Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
142 Cards in this Set
- Front
- Back
|
What is cytogenetics? |
study of chromosomes and their abnormalities
|
|
|
Why is colcemid used in chromosomal visualization?
|
arrests cells in metaphase
|
|
|
Why are cells placed in hypotonic solution for chromosomal visualization?
|
to swell and lyse the nucleus (release the chromosomes)
|
|
|
What is a karyotype?
|
ordered display of chromosomes from large to smallest
|
|
|
What are metacentric chromosomes?
|
centromere is in the center of the chromosome (p arm and q arm are similar sizes)
|
|
|
What are acrocentric chromosomes?
|
centromere is near the end of the chromosome
|
|
|
What are submetacentric chromosomes?
|
centromere is between end and center of the chromosome
|
|
|
What structure is found on the tip of each chromosome?
|
telomere
|
|
|
The short arm of a chromosome is labelled with what letter?
|
p
|
|
|
The long arm of a chromosome is labelled with what letter?
|
q
|
|
|
On what type of chromosome are the p and q arm almost the same size?
|
metacentric chromosomes
|
|
|
What does 47XX +21 tell us?
|
female with Down's Syndrome
|
|
|
What does 47XY +18 tell us?
|
male with Edward's syndrome
|
|
|
What phase of the cell cycle is used for High-resolution banding techniques?
|
prophase/prometaphase (early metaphase)
|
|
|
Why does observing cells in prophase give us a higher resolution banding pattern of a chromosome?
|
the chromosome is still not condensed (is larger/more spread out) so more bands are observable
|
|
|
When using a Giemsa Stain to see chromosome bands, chromosomal proteins must be treated with what enzyme first?
|
trypsin
|
|
|
FISH can be used to check for what types of chromosomal abnormalities?
|
deletions, additions, translocations
|
|
|
What could we use CGH (comparative genomic hybridization) to check for?
|
losses, duplications of chromosomes or regions
|
|
|
A patients CGH results show an area that fluoresces red. What has occurred at that red spot?
|
excess red indicates a duplication of that region of the patient's DNA; the red color comes from patient DNA that has not matched up with any DNA from the control set
|
|
|
A patients CGH results show an area that fluoresces green. What has occurred at that green spot?
|
excess green indicates a deletion of that region of the patient's DNA; the green color comes from the control DNA that has not matched up with any part of the patient's DNA
|
|
|
If a duplication/deletion is too small to be seen by a normal CGH, what technique can be used?
|
array CGH
|
|
|
In a CGH, what color is the patients DNA?
|
red
|
|
|
In a CGH, what color is the control DNA?
|
green
|
|
|
What technique for visualizing chromosomal abnormalities does not require dividing chromosomes? (can be in prophase)
|
CGH (and high-resolution banding)
|
|
|
Why can CGH detect unbalanced rearrangements, but not balanced rearrangements?
|
CGH detects excess or loss of DNA. balanced rearrangement = no change in amount of DNA
|
|
|
What type of rearrangement could a CGH detect? (balanced or unbalanced)
|
CGH could detect an unbalanced rearrangement because that would result in a loss/gain of DNA. CGH detects losses and gains in DNA
|
|
|
What is euploidy?
|
has some multiple of 23 chromosomes (n=23, 2n=46, 3n=69, 4n=92)
|
|
|
What does 92XXXX tell us?
|
euploidy; female patient has 4 copies of DNA
|
|
|
Most common cause of triploidy?
|
dispermy; 2 sperm fertilize the same egg = 3 sets of DNA (1 mom and 2 dad); other less common cause is a diploid gamete
|
|
|
How can meiotic failure lead to triploidy?
|
nondisjunction of a gamete = diploid gamete. when it is fertilized by a haploid gamete, there are now 3 sets of DNA
|
|
|
What is aneuploidy?
|
excess/loss of 1 chromosome (not entire set, like in euploidy)
|
|
|
Which is worse monsomy or trisomy?
|
monosomy; loss of genetic material is almost always worse than excess
|
|
|
What is trisomy 21?
|
Down's syndrome; extra chromosome 21
|
|
|
Why do some patients with Down's syndrome have pulmonary hypertension?
|
AV septal defect = left to right shunt = higher pressure on the right side than normal =
|
|
|
What is Mosaicism with regard to Down's Syndrome?
|
some patients have less severe symptoms because some embryonic cells deleted the extra 21 chromosome
|
|
|
Over expression of DRYK1A in Down's Syndrome patients leads to ...
|
learning/memory defects= mental retardation
|
|
|
Patients with Down's Syndrome are at higher risk for Alzhemier's due to what extra gene on chromosome 21?
|
APP= encodes amyloid-B-precursor protein
|
|
|
What is trisomy 18?
|
Edward's syndrome; extra chromosome 18
|
|
|
What is trisomy 13?
|
Patau's Syndrome
|
|
|
In cases of trisomy 21, the mutation is usually found in the maternal egg. At what age does risk for trisomy 21 increase exponentially?
|
35
|
|
|
Why is it hypothesized that maternal age increases risk for trisomy's?
|
eggs are suspended as primary oocytes in prophase 1 until fertilization or menstruation; longer time in prophase (higher maternal age) has a role in inhibiting proper separation of chromosomes
|
|
|
What is monosomy X?
|
1 X chromosome (Turner's Syndrome)
|
|
|
Why do patients with Turner's syndrome not develop secondary sex characteristics?
|
they only have 1 X chromosome so they do not have proper ovaries = irregular hormonal balances
|
|
|
Why do patients with Turner Syndrome have short stature?
|
SHOX gene is found on the ends of X and Y; because they only have 1 X, they have haploinsufficiency of this gene = shorter
|
|
|
How could a patient with XY (male), have a female phenotype?
|
loss of function of the SRY region on the Y chromosome
**bc normally the SRY inhibits DAX1, which allows SRY to initiate differentiation into a male. |
|
|
How could a patient with XX (female), have a male phenotype?
|
If crossing over of the XY in the father includes the SRY region, the father will have an X chromosome with an SRY gene. His daughter could get his X chromosome, but it has an SRY gene on it so she will be male
|
|
|
How could a patient with XX (female), have a male phenotype?
|
If crossing over of the XY in the father includes the SRY region, the father will have an X chromosome with an SRY gene. His daughter could get his X chromosome, but it has an SRY gene on it so she will be male
|
|
|
What is 47 XXY?
|
Klinefelter's Syndrome; males with an extra X chromosome
|
|
|
Why is mastectomy recommended for patients with Klinefelter's Syndrome?
|
higher risk of breast cancer in the males; due to low testosterone
|
|
|
What is an unbalanced rearrangement?
|
rearrangement causes gain or loss of chromosomal material
|
|
|
What is a balanced rearrangement?
|
rearrangement doesn't cause gain or loss of chromosomal material
|
|
|
What are clastogens?
|
agents that cause chromosomal breaks
|
|
|
What is a reciprocal translocation?
|
genetic material is switched form 1 chromosome to another nonhomologus chromosome; usually not that bad since all the genetic material is still there
|
|
|
What is a derivative chromosome?
|
result of a reciprocal translocation
|
|
|
What are Robertsonian translocations?
|
short arms of 2 non-homologous chromosomes are lost and long arms fuse at centromere
Confined to acrocentric chromosomes: 13,14,15,21, and 22 Usually asymptomatic and 45 chromosomes in each cell |
|
|
Wolf-Hirschorn Syndrome is caused by what chromosomal anomaly?
|
a very small telemetric deletion on chromosome 4p
|
|
|
Prader-Willi Syndrome is caused by what chromosomal anomaly?
|
micro-deletion on 15q 11-13
|
|
|
What is contiguous gene syndrome?
|
deletion of series of adjacent genes
ex. WAGR |
|
|
What is WAGR syndrome?
|
11p deletion; WAGR= Wilms tumor, Anirida, Genitourinary abnormalities, and mental Retardation
|
|
|
What are sub-telometric rearrangements?
|
deletions/duplications in the gene-rich regions of telomeres
|
|
|
What is uniparental disomy?
|
one parents contributes 2 copies of the same chromosome, the other parent contributes none
*first one seen in CF, exs. Prader-willi, angleman syndrome, Russel-silver syndrome, hemophilia A, Beckwith-Wiedemann |
|
|
What is isodisomy?
Heterodisomy? |
1 parent gives 2 copies of different chromosomes, the other gives none
Each parent has contributed one copy of each chromosome |
|
|
How can the presence of a ring chromosome lead to monosomy?
|
The ring chromosome will be degraded, leaving only 1 copy of a certain chromosome
|
|
|
What is a pericentric inversion?
|
an inversion that involved the centromere
|
|
|
What is a paracentric inversion?
|
an inversion that doesn't involve the centromere
|
|
|
Why might inversions lead to problems during meiosis?
|
since bases align in order during prophase, the inverted chromosome must loop to correctly match up the bases
|
|
|
What is an isochromosome?
|
a chromosome that divides along the wrong axis; has 2 copies of 1 arm, 0 copies of the other arm
|
|
|
What is the Philadelphia chromosome?
|
9/22 translocation; it is associated with CML (chronic myeloid leukemia)
|
|
|
What are low copy repeats and what do they do?
|
multiple repeated sequences at the deletion boundary. the repeated sequences promote unequal crossing over which then produces duplications and deletions of the region of the repeat elements.
|
|
|
How is the 9/22 translocation implicated in CML (chronic myelogenous leukemia)
|
ABL gene (tyrosine kinase) on 9q moves to 22q; altered gene expression = mostly on = more cell activation= over expression
|
|
|
How is a 8/14 translocation implicated in Burkitt's Lymphoma?
|
MYC gene is moved from 8q to 14q; altered expression = always on = higher gene transcription
*near the immunoglobulin loci |
|
|
What are chromosome instability syndromes?
|
patients have DNA that is easily broken/damaged/poor repair
|
|
|
Why is colcemid used in chromosomal visualization?
|
arrests cells in metaphase
|
|
|
Why are cells placed in hypotonic solution for chromosomal visualization?
|
to swell and lyse the nucleus (release the chromosomes)
|
|
|
What is a karyotype?
|
ordered display of chromosomes from large to smallest
|
|
|
Can an isochromosome be formed by Robertsonian translocation?
|
Yes, if it occurs between HOMOLOGUS chromosomes
|
|
|
What are acrocentric chromosomes?
|
centromere is near the end of the chromosome
|
|
|
What are submetacentric chromosomes?
|
centromere is between end and center of the chromosome
|
|
|
What structure is found on the tip of each chromosome?
|
telomere
|
|
|
The short arm of a chromosome is labelled with what letter?
|
p
|
|
|
The long arm of a chromosome is labelled with what letter?
|
q
|
|
|
On what type of chromosome are the p and q arm almost the same size?
|
metacentric chromosomes
|
|
|
What does 47XX +21 tell us?
|
female with Down's Syndrome
|
|
|
What does 47XY +18 tell us?
|
male with Edward's syndrome
|
|
|
What phase of the cell cycle is used for High-resolution banding techniques?
|
prophase/prometaphase
|
|
|
Why does observing cells in prophase give us a higher resolution banding pattern of a chromosome?
|
the chromosome is still not condensed (is larger/more spread out) so more bands are observable
|
|
|
When using a Giemsa Stain to see chromosome bands, chromosomal proteins must be treated with what enzyme first?
|
trypsin
|
|
|
FISH can be used to check for what types of chromosomal abnormalities?
|
deletions, additions, translocations
|
|
|
What could we use CGH (comparative genomic hybridization) to check for?
|
losses, duplications of chromosomes or regions
|
|
|
A patients CGH results show an area that fluoresces red. What has occurred at that red spot?
|
excess red indicates a duplication of that region of the patient's DNA; the red color comes from patient DNA that has not matched up with any DNA from the control set
|
|
|
A patients CGH results show an area that fluoresces green. What has occurred at that green spot?
|
excess green indicates a deletion of that region of the patient's DNA; the green color comes from the control DNA that has not matched up with any part of the patient's DNA
|
|
|
If a duplication/deletion is too small to be seen by a normal CGH, what technique can be used?
|
array CGH
|
|
|
In a CGH, what color is the patients DNA?
|
red
|
|
|
In a CGH, what color is the control DNA?
|
green
|
|
|
What technique for visualizing chromosomal abnormalities does not require dividing chromosomes? (can be in prophase)
|
CGH (and high-resolution banding)
|
|
|
Why can CGH detect unbalanced rearrangements, but not balanced rearrangements?
|
CGH detects excess or loss of DNA. balanced rearrangement = no change in amount of DNA
|
|
|
What type of rearrangement could a CGH detect? (balanced or unbalanced)
|
CGH could detect an unbalanced rearrangement because that would result in a loss/gain of DNA. CGH detects losses and gains in DNA
|
|
|
What is euploidy?
|
has some multiple of 23 chromosomes (n=23, 2n=46, 3n=69, 4n=92)
|
|
|
What does 92XXXX tell us?
|
euploidy; female patient has 4 copies of DNA
|
|
|
Most common cause of triploidy?
|
dispermy; 2 sperm fertilize the same egg = 3 sets of DNA (1 mom and 2 dad); other less common cause is a diploid gamete
|
|
|
How can meiotic failure lead to triploidy?
|
nondisjunction of a gamete = diploid gamete. when it is fertilized by a haploid gamete, there are now 3 sets of DNA
|
|
|
What is aneuploidy?
|
excess/loss of 1 chromosome (not entire set, like in euploidy)
|
|
|
Which is worse monsomy or trisomy?
|
monosomy; loss of genetic material is almost always worse than excess
|
|
|
What is trisomy 21?
|
Down's syndrome; extra chromosome 21
|
|
|
Why do some patients with Down's syndrome have pulmonary hypertension?
|
AV septal defect = left to right shunt = higher pressure on the right side than normal =
|
|
|
What is Mosaicism with regard to Down's Syndrome?
|
some patients have less severe symptoms because some embryonic cells deleted the extra 21 chromosome
|
|
|
Over expression of DRYK1A in Down's Syndrome patients leads to ...
|
learning/memory defects
|
|
|
Patients with Down's Syndrome are at higher risk for Alzhemier's due to what extra gene on chromosome 21?
|
APP
|
|
|
What is trisomy 18?
|
Edward's syndrome; extra chromosome 18
|
|
|
What is trisomy 13?
|
Patau's Syndrome
|
|
|
In cases of trisomy 21, the mutation is usually found in the maternal egg. At what age does risk for trisomy 21 increase exponentially?
|
35
|
|
|
Why is it hypothesized that maternal age increases risk for trisomy's?
|
eggs are suspended as primary oocytes in prophase 1 until fertilization or menstruation; longer time in prophase (higher maternal age) has a role in inhibiting proper separation of chromosomes
|
|
|
What is monosomy X?
|
1 X chromosome (Turner's Syndrome)
|
|
|
Why do patients with Turner's syndrome not develop secondary sex characteristics?
|
they only have 1 X chromosome so they do not have proper ovaries = irregular hormonal balances
|
|
|
Why do patients with Turner Syndrome have short stature?
|
SHOX gene is found on the ends of X and Y; because they only have 1 X, they have haploinsufficiency of this gene = shorter
|
|
|
How could a patient with XY (male), have a female phenotype?
|
loss of function of the SRY region on the Y chromosome
|
|
|
How could a patient with XX (female), have a male phenotype?
|
If crossing over of the XY in the father includes the SRY region, the father will have an X chromosome with an SRY gene. His daughter could get his X chromosome, but it has an SRY gene on it so she will be male
|
|
|
How could a patient with XX (female), have a male phenotype?
|
If crossing over of the XY in the father includes the SRY region, the father will have an X chromosome with an SRY gene. His daughter could get his X chromosome, but it has an SRY gene on it so she will be male
|
|
|
What is 47 XXY?
|
Klinefelter's Syndrome; males with an extra X chromosome
|
|
|
Why is mastectomy recommended for patients with Klinefelter's Syndrome?
|
higher risk of breast cancer in the males; due to low testosterone
|
|
|
What is an unbalanced rearrangement?
|
rearrangement causes gain or loss of chromosomal material
|
|
|
What is a balanced rearrangement?
|
rearrangement doesn't cause gain or loss of chromosomal material
|
|
|
What are clastogens?
|
agents that cause chromosomal breaks
|
|
|
What is a reciprocal translocation?
|
genetic material is switched form 1 chromosome to another; usually not that bad since all the genetic material is still there
|
|
|
What is a derivative chromosome?
|
result of a reciprocal translocation
|
|
|
What are Robertsonian translocations?
|
short arms of 2 non-homologous chromosomes are lost and long arms fuse at centromere
|
|
|
Wolf-Hirschorn Syndrome is caused by what chromosomal anomaly?
|
deletion on chromosome 4p
|
|
|
Prader-Willi Syndrome is caused by what chromosomal anomaly?
|
micro-deletion on 15q 11-13
|
|
|
What is contiguous gene syndrome?
|
deletion of series of adjacent genes
|
|
|
What is WAGR syndrome?
|
11p deletion; Wilm's tumor, aniridia, genitourinary problems, retardation
|
|
|
What are sub-telometric rearrangements?
|
deletions/duplications in the gene-rich regions of telomeres
|
|
|
What is uniparental disomy?
|
one parents contributes 2 copies of the same chromosome, the other parent contributes none
|
|
|
What is isodomy?
|
1 parent gives 2 copies of different chromosomes, the other gives none
|
|
|
How can the presence of a ring chromosome lead to monosomy?
|
The ring chromosome will be degraded, leaving only 1 copy of a certain chromosome
|
|
|
What is a pericentric inversion?
|
an inversion that involved the centromere
|
|
|
What is a paracentric inversion?
|
an inversion that doesn't involve the centromere
|
|
|
Why might inversions lead to problems during meiosis?
|
since bases align in order during prophase, the inverted chromosome must loop to correctly match up the bases
|
|
|
What is an isochromosome?
|
a chromosome that divides along the wrong axis; has 2 copies of 1 arm, 0 copies of the other arm
|
|
|
What is the Philadelphia chromosome?
|
9/22 translocation
|
|
|
How is the 9/22 translocation implicated in CML (chronic myelogenous leukemia)
|
ABL gene (tyrosine kinase) on 9q moves to 22q; altered gene expression = mostly on = more cell activation
|
|
|
How is a 8/14 translocation implicated in Burkitt's Lymphoma?
|
MYC gene is moved from 8q to 14q; altered expression = always on = higher gene transcription
|
|
|
What are chromosome instability syndromes?
|
patients have DNA that is easily broken/damaged/poor repair
|
