Answer:
An anticodon is a trinucleotide sequence complementary to that of a corresponding codon in a messenger RNA (mRNA) sequence. An anticodon is found at one end of a transfer RNA (tRNA) molecule.
Explanation:
A nonfunctional CD4 protein on a helper T cell would result in the helper T cell being unable to interact with a class II MHC-antigen complex
Importance of Class II MHC-Antigen complex
- CD4+ T cell-dependent immunological responses need antigen presentation restricted to MHC class II.
Professional antigen-presenting cells (APCs) perform a range of functions that are essential for the generation of an effective and specific immune response.
- Dendritic cells (DCs) investigate their surroundings and gather foreign antigens, such as those derived from bacteria or viruses, before activating CD4+ and CD8+ T cells to initiate adaptive immune responses against these antigens.
- The thymus' DCs and epithelial cells express (and also capture) a diverse set of self-proteins that contribute to both central and peripheral tolerance.
Recognizing the processes involved in the creation (and stability) of peptide-MHC class II complexes in APCs provides crucial information about T cellular metabolism including both normal and pathological settings.
Hence, the correct answer is option D
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Answer: Natural selection is selection due to environmental conditions from random genetic mutations in a population. Among the variants in a population, some will be slightly better adapted to conditions and will eventually out-compete the rest of the population. Survival of the fittest actually means survival of the best adapted, or fittest for purpose, i.e. to survive and thrive.
Explanation: This phrase has caused much miunderstanding of the evolutionary process. ‘Fittest’ has been equated with biggest, or strongest or fastest, but this was a description originating in the nineteenth century, when it was understood quite differently.
Natural selection arises from genetic variation in a population. Jaques Monod, an esteemed scientist, described evolution as where chance and opportunity meet. Chance lies in the genome of a species, random mutations, and the resulting genetic variation in the population.
Opportunity lies in the environment. Environmental change creates opportunities for some, extinction for others. Opportunities can also be from exploiting new environmental niches.
Natural selection is the process by which some random genetic variation gives some of a population a competitive advantage. competition eventually results in one population out-competing all others in its niche. The end-result of competition in nature is monopoly.
But this process continues and further random mutations can result in another population becoming better adapted. That is the actual meaning of survival of the fittest: in modern terms we might say ‘fittest for purpose’, that is, the species orvpopulation best adapted to survive and thrive in that environment.
Answer: answer A
Explanation:
All of the cells definitions are correct and that’s how we learned which one was different
Answer:
The key role of checkpoint proteins is to detect DNA damage and send a signal to delay cell cycle advance until the damaged chromosomes are repaired
Explanation:
