Please enable JavaScript.
Coggle requires JavaScript to display documents.
CH's 16-17 (Chapter 17: Gene Expression (Translation- synthesis of a…
CH's 16-17
Chapter 17: Gene Expression
Transcription- the synthesis of RNA using DNA
result is mRNA that carries genetic information protein synthesizing parts of the cell
RNA Polymerase- tears apart the two strands of DNA and replaces complementary DNA with complementary RNA (assembles in a 5' to 3' direction)
the promoter initiates transcription and the terminator stops transcription
transcription unit- where DNA is transcribed into RNA
three steps
initiation- polymerase binds to the promoter and unwinds DNA, then, RNA synthesizes at the start point
elongation- RNA continues to elongate as it transcribes the DNA
termination- RNA transcript is released and polymerase detaches from the DNA
RNA Processing
triplet codes- groups of 3 DNA bases that code for certain codons
the strand of DNA that is transcribed is called a template strand
the mRNA created here is complementary to the DNA
mRNA nucleotide triplets are called codons (written in the 5' to 3' direction)
codons can also be the nucleotide triplets along the non-coding DNA strand (aka: the coding strand since it's similar to the mRNA)
amino acids that are created in translation run in the 5' to 3' direction
there are 3 stop codons and one start codon
Start: AUG
Stop: UAA, UAG, and UGA
The mRNA ends
the 5' end gets a 5' cap (a modified form of guanine
occurs after transcription of the first 20-40 nucleotides
a poly-A tail (50-250 adenine) is added to the 3' end
the end caps, help ribosomes attach to the 5' end, protect the RNA, and facilitate the exit of mRNA from the nucleus
Splicing- when parts of the RNA are removed and the rest is reconnected
introns- non-coding sequences of nucleotides
sometimes functions as a ribozyme
extons- the coding sequences of nucleotides
spliceosomes carry out this process
Translation- synthesis of a polypeptide using mRNA
takes place in the ribosomes
three sites
P site- holds tRNA
A site- holds the tRNA that's holding the next amino acid in the sequence
E site- the exit for tRNA
turns mRNA into amino acids
acts as a translator and translates mRNA codons into amino acids
anticodons are nucleotide triplets that are complementary to mRNA (written in the 3' to 5' direction
aminoacyl-tRNA synthase makes sure the tRNA molecule is carrying the correct amino acid
some tRNA's can bind to more than one codon because the first and third bases can be swapped
this is called wobble
translation also has intiation, elongation, and termination
the polypeptide chains formed during translation are then folded into its secondary and tertiary structures
polypeptides
sent to specific locations
free ribosomes go free in the cytosol
bound ribosomes are attached to the ER
marked by a signal peptide which in turn is recognized by a signal-recognition particle
polypeptide codes the ribosome's location
a ribosome can make one in less than a minute
Gene Expression- the process by which DNA direct protein synthesis to express certain phenotypes
two stages for coding of genes in to proteins
transcription
translation
DNA -> RNA -> Protein = Central Dogma
History of Genes and Proteins
Archibald Garrod was the first to connect genes, enzymes, and phenotypes in 1902
he also said the genetic issues are linked to an inability to make a certain enzyme
George Beadle and Boris Ephrussi discovered that fruit fly mutations in the eye are caused by a lack of a certain enzyme being made in the 1930's
one gene one enzyme hypothesis
this hypothesis has since been edited
not all proteins are enzymes
one gene one polypeptide hypothesis
Marshall Nirenberg discovered the first codon in 1961
all of the codons were found by the mid-1960's
Mutations- changes to the genetic information of a cell
point mutation- changes of a nucleotide
small scale mutations
nucleotide-pair substitution- one pair of nucleotides is wapped out for another
silent doesn't change the resulting protein
missense changes the amino acid but has little effect on the resulting protein
most common
nonsense prematurely ends translation but putting in a stop codon
frameshift mutation- inserts or deletes a nucleotide pair
way more disastrous than a point mutation
mutagens- physical and chemical agents that interact with DNA
Chapter 16: Molecular Inheritance
Molecular Structure of DNA and How it Contains the Information of Genetic Inheritance
DNA is your "genetic endowment" meaning that you inherited traits from both of your parents and that genetic information is stored here
early in the 20th century, finding the molecules that genetic information are made up of was a huge challenge
until the 1940's many thought that proteins contained genetic information
in 1928, Frederick Griffith discovered that the genetic information of dead, pathogenic bacteria can be inherited by living, nonpathogentic bacteria in their area and still infect the host.
this process was called transformation
transformation- a change in the genotype and phenotype by an external source
scientists also studied bacteriophages to prove that DNA was the genetic material
In 1952, Alfred Hershey and Martha Chase showed that DNA is the genetic material of bacteriophages
DNA is a polymer of nucleotides
3 Components
Nitrogenous base
The base can be one of 4 bases
Adenine (A) purine
Thymine (T) pyrimidine
Guanine (G) purine
Cytosine (C) pyrimidine
A pairs with T and G pairs with C because a purine must always pair with a pyrimidine
In 1950, Erwin Chargaff discovered that the composition of DNA is different for different species
pentose sugar (deoxyribose)
this is backbone of DNA
they run antiparallel to each other
phosphate group
After most scientists accepted tha DNA was genetic material, the next challenge was finding its 3D shape
this was discovered by James Watson and Francis Crick
the shape of DNA is a double helix
Key Proteins in DNA Replication
DNA Replication- the process by which DNA copies itself
DNA strands are complementary to each other and thus contain the information for creating another complementary strand
That's how DNA replicates itself
there are 3 modeels for DNA replication
conservative- parental strands still pair after replication
semiconservative- the parental strand splits and pairs with the daughter strands and then in the second generation two out of the four granddaughter stands contain the parental genetic information
this is the one that turned out to be true
dispersive- parental strand is split evenly among all daughter strands for all generations
each somatic cell has 46 DNA molecules (1 molecule per chromosome)
the process of replication is pretty much the same for both prokaryotes and eukaryotes
Replicating DNA 101
begins at the origins of replication
Helicases unwind the DNA strand
single-strand binding proteins bind to the strand to keep it from repairing
Topoisomerase relieves the strain on parental DNA by breaking, swiveling, and rebinding. The strain is caused by the unwinding.
the short chain of RNA produced during synthesis is called a primer (this is synthesized by primase)
the primer is the synthesized by DNA Polymerase III
1 more item...
DNA vs Chromatin vs Chromosomes
chromosomes- carriers of genetic information (DNA)
interphase chromosomes are attached to the nuclear lamina
chromatin- DNA +protein inside the nucleus
heterochromatin can NOT be transcribed
euchromatin can be transcribed
DNA- genetic information