Chromosomal Abnormalities Flashcards
Abnormal chromosomes account for at least____ percent of spontaneous abortions, yet only____ percent of newborns have abnormal chromosomes.
Therefore, most embryos and fetuses with abnormal chromosomes stop developing before birth.
50
0.65
When one chromosome is missing
Monosomy
Example:
A fruit fly could be lacking a single chromosome, such as chromosome 1, and contain a total of seven chromosomes (2n-1).
This animal is_____ and is described as having____
monosomic
monosomy 1.
When one extra chromosome is present
Trisomy
Example:
An abnormal fruit fly could have 9 chromosomes instead of 8 because it has three copies of chromosome 2 instead of the usual number of two copies.
Instead of being perfectly diploid (2n), a_______ animal is 2n +1
Trisomy
trisomic
The abnormalities in the number of chromosomes.
Changes to the number of chromosomes present.
NUMERICAL ABERRATONS
A normal chromosome number which means “good set”
Where an organism has the correct number of complete chromosome sets
EUPLOIDY
A cell with “extra sets” of chromosomes.
Occurs when an organism has more than two complete sets of chromosomes.
POLYPLOIDY
Very common among flowering plants, including roses, banana, strawberry, cotton, barley, and wheat, and in some insects.
The human liver has tetraploid (4N) and octaploid (8N) cells.
Polyploidy
Uneven distribution of chromosomes in meiosis.
A chromosome pair fails to separate at anaphase of either the first or second meiotic division. This produces a sperm or oocyte that has two copies of a particular chromosome, or none, rather than the normal one copy.
NONDISJUNCTION
When such a gamete fuses with its partner at fertilization, the zygote has either 45 or 47 chromosomes, instead of the normal 46.
Meiotic error that causes aneuploidy
NONDISJUNCTION
Cells missing a single chromosome or having an extra one, which means “not good set”.
Presence of an abnormal number of chromosomes in a cell.
ANEUPLOIDY
Occurs when there is an extra chromosome (trisomy) or a missing chromosome (monosomy) within a chromosome pair.
Trisomies are less severe than monosomies
ANEUPLOIDY
The meiotic error that causes aneuploidy is called.
nondisjunction
______ is common in aneuploidy because development of the brain is so complex and of such long duration that nearly any chromosome-scale disruption affects genes whose protein products affect the brain.
Mental retardation
Abnormalities in the number of autosomal chromosomes, which are the non-sex chromosomes.
More severe than Sex Chromosome Aneuploids
Autosomal Aneuploids
Down syndrome (trisomy 21) is the most common autosomal aneuploid, followed by trisomies 18 (Edwards syndrome) and trisomy 13 (Patau syndrome)
Most________ are spontaneously aborted. Those that survive have specific syndromes, with symptoms depending upon which chromosomes are missing or extra.
Autosomal Aneuploids
People with sex chromosome aneuploidy have extra or missing sex chromosomes.
Sex chromosome aneuploidy usually produces milder symptoms.
Sex Chromosome Aneuploids
Sex Chromosome Aneuploids
Turner syndrome (X)
Triplo X syndrome (XXX)
Klinefelter syndrome (XXY)
XXYY syndrome
XYY syndrome
______ have extra sets of chromosomes and do not survive for long.
______have extra or missing chromosomes.______ during meiosis causes aneuploidy.
_______are less severe than monosomies, and _______ aneuploidy is less severe than autosomal aneuploidy.
Polyploids
Aneuploids
Nondisjunction
Trisomies
sex chromosome
Mitotic nondisjunction produces chromosomal______.
_______ is the most common autosomal aneuploid, followed by trisomies 18 and 13.
Sex chromosome aneuploid conditions include (5) syndromes.
mosaics
Down syndrome (trisomy 21)
XO, triplo-X, XXY, XXYY, and XYY
Missing, extra, or inverted genetic material within a chromosome or combined or exchanged parts of non-homologs (translocations)
STRUCTURAL VARIATIONS
normal amount of genetic material persists (inversions and balanced transloca- tions)
BALANCED
if excess or deficient DNA results (dupli- cations and deletions, which may be caused by inversions or translocations).
UNBALANCED
one segment of a chromosome becomes attached to a different chromosome or to a different part of the same chromosome.
TRANSLOCATION
Types of invertion: SURRI
Simple Translocaction
Unbalance Translocation
Reciprocal Translocation
Rebertsonian Translocation
Insertional Translocation
Single piece of chromosome is attached to another chromosome
SIMPLE TRANSLOCATION
Two different chromosomes exchange pieces, altering total amount of genetic material is not altered occur without any phenotypic consequences
RECIPROCAL TRANSLOCATION (BALANCED TRANSLOCATIONS)
Significant portions of genetic material are duplicated and/or deleted.
Generally associated with phenotypic abnormalities or may even be lethal.
UNBALANCED TRANSLOCATIONS
William Robertson, who first described this type of rearrangement in grasshoppers.
Arises from breaks near the centromeres of two nonhomologous acrocentric chromosomes.
Most common type of translocation that occurs in humans
ROBERTSONIAN TRANSLOCATION
A rare type of translocation
One chromosome inserts into a nonhomologous chromosome
INSERTIONAL TRANSLOCATION
Segment of chromosomal material is missing.
Deficient in a significant amount of genetic material.
DELETION
TYPES OF DELETION
________: chromosome has broken in two places and the broken ends have fused, leaving out the deleted segment.
________: a deletion that occurs towards the end of a chromosome.
Interstitial deletion
Terminal Deletion
CRI-DU-CHAT
Caused by a deletion in a segment of the_____ arm of human chromosome 5____
mental deficiencies, unique facial anomalies, and, in infancy, an unusual catlike cry,
short; (five)
A part of the chromosome is present more than once.
Ex. Down syndrome
DUPLICATION
A position of one chromosome has been deleted from its normal place and inserted into another chromosome.
ex
Chronic Myelogenous Leukemia (CML)
INSERTION
a rearrangement of chromosome that involves two breaks within a single chromosome
INVERTION
Types of invertion:
________
An inversion involving only one arm of the chromosome
_________
If the breaks are on opposite sides of the centromere
Pericentric inversion
Paracentric inversion
A chromosome abnormality when one arm of the chromosome is DUPLICATED and the other is LOST or DELETED
Chromosome divides in a HORIZONTAL/TRANSVERSE pattern
The resultant chromosome are IDENTICAL (ISO-MIRROR IMAGE, SAME
ISOCHROMOSOME
Most common sex chromosome abnormality in FEMALES
An isochromosome of the long arm, 46,X,i(X)(q10) resulting in the loss of the SHORT ARM
characteristics include SHORT STATURE and INFERTILITY
TURNER’S SYNDROME. 46,X,I(XQ)
may form when telomeres are LOST, leaving sticky ends that adhere forming a circular or a ring shaped
These problems could include things like learning disabilities, seizures, developmental delays, and other health problems, DEPENDING on which part of the chromosome is affected
RING CHROMOSOME
EXAMPLES OF RING CHROMOSOME DISORDERS
__________
developmental delay, slow growth and short stature, feeding difficulties, learning difficulties, a small head size, abnormal formation or positioning of the feet and/or toes, and/or abnormalities of the palate
___________
Early onset refractory epilepsy, a seizure disorder, Intellectual disability Autism spectrum disorder, Characteristic facial features. Other health issues, including feeding difficulties
Ring chromosomes 13
Ring chromosome 14
Types Of abnormality associated with the chromosome number
- Extra chromosome sets
- An extra or missing chromosome (“not good set.”)
- One chromosome absent
- One chromosome extra
Polyploidy
Aneuploidy
Monosomy
Trisomy
