Monster Creation

• Decoding DNA

Triplets Codes and Codons

The most common organic bases are

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

The bases 5

A molecule of DNA is formed by millions of nucleotides joined together in a long chain

PO4

PO4

PO4

PO4

sugar-phosphate backbone

+ bases

Joined nucleotides 7

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

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PO4

2-stranded DNA 9

One strand bonds with another strand,creating the double-helix shape

Adenine forms a bond with Thymine

and Cytosine bonds with Guanine

Bonding 1 10

Adenine Thymine

Cytosine Guanine

PO4

PO4

PO4

thymine

PO4

PO4

PO4

PO4

adenine

cytosine

PO4

guanine

Bonding 2 11

Before a cell divides, the DNA strands unwind and separate

Each strand makes a new partner by addingthe appropriate nucleotides

The result is that there are now two double-stranded DNA molecules in the nucleus

So that when the cell divides, each nucleus contains identical DNA

This process is called replication

replication 16

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The strands separate

17

PO4

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PO4

Each strand builds up its partner by adding the appropriate nucleotides

18

How your cell makes very important proteins

• 3 phases:

1. Transcription

2. RNA processing

3. Translation

• DNA RNA Protein

14

RNA (ribonucleic acid)

3 forms of RNA– mRNA (messenger)– tRNA (transfer)– rRNA (ribosomal)

RNA is used to take the information in DNA and make proteins (gene expression)

15

During gene expression, the info in DNA is first transcribed as mRNA (messenger RNA) and then translated via tRNA (transfer RNA) and used to build a protein.

The Big Idea…

– The DNA is transcribed into RNA, which is translated into the polypeptide

Figure 10.6A

DNA

RNA

Protein

TRANSCRIPTION

TRANSLATION

• The information constituting an organism’s genotype is carried in its sequence of bases

The Big Idea…

• In transcription, DNA helix unzips

– RNA nucleotides line up along one strand of DNA, following the base-pairing rules

– single-stranded messenger RNA peels away and DNA strands rejoin

Figure 10.9B

• The “words” of the DNA “language” are triplets of bases called codons– The codons in a gene specify the amino acid

sequence of a polypeptide

Translation of nucleic acids into amino acids

For example

Cytosine

Adenine Codes for Valine

Cytosine (C)

Guanine (G)

Adenine (A)

Codes for Alanine

Thymine

Coding 21

U C A G

U

C

A

G

GACU

GACU

GACU

GACU

UUUUUCUUAUUG

CUUCUCCUACUG

AUUAUCAUAAUG

GUUGUCGUAGUG

phe

leu

leu

ile

met (start)

val

UCUUCCUCAUCG

CCUCCCCCACCG

ACUACCACAACG

GCUGCCGCAGCG

ser

pro

thr

ala

UAUUACUAAUAG

CAUCACCAACAG

AAUAAC

AAGAAA

GAUGACGAAGAG

tyr

stopstop

his

gln

asn

lys

asp

glu

UGUUGCUGAUGG

CGUCGCCGACGG

AGUAGCAGAAGG

GGUGGCGGAGGG

cys

stoptrp

arg

ser

arg

gly

Firs

t B

ase

Third

Base

Second Base

Virtually all organisms share the same genetic code “unity of life”

When a sequence of triplets in the DNA molecule code for a complete protein, the sequence forms agene

There may be a thousand or more bases in one gene

Genes 24