5.3 Flashcards
compare the DNA in eukaryotes and prokaryotes
number of chromosomes : 1/2
shape : closed loop/linear’
location: cytoplasm/nucleus
presence of histone: coiled around/none
presence of non coding introns : no intro/intron sequences
what are the three main reasons polypeptide synthesis is important
- Vast majority of proteins created are enzymes and life just simply would not occur without such proteins such as amylase and lactase.
2.polypeptide synthesis allows growth, structure, repair and regulation of the bodies functions and tissues. (haemoglobin)
- Proteins additionally creates a characteristic (Phenotypic or genotypic) which will either be favourable for an organism or can create diseases or mutations, harming the organism.
what is the function of polypeptide synthesis
the genetic information stored in DNA is transferred into a specific sequence of amino acids in a polypeptide which then forms a protein. This is called GENE EXPRESSION.
what is the basic structure of proteins?
- A polypeptide is a chain of amino acids joined by peptide bonds.
- A protein molecule consists of one or more polypeptide chains.
- The polypeptides may be folded and twisted to form a complex, 3-dimensional shape.
what is the difference between RNA n DNA
DNA : RNA
deoxyrbonucleic acid : ribonucleic acid
2:1
deoxyribose: ribose sugar
thymine : uracil
where does the process of polypeptide synthesis initiate?
the nucleus with dna providing instructions for a specific gene
what occurs in initiation of transcription
Initiation begins as an enzyme referred to as RNA polymerase attaches to the gene’s promoter region, breaking hydrogen bonds in the DNA. This unwinds the double helix, and links ribonucleoside triphosphates to the exposed DNA template strand, forming complementary mRNA strands. It is important to note that the mRNA strand will not contain thymine hence is replaced by uracil.
what occurs in elongation of transcription
During elongation, RNA polymerase synthesizes mRNA from the 5’ to the 3’ end, reading the DNA template in the opposite direction. As RNA polymerase progresses, mRNA is synthesized, aligning with the DNA template strand, while the coding strand remains unutilized.
what occurs in termination of transcription
Termination occurs as RNA polymerase disconnects from the gene post mRNA synthesis, carrying identical genetic information as the DNA coding strand. This mRNA, containing introns which is the (non-coding region) and exons the (coding region), undergoes RNA splicing to remove introns, leaving only exons crucial for protein synthesis.
the finalized mRNA, comprising solely protein-coding exons, exits the nucleus, primed for translation and subsequent protein synthesis. This mRNA’s 3’ end is capped by Poly A polymerase to protect it, completing the preparation for its role in protein production.
what are codons
of nucleotide base pairs, and these are clustered into groups of threes commonly known as codons.
what occurs in translation?
So once the mRNA strand is synthesised in the nucleus, it leaves the nucleus through its nuclear pores and enters the cytosol, where it ultimately collides with structures referred to as ribosomes.
The ribosome, comprising a small subunit at its base and a larger subunit occupying around two-thirds of its structure, houses three active sites known as E, P, and A. As the mRNA strand connects with the ribosome via the initiator codon ‘AUG’, the interaction with transfer RNA (tRNA) commences. Each tRNA molecule carries complementary nucleotide bases which are referred to as anticodons. Anti-codons align with the codons present in the mRNA sequence. This molecular alignment occurs during the initiation phase of protein synthesis.
During ribosomal attachment, tRNA with amino acids docks at the P site, forming peptide bonds via complementary bases. Subsequent tRNA at the A site joins, elongating the polypeptide. Termination occurs at stop codons, signalling release factors to end translation. The protein exits for Golgi modification, essential for its functional three-dimensional structure, vital in executing biological functions within the cell or organism.
why is dna put into rna form
The process of polypeptide synthesis initiates in the nucleus with DNA providing instructions for a specific gene. However, due to its size, the DNA molecule cannot leave the nucleus. To overcome this, a polymeric molecule referred to as messenger RNA (mRNA
what is the importance of mRNA
mRNA is important in ensuring that the organisms’ genes code for the correct mRNA codons. This allows the correct tRNA molecule with matching anticodons that correct the amino acid that corresponds to the mRNA codon to form the correct amino acid sequence for the polypeptide chain. Thus, the polypeptide chain(s) can fold correctly resulting in a correct protein structure and function.
What is the importance of tRNA?
ensuring that it’s anticodon specifies and binds to the correct amino acid. This will ensure that the resulting polypeptide chain will have the right amino acid sequence that allow the protein-folding process to occur correctly. If not, the protein will not have the correct shape (primary structure)!
This can be seen in the example of enzymes, a type of protein. Without enzymes, many metabolic processes such as cellular respiration simply will not occur as the reactants will not form chemical bonds with each other to create the products. The enzyme’s active site and the specific reactants’ shape matches specifically! So, if the enzymes’ (protein) shape is not correct due to incorrect amino acid sequence in protein synthesis, the enzymes’ (protein) cannot correctly perform its function in catalysing the required metabolic process such as cellular respiration.
whats the relationship between genes and environment?
The relationship between genes and phenotypic expression underscores the intricate process of protein synthesis. The sequential process results in functional proteins dictating an organism’s traits—be they structural, physiological, or behavioural.
Environmental factors exert a profound impact on gene expression, thereby influencing phenotypic outcomes. Variations in environmental conditions showcase how external factors modify gene expression. Beyond this, environmental stressors trigger genetic changes, modulating gene activity without modifying DNA sequences.
