Chromosomal Aberrations, Classification, and Viruses

Posted on Mar 2, 2025 in Biology

Chromosomal Aberrations

A chromosomal aberration is a change in the structure or number of chromosomes.


Types of Chromosomal Aberrations

Numerical

Polyploidy

triploidy (3n)

tetraploidy (4n)

Aneuploidy

monosomy (2n-1)

trisomy (2n+1)


Structural

Translocation

Deletion

Duplication

Inversion


*Humans only need one X chromosome; women have two. A condensed X chromosome is known as a Barr Body.*


Syndromes

Down Syndrome – In chromosome 21 (47,xy,+21) – 1 per 800

Edwards Syndrome – In chromosome 18 (47,xy,+13) – 1 per 6,000

Patau’s Syndrome – In chromosome 13 (47,xy,+13) – 1 per 10,000

Turner’s Syndrome – Missing X chrom (45,X)

Klinefelter’s Syndrome – 47(XXY)

Fluorescence in “situ Hybridization”. Used to detect chromosomal aberrations (uses nucleotides with fluorescent markers)

Diseases caused by translocation:

 Granulocytic leukemia

o Exchange between chromosome 9 and 22

 Burkitt’s lymphoma

o Exchange between chromosome 8 and 14

Syndrome caused by deletion:

Cri du chat syndrome (short end of chrom. 5 is deleted)

Caused by inversion:

(inversion of gene in long arm of X chrom.)

Caused by duplication:

Disorders in the nervous system (duplication of PMP-22 in chrom. 17)


Classification of Living Things

Biodiversity – all organisms living with their unique features

Systematics – classification of living things

  • Back then species were classified on very simple features (morphological & anatomical)


Types of features:

Anatomical, biochemical, morphological, physiological.

Dog: Canis Familiaris

Cat: Felis Catus

Tulip: Tulipa Gesnerana

  • First system of classification was made by Aristotle
  • Carolus Linnaeus = father of taxonomy
    • Wrote Sistema naturae (had the names of species)
  • Charles Darwin studied and published books about evolution of animals and humans.

Divisions:

Domain, kingdom, phylum, class, order, family, genus and species. KPCOFGS

3 Domains:

Archaea (Archaebacteria)

Bacterium (Eubacteria)

Eukarya (Protista, plantae, Animalia and fungi)

*Organisms are either prokaryotes or eukaryotes*

Prokaryotes: mostly bacteria

Eukaryotes: plants, animals and fungi

Taxonomy

Numerical – number of similar features

Evolutionary – common origin and similarities

Cladistic – common origin


Viruses

Differences between viruses and cells

  • Cells reproduce independently and viruses don’t
  • Viruses don’t have cell structure
  • Living cells go through metabolism
  • Cells have both RNA and DNA but viruses only have 1


Pathogens – microorganisms that can cause disease
Example: viruses, viroids and prions
Classification:
Type of NA, size, shape, envelope (present or
not) and their host.

Viral replication process:

  1. Virus attaches to the cell
  2. Viral genome enters the cell
  3. Genome replicates and proteins are made
  4. New viral units are formed from what was produced
  5. Viral units leave the cell

Caused by bacteria: Cholera, Plague, Scarlet fever, Tuberculosis, Syphilis, Salmonellosis, Whooping cough, Typhoid fever.

Caused by virus: Flu, Herpes, Measles, Chickenpox, Mumps, Yellow fever, Rabies, AIDS.

Host – organism where virus multiplies
Pathogenesis – disease development
Epidemic – many people with same disease in an area
Reservoir h. – organism that is source of infection
Latency – virus multiplies without notices
Prophylactic action – prevention against infections.

Other Types

Viroids:

  • The smallest pathogens
  • Have RNA with no protein coating
  • Inhabit plants (can transfer through pollen)

Prions

  • “misfolded proteins”
  • Causes brain diseases in humans and animals
  • Doesn’t show signs until already incubated