Central DogmaCentral DogmaDNA RNA DNA RNA Protein Protein

What are chromosomes? Where are they found?

Chromosome

Histones

DNA

double

helix

What is a gene?What is a gene? A sequence of A sequence of

DNA that codes DNA that codes for a protein and for a protein and thus determines a thus determines a trait.trait.

Where do we get our Where do we get our genes?genes?

It’s all in the DNA, It’s all in the DNA, and it’s and it’s hereditary!hereditary!

That means That means different different combinations of combinations of genes from mom genes from mom and dad make you and dad make you and all your and all your siblings!siblings!

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

DNA

Adenine Guanine Cytosine Thymine

Deoxyribose sugar

Phosphate group

DNA

Nitrogen Base

Nu

cle

oti

de

What are the rules of What are the rules of BASE BASE PAIRINGPAIRING??

In a DNA molecule, every In a DNA molecule, every nitrogenous base is paired:nitrogenous base is paired:– Adenine pairs with Adenine pairs with ThymineThymine– Guanine pairs with Guanine pairs with CytosineCytosine– Thymine pairs with Thymine pairs with AdenineAdenine– Cytosine pairs with Cytosine pairs with GuanineGuanine

RNARNA

Serves as a Serves as a messenger messenger between the between the nucleusnucleus and the and the ribosomesribosomes..

Carries Carries information in information in order to make order to make proteinsproteins from from aminoamino acidsacids..

RNA StructureRNA Structure

A= AdenineA= Adenine G= GuanineG= Guanine C= CytosineC= Cytosine U= UracilU= Uracil UracilUracil replaces replaces

ThymineThymine SingleSingle

stranded.stranded.

from to to make up

Concept MapSection 12-3

also called which functions to also called also called which functions towhich functions to

can be

RNA

Messenger RNA Ribosomal RNA Transfer RNA

mRNA Carry instructions

rRNACombine

with proteins tRNABring

amino acids toribosome

DNA Ribosome Ribosomes

Go to Section:

ReviewReview

Fill in the missing nitrogen bases to Fill in the missing nitrogen bases to make this DNA double-stranded.make this DNA double-stranded.

Use the green DNA strand as a Use the green DNA strand as a template to transcribe RNA:template to transcribe RNA:

TAC-ACG-TCC-ATA-CAT-GGT-CCA-ATTTAC-ACG-TCC-ATA-CAT-GGT-CCA-ATT

ATG-ATG- -TAA -TAA

Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)

Transcription

TranscriptionTranscriptionDNA is DNA is transcribedtranscribed into into RNARNA1.1. RNA polymerase attaches to RNA polymerase attaches to

DNA and unzips it.DNA and unzips it.

2.2. One strand of DNA is used as a One strand of DNA is used as a template.template.

3.3. RNA polymerase attaches RNA polymerase attaches nucleotides to the template to nucleotides to the template to make a single strand of RNA.make a single strand of RNA.

What does it mean to What does it mean to transcribe?transcribe? To transcribe means to rewrite in To transcribe means to rewrite in

a different script (lettering)a different script (lettering) Remember DNA consists of A, Remember DNA consists of A, TT, ,

G, CG, C RNA consists of A, RNA consists of A, UU, G, C, G, C

TranscriptionTranscription

Codons (Found on Codons (Found on mRNA)mRNA) CodonsCodons consist of three consist of three

nucleotides that nucleotides that code forcode for a a particular particular amino acidamino acid

Example: Example: – UCGCACGGU should be read as…UCGCACGGU should be read as…– UCG-CAC-GGU which codes forUCG-CAC-GGU which codes for– Serine-Histidine-Glycine Serine-Histidine-Glycine

Anticodons (Found on Anticodons (Found on tRNA)tRNA) AnticodonsAnticodons consist of three consist of three

unpaired nucleotides that are unpaired nucleotides that are complementary complementary toto one mRNA one mRNA codoncodon

FunctionsFunctions to attach tRNA to mRNA to attach tRNA to mRNA so that amino acids can attach to so that amino acids can attach to one anotherone another

Example:Example:– (1) mRNA: UCG-CAC-GGU(1) mRNA: UCG-CAC-GGU– (3) tRNA: AGC GUG CCA(3) tRNA: AGC GUG CCA

TRANSCRIPTION & TRANSCRIPTION & TRANSLATIONTRANSLATION

TranslationTranslation

1.1. mRNA attaches to ribosomemRNA attaches to ribosome

2.2. tRNA brings amino acids to mRNAtRNA brings amino acids to mRNA

3.3. Anticodons (on tRNA) bind to codons Anticodons (on tRNA) bind to codons (on mRNA) starting at “start” codon, (on mRNA) starting at “start” codon, AUGAUG

4.4. Ribosome joins the amino acids Ribosome joins the amino acids together to make a polypeptide chain together to make a polypeptide chain (protein) until a “stop” codon is (protein) until a “stop” codon is reached.reached.

Translation

Translation cont.

Genetic CodeGenetic Code