CENTRAL DOGMA OF BIOLOGY - PowerPoint Presentation

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CENTRAL DOGMA OF BIOLOGY

DNA -> RNA -> Protein

This is the secret to life folks.

So what is RNA?

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DNA has the information for our cells to make proteins.

Copyright © 2010 Ryan P. Murphy

Keep your

hard copy

safe in the nucleus

Except

Proteins

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RNA

- Single strand

- Uracil replaces Thymine

Copyright © 2010 Ryan P. Murphy

Just Ribose sugar, not

deoxy

like DNA

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3 Types

of RNA

Messenger RNA (mRNA)

:

the RNA molecules that carry copies of the

instructions to make proteins

-

Genes

contain instructions for assembling proteins, mRNA carries these instructions

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Ribosomal RNA (

rRNA

):

the RNA, in addition to proteins, that

make up a ribosome

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Where are ribosomes made???

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Transfer RNA (

tRNA

)

:

the RNA molecule that contains the

anticodon to match

with the codon on mRNA and carries amino acids to the ribosome

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http://

www.pbs.org/wgbh/nova/body/rnai.html

https://

www.youtube.com/watch?v=Vh3-NHdjnyQ

RNAi is a newly discovered form of RNA!

Holy scientific breakthrough Batman!

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DNA through

transcription

makes mRNA.

mRNA = Messenger RNA.

Copyright © 2010 Ryan P. Murphy

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Transcription, Learn more at

http://biology.about.com/od/cellularprocesses/ss/Dna-Transcription.htm

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mRNA through

translation

makes proteins with the help of

ribosomes.

Copyright © 2010 Ryan P. Murphy

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“Cytosine walks into a bar and see’s Uracil.”

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“Cytosine walks into a bar and see’s Uracil.”

“He leans over and says…”

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“Cytosine walks into a bar and see’s Uracil.”

“He leans over and says…”

“I wish I was adenine so I could bond with U.”

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RNA and Protein Synthesis

In order for a cell to get information from the nucleus to the ribosomes, we must use RNA as a messenger.

What are three ways RNA differs from DNA?

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RNA and Protein Synthesis

Transcription

:

copying part of a DNA sequence into a

complementary strand of mRNA

- DNA to mRNA

-

like

burning a copy of a CD, almost the same as the original, but not

quite.

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Transcription:

DNA to mRNA

1.

RNA polymerase

both unwinds and unzips DNA helix

2.

RNA

polymerase

also adds

complementary

RNA nucleotides to the DNA strand.

3.

Process

continues until RNA polymerase reaches

termination signal

(specific sequence of nucleotides

that tells

RNA polymerase to STOP!!)

3.

RNA polymerase

releases both DNA & new mRNA

-mRNA strand leaves nucleus & begins translation

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mRNA Editing

Before it leaves nucleus it has to be edited.

Exons-

Expressed in the final geneIntrons- Cut out of the final sequence

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RNA and Protein Synthesis

Translation

:

decoding/

translating

mRNA into an amino acid chain (a.k.a. a polypeptide or

protein

)

-like

going from CD language to mp

3

language

-going

from English to

German

-requires the use of

tRNA

-

tRNA

has an anticodon that is

complementary

to the codon on mRNA

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RNA and Protein Synthesis

Translation

:

Codon

: a set of

three mRNA nucleotides

using the letters A, G, C, and U in groupings of 3.

Anticodon

: complementary bases to a specific codon. An

anticodon is specific to 1 amino acid.

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I’ll give you the codon…you give me the anticodon…

Codon (on mRNA)

AUG

UUUACGCAUGGA

Anticodon (on tRNA)UACAAAUGCGUACCU

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-Translation always begins with AUG, or the

START codon

that codes for the amino acid methionine

.

-The codon base-pairs with the anti-codon

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-The amino acids are transferred and joined by a

peptide bond.

-There are three

STOP codons

. UAA, UAG and UGA all code for the stopping of translation.

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There are 20 different amino acids.

In strands of any length, there are almost an infinite number of possibilities for the kinds of proteins we can make!

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Genetics and Genes

Proteins are the connection between the gene code in the DNA and how the gene is expressed.

Flower colors, enzymes, blood type, etc.

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Mutations

When doing all of this copying, things can go wrong.

Two major types of mutations…

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Point mutation –

change in one

gene

Chromosomal mutation – change that is manifested in an entire chromosome. These can be caused by copying DNA in cells, copying mRNA incorrectly, or even by the environment.

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Types of point mutations

Substitution –

changes one base for another

Deletion – piece of DNA code for one gene is lostInsertion – piece of DNA code for gene is copied too many times

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Substitution

A T

T

C G A G C TA T T C T A G C TThis causes Sickle Cell Anemia

-A changed to T so the amino acid glu changes to val. -Changes the shape of your blood cells

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Deletion

Causes Duchenne Muscular Dystrophy

Deletes part of a gene that codes for muscle protein

Wheelchair bound

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Insertion

Cystic Fibrosis

Excess of mucus in the lungs

Will eventually suffocate on your own bodily fluids

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Frameshift

If the insertion or deletion is not in a multiple of three nucleotides (a codon’s length) it shifts the whole frame over.

THE FAT CAT ATE THE FAT RAT

THE FAT CAA TET HEF ATR ATTHE FAT CAT AAT ETH EFA TRA TThese mutations can alter the resulting protein so much that it can no longer function

Mutations early in the code are MUCH more dangerous

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Causes of Gene Mutations

Environmental Factors

Mutagens – causes mutation in DNA

Radiation

Tobacco

Nuclear accidentsCarcinogens – a type of mutagen that causes cancer

tar in cigarettescertain drugssome minerals (asbestos)chemicals in smoked meatssome chemicals in hair dyesvirusesradiationTeratogens – a type of mutagen Cause deformation

ThalidomideAlcohol

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