DNA / RNA

1. DNA / RNA Chapter 08

2. DNA • Deoxyribonucleic acid (DNA) is a nucleic acid that contains the blueprint for making the proteins the cell needs. • DNA contains genes. • Genes are specific messages instructing the cell on how to construct a protein.

3. DNA • DNA is the chemical used to pass genetic information on to the next generation of organisms. • DNA controls the synthesis of proteins, which helps determine the characteristics of the organism and regulate the cell’s metabolism.

4. DNA • DNA contains the genetic instructions used in the development of all known living organisms and some viruses. • DNA molecules are used for long term storage of information. • DNA carries the instructions necessary to create RNA and proteins; therefore, it is often compared to a blueprint.

5. DNA Structure • DNA is a nucleic acid. • Nucleic acids are large polymers of nucleotides.

6. DNA Structure • DNA consists of two long polymers of simple units known as nucleotides. • These two strands run in opposite directions to each other and are therefore known as anti-parallel. • The strands have backbones made of sugars with phosphate groups attached.

7. DNA Structure • Attached to each sugar is one of four types of molecules called bases. • Information is encoded in the sequence of these four bases along the backbone. • The information is read using the genetic code.

8. DNA Structure • The genetic code specifies the sequence of amino acids within proteins. • The code is read by copying stretches of DNA into RNA (A process known as transcription).

9. DNA Structure • A nucleotide consists of a sugar molecule, a phosphate group, and a nitrogenous base. • There are four different nitrogenous bases in DNA:

10. DNA Structure • Adenine (A), guanine (G), cytosine (C), and thymine (T). • The DNA nucleotides can combine into a long linear DNA molecule that can pair with another linear DNA molecule.

11. DNA Structure • The two paired strands of DNA form a double helix with sugars and phosphates on the outside and the nitrogenous bases on the inside. • The nucleotides form hydrogen bonds with one another, which helps to stabilize the helical structure.

12. DNA Structure • Adenine pairs with Thymine (A-T). • Guanine pairs with Cytosine (G-C).

14. Nitrogenous Bases • The nucleotide bases are nitrogenous bases that are involved in pairing in DNA and RNA. This is known as base pairing. • In genetics they are simply called bases. • Adenine, Guanine, Cytosine, and Thymine are DNA bases. • Adenine, Guanine, Cytosine, and Uracil are RNA bases.

15. Adenine

16. Guanine

17. Thymine

18. Cytosine

19. Uracil

20. Chromosomes • Within cells, DNA is organized into structures called chromosomes.

21. Chromosomes • The chromosomes are duplicated before the cell divides, a process known as DNA replication. • Within the chromosomes, chromatin proteins such as histones compact and organize DNA. The chromatins help determine which parts of the DNA are transcribed.

22. Eukaryotes Vs. Prokaryotes • Eukaryotic organisms (animals, plants, fungi, and protists) store their DNA inside the cell nucleus. • Prokaryotic organisms (bacteria and archae) have no nucleus; therefore, the DNA is found in the cytoplasm.

23. DNA Replication • When a cell grows and divides, two new cells result. • DNA replication is the process by which a cell makes another copy of its DNA. • Base pairing rules and many enzymes make replication possible.

24. DNA Replication • DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules.

25. DNA Replication • Each DNA strand holds the same genetic information; therefore, both strands can serve as a template for the reproduction of the complementary strand. • The template strand is conserved in its entirety and the new strand is assembled from nucleotides. This is known as semiconservative replication.

26. DNA Replication • The resulting double-stranded DNA molecules are identical. • DNA replication must happen before cell division can occur.

27. DNA Replication • Helicases are enzymes that bind to the DNA and separate the two strands of DNA. • DNA polymerase incorporates DNA nucleotides into the new DNA strand. The nucleotides enter according to the base pairing rules.

28. DNA Replication • In prokaryotic cells, this replication process starts at only one place along the DNA molecule (origin of replication). • In eukaryotic cells, the replication starts at the same time along several different places of the DNA molecule.

29. DNA Replication • Two new identical, double-stranded DNA molecules are formed. • The new strands of DNA form on each side of the old DNA strands.

30. DNA Replication • The exposed nitrogenous bases of the original DNA serve as the pattern on which the new DNA is formed. • Two double helices are formed with identical nucleotide sequences. • A portion of the DNA polymerase molecule edits the newly created DNA molecule and makes corrections if needed.

31. DNA Replication

32. Repair of Genetic Information • If an error or damage occurs to the DNA helix on one strand, the pairing arrangement of nitrogenous bases on the other undamaged strand can be read. • This information is used to repair the damaged strand.

33. DNA Code • DNA stores information. • The order of the nitrogenous bases is the genetic information that codes for proteins. • The nucleotides are read in sets of three. • Each sequence of three nucleotides is a codeword for a single amino acid. • The information to code one protein can be thousands of nucleotides long.

34. RNA Structure And Function • Ribonucleic Acid (RNA) is important in protein production. • RNA’s nucleotides contain a ribose sugar whereas DNA’s nucleotides contain a deoxyribose sugar. • Ribose has an –OH group and deoxyribose has an –H group on the second carbon atom.

35. RNA Structure And Function • RNA contains the nitrogenous bases Uracil (U), guanine (G), cytosine (C), and adenine (A). • DNA is found in the cell’s nucleus, while RNA is made in the nucleus and then moves out into the cytoplasm of the cell.

36. RNA Structure And Function • DNA directs protein synthesis by using RNA. • RNA is made by enzymes that read the protein coding information in DNA. • RNA nucleotides pair with DNA nucleotides. • RNA contains Uracil instead of Thymine so adenine in DNA pairs with Uracil in RNA.

37. Nucleic Acid Base Pairing Rules

38. Transcription • Transcription is the process of using DNA as a template to synthesize RNA. • The RNA polymerase enzyme reads the sequence of DNA nucleotides and follows the base pairing rules between DNA and RNA to build the new RNA molecule.

39. Transcription • The two strands of the double stranded DNA molecule are separated to expose the nitrogenous bases. • The DNA’s nitrogenous bases are read and paired with the RNA nucleotides. • Only one strand of the DNA molecule is read (the coding strand). The other strand is referred to as the non-coding strand.

40. Transcription • Promoter sequences are specific sequences of DNA nucleotides that RNA polymerase uses to find a protein-coding region of DNA and to find out which strand of DNA is the coding strand.

41. Transcription • Termination sequences are DNA nucleotide sequences that indicate when RNA polymerase should finish making an RNA molecule.

42. 3 Types of RNA • Messenger RNA (mRNA) – carries the blueprint for making the necessary protein. • Transfer RNA (tRNA) – reads mRNA and brings in the necessary amino acids. • Ribosomal RNA (rRNA) – reads the mRNA and brings in the necessary amino acids.

43. Translation • Translation is the process of using information in RNA to direct protein synthesis. • mRNA is read in sets of three nucleotides called codons.

44. Translation • A codon is a set of three nucleotides that codes for a specific amino acid. • The ribosome is made up of proteins and ribosomal RNA (rRNA). • The ribsome holds the mRNA in place and reads it’s codons.

45. 3 Phases of Translation • Initiation • Elongation • Termination

46. Initiation • The small ribosomal subunit binds to the mRNA and moves along until it reaches an AUG codon to signal the beginning of translation. • Transfer RNA (tRNA) carries amino acids to the mRNA complex.

47. Initiation • The anticodon portion of the tRNA interacts with the mRNA to match the correct amino acid to the codon in the mRNA nucleotide sequence. • The tRNA that binds to the AUG codon that signals the beginning of translation carries the amino acid methionine; therefore, every protein begins with this amino acid.

48. Elongation • The ribosome functions as an assembly line. • New amino acids are carried by tRNA to the corresponding mRNA segment. • The anticodon on tRNA matches with the codon on mRNA. • The amino acid is then attached to the end of the chain and the protein becomes elongated.

49. Termination • The ribosome will continue to add new amino acids until a stop signal is reached on the mRNA molecule. • The stop codon can be either UAA, UAG, or UGA.

50. Termination • When these codons are encountered, a release factor enters the ribosome. The ribosomal subunits release mRNA. • The mRNA can then either be reused or broken down to stop protein production.