Genetic Control of Protein Synthesis, Cell Function, and Cell reproduction
Cell genes control protein synthesis. The proteins that a cell produce determine the cell function. Proteins act as catalytic enzymes and physical components of cell structure.
Nucleotides are organised to form two strands of DNA that are loosely bound to each other.
Double stranded helical DNA that are composed of 3 basic building blocks: (1) phosphoric acid, (2) deoxyribose (sugar), and (3) Four nitrogenous basis (two purines, adenine, and guanine, and two pyrimidines, thymine, and cytosine)
The genetic code consist of triplets of basis. Each group of three successive basis is called a code word, and these code word control the sequence of amino acids in protein. The sequence of successive code words is called the genetic code.
DNA CODE IS TRANSFERRED TO RNA CODE BY THE PROCESS OF TRANSCRIPTION
DNA controls cell function in the cytoplasm through RNA. The process where the DNA code is transferred to RNA is called transcription. The RNA diffuses from the nucleus to the nuclear pores into the cytoplasm, where it controls protein synthesis.
RNA is synthesized in the nucleus from DNA template. The code triplets in the DNA cause the formation of complementary code triplets (called codons) in the RNA.
RNA is made up of AGCU - adenine, guanine, cytosine and uracil (and not AGCT)
The sugar ribose of RNA replaced the sugar dioxyribose of DNA and the pyrimadine Uracil replaces thymine.
The next step in the synthesis of RNA is the activation of the nucleotides. This is done by adding two phosphates with the nucleotide by high energy phosphate bonds, which are derived from the ATP of cells.
The DNA strand is used as a template to assemble the RNA molecule from activated nucleotides. RNA assembly under the influence of the enzyme polymerase:
The DNA stand immediately ahead of the gene that is to be transcribed is a sequence of nucleotides called the promoter. RNA polymerase recognises this promoter and binds to it.
The polymerase causes unwinding of the two turns of the DNA helix and separation of the unwound portions.
The polymerase moves along the DNA strand and begins forming RNA molecules by binding complementary RNA nucleotides to the DNA strands.
The successive RNA nucleotides then bind to each other to form an RNA strand.
When the RNA reaches the end of the DNA gene, it encounters the chain-terminating sequence; this causes the polymerase to break away from the DNA strand. The RNA is then released into the nucleoplasm.
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There are three different types of RNA
mRNA - carries genetic code to the cytoplasm to control the formation of proteins.
ribosomal RNA - along with proteins form the ribosomes, the structures in which are actually assembled; and
transfer RNA - tRNA - transports activated amino acids to the ribosomes to be used in the assembly of the proteins.
Each of the 20 tRNA binds specifically to each of the 20 different amino acids and carries the amino acid to the ribosomes to combine into proteins. tRNA recognises specific codons - is a specific codon called an anticodon.
TRANSLATION IS SYNTHESIS OF POLYPEPTIDES ON THE RIBOSOMES FROM THE GENETIC CODE CONTAINED IN THE RNA
To manufacture proteins, one end of the mRNA stand enters the ribosome, and then the entire strand treads its way through the ribosome. The ribosome causes the proper succession of amino acids to bind together to form chemical bonds called peptide linkages. The mRNA recognises the different tRNA - and does not have to bother recognising the different amino acids as each tRNA is specific for each amino acid.
As the mRNA passes through the ribosome, each of its codons attracts to it a specific tRNA, that in turn delivers a specific amino acid. The amino acid then combines with the preceding amino acids to form a peptide linkage, a sequence once complete forms a protein molecule. A chain-terminating process indicating the completion of the process and the protein is then released into the cytoplasm.
CONTROL OF GENETIC FUNCTION AND BIOCHEMICAL ACTIVITY IN CELLS
Genes control the function of cells by determining the relative proportion of the different types of enzymes and structural proteins that are formed.
The operons of the DNA stand control biochemical synthesis and are activated by the promoter. Enzymes needed for the specific synthetic synthesis from DNA is located on the DNA and is called an operon, and the genes in the operon are called structural genes. The promoter has a specific affinity for RNA polymerase. The polymerase must bind to the promoter before the polymerase can move along the DNA strand for RNA synthsis. The promoter is essential for the activation of the operon.
The operon is controlled by a repressor operator. A repressor protein binds on the repressor operator and prevents the attachment of RNA polymerase to the promotor, therefore blocking transcription in the operon. Repressor proteins can either be stimulated or inhibited by various non-protein substances in the cell - allowing feedback control of protein substances.
The operon is also controlled by an activator operator.
When the activator protein binds to the operator it attracts RNA polymerase to the promoter and activates the operon. The activator operator is also controled by molecular feedback (as is the repressor operator).
An inducer (protein) can displace a repressor (protein) from the operator site (DNA), which results in an uninhibited operon.
Transcription is also controlled by the operon through the following mechanisms:
(1) An operon may be controlled by a regulatory gene
(2) Regulatory proteins functions as an activator for one operon and an repressor for a second series of genes, allowing different operons to be controlled by the same regulatory protein.
(3) Selection of areas of chromosomes to become decompacted allowing RNA transcription.
Nucleotides are organised to form two strands of DNA that are loosely bound to each other.
Double stranded helical DNA that are composed of 3 basic building blocks: (1) phosphoric acid, (2) deoxyribose (sugar), and (3) Four nitrogenous basis (two purines, adenine, and guanine, and two pyrimidines, thymine, and cytosine)
The genetic code consist of triplets of basis. Each group of three successive basis is called a code word, and these code word control the sequence of amino acids in protein. The sequence of successive code words is called the genetic code.
DNA CODE IS TRANSFERRED TO RNA CODE BY THE PROCESS OF TRANSCRIPTION
DNA controls cell function in the cytoplasm through RNA. The process where the DNA code is transferred to RNA is called transcription. The RNA diffuses from the nucleus to the nuclear pores into the cytoplasm, where it controls protein synthesis.
RNA is synthesized in the nucleus from DNA template. The code triplets in the DNA cause the formation of complementary code triplets (called codons) in the RNA.
RNA is made up of AGCU - adenine, guanine, cytosine and uracil (and not AGCT)
The sugar ribose of RNA replaced the sugar dioxyribose of DNA and the pyrimadine Uracil replaces thymine.
The next step in the synthesis of RNA is the activation of the nucleotides. This is done by adding two phosphates with the nucleotide by high energy phosphate bonds, which are derived from the ATP of cells.
The DNA strand is used as a template to assemble the RNA molecule from activated nucleotides. RNA assembly under the influence of the enzyme polymerase:
The DNA stand immediately ahead of the gene that is to be transcribed is a sequence of nucleotides called the promoter. RNA polymerase recognises this promoter and binds to it.
The polymerase causes unwinding of the two turns of the DNA helix and separation of the unwound portions.
The polymerase moves along the DNA strand and begins forming RNA molecules by binding complementary RNA nucleotides to the DNA strands.
The successive RNA nucleotides then bind to each other to form an RNA strand.
When the RNA reaches the end of the DNA gene, it encounters the chain-terminating sequence; this causes the polymerase to break away from the DNA strand. The RNA is then released into the nucleoplasm.
GC
CG
AU
TA
There are three different types of RNA
mRNA - carries genetic code to the cytoplasm to control the formation of proteins.
ribosomal RNA - along with proteins form the ribosomes, the structures in which are actually assembled; and
transfer RNA - tRNA - transports activated amino acids to the ribosomes to be used in the assembly of the proteins.
Each of the 20 tRNA binds specifically to each of the 20 different amino acids and carries the amino acid to the ribosomes to combine into proteins. tRNA recognises specific codons - is a specific codon called an anticodon.
TRANSLATION IS SYNTHESIS OF POLYPEPTIDES ON THE RIBOSOMES FROM THE GENETIC CODE CONTAINED IN THE RNA
To manufacture proteins, one end of the mRNA stand enters the ribosome, and then the entire strand treads its way through the ribosome. The ribosome causes the proper succession of amino acids to bind together to form chemical bonds called peptide linkages. The mRNA recognises the different tRNA - and does not have to bother recognising the different amino acids as each tRNA is specific for each amino acid.
As the mRNA passes through the ribosome, each of its codons attracts to it a specific tRNA, that in turn delivers a specific amino acid. The amino acid then combines with the preceding amino acids to form a peptide linkage, a sequence once complete forms a protein molecule. A chain-terminating process indicating the completion of the process and the protein is then released into the cytoplasm.
CONTROL OF GENETIC FUNCTION AND BIOCHEMICAL ACTIVITY IN CELLS
Genes control the function of cells by determining the relative proportion of the different types of enzymes and structural proteins that are formed.
The operons of the DNA stand control biochemical synthesis and are activated by the promoter. Enzymes needed for the specific synthetic synthesis from DNA is located on the DNA and is called an operon, and the genes in the operon are called structural genes. The promoter has a specific affinity for RNA polymerase. The polymerase must bind to the promoter before the polymerase can move along the DNA strand for RNA synthsis. The promoter is essential for the activation of the operon.
The operon is controlled by a repressor operator. A repressor protein binds on the repressor operator and prevents the attachment of RNA polymerase to the promotor, therefore blocking transcription in the operon. Repressor proteins can either be stimulated or inhibited by various non-protein substances in the cell - allowing feedback control of protein substances.
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| In the case of a repressor, the repressor protein physically obstructs the RNA polymerase from transcribing the genes. |
The operon is also controlled by an activator operator.
When the activator protein binds to the operator it attracts RNA polymerase to the promoter and activates the operon. The activator operator is also controled by molecular feedback (as is the repressor operator).
An inducer (protein) can displace a repressor (protein) from the operator site (DNA), which results in an uninhibited operon.
The operon is controlled through negative feedback by cell product.
Genes make proteins. When there is sufficient protein this causes negative feedback inhibition of the operon that is responsible for its synthesis. This inhibition can be accomplished by causing regulatory repressor protein to bind to the repressor operator or cause the regulatory activator protein to break away from the activator operon. Transcription is also controlled by the operon through the following mechanisms:
(1) An operon may be controlled by a regulatory gene
(2) Regulatory proteins functions as an activator for one operon and an repressor for a second series of genes, allowing different operons to be controlled by the same regulatory protein.
(3) Selection of areas of chromosomes to become decompacted allowing RNA transcription.
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