Q. What are the causes of genetic variation?
Genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism’s offspring).
Q. Why is the genetic code important?
The genetic code is (nearly) universal Even in organisms that don’t use the “standard” code, the differences are relatively small, such as a change in the amino acid encoded by a particular codon. A genetic code shared by diverse organisms provides important evidence for the common origin of life on Earth.
Q. How does the genetic code affect gene expression?
Gene expression is the process the cell uses to produce the molecule it needs by reading the genetic code written in the DNA. To do this, the cell interprets the genetic code, and for each group of three letters it adds one of the 20 different amino acids that are the basic units needed to build proteins.
Q. What are three factors that affect gene expression?
Various factors, including genetic makeup, exposure to harmful substances, other environmental influences, and age, can affect expressivity.
Q. What controls gene expression in eukaryotes?
Gene expression in eukaryotic cells is regulated by repressors as well as by transcriptional activators. Like their prokaryotic counterparts, eukaryotic repressors bind to specific DNA sequences and inhibit transcription. Other repressors compete with activators for binding to specific regulatory sequences.
Q. What is the process of gene expression in eukaryotic cells?
In eukaryotic cells, the DNA is contained inside the cell’s nucleus where it is transcribed into RNA. Eukaryotic gene expression is regulated during transcription and RNA processing, which take place in the nucleus, and during protein translation, which takes place in the cytoplasm.
Q. How do you control and regulate gene expression?
It therefore became possible to control gene expression by regulating transcription in the nucleus, and also by controlling the RNA levels and protein translation present outside the nucleus. Some cellular processes arose from the need of the organism to defend itself.
Q. What happens at the beginning of translation?
Initiation of translation occurs when mRNA, tRNA, and an amino acid meet up inside the ribosome. Once translation has begun, it continues down the line as mRNA shifts along through the ribosome. Each new codon matches with a new tRNA anticodon, bringing in a new amino acid to lengthen the chain.
Q. What are the 3 sites on a ribosome?
Each ribosomal subunit has three binding sites for tRNA: designated the A (aminoacyl) site, which accepts the incoming aminoacylated tRNA; P (peptidyl) site, which holds the tRNA with the nascent peptide chain; and E (exit) site, which holds the deacylated tRNA before it leaves the ribosome.
Q. What are the A P and E sites on the ribosome?
The P-site (for peptidyl) is the second binding site for tRNA in the ribosome. The other two sites are the A-site (aminoacyl), which is the first binding site in the ribosome, and the E-site (exit), the third. During protein translation, the P-site holds the tRNA which is linked to the growing polypeptide chain.
Q. What is the purpose of the A P and E sites in ribosomes?
The intact ribosome has three compartments: the A site binds incoming aminoacyl tRNAs; the P site binds tRNAs carrying the growing polypeptide chain; the E site releases dissociated tRNAs so that they can be recharged with amino acids.
Q. What is the role of the E site in translation?
In translation, the codons of an mRNA are read in order (from the 5′ end to the 3′ end) by molecules called transfer RNAs, or tRNAs. The E site is where a tRNA goes after it is empty, meaning that it has transferred its polypeptide to another tRNA (which now occupies the P site).
Q. What is the end result of translation?
amino acid sequence
Q. Why do 40S and 60S make 80s?
The same way an eukaryotic ribosome has a large sub-unit that sediments at 60s, a small one that sediments at 40s, but the whole structure sediments at 80s, not 100s. Essentially the sedimentation coefficient serves to normalize the sedimentation rate of a particle by the acceleration applied to it.
Q. What is the function of 80S ribosome?
Synopsis of Eukaryotic Ribosome Assembly. Ribosomes are the molecular machines that translate the genetic information from the intermediary mRNA templates into proteins [1]. Eukaryotic 80S ribosomes comprise two unequal subunits that contain four different rRNAs and around 80 r-proteins (Figure 1).
Q. What does S stand for in 70S ribosomes?
svedbergs
Q. Do humans have 70S ribosomes?
Mammalian mitochondrial ribosomes (55S) differ unexpectedly from bacterial (70S) and cytoplasmic ribosomes (80S), as well as other kinds of mitochondrial ribosomes.
Q. Why do prokaryotes have 70S ribosomes?
The purpose of the ribosome is to take the actual message and the charged aminoacyl-tRNA complex to generate the protein. All prokaryotes have 70S (where S=Svedberg units) ribosomes while eukaryotes contain larger 80S ribosomes in their cytosol. The 70S ribosome is made up of a 50S and 30S subunits.
Q. What does Svedberg unit mean?
Medical Definition of svedberg : a unit of time amounting to 10−13 second that is used to measure the sedimentation velocity of a colloidal solution (as of a protein) in an ultracentrifuge and to determine molecular weight by substitution in an equation. — called also svedberg unit.
Q. What is the value of Svedberg unit?
10−13 seconds
Q. Why do 50S and 30S make 70S?
The 30S subunit contains 16S rRNA and 21 proteins; the 50S subunit contains 5S and 23S rRNA and 31 proteins. The two subunits combine during protein synthesis to form a complete 70S ribosome about 25nm in diameter.
Q. What is the Svedberg equation?
An equation relating the relative molecular mass, Mr, of a solute to its sedimentation velocity in an applied centrifugal field.
