LS Ch 10 new

DNA Structure

The bases are inside the helix The helix is double and A pairs with T and C pairs with G since a double ring must pair up with a single ring base for the helix diameter to remain constant.


DNA Structure

DNA and RNA are composed of nucleotide subunits

Байду номын сангаас
These have a phosphate group (PO4), a sugar (either ribose or deoxyribose) and a nitrogencontaining base (adenine, thymine, guanine, cytosine, or uracil)


One gene one polypeptide
Translation


Translation uses transfer RNA to “read” and translate mRNA into sequence of animo acids Occurs on ribosomes in cytoplasm and on Rough ER

http://genome.imim.es/courses/Madrid04/exercises/ensembl/images/Transcription.01.GIF
Flow of Information:

It attaches to ribosomes and is “translated” into protein through the action of tRNA. DNA mRNA polypeptide

EXAMPLES:

Point Mutation

THE DOG BIT THE CAT THE LOG BIT THE CAT

Frame Shift Mutation [keep words to three letters – that’s the code]

THE SDO GBI TTH ECA T [here an extra base (“S”) was added – a similar problem would occur if a base was omitted – say “D”].

Bacteriophage

Lytic cycle:

Viral DNA enters cell and makes the cell into a virus-producing factory Uses cell’s own DNA replication and protein making machinery Makes lots of viruses – cell ruptures [lyses] releasing the viruses


Bacteriophage

The incorporated viral DNA is called a prophage
Prophages can re-emerge under stress or with other factors and switch to the lytic cycle

Semi-conservative – each “new” DNA molecule is actually half “old” and half new
Flow of Information:

mRNA is made from the DNA template [transcription] It travels from the nucleus into the cytoplasm to the rough endoplasmic reticulum
DNA CODE

The magic code of life is the base sequence of the DNA Series of three bases (codons) translates into a specific amino acid Overall sequence of bases determines the sequence of amino acids in proteins

THE OGB ITT HEC AT
VIRUSES: GENES IN PACKAGES


Many viruses cause disease in animals
DNA viruses – chicken pox, genital herpes

Viral DNA may become part of the host chromosome – may become latent and be passed from one generation to the next – maybe breast cancer


Figure 10.26_2
Bacteriophage

Lysogenic cycle:

Viral DNA enters cell and inserts into the cell’s own chromosome[s]. The host cell replicates the viral DNA with its own. Viral DNA can be passed through successive generations of the bacteria
DNA REPLICATION


Polymerases [enzymes] join the nucleotides together The DNA progressively adds nucleotides down the chain until it reaches the end
DNA REPLICATION
Figure 10.2
DNA Structure

Chargaff’s rule – Found that the amount of A always was equal to the amount of T and the amount of G was always equal to the amount of C.
Rosalind Franklin – By X-ray crystallography found that DNA is a helix

DNA Structure

Watson and Crick – Put all info together

Working with models, determined that the sugar and phosphate joined in chains for backbones, and

/resources/DNA-replication.jpg
/wikipedia/commons/thumb/9/9f/DNA_replication.svg/691px-DNA_replication.svg.png


May be how viruses cause cancer
Many bacteria that are pathogenic would be harmless without prophage infection [diphtheria, botulism, scarlet fever]

Figure 10.5
DNA REPLICATION

Proteins attach to the DNA and causes it to unwind at a given site
The strands separate At 3’ end of a strand, new nucleotides match up with their partners


OMIT –Transcription, Processing, Translation sections [p.181-186].
MUTATIONS

Small changes in DNA can cause big problems. Changing one base (base substitution) can change and amino acid, which changes a protein which may perform a vital function. Many “in born disorders of metabolism” involve a mutation at a single base


MUTATIONS

With changes in bases, one can get frame shift reading errors from deletions and insertions as well.
Agents that can increase the occurrence of mutations are called mutagens – can be energy like U or other radiation, or chemical, like nicotine.