Mutations that result in no gene product or totally nunfunctional gene products are called:
a. isomers
b. isoalleles
c. null alleles
d. lethal alleles
e. forward alleles

c. null alleles

Explanation:

Genetic mutation can produce a non functional allele called as null allele. There might not be any product from this allele or a defective product might be produced. If the mutant allele does not even produce a RNA transcript, it is called as RNA null. If it is not able to produce the final protein product, it is called a protein null.

An example of null allele is The O blood group. Due to a mutation in the gene producing A antigen, an enzymatically inactive protein is produced by O blood group people. Both the copies of null allele O are required for O phenotype to be present.  

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation:

what's the question ?