Chapter 3. Forms of pathology caused by changes in the genome
12 topics with brief reviews: definitions, key facts, and seminar questions.
In this chapter, we examine how DNA and chromosomal aberrations lead to the development of diseases. You will study the nature of mutagens, the classification of gene and chromosomal mutations, as well as the mechanisms underlying congenital malformations and multifactorial diseases.
A separate section is dedicated to the transmission of pathological traits. We will cover all types of inheritance—from autosomal to sex-linked and mitochondrial. This knowledge will serve as the foundation for understanding the principles of clinical genetics and modern diagnostic methods for hereditary diseases.
In seminars and colloquiums, instructors most often require practical skills: you will independently perform pedigree analyses, determine the likely mode of inheritance from clinical cases, and clearly differentiate classical gene disorders from chromosomal syndromes.
Mutagenesis, or the mutational process, is the set of changes leading to the origin of mutations. As a result of this process, various types of mutations are formed.
Are somatic mutations inherited by children?
No, they are not inherited by the next generation. Somatic mutations manifest only in the individual and are passed exclusively from one somatic cell to another during its division (mitosis).
Why do neutral mutations show no phenotypic manifestation?
This is due to the degeneracy of the genetic code. A nucleotide substitution leads to the formation of a new codon that encodes the same amino acid, so the structure and function of the protein do not change.
In what state does the mutant gene manifest in an autosomal dominant disorder?
The mutant gene in an autosomal dominant type manifests in the heterozygous state.
Can healthy parents have children with an autosomal dominant disease?
Yes, but only as an exception—if the disease is the result of a newly arising mutation (de novo). In all other cases, at least one of the patient's parents must be affected.
Why are X-linked recessive diseases extremely rare in females?
For the disease to manifest, a female must receive the pathological gene from both parents, whereas a male requires only a single copy from the mother.
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