Gene Gene ExpressionExpression

How is the information in How is the information in DNA used to determine an DNA used to determine an organism’s characteristics?organism’s characteristics?

An organisms An organisms trait’s are trait’s are determined by determined by proteins that proteins that are built are built according to the according to the plans specified plans specified in its DNA.in its DNA.

What are Genes?What are Genes?

Hold information specifying Hold information specifying how to build particular how to build particular proteins.proteins.

Referring back to the gym Referring back to the gym socks what part of the sock socks what part of the sock did the gene represent?did the gene represent?

Genes are the DNA-encoded Genes are the DNA-encoded information that specifies information that specifies particular proteins; each particular proteins; each gene is made of a specific gene is made of a specific sequence of ____________???sequence of ____________???

nucleotidesnucleotides

Transcribe and Transcribe and Translate a GeneTranslate a Gene

The DNA that makes up the The DNA that makes up the human genome can be subdivided human genome can be subdivided into information bytes called into information bytes called genes. Each gene encodes a genes. Each gene encodes a unique protein that performs a unique protein that performs a specialized function in the cell. specialized function in the cell. The human genome contains The human genome contains more than 25,000 genes. more than 25,000 genes.

Cells use the two-step process of Cells use the two-step process of transcriptiontranscription and and translationtranslation to read each gene and produce to read each gene and produce the string of amino acids that the string of amino acids that makes up a protein. The basic makes up a protein. The basic rules for translating a gene into rules for translating a gene into a protein are laid out in the a protein are laid out in the Universal Genetic Code.Universal Genetic Code.

How do you buildHow do you build a a proteinprotein??

It goes through two steps.It goes through two steps.

The first step is to undergo The first step is to undergo TRANSCRIPTION and TRANSCRIPTION and make RNA!!!make RNA!!!

Transcription 1Transcription 1stst step step

In the nucleolus the cells In the nucleolus the cells machinery copies the gene machinery copies the gene sequence into messenger RNA sequence into messenger RNA (mRNA), a molecule that is (mRNA), a molecule that is similar to DNA. Like DNA, similar to DNA. Like DNA, mRNA has four-nucleotide mRNA has four-nucleotide bases-but in mRNA, the base bases-but in mRNA, the base uracil (U) replaces thymine (T). uracil (U) replaces thymine (T).

Creating new strandsCreating new strands

DNA:DNA:GGTATCGATTGG    GGTATCGATTGG   

Complimentary:Complimentary:CCATAGCTAACC     CCATAGCTAACC    

RNARNAGGUAUCGAUUGG   GGUAUCGAUUGG  

DNA vs. RNADNA vs. RNA

DNADNA Double strandDouble strand 5-C sugar 5-C sugar

deoxyribosedeoxyribose Nitrogen Nitrogen

bases: ATCGbases: ATCG

RNARNA Single strandSingle strand 5-C sugar 5-C sugar

riboseribose Nitrogen bases: Nitrogen bases:

AUCGAUCG Uracil is Uracil is

complementary complementary to adenineto adenine

                                                           

RNA polymeraseRNA polymerase

Binds to a promoterBinds to a promoter Unwinds and breaks Unwinds and breaks

sequencesequence Builds up sequence by Builds up sequence by

pairing up each nucleotide pairing up each nucleotide with its complementary basewith its complementary base

What is the Role of DNA in this Process?

Step 1: RNA polymerase Step 1: RNA polymerase binds to gene’s promoterbinds to gene’s promoter

Step 2: The two DNA Step 2: The two DNA strands unwind and strands unwind and

separateseparate

Step 3: Complementary Step 3: Complementary RNA nucleotides are addedRNA nucleotides are added

Step 4Step 4

Step 5Step 5

TranscriptionTranscription

                                                                                                                                                                  

Transcription copies the DNA Transcription copies the DNA code of a gene and converts it to code of a gene and converts it to messenger RNA (m RNA). The m messenger RNA (m RNA). The m RNA will be used at the ribosome RNA will be used at the ribosome to make polypeptides (proteins). to make polypeptides (proteins). However all of the code contained However all of the code contained in the m RNA molecule is not in the m RNA molecule is not needed to produce the needed to produce the polypeptide. The sections of m polypeptide. The sections of m RNA which do not code for RNA which do not code for translation of polypeptide are translation of polypeptide are called introns. called introns.

As the m RNA readies itself to As the m RNA readies itself to leave the nucleus, enzymes cut leave the nucleus, enzymes cut out and remove the introns. The out and remove the introns. The remaining exons are spliced back remaining exons are spliced back together again by a different together again by a different enzyme. This modified m RNA is enzyme. This modified m RNA is what comes to the ribosome to be what comes to the ribosome to be translated into polypeptides.translated into polypeptides.

RNARNA

3 TYPES:3 TYPES:

messenger RNA messenger RNA (mRNA)(mRNA)

ribosomal RNA (rRNA)ribosomal RNA (rRNA)

transfer RNA transfer RNA (tRNA) (tRNA)

mRNAmRNA

Holds the information from DNA Holds the information from DNA and passes it on to create a and passes it on to create a proteinprotein

It’s an RNA copy of a gene used It’s an RNA copy of a gene used as a blueprint for a protein.as a blueprint for a protein.

When a cell needs a particular When a cell needs a particular protein, a specific mRNA is protein, a specific mRNA is made.made.

rRNArRNA

Associates with protein to Associates with protein to form the ribosomeform the ribosome

tRNAtRNAActs as an interpreter Acts as an interpreter

molecule, translating molecule, translating mRNA sequences into mRNA sequences into amino acid sequencesamino acid sequences

Genetic CodeGenetic Code

After transcription the genetic After transcription the genetic material message is ready to be material message is ready to be translated from the language of translated from the language of RNA to the language of proteins.RNA to the language of proteins.

The instructions for building a The instructions for building a protein are written as a series of protein are written as a series of 3 nucleotide sequences called 3 nucleotide sequences called codons. codons.

Translation: 2Translation: 2ndnd Step Step The protein-making machinery, The protein-making machinery,

called the ribosome, reads the mRNA called the ribosome, reads the mRNA sequence and translates it into the sequence and translates it into the amino acid sequence of the protein. amino acid sequence of the protein. The ribosome starts at the sequence The ribosome starts at the sequence AUG, then reads 3 nucleotides at a AUG, then reads 3 nucleotides at a time. Each 3-nucleotide codon time. Each 3-nucleotide codon specifies a particular amino acid. specifies a particular amino acid. The “stop” codons (UAA, UAG, and The “stop” codons (UAA, UAG, and UGA) tell the ribosome that the UGA) tell the ribosome that the protein is complete. protein is complete.

TranslationTranslation

Transcribe and Translate a Transcribe and Translate a Gene.htmGene.htm

OverviewOverview

DNA duplicates itself in replication. DNA duplicates itself in replication. DNA produces RNA in transcription. DNA produces RNA in transcription. RNA produces proteins in translation.RNA produces proteins in translation.

DNA, RNA, and Proteins

                                                                                                                                           

Protein builderProtein builder

Transcribe a DNA Transcribe a DNA sequence into a sequence into a

proteinproteinProteinProtein

Extra SlidesExtra Slides

TranscriptionTranscription Transcription is the process of creating RNA Transcription is the process of creating RNA

from DNA. from DNA. Transcription occurs in the cell's nucleus. Transcription occurs in the cell's nucleus. RNA polymerase is the protein molecule that RNA polymerase is the protein molecule that

reads the DNA and creates the RNA reads the DNA and creates the RNA intermediary.intermediary.

Transcription requires: DNA, RNA Transcription requires: DNA, RNA polymerase, ribonucleotides, and some ATP polymerase, ribonucleotides, and some ATP for energy.for energy.

Uracil (U) is substituted for thymine (T) in Uracil (U) is substituted for thymine (T) in RNA.RNA.

Transcription initiation is the main point of Transcription initiation is the main point of regulation of gene expression.regulation of gene expression.