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Transcription is the first of overall two protein synthesis steps

Now that we’ve described DNA and RNA, it’s time to take a look at the process of protein synthesis

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Protein Synthesis Steps In Brief


Similar signals
in DNA cause transcription to
stop
when the new RNA molecule is
completed.
RNA Editing
Our DNA contains
sequences of nucleotides
called
introns
that are
not involved in coding for proteins.
The
DNA sequences
that
code for proteins
are called
exons
because they are
"expressed"
in the synthesis of proteins.
When
RNA molecules
are
formed,
both the
introns
and
exons
are
copied
from the
DNA.
However, the
introns are cut out of RNA
molecules while they are still in the
nucleus.
The remaining
exons
are then
spliced back together
to form the
final strand of mRNA.
The Genetic Code
Proteins

are made by
joining amino acids
into

long chains
called
polypeptides.

SparkNotes: SAT Subject Test: Biology: Protein Synthesis

Humans have roughly 22,000 genes.
The first step in decoding these genetic messages is to copy part of the nucleotide sequence from DNA into RNA, or ribonucleic acid.
These RNA molecules contain coded information for making proteins
RNA,
like DNA,
consists of a long chain of nucleotides,
and is made up of the
same things as DNA
(a 5-carbon sugar, a phosphate group and a nitrogenous base)
except

for one small difference:
the sugar group in RNA is ribose.
RNA also differs from DNA
in the fact that it is
single stranded, and has the base uracil instead of thymine
(therefore, in RNA
A bonds with U
).
RNA is like a
disposable copy
of a
segment of DNA
In many cases, an
RNA molecule is a working copy of a single gene.
The ability to
copy a single DNA sequence into RNA
makes it possible for a
single gene to produce hundreds or even thousands of RNA molecules
There are
three main types
of RNA:
1.) messenger RNA (mRNA)
2.) ribosomal RNA (rRNA)
3.) transfer RNA (tRNA)
The job of
messenger RNA (mRNA)
is to
carry copies of instructions
for the
assembly of amino acids into proteins from DNA
to the rest of the cell
The job of
transfer RNA (tRNA)
is to
transfer, or move, amino acids to ribosomes
during
protein synthesis
The job of
ribosomal RNA (rRNA)
is to
make up the major part of ribosomes.

Protein Synthesis -Translation and Regulation

Each three-letter
"word" in mRNA
is known as a
codon.
A
codon
consists of
three
consecutive nucleotides that specify a
single amino acid
that is to be
added
to the
polypeptide.
For example, consider the following RNA sequence:
UCGCACGGU

It would be read three bases at a time:
UCG-CAC-GGU

And these three codons represent the different amino acids:
UCG- CAC- GGU
Serine-Histidine-Glycine
Because there are
four different bases,
there are
64
possible three-based codons (4x4x4 =64)
This wheel shows all 64 possible codons of the genetic code.

Some amino acids
can be specified by
more than one codon.
You start at the center of the circle and move outwards to find the amino acid.
There is also one codon,
AUG
, that can either specify for the
amino acid methionine
or serve as the

"start" codon
for protein synthesis.
There are also
three "stop" codons
that do
not
code for
any amino acid.


Translation takes place on
ribosomes.
During
translation
,
the cell uses
information from mRNA
to produce
proteins.
Before
translation occurs,
mRNA is transcribed from DNA
in the
nucleus
and
released
into the
cytoplasm.
Translation
begins

when an
mRNA molecule
in the cytoplasm
attaches
to a
ribosome
.

nucleic acids & protein synthesis notes b1 - Biology …

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  • Nucleic Acids - Biology Junction

    23/10/2017 · RNA molecules are unique nucleic acids that are essential to protein synthesis

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    Protein Synthesis

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