17 topics with brief breakdowns: definitions, key facts, and class questions.
Molecular genetics studies how hereditary information is stored, transmitted, and expressed at the biochemical level. It is the fundamental basis required to understand the pathogenesis of hereditary diseases and the principles of molecular diagnostics.
In this section, we will analyze in detail the structure of DNA and types of RNA, template-directed processes (replication, transcription, translation, and processing), and mechanisms of genome defense—repair. A separate focus is placed on the regulation of gene activity: from classical prokaryotic operons and hormone action to eukaryotic epigenetics, including chromatin remodeling and genomic imprinting.
Classes and exams most frequently require explaining the properties of the genetic code, the mechanism of transcription factors, and ribosomes. Pay special attention to the concepts of penetrance and expressivity, as well as epigenetic mechanisms—currently the most relevant and frequently asked topics at the intersection of fundamental biology and medicine.
This is a situation where a mutant gene phenotypically manifests in 100% of its carriers, without any exceptions.
What is bacterial transformation?
This is the process of transferring hereditary traits from one set of cells (even deceased ones) to another. During transformation, living cells absorb foreign material factors and acquire new genetic traits that were not previously characteristic of them and are passed on to offspring.
What does the antiparallelism of DNA strands mean?
This is the principle of spatial organization in which two polynucleotide strands run in opposite directions. As a result, the 5'-end of one strand always corresponds to the 3'-end of the other.
What is the central dogma of molecular biology?
This is a postulate describing the direction of genetic information flow in living systems: data are read from DNA, translated into RNA format, and then used for protein synthesis.
Why does synthesis on the lagging strand occur discontinuously?
DNA polymerase is capable of attaching nucleotides in only one direction—from the 5'- to the 3'-end. Since DNA strands are antiparallel and the fork unwinds in one direction, synthesis on the lagging strand is forced to proceed 'backwards' in short segments (Okazaki fragments).
Which enzyme is key in the process of photoreactivation?
The main role is played by the enzyme photolyase. Upon activation by a quantum of visible light, it cleaves the bonds in pyrimidine dimers formed under the influence of UV radiation.
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