Answer:
Please find the detailed explanation of this statement below
Explanation:
Firstly, a repressed gene is a gene whose expression has been inhibited or repressed. The lac operon in E.coli bacteria is a regulatory unit containing structural genes, a single promoter and operator regions. The promoter is the region where the transcription enzyme (RNA polymerase) binds to in order to transcribe the genes in the lac operon. The structural genes in the lac operon can only be expressed in the presence of lactose sugar.
However, in the absence of lactose, LAC REPRESSOR, which is a transcription factor (protein), prevents the binding of RNA polymerase to the PROMOTER region by binding to the OPERATOR region of the lac operon. This inhibits the expression of the lactose genes in the operon.
Note that, the structural genes in the lac operon (lacZ, lacY, lacA) code for proteins that help break down lactose sugar for energy in the E.coli bacteria. Therefore, a bacteria cell with a repressed lac operon will be unable to degrade lactose sugar.
Answer:
All of these are correct
Explanation:
According to the question, marble is a rock formed from limestone, which in turn is also formed from Calcite. This shows that marble is a kind of metamorphic rock because a metamorphic rock is any rock that is formed by the alteration of other rocks caused by heat, pressure or chemicals etc. These changes that occurs in the previously existing rocks are called METAMORPHOSIS.
Hence, since marble is formed from limestone, it concludes that marble is a metamorphosed rock formed from a previously existing limestone rock. Also, since Calcite, a precursor of limestone that marble is formed from can be degraded by acids, both limestone and marble which are formed from it will also be dissolvable by acids.
Answer:
The vacuole. Large in plant cells but small in animal cells
Carbon dioxide is a colorless and non-flammable gas at normal temperature and pressure. Although much less abundant than nitrogen and oxygen in Earth's atmosphere, carbon dioxide is an important constituent of our planet's air. A molecule of carbon dioxide (CO2) is made up of one carbon atom and two oxygen atoms. Carbon dioxide is an acidic colorless gas with a density about 53% higher than that of dry air. Carbon dioxide molecules consist of a carbon atom covalently double bonded to two oxygen atoms. It occurs naturally in Earth's atmosphere as a trace gas.