dna , protein synthesis, and gene expression

42
DNA, PROTEIN SYNTHESIS, AND GENE EXPRESSION

Upload: eugene

Post on 24-Jan-2016

58 views

Category:

Documents


0 download

DESCRIPTION

Dna , Protein Synthesis, and gene expression. Inheritance. Search for the Genetic Code. Griffith’s Transformation Experiment (1928). Avery, MacLeod, and McCarty (1944). Repeated Griffith’s experiments Used enzymes to destroy one of the _____________ during each round - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: Dna , Protein Synthesis, and gene expression

DNA, PROTEIN SYNTHESIS, AND GENE EXPRESSION

Page 2: Dna , Protein Synthesis, and gene expression

Inheritance

Page 3: Dna , Protein Synthesis, and gene expression

Search for the Genetic Code

Griffith’s Transformation Experiment (1928)

Page 4: Dna , Protein Synthesis, and gene expression

Avery, MacLeod, and McCarty (1944) Repeated Griffith’s

experiments Used enzymes to

destroy one of the _____________ during each round

Transformation was only stopped when ______ was destroyed

Page 5: Dna , Protein Synthesis, and gene expression

Hersey and Chase (1952)

Page 6: Dna , Protein Synthesis, and gene expression

Levene

Discovered the sugar difference between RNA and DNA RNA- ____________ DNA- ____________

Discovered the components of a nucleotide 5-carbon __________ Phosphate group Nitrogenous ________ (four types)

Page 7: Dna , Protein Synthesis, and gene expression

Chargaff

DNA contains equal amounts adenine (A) and thymine (T) and equal amounts cytosine (C) and guanine (G)

The amounts of A and T does _____ have to equal the amounts of C and G

Known as Chargaff’s rule

Page 8: Dna , Protein Synthesis, and gene expression

Franklin

Created X-ray diffraction images of DNA

Photo 51 allowed scientists to create a model of the sugar phosphate backbone (helix)

Close to figuring out bases

Picture shown to Watson and Crick without her knowing by colleague Wilkins

Page 9: Dna , Protein Synthesis, and gene expression

Watson and Crick

Able to make backbone based on Photo 51

First to propose structure of DNA

Watson, Crick, and Wilkins received Nobel Prize

Page 10: Dna , Protein Synthesis, and gene expression

DNA Nucleotides

Three Parts Phosphate Group

(PO4) Deoxyribose Nitrogenous Base

Adenine (A) Guanine (G) Thymine (T) Cytosine (C)

Page 11: Dna , Protein Synthesis, and gene expression

DNA Bases

Pyrimidines- _________ structure; C and T Purines- __________ structure; A and G

Page 12: Dna , Protein Synthesis, and gene expression

DNA Backbone

Composed of phospate groups and sugar

Strands of DNA are ______________ One runs 3’ to 5’;

other runs 5’ to 3’

Page 13: Dna , Protein Synthesis, and gene expression

Complementary Base Pairing

A always pairs with T Held together by

___ hydrogen bonds C always pairs with

G Held together by

____ hydrogen bonds

Page 14: Dna , Protein Synthesis, and gene expression

Double Helix

Page 15: Dna , Protein Synthesis, and gene expression

DNA Coiling

Double Helix ________________

Helix is wrapped around bundle of eight histone proteins (a pair of each of the four types)

Fifth type of histone anchors the nucleosome to linker regions of DNA

30 nm fiber- coiling of nucleosomes

_________ proteins- 30 nm fibers coil around the protein

Page 16: Dna , Protein Synthesis, and gene expression

Forms of DNA

__________- found throughout most of cell cycle

Chromosome- tightly packed DNA form during _________________

Page 17: Dna , Protein Synthesis, and gene expression

DNA Replication

Copy DNA into ______ Performed during ____ phase

of Interphase Occurs before division in

mitosis and meiosis ___________________

Each original DNA is still intact Each original strand has a new

partner (a newly made complement)

<>

Page 18: Dna , Protein Synthesis, and gene expression

DNA Replication (cont)

Step 1- Unwinding of DNA stand Performed by ____________ Held apart by binding proteins Occurs at many replication fork along the

length of the strand Step 2- Formation of RNA primers

Performed by __________ Complementary base pairs are lined up to

form the short primer

Page 19: Dna , Protein Synthesis, and gene expression

DNA Replication (cont)

Step 3- Replication Performed by ___________________(DNAP) DNAP can only attach bases to existing

polymer (primer) DNAP bring in complementary base pairs

for each stand of DNA Can only replicate in the ________ direction

3’ to 5’ original strand is replicated continously 5’ to 3’ is replicated discontinously in sections

called Okazaki fragments

Page 20: Dna , Protein Synthesis, and gene expression

DNA Replication (cont)

Step 4- Sealing the Backbone Performed by ____________ Bonds backbones of fragments together

Step 5- Proofreading Performed by ___________ Checks bases and cuts out incorrect one to

replace them with the correct one Cuts out RNA primer and replaces with DNA

nucleotides Ligase seals all the backbones

Page 21: Dna , Protein Synthesis, and gene expression
Page 22: Dna , Protein Synthesis, and gene expression

From Gene to Protein

Genes code for protein; protein creates _________

Protein Synthesis- creating a protein Transcription- _______________

Occurs in the ____________ DNA is copied into messenger RNA (mRNA) mRNA takes message to ___________

Translation- ______________ Occurs in cytoplasm at ____________ mRNA is decoded into amino acids Transfer RNA (tRNA) brings amino acids to ribosome

Page 23: Dna , Protein Synthesis, and gene expression

RNA Nucleotides

Three parts Phosphate Group

(PO4) Ribose Nitrogenous Base

Adenine (A) Guanine (G) Uracil (U) Cytosine (C)

Page 24: Dna , Protein Synthesis, and gene expression

Ribosome Structure

Single Strand of Nucleotides

Shape will be determined by base pairing within the strand

Page 25: Dna , Protein Synthesis, and gene expression

Types of RNA

Three Major Types mRNA-

Copy of DNA instructions Also called ______________ 500-4500 bases; depending on size of gene Every three bases are called a ___________

tRNA- 75-80 bases that bind in cloverleaf shape One end bonds to a specific amino acid One end has a three base code called the _________

Ribosomal RNA (rRNA)- 100-3000 bases long Form structure of ribosome with proteins ___________- catalyze peptide bond formation between amino

acids

Page 26: Dna , Protein Synthesis, and gene expression

Transcription

Step 1- Initiation _________ binding protein (transcription factor)

binds to TATA box within gene promoter region Other transcription factors bind to this area

forming complex RNA polymerase binds to complex

Step 2- Elongation RNA polymerase adds RNA nucleotides

complementary to DNA Only occurs in _______direction (reading the 3’ to 5’ DNA

strand) DNA stand being copied is called the ________; the other

DNA strand not being copied is the _________ strand The coding strand may be the template strand for

another gene

Page 27: Dna , Protein Synthesis, and gene expression

Transcription (cont)

Step 3- Termination RNA polymerase reaches a terminator

sequence in DNA Transcription is stopped

More than one transcript may be forming at a site at one time

Page 28: Dna , Protein Synthesis, and gene expression
Page 29: Dna , Protein Synthesis, and gene expression

Base Pairing Rules

If DNA is A Then RNA is ___

If DNA is T Then RNA is ___

If DNA is C Then RNA is ____

If DNA is G Then RNA is ___

Page 30: Dna , Protein Synthesis, and gene expression

Processing mRNA

Transcript is altered in the nucleus before it leaves

Cap is placed at 5’ end G base is inverted and _____________

Poly A tail Tail of around 200 adenines added to __________

Removal of Introns Pre-mRNA still contains sections that don’t code

for protein and must be spliced out of transcript Some introns are ribozymes that associate with

proteins to form small nuclear ribonucleoproteins (snRNP’s) that will preform the splicing

Final transcript only contains ___________

Page 31: Dna , Protein Synthesis, and gene expression

Processing mRNA (cont)

Page 32: Dna , Protein Synthesis, and gene expression

Consequences of Processing We create more proteins than we have

genes How do we do it?

Alternate splicing- mRNA is spliced to be shorter or longer to create a different protein

Different use of introns and exons- same pre-mRNA may have different areas spliced depending on the protein to be made

Page 33: Dna , Protein Synthesis, and gene expression

Translation

Step 1- Initiation mRNA leader sequence bond to small ribosome subunit First codon (always AUG) bonds with tRNA anticodon (UAC);

this type of tRNA always has methionine attached Step 2- Elongation

Large subunit attaches to small subunit First codon/anticodon are put in the P site A site exposes the second codon The matching tRNA anticodon base pairs with the exposed

codon bringing its amino acid A peptide bond forms between the amino acids (catalyzed by a

ribozyme) The mRNA shifts down a spot

P site holds second codon with two amino acids attached A site exposes next codon to base pairs with a matching anticodon First tRNa (UAC) returns to cytoplasm to find another methionine

Page 34: Dna , Protein Synthesis, and gene expression

Translation (cont)

Step 3- Termination Exposed codon at A site is one of the stop

codons No tRNA’s match; release factor binds and

releases mRNA and poypeptide mRNA may be translated by several

ribosomes at the same time

Page 35: Dna , Protein Synthesis, and gene expression
Page 36: Dna , Protein Synthesis, and gene expression

Cystic Fibrosis

Page 37: Dna , Protein Synthesis, and gene expression

Protein Folding

Creates final ______________ of protein Occurs in ER Shape is created by

Attraction between neighboring amino acids

Polarity of amino acids Sulfur bridges

Page 38: Dna , Protein Synthesis, and gene expression

Protein Folding (cont)

Chaperone proteins stabilize shapes as the form

Folding catalysts held fold protein Folding sensors proofread shape

Misfolded proteins are tagged Can be refolded properly Could be destroyed by proteasome

1⁰- ________________________________ 2⁰- localized folding (α- helix and β-sheet) 3 ⁰- _________ polypeptide folds together 4 ⁰- ________________ polypeptide folds together

Page 39: Dna , Protein Synthesis, and gene expression

Protein Folding (cont)

Page 40: Dna , Protein Synthesis, and gene expression

Gene Expression

Not all genes are expressed at the same time

An organisms expresses genes at different times in different areas

Each cell type will express a different subset of genes

This can be seen by looking at the ____________

Page 41: Dna , Protein Synthesis, and gene expression

What Effects Gene Expression? Chromatin Remodeling

Histones can expose or shield gene; groups can be added to histone to change it Acetyl and phosphate groups- turn on gene when

added ___________ groups- turn off gene when added

RNA interference (RNAi) RNA form a double strand when a single strand

makes a hairpin turn and bonds with itself Dicer (enzyme) cuts the RNA into small segments

called small interfering RNA’s (siRNA’s) siRNA’s

Methylate histones Attach to transcrpts, tagging them to be destroyed

Page 42: Dna , Protein Synthesis, and gene expression

Noncoding Regions of DNA

Do not code for protein RNA’s besides mRNA Introns Promotors and control regions Repeats

Transposons- repeats that can move and insert into new chromosomes

Telemeres Centromeres