino acids to the ribosomes for addition to the polypeptide (protein) chain
Ribosomal RNA—rRNA—makes up part of the ribosome & links amino acids together to form proteins; most of the RNA found in a typical eukaryotic cell is rRNA

8. Types of RNA
Messenger RNA—mRNA—copies the genetic code & transfers it to the ribosomes
Transfer RNA—tRNA—transfers amino acids to the ribosomes for addition to the polypeptide (protein) chain
Ribosomal RNA—rRNA—makes up part of the ribosome & links amino acids together to form proteins; most of the RNA found in a typical eukaryotic cell is rRNA

9. Types of RNA
Messenger RNA—mRNA—copies the genetic code & transfers it to the ribosomes
Transfer RNA—tRNA—transfers amino acids to the ribosomes for addition to the polypeptide (protein) chain
Ribosomal RNA—rRNA—makes up part of the ribosome & links amino acids together to form proteins; most of the RNA found in a typical eukaryotic cell is rRNA

10. …& more types of RNA
Small nuclear RNA (snRNA)—functions in the nucleus in processing mRNA
Micro-RNA (miRNA)—very short RNA segments; roles still being determined
Small interfering RNA (siRNA)—control gene expression & protect cells from viral attack

11. GENE EXPRESSION (protein synthesis)
The use of information in the DNA to direct the production of proteins.
2 stages:
transcription
translation

12. TRANSCRIPTION Construction of mRNA along portions of the DNA molecule
Each group of 3 bases =codon
=1 amino acid
See transcription!!!

13. TRANSLATION
The process in which the mRNA code is read & converted into a specific amino acid sequence in a protein chain.
Amino acids are linked to form the protein
See Translation!!!

14. Resources Try these processes at