7.1 From Gene to Protein Flashcards
importance of genes
Archibald Garrod, in 1896, began studying
alkaptonuria which is a condition where a
person’s urine turns black on contact with air.
He found that people with alkaptonuria excrete a
particular chemical in their urine.
He hypothesized that people with this disorder
were not able to break down this chemical
Later research proved that people with
alkaptonuria have a mutated gene that codes for
a defective enzyme that can no longer break
down the amino acid tyrosine
one gene-one polypeptide hypothesis
Each gene codes for the synthesis of one
polypeptide
Different polypeptides can be combined to
form more complex proteins
Can form hormones, enzymes, antibodies etc.
central dogma
the fundamental
principle of molecular genetics, which
states that genetic information flows
from DNA to RNA to Proteins
Includes Transcription, Translation,
and Folding
from DNA to RNA
Transcription – information in DNA is copied into RNA
RNA can exit the nucleus and enter the cytosol
RNA acts as a copy of the instructions contained in DNA that can be transported outside of the nucleus
RNA can then be used to build proteins
translation
information contained within RNA is used to build proteins
RNA contains instructions coding for a specific
amino acid sequence
Involves the use of Ribosomes
folding
changing shape of an amino acid chain into a functioning protein
Amino acid chains must fold properly in order
to become functioning proteins
RNA
Single Stranded
Adenine pairs with Uracil (A-U not A-T)
Contains Ribose sugar instead of
deoxyribose sugar in DNA
3 major types of RNA
Messenger RNA (mRNA), Transfer RNA
(tRNA) and Ribosomal RNA (rRNA)
Messenger RNA (mRNA)
translated by ribosomes into a protein
-Used to move the information from DNA to the ribosome where it can be
translated
Varies in length depending on the length of the gene being copied
transfer RNA (tRNA)
a carrier molecule that
binds to a specific
amino acid and adds
the amino acid to the
growing polypeptide
chain
Transfers amino acids to ribosomes to help build proteins
ribosomal RNA (rRna)
RNA molecules used
with proteins to make up ribosomes
Allow mRNA and tRNA to bind to ribosome
Major component of ribosomes
transcription
RNA Polymerase – enzyme that reads DNA and creates a complimentary strand of RNA
RNA is created 5’ to 3’
DNA strand is called the Template Strand
Initial RNA strand has to be modified before it
can become mRNA and is called pre-mRNA or
Precursor mRNA
RNA Polymerase
enzyme that reads DNA and
creates a complimentary strand of RNA
genetic code
specific coding relationship
between bases and the amino acids they code
for
DNA alphabet consists of:
ATCG
RNA alphabet consists of:
AUCG
codon
three base pairs that code for an
individual amino acid
3’ to 5’
DNA
5’ to 3’
RNA
start codon (AUG)
used to initiate translation
(methionine)
stop codon
used to stop translation (UAA,UAG or
UGA)
universality of genetic code
The same codons specify the same
amino acids in all living things (there
are a few exceptions)
This demonstrates the fact that DNA
evolved early in our evolution and
remained relatively unchanged
throughout our history
one gene-one enzyme hypothesis
proposes each gene is unique and codes for the synthesis of a single enzyme
one gene-one polypeptide hypothesis
proposes that each gene is unique and codes for the synthesis of a single polypeptide
central dogma
the fundamental principle of molecular genetics, which states that genetic information flows from DNA to RNA to proteins
transcription
mechanism by which the info coded in nucleic acids of DNA is copied into the nucleic acids of RNA; something rewritten in the same language
translation
mechanism by which the info coded in the nucleic acids of RNA is copied into the amino acids of proteins
messenger RNA
the end product of the transcription of a gene; mRNA is translated by ribosomes into a protein
transfer RNA
a carrier molecules that binds to a specific amino acid molecule and adds the amino acid to the growing polypeptide chain
ribosomal RNA
an RNA molecule within the ribosome that bonds the correct amino acid to the polypeptide chain
RNA polymerase
an enzyme that reads a DNA strand and creates a complementary strand of RNA
template strand
the DNA strand that is copied into an mRNA molecule during gene transcription
precursor mRNA
the initial RNA transcription product
genetic code
the specific coding relationship between bases and the amino acids they specify; the genetic code can be expressed in terms of either DNA or RNA bases
start codon (initiator codon)
codon that signals the start of a polypeptide chain and initiates translation
stop codon
a codon that signals the end of a polypeptide chain and causes the ribosome to terminate translation
