Termination and translations Flashcards
RNA is the________between genes and proteins for which they code
Intermediate
Transcription
The synthesis of RNA under the direction of DNA
Produces mRNA-messenger RNA
Translation
Is the synthesis of a polypeptide which occurs under the direction of mRNA
Ribosomes
Are the sites of translation
DNA template strand
A T and CG
Transcription mRNA strand
Codon
UA and GC
Translation proteins
amino acid Strand
Specific proteins
Eukaryotic cells ________ RNA after transcription.
Modify
Enzymes in the eukaryotic nucleus modify pre-mRNA before
The genetic messages are dispatched to the cytoplasm
Some interior parts of the molecule are cut out and the other parts spliced together
Most eukaryotic genes and their RNA transcript have long non-coding stretches of…
Nucleotides that lie between coding regions
Intervening sequences or Intron’s
Non-coding regions
Exons
Other region then intron
it’s called Exon because they are eventually expressed, usually translated into amino acid sequences
RNA splicing
Removes Intron’s and joins exons creating an mRNA molecule with the continuous coding sequence
Alternative RNA splicing
Some genes can encode more than one kind of polypeptide depending on which segments are treated as exons during RNA splicing
Transfer RNA a.k.a. tRNA
A cell translates an mRNA message into protein with the help of tRNA
Molecules of tRNA are not identical
Each TRNA carriers A specific amino acid on one end and an ______ on the other end ;the anti-codon base-pairs with a complementary_______on mRNA
Anticodon
Codon
Ribosomes facilitate specific coupling of _______ anti-codons with_______codons in protein synthesis
TRNA
mRNA
To ribosomal subunits (large and small) are made of two things
Proteins and ribosomal RNA or a.k.a. RRNA
A ribosome has three binding sites for tRNA
P site
A site
E site
P site
Holds the tRNA that carries the growing polypeptide chain
A site
Holds the tRNA that carries the next amino acid to be added to the chain
E site
The exit site where discharged tRNAs leave the ribosome
The initiation stage of translation
Brings together mRNA, tRNA with the first amino acid, and the two ribosomal subunits
steps in the initiation stage
A small ribosomal subunits bind with mRNA and the special initiator tRNA
Next the small subunit moves along the mRNA until it reaches the start codon AUG
During elongation stage
Amino acids are added one by one to the preceding amino acid
Termination occurs when
A Stop codon in the mRNA reaches the A site of the ribosome
The A site accepts the protein called a release factor
the release factor causes the addition of a water molecule instead of an amino acid
Often translation is not sufficient to make a
Functional protein
Polypeptide chains are modified _____ translation
After
Completed proteins are targeted to ______ sites in the cell
Specific
During and after synthesis
A polypeptide chain spontaneously coils and folds into a three-dimensional shape
Proteins may also require
post translational modifications before doing their job
Two populations of ribosomes are evident in cells
Free ribosomes in The cytosol and
bound ribosomes attached to the ER
Free ribosomes
Mostly synthesize proteins that function in the cytosol
Mutations
Changes in the genetic material of a cell or virus
Point mutations
Are chemical changes in just one base pair
The change of a single nucleotide in a DNA strand can lead to
The production of an abnormal protein
Point mutations within a gene can be divided into two general categories
Base pair substitutions
Base pair insertions or deletions
Base pair substitution
Replaces one nucleotide and it’s partner with another pair of nucleotides
Silent mutation
Have no affect on the Amino acid produced by a codon because of redundancy in the genetic code
Missense mutations
Still code for an amino acid but not necessarily the right amino acid
Nonsense mutation
Change an amino acid codon into a stop codon nearly always leading to a non-functional protein
Types of substitutions
Missense and nonsense mutations
Insertions and deletions
Are additions or losses of nucleotide pairs in a gene which is more damaging
insertion or deletion of nucleotides may alter the reading frame producing a frameshift mutation
Mutagens
Physical or chemical agents that can cause mutations
Spontaneous mutations can occur during
DNA replication or recombination or repair
While gene expression differs among the domains of life the concept of a gene is…
Universal
Archaea
Prokaryotes but share many features of gene expression with eukaryotes
Bacteria and Eukarya differ in
Their Rna polymerases and termination of transcription and ribosomes
Archaea tend to resemble you Eukarya in these respects
The idea of the gene itself is a unifying concept of life
discrete unit of inheritance
Region of specific nucleotide sequence in a chromosome
DNA sequence that codes for a specific polypeptide chain
Gene can be defined as
A region of DNA that can be expressed to produce a final functional product which is either a polypeptide or an RNA molecule
