Basics of Medical Genetics - Buzhiyevska T.I. 2001

Medical and Genetic Counseling
Genetic Glossary

Acrocephaly — a "steeple" or tower-like HEAD shape.

Allele — one of two or more alternative versions of a Gene that have a unique nucleotide sequence.

Alopecia — absence or loss of Hair; baldness.

Angiomatosis — a pathological condition of Blood Vessels involving The formation of angiomas.

Aneuploidy — a condition in which a Cell, tissue, or Organism has an abnormal number of Chromosomes, lacking one or more or having additional copies.

Aniridia — absence of the iris of the eye.

Ankylosis — stiffness or immobility of a joint.

Anodontia — Congenital absence of Teeth.

Anomalad — a developmental anomaly accompanied by various secondary defects resulting from the primary malformation.

Anonychia — absence of the nail on one, several, or all fingers or toes.

Aplasia — congenital absence of an organ or tissue.

Arachnodactyly — abnormally long and slender fingers and toes ("spider fingers").

Atresia — absence, closure, or obliteration of a natural body channel or opening.

Autosome — any chromosome other than a sex chromosome.

Blepharophimosis — narrowing of the palpebral fissure.

Brachydactyly — shortness of fingers and toes.

Brachycephaly — disproportionate shortness of the transverse diameter of the head (broad head).

Buphthalmos — congenital glaucoma.

Vitiligo — a condition characterized by the appearance of depigmented patches on the Skin.

Haploid — Cells (such as Gametes) containing half the number of chromosomes found in somatic cells.

Haplotype — a combination of alleles at tightly linked loci; a combination of specific nucleotide sequences on a single DNA molecule.

Hemizygous gene — a gene that is present in only a single copy in the genotype.

Gene — the fundamental structural unit of heredity; a nucleotide sequence with a specific function, such as coding for Polypeptides, rRNA, and tRNA, or regulating the METABOLISM/31.html">Transcription of another gene.

Genetic monitoring — tracking the rate and spectrum of the Mutational Process.

|Genocopies — disorders that share the same or similar clinical phenotype.

Genome — the genetic constitution of haploid organisms or cells with a haploid chromosome set.

Genotype — The system of interacting genes within an organism.

Gene pool — the complete set of genes within a population.

Heterozygote — a cell or organism carrying two different alleles at a corresponding locus on homologous chromosomes.

Heterozygosity — the proportion of individuals in a population that are heterozygous at a given locus, or the proportion of heterozygous loci within a genotype.

Hybrid — the offspring resulting from a cross between two genetically distinct organisms.

Hyperhidrosis — excessive sweating.

Hypertelorism — an abnormal increase in the distance between paired Organs (such as the eyes or nipples).

Hypertrichosis — excessive hair growth.

Hypogeusia — reduced sense of taste.

Hypospadias — an abnormality in which the urethral opening is on the underside of the Penis.

Hypotrichosis — abnormal deficiency of hair.

Hirsutism — abnormal hairiness or excessive hair growth.

Homozygote — a cell or organism carrying two identical alleles at a specific locus on homologous chromosomes.

Homozygosity — the proportion of individuals in a population that are homozygous at a given locus, or the proportion of homozygous loci within a genotype.

Homologous chromosomes — chromosomes (or chromosome segments) identical in the arrangement of their loci; members of the same chromosome pair.

Deletion — a chromosomal or gene mutation resulting in the loss of a specific segment of a chromosome or gene.

Sprengel's deformity — a congenital downward Displacement of the scapula.

Diploid — a cell, tissue, or organism containing two complete sets of chromosomes.

Diastema — a space or gap between the upper central incisors.

Dolichostenomelia — excessively long and slender limbs.

Dolichocephaly — an elongated Skull shape.

Dominant — an allele or phenotypic trait that is expressed in the heterozygous state.

Exon — a DNA sequence corresponding to a portion of the transcript that is retained in mature mRNA after the removal of introns.

Expressivity — the degree or extent to which a genotype is phenotypically expressed.

Ectopia lentis — dislocation of the crystalline lens of the eye.

Epicanthus — a vertical fold of skin near the inner corner of the eye.

Episome — a genetic element (a DNA molecule that exists either as an integrated part of the host DNA molecule or as a autonomously replicating DNA molecule (plasmid) not linked to The Cell chromosome.

Epispadias — a congenital condition where the Urethra opens on the dorsal surface of the penis.

Linkage — the degree of association between alleles of different genes during Meiosis or genetic crossing.

Imprinting — epigenetic marking of DNA that occurs during gametogenesis and causes stable modifications in the expression of homologous genes.

Inbreeding — mating between closely related individuals.

Intron — a non-coding nucleotide sequence in eukaryotic DNA that splits a gene into parts.

Iridodonesis — tremor of the iris associated with dislocation of the crystalline lens.

Camptodactyly — flexion deformity of one or more fingers involving the proximal interphalangeal joints.

Karyotype — the chromosomal Complement of a cell or organism, characterized by the number, size, and configuration of the chromosomes.

Keratoconus — a cone-shaped protrusion of the cornea.

Code — a set of rules for translating information from one language into another.

Codon — a sequence of three adjacent NUCLEOTIDES in a DNA or mRNA molecule that encodes a specific amino acid or signals the termination of Protein Synthesis.

Inbreeding coefficient — the probability that two alleles at a given locus are identical by descent.

Coloboma — a congenital cleft-like defect, most commonly found in Anomalies of the Eyeball.

Cryptorchidism — failure of one or both Testes to descend normally into the Scrotum.

Cryptophthalmos — a congenital anomaly characterized by complete fusion of the eyelids.

Xerostomia — dryness of the Mouth.

Lagophthalmos — incomplete closure of the eyelids.

Lethal mutation — a gene or chromosomal mutation that causes the death of the organism (all carriers in the case of dominance, or homozygous carriers in the case of recessiveness) before reaching reproductive age.

Locus — the specific physical Location of a gene or mutation on a genetic map; often used interchangeably with the terms 'mutation' or 'gene'.

Macroglossia — abnormal enlargement of the Tongue with prominent folding of the mucous membrane.

Macrosomia (gigantism) — excessive enlargement of the body and Internal Organs.

Macrostomia — excessive width of the oral fissure (mouth).

Template — a single-stranded DNA complementary to the DNA or RNA strand being synthesized on it; it determines The nucleotide sequence in the newly synthesized strand.

Microglossia — an abnormally small tongue.

Micrognathia — underdevelopment of the upper jaw.

Micromelia — abnormal reduction or shortening of the limbs.

Microphakia — reduction in the size of the eye lens caused by arrested development.

Microphthalmia — reduction in all dimensions of the eye.

Microcephaly — abnormally small head.

Monozygotic twins — twins derived from a single zygote.

Mutagens — factors that induce Mutations.

Mutant — an organism carrying a mutant allele.

Mutation — a stable, spontaneously occurring change in the genetic apparatus that leads either to the transition of a gene from one allelic state to another, or to various alterations in the number or Structure of chromosomes.

Mutagenesis — the process by which heritable changes appear in the genetic program.

Nystagmus — involuntary, rapid movement of the eyeballs, either horizontal or vertical.

Norm of reaction — the range of all possible phenotypes that can develop from a given genotype under various environmental conditions.

Sex-limited traits — genetically determined traits that phenotypically manifest in individuals of only one sex.

Omphalocele — an umbilical hernia.

Oncogene — a gene whose alteration can lead to the malignant Transformation of a cell.

Penetrance — the probability of phenotypic expression of a specific trait encoded by a dominant gene or by a recessive gene in the homozygous state.

Pleiotropy — The Influence of a single gene on multiple phenotypic traits.

Polygenic traits — traits encoded by many genes, each of which individually has a minor effect on the degree of trait expression.

Polydactyly — an increased number of fingers on the hands or toes on the feet.

Polymorphism — the presence of Multiple Forms of a gene within a population.

Polyploid — a cell, tissue, or organism possessing three or more sets of chromosomes.

Polyphagia — excessive appetite, gluttony.

Population — a group of organisms of the same species inhabiting a specific area for a long period (over many generations), capable of freely interbreeding, yet separated from neighboring groups by some form of isolation.

Proband — an affected or unaffected individual who seeks MEDICAL Genetic Counseling and from whom the pedigree chart is initiated.

Prognathia — excessive protrusion of the lower jaw.

Pterygium colli (webbed neck) — a congenital thick skin fold on the lateral aspect of the neck.

Ptosis — drooping of the upper eyelid.

Retrognathia — posterior displacement of the upper jaw relative to the normal facial profile.

Recessive — an allele or trait that is expressed only in the homozygous state.

Pedigree — a diagram illustrating the familial relationships among members of a family across two or more generations.

Segregant — an individual who has inherited a mutant gene from phenotypically healthy heterozygous carrier parents for a recessive gene, or from carriers of a non-penetrant dominant gene.

Segregation — the inheritance of mutant genes from parents.

Syndactyly — partial or complete fusion of two or more fingers or toes.

Synophrys — broadening and fusion of the eyebrows.

Sirenomelia — fusion of the lower limbs.

Sex chromosomes — chromosomes that differ between the sexes and determine the sex of an individual.

Strabismus — squint or crossed eyes.

Telecanthus — increased distance between the inner corners of the eyes with normally positioned orbits.

Transcription — the process by which Genetic information encoded in a DNA nucleotide sequence is copied into a complementary RNA nucleotide sequence.

Translation — the decoding of instructions from the language of DNA (nucleotide alphabet) into the language of Proteins (amino acid alphabet).

Phen — an observable trait or characteristic of an organism.

Phenocopies — non-hereditary phenotypic modifications that mimic the phenotype of a hereditary mutation.

Phenotype — the observable characteristics of an organism resulting from the expression of its genotype in a given environment.

Philtrum — the vertical groove between the Nose and the upper lip.

Phocomelia — absence of certain proximal PARTS OF THE limbs.

Chromatids — the two longitudinal subunits of a duplicated chromosome visible during Mitosis and Meiosis.

Chromosome — a thread-like structure in the Cell Nucleus consisting of linearly arranged genes; in Eukaryotic cells, the DNA molecule forms a complex with Histones and other proteins.

Chromosome set — the complement of chromosomes in The Nucleus of a germ or somatic cell.

Cyclopia is a single or doubled eye located in the middle of the forehead.

Answers TO Questions and Problems

1. Genotype is the system of interacting genes of an organism.

2. Hereditary diseases are disorders associated with damage to genetic structures.

3. DNA Diagnostics, determination of an abnormal gene product or its deficiency.

4. Guthrie test, biochemical blood and urine tests, DNA diagnostics.

5. Cytogenetic, clinical-genealogical.

6. Alternative.

7. Allelic genes are alternative forms of a gene characterized by a unique nucleotide sequence.

8. Gamete is a mature germ cell capable of fusing with a similar cell of the opposite sex.

9. Dominant gene is an allele that is expressed in a heterozygous organism.

10. An organism heterozygous for a given trait is one that carries different alleles at a given locus on homologous chromosomes.

11. Phenotype is the set of observable characteristics of an organism.

12. 25%.

13. 0%

14. 50%

15. 0%

16. 50%.

17. Yes.

18. 50%.

19. Combinative Variability is the recombination of genes and chromosomes with different alleles, resulting in a diversity of offspring.

20. Mutational variability is The Emergence of new variants of discrete units of genetic material.

21. Gene, chromosomal, and genomic mutations.

22. Mutations induced by physical, chemical, and biological factors.

23. Genetic structures of the nucleus, Mitochondria, and Plasmids.

24. Deletions, insertions, rearrangements, base-pair substitutions, etc.

25. Deletions, deficiencies, duplications, insertions, inversions, translocations; chromatid, interchromatid, chromosomal.

26. In the form of lethal and sub-lethal effects, Mendelian and hereditary diseases, congenital malformation syndromes, and

also as a basis for The Development of ecogenetic pathology and in the form of organismal trait polymorphism.

27. In the form of Chromosomal diseases and cytogenetic disorders of chromosome number or structure.

28. Modification Variability — alteration of an organism's phenotype within the norm of reaction in response to a specific change in environmental conditions.

29. Pharmacogenetics — the science studying the genetic determination of an organism's response to drugs.

30. Genomic Imprinting — structural and molecular changes in genes occurring during gametogenesis that lead to stable modifications of homologous Gene Expression.

31. In all nucleated cells (Somatic and Germline),

32. Hereditary metabolic defects.

33. Non-selectivity, mass scale, preventive nature.

34. Defect at the gene product level.

35. Clinical-genealogical analysis, urinalysis, Thin-Layer Chromatography, Guthrie test, spectrofluorometry, DNA diagnostics.

36. Glycosaminoglycans and specific Enzymes of mucopolysaccharide metabolism.

37. A defined nucleotide sequence in DNA and RNA molecules.

38. Transcription — copying of information from a double-stranded DNA molecule to a single-stranded RNA molecule.

39. Translation — The process of Protein Synthesis on Ribosomes guided by a Messenger RNA template, or the translation of information from the language of Nucleic Acids into the language of proteins.

40. Triplet, degenerate, continuous, universal.

41. Patau syndrome.

42. No.

43. Galactosemia.

44. To chromosomal diseases.

45. Purine metabolism disorders.

46. No.

47. Thin-layer chromatography of urinary CARBOHYDRATES.

48. De Toni — Debré — Fanconi Syndrome.

49. Prader — Willi syndrome.

50. By means of Cytogenetic Methods and DNA diagnostics.

51. Celiac disease.

52. In a heterozygous mother and an affected father (most commonly in consanguineous marriages).

53. 45,X0.

54. Noonan syndrome.

55. Milk and dairy products.

56. Wilson — Konovalov disease.

57. 40-50%.

58. Homocystinuria.

59. Gangliosidoses, mucolipidoses.

60. Autosomal dominant with incomplete penetrance and expressivity.

61. In the second half of life.

62* Mitochondrial defects associated with chromosomal or mitochondrial mutations, whether inherited or acquired.

63. Yes.

64. Molecular diagnostic methods at the DNA level.

65. At middle age, after 30 — 40 years.

66. In the first years of life.

67. Determination of alpha-fetoprotein, Ultrasound examination.

68. Ultrasound examination and obstetrician-gynecologist supervision.

69. Chorionic villus sampling for cytogenetic analysis, ultrasound examination.

70. Fetal ultrasound examination, determination of serum alpha-fetoprotein, amniocentesis (cytogenetic analysis of fetal cells).