Chapter 14 Flashcards
The DNA inherited by an organism leads to specific traits by dictating ___ and of _____ involved in ____.
the synthesis of proteins, RNA molecules, protein synthesis
proteins are?
the link between genotype and phenotype
gene expression
process by which DNA directs protein synthesis
2 stages of gene expression
transcription and translation
metabolic pathway
cells synthesize and degrade molecules in a series of steps
Beadle and Tatum began studying the haploid bread mold ____ because it would be____?
Neurospora crassa, easier to detect recessive mutations
Beadle and Tatum generated ___, each of which was ___.
nutritional mutants, unable to synthesize a particular essential nutrient
For Neurospora one set of mutants all required ___ for ___.
arginine, growth
Some proteins are not ___, so researches revised the ____ hypothesis to ___.
enzymes, one gene-one enzyme, one gene-one protein
Beadle and Tatum’s hypothesis is now restarted as the ___ hypothesis.
one gene-one polypeptide
____ is the bridge between __ and ___ synthesis.
RNA, protein, DNA
2 stages of getting DNA to protein
transcription and translation
Transcription
synthesis of RNA using info in DNA
Transcription produces?
mRNA
Translation
synthesis of a polypeptide using info in mRNA
Sites of translation
Ribosomes
In eukaryotes, the nuclear envelope separates?
transcription from translation
Eukaryotic RNA transcriptions are modified through ___ to yield __
RNA processing, mRNA
Primary transcript
initial RNA transcript from any gene prior to processing
Central dogma
concept that cells are governed by a cellular chain of command
There are only ___ nucleotides bases to specify ___ amino acids
4, 20
The flow of info from ___ to ___ is based on __
gene, protein, triplet code
triplet code
a series of nonoverlapping three-nucleotide words of mRNA
The words from mRNA are then translated into?
a chain of amino acids forming a polypeptide
During transcription, the template strand?
provides a template for ordering the sequence of complementary nucleotides in an RNA transcript
codons
mRNA triplets
codons are read in the ___ direction.
5’-3’
coding strand
nontemplate DNA strand
The genetic code is __
redundant
redundant
more than one codon may specify a particular amino acid
No codon specify ___
more than one amino acid
Codons must be read in the correct ___ in order for the ___.
reading frame, specified polypeptide to be produced
The genetic code is nearly ____?
universal
Genes can be ___ and ___ after being transplanted from ___ .
transcribed, translated, one species to another
A language shared by all living things must have?
been operating in the common ancestor of all present-day organisms
What is the first stage of gene expression?
transcription
RNA polymerase
pries the DNA strands apart and joins together complementary RNA nucleotides
RNA polymerase assemble polynucleotides only in the ___ direction
5’-3’
Promoter
DNA sequence where RNA polymerase attaches
terminator
In bacteria, the sequence signaling the end of transcription
transcription unit
stretch of DNA that is transcribed
3 stages of transcription
-Initiation
-Elongation
-Termination
Promoters signal the transcriptional ___ and usually extend __.
start point, several dozen nucleotide pairs upstream of the start point
Transcription factors
mediate the binding of RNA polymerase and the initiation of transcription
transcription inition complex
complicated assembly of transcription factors and RNA polymerase ll bound to a promoter
TATA Box
promoter DNA sequence
TATA Box is crucial in forming ___
the initiation complex in eukaryotes
In bacteria, the polymerase stops ___ at the end of the ___ and the ___.
transcription, terminator, mRNA can be translated without further modification
Enzymes in the eukaryotic nucleus modify __ before the __.
pre-mRNA, genetic messages are dispatched to the cytoplasm
pre-mRNA
RNA processing
5’ end of pre-mRNA receives
a modified G nucleotide 5’ cap
3’ end of pre-mRNA recieves
poly-A tail
modifications to mRNA ends helps facilitate?
the export of mRNA to the cytoplasm
RNA splicing
large portions of the RNA molecules are removed and remaining portions are reconnected
introns
noncoding regions
exons are usually?
translated into amino acid sequences
In the process of splicing, introns are ___ and the exons __
cut out of the molecule, are joined together
alternative RNA splicing
exons from the same gene are joined in different combinations, leading to different, but related, mRNA transcripts
Spliceosomes consist of?
proteins and small RNA’s
Ribozymes
RNA molecules that function as enzymes
transfer RNA
helps translate an mRNA message into protein
tRNA’s transfer __ to the ___ in a ___
amino acids, growing strand, ribosome
Each tRNA enables the translation of___
a particular mRNA codon into a certain amino acid
In 3D, tRNA is ___ shaped
L
tRNA has one end which contains the ___ and the other end an __
anticodon, amino acid
anticodon
recognizes a specific codon on mRNA
There are no introns in?
bacteria
2 steps of accurate translation
-correct match between tRNA and amino acid done by aminoacyl-tRNA synthetase.
-Correct match between the tRNA anticodon and an mRNA codon.
wobble
flexible pairing at the third base of a codon
Ribosomes facilitate specific ___ during ___.
coupling of tRNA anticodons with mRNA, protein synthesis
The large and small proteins are made of?
proteins and ribosomal RNA’s
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
exit site where discharged tRNAs leave the ribosome
Energy is provided in the translation process by?
GTP
A start codon is important because
it establishes the reading frame for the mRNA
During elongation, amino acids are added ___ to the previous ___ at the ___
one by one, amino acid, C-terminus
Termination occurs when?
a stop codon in mRNA reaches the A site of the ribosome
The release factor at the A site causes?
the addition of a water molecule instead of an amino acid
During synthesis, a polypeptide chain spontaneously?
coils and folds into its 3D shape
Proteins may also require?
post translation modifications before doing their jobs
Bound ribosomes make?
proteins of the endomembrane system and proteins that are secreted from the cell.
Polypeptide synthesis always begins in the?
cytosol
Polypeptides destined for the ER or for secretion are marked by a ___ which ___
signal peptide, targets the protein to the ER
Signal-recognition particle binds to?
signal peptide
Once a ribosome is far enough past the start codon, another ribosome
can attach to the mRNA
Bacteria and eukaryotes can also transcribe multiple
mRNA’s from the same gene
mutations
changes in the genetic material of a cell
point mutations
chemical changes in just one nucleotide pairs of a gene
The change of a single nucleotide in a DNA template strand can lead to?
production of abnormal protein
If a point mutation occurs in a gamete, it may be?
transmitted to offspring
2 categories of small-scale mutations within a gene
-single nucleotide-pair substitutions
-nucleotide-pair insertions or deletions
nucleotide pairs substitution
replaces one nucleotide and its partner with another pair of nucleotides
silent mutations
have no effect on amino acid due to redundancy in genetic code
missense mutations
change one amino acid to another
nonsense mutations
change an amino acid codon into a stop codon, leading to nonfunctional protein
insertions/deletions
additions or losses of nucleotide pairs in a gene
Insertions or deletions have a ____ effect on the resulting __
disastrous effect, protein more often than substitutions do
insertions or deletions of nucleotides may alter the ___ producing a ___
reading frame, frame shift mutation
mutagens
physical or chemical agents that can cause mutations
Most carcinogens are?
mutagenic
we consider a gene as a DNA sequence that
codes for a specific polypeptide chain
A gene can be defined as a region of DNA that can be expressed to?
produce a final functional product, either a polypeptide or an RNA molecule
