8 topics with a brief review: definitions, key facts, and classroom questions.
This section focuses on the ability of living organisms to acquire new traits during ontogenesis and across generations. You will examine how the phenotype adapts to the environment (modificatory variability) and how gene shuffling creates unique combinations in offspring (combinative variability).
Special attention is paid to mutational variability, the basis of evolution and the pathogenesis of many hereditary diseases. The articles provide detailed breakdowns of gene, chromosomal, and genomic mutations, as well as the nature of mutagenic factors that trigger these alterations. RNA interference, a critical mechanism of gene expression regulation, is also covered.
In practical classes and exams, instructors most frequently ask students to classify mutations by the level of DNA damage, clearly distinguish between non-hereditary and hereditary variability, and provide examples of human chromosomal and genomic pathologies associated with specific mutagens.
These are small interfering RNAs (siRNAs). Structurally, they are short double-stranded RNA molecules consisting of exactly 21–23 base pairs.
Are modifications inherited?
No, modificatory changes themselves are not inherited because they do not affect genes. Only the norm of reaction—the genetic boundaries within which a trait can vary—is passed on.
Does the structure of the genes themselves change during combinative variability?
No, the genes themselves remain unchanged. Only their combination changes, leading to the appearance of new trait complexes in the offspring.
Are somatic mutations inherited?
During sexual reproduction, no. They occur in somatic body cells rather than germ cells, and therefore are not transmitted to offspring.
What is the main difference between transition and transversion?
During transition, bases of the same type are substituted for one another (purine for purine, pyrimidine for pyrimidine). Transversion involves a cross-substitution where a purine is replaced by a pyrimidine or vice versa.
What happens to a chromosome fragment if it breaks off without a centromere?
Such a region is called acentric. During the nearest mitosis, it cannot attach to the spindle fibers and is permanently lost by the cell.
Master the entire topic in the "Biology" course
This is a summary. The course covers everything tested in classes and exams.
3,793 pages of study guides across all topics
Assignments and quizzes after every topic — just like in a colloquium