Operon is not transcribed:
-lac operon: lactose absent
-trp operon: tryptophan present
Positive control transcription of Operon does not speed it up:
Lactose and glucose are present, -lac operon
Tryptophan is lacking in the -trp operon.
Operon is transcribed quickly through positive control:
-lac operon: lactose present, glucose not
Only negative control is used to regulate the trp operon. The operon genes are not transcribed when tryptophan is present.
Both positive control and negative control are used to control the lac operon.
Negative control: —Transcription is inhibited when lactose is missing due to the activity of the repressor protein.
—The repressor protein is deactivated and transcription is triggered when lactose is present.
Positive control: —In the absence of glucose, another regulatory protein (CAP) attaches to the lac operon's promoter, speeding up transcription in the presence of lactose.
Learn more about lac operons here:
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DNA and RNA perform different functions in humans. DNA is responsible for storing and transferring genetic information while RNA directly codes for amino acids and as acts as a messenger between DNA and ribosomes to make proteins.
Answer:
C. Joining of self-replication molecules into protocells.
Explanation:
For the origin of life, at least three conditions are needed.
- there must have been a supply of replicators, that is, self-replicating molecules.
- copying of these replicators must have been subject to error through mutation.
- the system of replicators must have required a continuous supply of free energy and partial isolation from the general environment.
The radiation received from the sun on the early earth must have fulfilled the requirement of mutation. The mutation is necessary for bringing variation in the genetic material thus driving evolution. To protect the self-replicating molecules from the external environment and to keep them together, the molecules must have been enclosed in a membrane barrier, which should be selectively semipermeable, to facilitate the exchange of molecules.
Answer no 8:
The correct option is D) Antelopes with muscular legs are bale to outrun their predators better than antelopes with poor muscle tone. Thus they lived to reproduce.
Explanation:
Genetic variations in a population are the main reason that natural selection tends to occur. Natural selection favours those organisms which have better characteristics.The organisms with better traits are able to reproduce and pass on their characteristics to their offsprings.
Answer No 10:
The correct option is A) Phenotype directly influences the interaction of an organism with its environment.
Explanation:
The interactions between the phenotypic traits and the environment analyze whether a particular organism will be able to survive and pass on its characteristics to its offspring. Hence, the phenotype directly influences the interaction of an organism with its environment.
Answer No 9
The correct option is A) resistance to a virus
Explanation:
Mutations can be described as any changes which occur in the DNA of an organism. Mutations might be beneficial or harmful depending on the location where the mutation arises. Viruses are usually harmful for eukaryotes. Hence, the correct option is A.
Answer No 11:
The correct option is C) Giraffes with longer necks survived because they were better suited to the environment.
Explanation:
Natural selection tends to favour those organsims which are better suited to live in an environment. Those organisms with better characteristics are able to survive and pass on their traits to their offsprings.
The giraffes with longer necks were better adapted to live in the environment and hence were favoured by natural selection.
Answer No 12:
The correct option is D) selective breeding
Explanation:
Selective breeding can be described as a technique in which organisms with better characteristics are crossed, so that offsprings with better characteristics can be produced. Selective breeding is done by humans where as natural selection is done by the nature.
This is a very confusing question since it sounds more like a statement. sorry really wish I could help :(
