Clincal Cytogenetics Flashcards
Cytogenetics
Chromosomal abnormalities that may involve the presence of extra chromosomes, loss of chromosomes, or structural alterations
Dispermy
The fertilization of an ovum by two sperm cells
Triploidy
Cells that contain three copies of each chromosome 69 total
Robertsonian translocation involves the loss of
The short arms of the two Acrocentric chromosomes and the fusion of the long arms at the centromere
Monopolidy
The loss of a chromosome set- never seen in humans
Polyploidy
The gain of one of more entire chromosome sets
Trisomy 13 is also referred to as
Patau syndrome
Nondisjunction can occur in the gametes of
Both men and women
What is the most common trisomy among still borns
Trisomy 18 Edward Syndrome
Robertsonian translocation only involve ________ chromosomes which are:
Acrocentric
13, 14, 15, 21, 22
Down Syndrome characteristics
Intellectual disability Almond eyes GI tract obstruction Congenital heart defect High risk for leukemia Alzheimer’s-like symptoms later in life Male sterility Hearing loss Eye abnormalities
Robertsonian translocation is not seen in which trisomy
18, Edward syndrome
Instead of 46 XX or 46 XY *normal, a Robertsonian translocation will have
45 XX or 45 XY
In a child-bearing female with Robertsonian translocation, the risk of Down Syndrome occurrence is:
Much higher than the risk in general population
Small arm of chromosome
P
Why are the individuals with Robertsonian translocations phenotypically normal
The short arms of the Acrocentric chromosomes contain redundant material (rRNA genes)
Which tirsomy is most compatible with live birth
Trisomy 21
Reciprocal translocation:
Chromosomal breaks on two chromosomes, the broken chromosomes exchange material resulting in derivative chromosomes
Aneuploidy
The gain of one or loss of a single chromosome
Why are abnormalities of the sex chromosomes more tolerated than abnormalities of the autosomes?
X-inactivation of most genes on X chromosome
An individual who has a sex chromosome abnormality either _______ or ________ gene dosage of ______
Increased or decreased gene dosage of PAR1 and PAR2
A translocation is the interchange of genetic material between:
Non-homologous chromosomes
All autosomal monosomies are:
LETHAL
Trisomy 18 is also referred to as
Edward Syndrome
Alternate segregation
Two normal or two abnormal chromes in the gamete (no phenotype)
5% of trisomy 13 is a result of
Robertsonian translocation
Signs of Turner syndrome
Kidney abnormalities, congenital heart defects, ovarian dysgenesis, hypothyroidism, no intellectual disability but some learning disabilities
Klinefelter syndrome:
47 XXY
Symptoms of Trisomy 18 Edward syndrome
Death within one year Intellectual/developmental disabilities Diaphragmatic hernia/omaphalocele Small eyes/mouth, receding jaw Kidney defects Clenched fists/overlapping fingers Rocker-bottom feet, flexed big toe
Trisomy 13 Patau syndrome symptoms
Death within a year Holoprosencephaly *brain does not make two lobes Postaxial polydactyly Cleft lip/palate Deaf Small eyes
Why are autosomal trisomies 13, 18, and 21 compatible with life
Fewer genes on these chromosomes
Most common sign of Klinefelter syndrome
Infertility
Which autosomal trisomies are compatible with survival
13, 18, 21
Monosomy for X chromosome is called
Turner syndrome 45, X
XX males and XY females are errors during:
Recombination during the generation of gametes, SRY gene translocated
Women under/over the age of 35 have 80% of the babies with Down syndrome?
Under
Adjacent segregation
One normal and one abnormal chromosomes in the gamete (abnormal phenotype)
Treatment for Turner syndrome
Growth hormone and estrogen therapy
Why is Robertsonian translocation not possible in trisomy 18
Chromosome 18 is not Acrocentric
The only kind of survivable monosomy:
X chromosome
Nondisjunction
The failure of the two members of the chromosome pair to disjoin or separate during meiosis 1 or meiosis 2
Long arm of chromosome
Q
Chromosome abnormalities are the leading cause of:
Pregnancy loss and intellectual disability syndromes
In Trisomy 13, 95% of cases are due to
Nondisjunction in the mother’s gametes
What are the two types of translocation
Robertsonian
Reciprocal
5% of trisomy 21 cases result from
Robertsonian translocation
In 95% of trisomy 21 cases, the additional chromosome is contributed by:
The mother due to nondisjunction
In males with 46, XX, where was the error
In the father of the individual, there was an aberrant recombination between the X and Y chromosomes that transferred the SRY gene to the X chromosome
