Lecture 9 - Nucleic Acid Replication and protein synthesis Flashcards
In genetics, what is replication?
Replication means DNA or RNA is manufactured from nucleotides and the code from DNA.
What is genetics?
Genetics is the scientific study of gene expression.
In genetics, what is transcription?
The key to protein synthesis. How RNA and DNA is replicated.
Where are DNA and RNA replicated?
In the cell nucleus.
How is the sequence of amino acids determined in the manufacturing of RNA?
By the DNA on the original gene.
How and when are proteins expressed from DNA?
How and when proteins are expressed from DNA is a complicated process of providing the nucleus with signals to turn on and turn off gene expression. This signaling is a deeply subtle process. Epigenetics is a new approach to understanding gene expression. In OM, gene expression is seen in the Jing and the animation of Jing by Shen.
review: What is the structure of DNA?
A double strand, helical nucleic acid with a backbone of deoxyribose sugar and phosphate, with four nitrogenous bases.
review: What is the structure of RNA?
A single strand nucleic acid with a ribose sugar and phosphate backbone, with four nitrogenous bases. There are three forms of RNA.
review: what are the three forms of RNA?
rRNA
tRNA
mRNA
review: Purine and pyrimidine make up what?
- nitrogenous bases
- purine has 2 nitrogenous rings
- pyrimidine has 1 nitrogenous ring
review: a nitrogenous base bonded to a ribose or deoxyribose sugar is called what?
nucleoside
review: A nucleoside bonded with a phosphate group is called?
nucleotide
review: What is the backbone of DNA and RNA?
sugar phosphate backbone
review: nucleotides hydrogen bond to form their specific couples. What are the base pairing rules for DNA and RNA?
DNA: Adenine & Thymine, Guanine & Cytosine
RNA: Adenine & Uracil, Guanine & Cytosine
What is transcription?
The writing of DNA genetic code into mRNA
What enzyme makes transcription happen?
RNA polymerase enzyme
What are chromatin?
tightly bound genes that are unavailable for replication.
What are Euchromatin?
more accessible chromatin that are available for replication.
What is the function of Histones?
histones are a protein that allow the DNA double helix to group around them to form a ball-like structure, tightly bound.
What is heterochromatin?
tightly bound DNA that is conserved and almost never accessed for transcription.
What is the condensed fiber?
This is what will bundle itself into Chromatin. It is the DNA double helix coiled around the histone proteins
How is RNA transcribed?
RNA polymerase finds the site of code on the DNA that is to be transcribed. It unzips the DNA, replicates the DNA using RNA nucleotides, and rezips the DNA. All RNAs are made this way.
Is ATP used during the RNA polymerase’s enzymatic work?
yes, copious amounts.
How many strands of RNA are transcribed from DNA at a time?
many strands are replicated simultaneously.
Where is mRNA made?
mRNA is produced in the nucleus, then transported to the cytoplasm for the ribosome to do its work with translation.
what form does mRNA take?
it is a strand, it does not fold
Is mRNA used to make protein more than once?
yes, it will pass through ribosome multiple times until enough of that protein has been created and the mRNA breaks apart from use and abuse. (negative feedback loop)
When is DNA replicated?
Only when a cell divides.
What two types of cells do not divide?
nerve cells and muscle cells
What kind of cells divide all the time (which organ)?
liver cells
How is DNA replication initiated?
helicase-topoisomerase-primase complex surrounds the DNA and unzips it to expose the nitrogenous bases, binding proteins hold the strands open so the DNA can be transcribed, and a daughter strand is formed.
What does helicase do in DNA replication?
untwists the primary helix structure by relieving the hydrogen bonding between the bases. binding proteins attach to the strands to keep them separated.
What does DNA Primase do in DNA replication?
bonds free floating nucleotides into the deoxyribose chain
What does DNA Ligase do in DNA replication?
connects together the bits of newly created nucleotide chain
What does DNA polymerase do in DNA replication?
finishes the bonding of nucleotides and rezips the strands as two daughter strands.
How do our cells maintain tissue integrity?
by creating and renewing a vast variety of proteins.
What are proteins used for?
1) enzymes: catalyze biochemical processes
2) structure: muscles, tendon, skin, ligaments, glands, organs, etc
3) function: hormones and messengers, cell membrane transport, metabolism, etc.
What is the basic process of protein synthesis?
- TRANSCRIPTION: the protein code from DNA is copied, writing the code in mRNA.
- TRANSLATION: the mRNA is moved out of the nucleus into the cytoplasm where it is TRANSLATED into an amino acid chain (polypeptide)
What is a codon?
a grouping of 3 nitrogenous bases that is read to indicate a specific amino acid
How does the codon function?
The mRNA strand that needs to be transcribed is a long chain of nucleic acids in groupings of three (codons) that will be read by the ribosome so that tRNA can attach the specific amino acids corresponding to that codon.
What other information does a codon provide?
various types of codons exist:
- promotion codons
- starter codons
- termination codons
Before mRNA leaves the nucleus, it needs to be spliced. What are the codons called that designates what part of the mRNA is removed?
Introns are codons removed from the mRNA, and the sections of mRNA that are left are called exons. The remaining exons are spliced together and the resulting strand is a mature mRNA that will be moved out of the nucleus into the ribosome for translation into protein.
What does tRNA carry?
a 3-base anticodon (using the base pairing rules). tRNA is specific to codons and amino acids, and will carry the specific amino acid needed to attach to the corresponding codon on the mRNA.
Can a specific tRNA be used more than once?
Yes, an enzyme called aminoacyl tRNA synthetase recycles tRNA by reloading emptied tRNAs with their specific amino acid.
When a codon on mRNA enters the ribosome and tRNA brings the specific amino acid to it, what is this process called?
translation - since the aminos being brought by the tRNA are bonding together (by dehydration synthesis) and forming a new polypeptide.
(transcription only occurs when DNA is being transcribed to RNA or DNA is being replicated)
Where is mRNA produced? Where is it matured? Where is it transported to?
- produced in nucleus
- matured in nucleus
- transported to cytoplasm to the ribosome
in what form are ribosomes found and where?
as subunits 30 and 50, found in the RER or floating freely in the cytoplasm
when the mRNA is sensed by the ribosome, what happens?
a 30 subunit and a 50 subunit come together around the mRNA to form a protein factory
When the mRNA enters the ribosome, what do the tRNA’s do?
loaded with their appropriate amino acid, tRNA enters the ribosome and lines up the amino acid on the peptide chain in accordance to the codon on the mRNA.
When the tRNA lines up an amino acids on the active site of the ribosome, how do the amino acids bond?
peptide bonds form
What are the A and P sites of the ribosome?
As the mRNA codons are moving past these active sites, the tRNA are actively bonding their aminos here. The ribosome keeps moving the mRNA through so that the aminos can bond consecutively, forming a chain.
When does this action of the mRNA and the ribosome, and the forming of a polypeptide chain stop?
When the TERMINATION CODON reaches the active site, translation will stop
After the termination codon arrives at the active site and after the polypeptide chain is formed, what happens?
The polypeptide chain moves out of the ribosome and folds or is modified into a protein. Often this happens in the Golgi Complex.
Where are vitamins and other cofactors inserted into the newly formed protein to create a holoenzyme for use or as a zymogen for storage?
in the ER or the Golgi Complex
