Chromosome Aberrations Flashcards
Aberrations
abnormalities
Polyploidy
embryo has three, four, or more SETS of chromosomes (complete set duplicated)
Aneuploidy
the embryo does not have an exact multiple of the number characteristic of that species (only part of that set is wrong)
Types of aneuploidy
trisomy and monosomy
Triploid
3 sets for polyploidy
Tetraploid
4 sets for polyploidy
What is polyploidy a result of?
result of unreduced gamete (2n) and a normal gamete (n)
Give two examples of how an embryo can become polyploidy:
- two sperm fertilizing one egg
- haploid sperm and a diploid egg
Chromosome nondisjunction
failure of homologous chromosomes to disjoin correctly during meiosis
The probability of nondisjunction in autosomes ______________ with age.
increases
If a gamete is fertilized from a nondisjunction in autosomes then what are the results?
trisomy or monosomy
Trisomy
one chromosome extra
Monosomy
one chromosome absent
X-Monosomy
Turners syndrome
Turners syndrome
XO; results when one of the X chromosomes is missing in females causes developmental problems
Changes in chromosome structure include:
- deletion
- duplications
- inversion
- translocation
Deletion
part of the chromosome is missing
What do deletions cause?
permanent loss of genetic material
Terminal deletion
deletion close to chromosome end
Interstitial deletion
deletion within a chromosome arm
Duplication
part of the chromosome is present TWICE
Inversion
results in the reversal of the gene sequence
What is curly calf syndrome caused by?
this genetic defect is a result of the deletion of a small segment of DNA which contains an essential gene
Polled Intersex Syndrome in Goats is caused by…
11.7 kb deletion in the FOX L2 Gene
Pseduohermaphroditism in horses is caused by…
200 kb deletion in ECA29 Gene
Metafemale
“XXX” affects only females and results in three X chromosomes instead of 2
Klinefelter syndrome
“XXY” where males are born with an extra X chromosome
Structural abnormalities are…
larger regions of deletion or duplication that increase the likelihood that there will be an associated phenotype
How do ringed chromosomes form?
- break in both arms
- terminal ends fuse together
- broken arms fuse together as a ring
What percent of ringed chromosomes arise spontaneously?
99% the rest may be formed following genetic damage
Translocation
part of one chromosome exchanges place with the corresponding part of a nonhomologous chromosome
Paracentric inversion
part breaks in chromosome and reinserts itself into a piece of DNA
Pericentric inversion
the centromere breaks in chromosome and is inverted and reinserted in DNA
What is tobiano spotting caused by?
an inversion
Balanced translocation
not losing any genetic information equal switch between chromosomes
Unbalanced translocation
when an offspring inherits a chromosome with extra or missing genetic information from a parent with a balanced translocation
What is REEL in horses caused by?
a balanced translocation
Balanced translocation in pigs causes what?
smaller litter size and is very common
Translocation 1/8 in cattle causes…
slightly lowered fertility
Robertsonian translocation
centric fusion
What does Robertsonian translocation do?
fragments from non-homologous chromosomes recombine in such a way that a single centromere is retained
What does Robertsonian translocation look like?
the centromere is now shared between chromosomes and a fragment is lost
