The right answer is <span>Refractory period.
At the moment when the action potential is emitted, the fiber being depolarized, it is impossible to depolarize it again. It is, therefore, necessary to wait until the membrane potential returns to a value below the critical threshold in order to be able to excite it again. We are thus led to distinguish two periods that characterize its excitability.
An absolute refractory period: during which any stimulation, even supraliminal, is ineffective since the fiber is already depolarized.
A relative refractory period: during which a second action potential can be omitted provided that the depolarization produced by the excitation reaches the critical threshold, which implies that it is more important since the value of the resting potential has not been restored yet.</span>
Answer:
Cystic fibrosis mutation is recessive to normal allele because only one functional or normal allele is enough to produce a functional protein. So, if mutation is present in one allele then also, a normal protein can be made from normal allele. The presence of normal protein prevents the expression of disease.
In addition, mutated allele only results in the loss of function of protein which can be compensated by the expression of normal allele. It does not add any toxic effect to the protein. Consequently, the disease is inherited in autosomal recessive fashion.
In contrast, Huntington mutation not only alters the structure of the functional protein but also adds toxicity to it. The altered protein is enable to interact with 100s of other proteins and inhibit or decrease their function. So, if only one allele is present then also, the mutated protein will be produced and it will result in the phenotype. Consequently, it is inherited as autosomal dominant fashion.
<span>Australopithecus afarensis</span>
Phenotype - short , Tall
Genotype - tt (short) , TT or Tt (tall)
<u>Explanation:</u>
In Mendelian Genetics, <em>Dominant traits</em> are represented by capital letters and <em>Recessive traits</em> are represented by small letters.
So if height is the character considered, then the traits would be short and tall.
Tall is the dominant phenotype and short is the recessive phenotype.
The alleles of the gene for height are T and t.
The genotype for Tall trait is TT or Tt.
The genotype for short trait is tt.
Therefore, the symbol representation of phenotype (Tall) is TT or Tt and for phenotype (short) is tt.
Answer:
The result of mitosis is two identical daughter cells, genetically identical to the original cell, all having 2N chromosomes. ... A chromatid, then, is a single chromosomal DNA molecule.
