DNA to Protein 12 Part one

1
DNA to Protein 12Part one

• AP Biology

2
What is a Gene?

• A gene is a sequence of DNA that contains the
  information or the code for a protein or an RNA
• What is a code? A code is a molecular message in
  the language of DNA or RNA that instructs the
  cell how to make a protein or a
• RNA molecule

3
What is the code?

• The code is written with the DNA alphabet of
  A,T,C, and Gs
• The words of DNA are in groups of three bases
  called triplets

4
Genes

• It had been estimated that because there are
  100,000 proteins that there must be 100,000 genes
• The Genome Project has revealed that there are
  actually less than 50,000 probably between 30,000
  and 40,000

5
The Early Concept of a Gene

• In the 1940s, Beadle and Tatum showed that when
  an altered gene resulted in an altered phenotype,
  that altered phenotype always showed up as an
  altered enzyme.

6
Wild type vs. mutant

• The normal enzyme is referred to as the wild type
• An altered enzyme is referred to as a mutant and
  reflects a change in the genetic message to make
  the protein

7
The Experiment That Demonstrated the Relationship
Between Gene and Protein
8
A Biochemical Pathway

• The pathway requires three enzymes to produce the
  product
• Each enzyme is a protein coded for by a gene

9
What is Gene Expression

• When the code of the gene is read and translated
  from the language of nucleic acids to the
  language of proteins( from bases to amino acids)

10
(No Transcript)
11
The structure of a gene
-100bp -40bp -30bp start
GENE
stop
GCGCGC CCAAT TATA BOX
3 TAC EXON! AT INTRON
CG EXON
ATT5
12
Transcription

• The process of making a copy of messenger RNA
  complementary to the DNA strand
• The molecule that copies the DNA is a RNA
  Polymerase
• RNA polymerase reads 3-5 and makes the RNA
  5---------3

13
RNA Polymerase

• Looks for the signals of the CAT BOX
• Sees the TATA
• Binds to the promoter( conserved or similar in
  eukaryotes)
• Transcription begins with 3TAC

14
Messenger RNA is made continuously

• Messenger RNA is made by the transcription of the
  bases in DNA into an RNA sequence
• This is called the primary sequence
• This sequence includes the introns and the exons
• As the m RNA( primary transcript) is made it is
  edited by a complex

15
Termination

• When the one of the three stop messages are
  reached the process of transcription ends
• The three stop messages are
• ATC 3 ATT 3 ACT 3

16
RNA

• The first two steps of processing pre-mRNA take
  place in the nucleus
• The G cap, a modified GTP, is added to the 5
  end. It facilitates the binding of mRNA to the
  ribosome and protects the mRNA from being
  digested by ribonucleases.
• A poly A tail is added to the 3 end. It is 100
  to 300 residues of adenine (poly A) in length.

17
RNA Splicing

• RNA splicing removes the introns and splices the
  exons together
• At the boundaries between introns and exons are
  consensus sequences.
• A small ribonucleoprotein particle (snRNP) binds
  to the consensus sequence at the 5 exonintron
  boundary.
• Another snRNP binds near the 3 exonintron
  boundary.
• Then other proteins bind, forming a large
  RNAprotein complex called a spliceosome. This
  complex cuts the RNA, releases the introns, and
  joins the ends of the exons.

18
Spliceosome

• The spliceosome edits the messenger RNA
  transcript
• It works with small RNAs
• This removes the introns by recognizing the
  intron border
• The exons are connected and the code for the
  protein is now continuous

19
Spliceosome and snurps I
Figure 14.10 The Spliceosome, an RNA Splicing
Machine (Part 1)
20
Spliceosome and snurps II
21
(No Transcript)
22
(No Transcript)