replication dna dna
DESCRIPTION
Replication DnA Dna. We lose from 30,000-40,000 cells/day……these need to get replaced Before a cell duplicates, it makes an exact copy of its DNA for new cell Double helix “unzips” through an enzyme ( helicase ) that breaks H bonds - PowerPoint PPT PresentationTRANSCRIPT
We lose from 30,000-40,000 cells/day……these need to get replaced
Before a cell duplicates, it makes an exact copy of its DNA for new cell Double helix “unzips” through an enzyme
(helicase) that breaks H bonds DNA polymerase attaches nucleotides to
DNA strand to form complementary strands
DNA never leaves the nucleus, is protected RNA is a copy of DNA that goes out of
nucleus to give cell instructions to make proteins
3 Main Differences between RNA to DNA Single stranded, smaller Contains ribose sugar Contains uracil in place of thymine
Ribose Sugar
Adenine: AUracil: UGuanine: GCytosine: C
DNA unzips at site of desired gene at promoters (specific base sequence signal for start)
RNA polymerase creates a complimentary strand of gene with RNA nucleotides
mRNA leaves nucleus to ribosome for protein synthesis
Sometimes in the RNA copy, there are some portions that don’t code for the protein (introns)
Introns get discarded and remaining portions (exons) of RNA get spliced back together.
Transcription happens in the nucleus. An RNA copy of a gene is made.
Then the mRNA that has been made moves out of the nucleus into the cytoplasm
Once in the cytoplasm, the mRNA is used to make a protein
Cytoplasm of cell
Nucleus
DNAmRNA
mRNA
Messenger RNA (mRNA)- carry info on polypeptide synthesis from nucleus to ribosomes
Ribosomal RNA (rRNA)- make up subunits that make ribosomes
Transfer RNA (tRNA)- bring amino acids to the ribosome and matches them to coded mRNA message
Table 14.2Types of RNA
Type of RNA Functions in Function
Messenger RNA(mRNA)
Nucleus, migratesto ribosomesin cytoplasm
Carries DNA sequenceinformation to ribosomes
Transfer RNA(tRNA)
Cytoplasm Provides linkage between mRNAand amino acids;transfers aminoacids to ribosomes
Ribosomal RNA(rRNA)
Cytoplasm Structural component of ribosomes
*Ribosome binds to mRNA in cytoplasm
•Genetic code is read in words that are 3 letters long called CODONS
• Each codon codes for an AMINO ACID
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”
mRNA AMINO ACID CHART
As each codon passes through ribosome, tRNA brings the proper amino acids to ribosome to build a polypeptide
Anticodon is used to base pair with mRNA codons
The polypeptide chain continues to grow until it reaches a “stop” codon on mRNA
Ribosome releases new polypeptide and mRNA, completing translation
TRANSLATION
Figure 10.8B
Startcodon
RNA
Transcribed strand
StopcodonTranslation
Transcription
DNA
Polypeptide
CODONS
Figure 10.16A
Normal hemoglobin DNA
mRNA
Normal hemoglobin
Glu
Mutant hemoglobin DNA
mRNA
Sickle-cell hemoglobin
Val
Mutations are changes in the DNA base sequence caused by errors in DNA replication or by
mutagens (chemical/physical agents) Point mutation involves change in one or
a few nucleotides
Types of mutations
Figure 10.16B
mRNA
NORMAL GENE
BASE SUBSTITUTION
BASE DELETION or INSERTION
Protein Met Lys Phe Gly Ala
Met Lys Phe Ser Ala
Met Lys Leu Ala His
Missing
*FrameshiftMutation (more serious)
FRAMESHIFT: Shifts entire sequence over, can result in defective protein
POINT Mutation- can produce defective protein
TAC GCC TGG AAA
AUG CGG ACC UUU
MET ARG THR PHE
Silent mutation (substitution) because there is more than one codon for each AA