Chapter 8: Abberations Flashcards
Chromosomes can be identified by
- location of centromere
- size
- banding patterns
Metacentric
centromere near the middle of the chromosome
Subcentric
centromere slightly off-center
Acrocentric
centromere significantly off-center but not at either end
Telocentric
centromere is at one end
Chromosomes are numbered according to
size (large to small)
Banding patterns are used if
multiple chromosomes have a similar size and centromere location.
Stains are applied to see what?
banding patterns
Deletion
the condition in which a segment of chromosomal materials is missing
Duplication
repetition of a segment of DNA more than once within a genome
Inversion
a change in the direction of genetic material along a chromosome in which a segment is flipped so it runs in the reverse direction
Translocation
the phenomenon in which one segment of a chromosome breaks off and becomes attached to a different chromosome or a different part of the same chromosome
_______ alters the total amount of genetic material in the chromosome
deletion
_______ tends to be terminal
deletion
_______ occurs when a chromosome breaks in 1 or more places and a fragment is lost
deletion
terminal deletion
at the end of a chromosome
interstitial deletion
internal segment lost
deletion effects depend on if __________ or ____________ genes were lost
essential, nonessential
_______ alter the total amount of genetic material in the chromosome
duplications
extra material is gained in
duplications
may be caused by abnormal crossing over i.e. misaligned homologous chromosomes
duplications
Pericentric inversion
the centromere is located within the inverted region of the chromosome
paracentric inversion
the centromere is found outside the inverted region
inversions cause it to run
in the opposite direction
does not affect the amount of genetic material
inversions
piece of a chromosome is attached to another, not its sister chromatid.
translocations
Balanced translocation
does not alter the total amount of genetic material
unbalanced translocation
results in a cell having too much or too little genetic material compared to a normal cell
Robertsonian translocation
*most common type in humans
* REARRANGEMENT OF GENETIC MATERIAL THAT ARISES FROM BREAKS NEAR THE CENTROMERES OF TWO NONHOMOLOGOUS ACROCENTRIC CHROMOSOMES
two types of changes in chromosome number
- variation in the number of SETS of chromosomes
- variation in the number of chromosomes WITHIN a set
Euploid
an organism in which the chromosome # is an exact multiple of a chromosome set.
Ex. Dipliod (2n), Triploid (3n), Tetraploid (4n)
Aneupliod
an abnormal variation in chromosome # such that the total # of chromosomes is not an exact multiple of a set or number.
Ex. 2n+1, 3n-1: an aberration of euploidy
Endopolyploidy
occurrence of cells that are polyploid in an otherwise diploid animal
Euploidy variations
variation in the # of sets of chromosomes
Aneuploidy variations
variation in the # of chromosomes within a set
causes an imbalance of gene expression
Aneuploidy variations
often detrimental to phenotype
Aneuploidy variations
Meiotic Nondisjunction
chromosomes do not segregate equally during meiosis
Mitotic Nondisjunction
chromosomes do not segregate equally during mitosis
- will result in gametes with the incorrect amount of chromosomes
- effects differ based on if it occurs in meiosis 1 or 2
Meiotic Nondisjunction
*Occurs in somatic cells
*Abnormality in chromosome # is occurring after fertilization
Mitotic Nondisjunction
Two possibilities of Mitotic Nondisjunction
- sister chromatids separate improperly
- sister chromatid improperly attached to mitotic spindle is degraded
Mosaic
cells of part of an organism differ genetically from the rest of the organism.
