Question

Полипептид состоит из 548 аминокислот, его ген содержит 2396 пар нуклеотидов. Определите структуру гена, его длину, массу, нуклеотидный состав, если размер 1 нуклеотида 0,34 нм, относительная молекулярная масса 300 и в гене содержится 12% аденина. Почему возможно образование разных изоформ белка?

Answer 1

Эти соединения состоят из аминокислот, связанных между собой пептидными связями. Молекулярная масса полипептидов составляет не более 10000 D. Они осаждаются сульфатом аммония, фосфоровольфрамовой кислотой, как белки, но, отличаются от белков тем, что не задерживаются целлофановой мембраной при диализе. Ди- и трипептиды не осаждаются этими реактивами.

Answer 2

Gene Structure, Length, and Mass

The gene in question contains 2396 base pairs (bp) of nucleotides Given that the size of one nucleotide is 0.34 nm, we can calculate the length of the gene as follows:

Length = Number of base pairs * Size of one nucleotide Length = 2396 bp * 0.34 nm/bp

To find the mass of the gene, we need to know the molecular weight of a nucleotide. The relative molecular mass of a nucleotide is 300. Therefore, the mass of the gene can be calculated as:

Mass = Number of base pairs * Molecular weight of a nucleotide Mass = 2396 bp * 300 g/mol

Nucleotide Composition

The nucleotide composition of the gene can be determined by analyzing the percentage of each nucleotide present. It is mentioned that the gene contains 12% adenine (A). To calculate the composition of the other nucleotides, we can assume that the remaining percentage is distributed equally among the other three nucleotides (cytosine, guanine, and thymine). Therefore, each of these nucleotides would constitute (100% - 12%) / 3 = 29.33% of the gene.

Formation of Different Protein Isoforms

The formation of different protein isoforms can occur due to various mechanisms, including alternative splicing, post-translational modifications, and differential gene expression. These mechanisms can lead to the production of proteins with different amino acid sequences or modifications, resulting in distinct protein isoforms.

Alternative splicing is a process in which different combinations of exons are included or excluded during mRNA processing, leading to the production of multiple mRNA transcripts from a single gene. Each mRNA transcript can then be translated into a different protein isoform with unique functional properties.

Post-translational modifications, such as phosphorylation, acetylation, and glycosylation, can also contribute to the formation of different protein isoforms. These modifications can alter the structure and function of the protein, allowing it to perform different roles within the cell.

Differential gene expression refers to the regulation of gene expression in different tissues or under different conditions. This can result in the production of different protein isoforms from the same gene in different cell types or in response to specific stimuli.

In summary, the formation of different protein isoforms can occur through alternative splicing, post-translational modifications, and differential gene expression, allowing for functional diversity and adaptation to different cellular contexts.