Answer:
genomic imprinting
Explanation:
Genomic imprinting is a mechanism for regulating gene expression that allows expression of only one of the parental alleles, although both alleles are functional. Unlike most genes in which expression is biallelic, genes that are subjected to this mechanism (imprinted genes) have monoalelic expression; By definition, in an imprinted loci, only one allele is active (maternal or paternal), and the inactive is epigenetically marked by histonic modification and / or methylation of cytosines.
Genomic imprinting can cause some disturbances, among them Prader-Willi syndrome, which is a genetic disorder that involves a partial deletion of chromosome 15q on the paternal chromosome.
A ribosome is a cell organelle. the function of a ribosome is like a micro-machine for making proteins. the ribosomes is composed of special proteins and nucleic acid. it is also formed from two sub units, locking together its function are to translate the encoded information from the cell nucleus provied by the messenger.
B) Oxygen may not have been able to accumulate in the atmosphere
Answer:
Mechanical barriers — which include the skin , mucous membranes , and fluids such as tears and urine — physically block pathogens from entering the body. Chemical barriers — such as enzymes in sweat , saliva , and semen — kill pathogens on body surfaces.
The answer is d. pheromones.
