1. Chapter 12 DNA and RNA

2. There are four kinds of bases in DNA:
adenine
guanine
cytosine
thymine

3. DNA Double Helix

4. DNA structure

5. Chapter 12-2 Chromosomes and DNA Replication
DNA makes up chromosomes!

6. DNA and Chromosomes DNA and Chromosomes
In prokaryotic cells, DNA is located in the cytoplasm.
Most prokaryotes have a single DNA molecule containing nearly all of the cell’s genetic information.

7. DNA and Chromosomes E. Coli Bacterium Chromosome
Most prokaryotes, such as this E. coli bacterium, have only a single circular chromosome. This chromosome holds most of the organism’s DNA.
E. Coli Bacterium
Bases on the Chromosomes

8. DNA and Chromosomes
Many eukaryotes have 1000 times the amount of DNA as prokaryotes.
Eukaryotic DNA is located in the cell nucleus inside chromosomes.
The number of chromosomes varies widely from one species to the next.

9. DNA and Chromosomes Chromosome Structure
Eukaryotic chromosomes contain DNA and protein, tightly packed together to form chromatin.
Chromatin consists of DNA tightly coiled around proteins called histones.
DNA and histone molecules form nucleosomes.
Nucleosomes pack together, forming a thick fiber.

10. DNA and Chromosomes Chromosomes in Prokaryotic Cells (bacteria)
One circular chromosome
Found in cytoplasm
Chromosomes in Eukaryotic Cells
Found in nucleus
DNA found in several chromosomes
Number of chromosomes will vary with species

11. DNA Replication
Each strand of DNA has all the information needed to reconstruct the other half
Strands are complementary and can be used to make the other strand
A C T C G T A
T G A G C A T

12. DNA Replication During DNA replication
The DNA molecule separates into two strands.
Produces two new complementary strands following the rules of base pairing.
Each strand of the double helix of DNA serves as a template for the new strand.

13. DNA Replication New Strand Original strand Nitrogen Bases Growth
Replication Fork
Replication Fork
DNA Polymerase
\\loyola2\bschuller$\Biology PresentationExpress\Chapter12\Section02\Resources\ActiveArt\index.html

15. DNA Replication
1. Enzymes unzips DNA by breaking hydrogen bonds. Strands separate at the replication fork.
Replication Fork

16. DNA Replication
New complementary nucleotides are added to make a new strand
The enzyme DNA polymerase attaches nucleotides to produce new strands. DNA polymerase proofreads each strand.

17. 12-3 RNA and Protein Synthesis
Genes are coded DNA instructions that control the production of PROTEINS.
Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA.
RNA contains coded information for making proteins.

18. Central Idea of Genetics!
DNA RNA PROTEIN
Transcription
Translation

19. RNA RNA – Ribonucleic Acid RNA DNA Ribose sugar Deoxyribose sugar
Composed of a long strain of nucleotides
Contains sugar, phosphate group, and nitrogen base
RNA
DNA
Ribose sugar
Deoxyribose sugar
Singe-stranded
Doubled-stranded
Uricil
Thymine

20. RNA
Types:
Messenger RNA (mRNA) – messenger from DNA to the rest of the cell
Ribosomal RNA (rRNA) – make up ribosomes
Transfer RNA (tRNA) – transfer amino acids to the ribosomes

21. Transcription
The process of making RNA by copying part of the DNA sequence into a complementary RNA sequence

22. Transcription Requires enzyme RNA polymerase
RNA Polymerase binds to DNA and separates strands
RNA Polymerase uses DNA as template and assembles complementary RNA strands

23. Transcription

24. Transcription Animations

25. RNA Editing RNA Editing
The DNA of eukaryotic genes contains sequences of nucleotides, called introns, that are not involved in coding for proteins.
The DNA sequences that code for proteins are called exons.
When RNA molecules are formed, introns and exons are copied from DNA.

26. RNA Editing 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

27. Protein Review Proteins are made by joining
AMINO ACIDS
Each protein contains a combination of the 20 amino acids
The function of the protein is determined by number and sequence of amino acids
(A polypeptide is a protein!)
Protein 1
Protein 2

28. Genetic Code The genetic code is the “language” of mRNA instructions.
A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid.
Each codon specifies a particular amino acid that is to be placed on the polypeptide chain.

29. Genetic Code RNA Sequence - Codon Sequence –
U C G C A C G G U
Codon Sequence –
U C G – C A C – G G U
Use the Amino Acid Guide to determine amino acid –
Amino acid sequence –
Serine – Histidine – Glycine

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

31. Translation
1. Messenger RNA is transcribed in the nucleus, and then enters the cytoplasm where it attaches to a ribosome.

32. Translation
2. The ribosome “reads” the mRNA codon and the corresponding amino acid is brought to the ribosome by the tRNA
Amino Acid
Amino Acid
codon

33. Translation
3. The ribosome forms bonds between the amino acids to form the protein
Bond formed

34. Translation
4. Translation continues until the ribosome reaches a stop codon on the mRNA and releases the protein (polypeptide)

35. The BIG Picture!

36. Translation Animation