Biochemistry - Cytogenetics I & Ii

Front 1

what is the difference between constitutional and acquired chromosome abnormality?

Back 1

constitutional chromosome abnormality is your chromosome make-up at birth (all tissues) while an acquired chromosome abnormality is an abnormality present only in malignant cells (some tissues only), e.g.

Front 2

in which cells is chromosome visualization and study limited?

Back 2

dividing cells (either in vivo or in vitro)

Front 3

where would one look in vivo to see meiosis? Mitosis?

Back 3

testis and embryonic ovaries; bone marrow, epithelium, tumors

Front 4

which cells can be visualized during mitosis in vitro?

Back 4

lymphocytes, skin, fibroblasts, amniotic fluid cells, chorionic villus cells

Front 5

to grow up peripheral blood for chromosomal study, T-lymphocytes are stimulated to divide by addition of what? How are these cells blocked in metaphase?

Back 5

PHA; colchicine

Front 6

what is the purpose of a hypotonic solution for growing up cells to observe chromosomes in mitosis?

Back 6

the cells swell which allows for spreading of the chromosomes

Front 7

which stain is used to visualize chromosomes?

Back 7

Giemsa

Front 8

what are the 3 categories of chromosomes based on the location of their centromeres?

Back 8

metacentric, submetacentric, acrocentric

Front 9

how are chromosomes prepared for the banding technique?

Back 9

they are treated with dilute trypsin then stained with Giemsa

Front 10

what is the name of the technique which allows fluorescent visualization of specific sequences in chromosomes?

Back 10

FISH (fluorescent in situ hybridization)

Front 11

how can subtle chromosomal rearrangements involving a certain locus be visualized using FISH?

Back 11

by using a DNA probe of known chromosomal location

Front 12

how can microdeletion syndromes be detected in chromosomes?

Back 12

by using FISH with DNA probes from the region that is commonly deleted in these patients

Front 13

what is the name given to simultaneous hybridization of a series of DNA probes from a specific human chromosome?

Back 13

chromosome painting

Front 14

what is special about FISH using alphoid repeat probes?

Back 14

the repeats can determine the copy number of a chromosomes in large number of dividing nuclei to identify trisomies or monomies (does not have to be in metaphase)

Front 15

what is the name for the primary constriction where the sister chromatids of a replicated chromosome are held together until anaphase stage of cell division?

Back 15

centromere

Front 16

what is the composition of the centromere?

Back 16

tandem, head-to-tail repeats of a 171-bp monomer that is further organized into higher-order repeats

Front 17

what is the function of telomeres?

Back 17

prevent fusion of chromosome ends and maintain chromosome integrity

Front 18

what is the composition of telomeres? By what are they replicated?

Back 18

tandem repeats of a simple sequence and an unknown number of proteins; telomerase

Front 19

what is a metacentric chromosome?

Back 19

chromosome with arms of approximately equal length, although the short and long arms are defined

Front 20

what is a submetacentric chromosome?

Back 20

chromosome with arms of unequal length with clearly identifiable short and long arms

Front 21

what is an acrocentric chromosome? What is the composition of the p arm?

Back 21

chromosome with centromere near one end; satellites and stalks which contain redundant copies of ribosomeal RNA genes

Front 22

in a chromosmes, which arm is p? q?

Back 22

short; long

Front 23

what is an ideogram?

Back 23

a schematic representation of chromosomes with their banding patterns

Front 24

what does 47,XY,21+ mean in cytogenetic nomenclature?

Back 24

male with 47 chromosomes (3 on the 21st). This is trisomy 21

Front 25

what is euploidy?

Back 25

cells containing a multiple of 23 chromosomes (e.g. triploidy, tetraploidy)

Front 26

what is aneuploidy?

Back 26

cells that do not contain a multiple of 23 chromosomes (e.g. trisomy or monosomy)

Front 27

what is a structural chromosomal abnormality?

Back 27

rearrangement of chromosomes such as missing a piece or an exchange with another chromosome

Front 28

what percentage of 1st trimester spontaneous abortions are chromosomally abnormal?

Back 28

50%

Front 29

what is the most common genetic cause of moderate mental retardation?

Back 29

trisomy 21

Front 30

what is the most common cause of trisomy 21?

Back 30

non-disjunction most commonly in marternal meiosis I, associated with advanced maternal age

Front 31

analysis of DNA polymorphisms in patients with numerical chromosomal anomalies allows which information to be determined?

Back 31

parental origin and cell stage where non-disjunction occurred

Front 32

Robertsonian translocations occur in which types of chromosomes?

Back 32

acrocentric chromosomes

Front 33

what is the phenotype of a patient with a Robertsonian translocation?

Back 33

normal

Front 34

what is mosaic trisomy 21?

Back 34

when non-disjunction takes place in a non-mitotic cell division such that some cells in the body will have a normal karyotype while others will have an extra cheomosome 21

Front 35

what is another name for trisomy 18? Trisomy 13?

Back 35

Edwards Syndrome; Patau syndrome

Front 36

what are the 4 most common trisomies clinically?

Back 36

13,18,22,21

Front 37

which trisomies have the bleakest life expectancy?

Back 37

13 and 18

Front 38

in triploidy, how many chromosomes are present in each cell? Where do the extra chromosomes normally come from?

Back 38

69 chromosomes; the father

Front 39

what is the major risk of a balanced chromosomal rearrangement (translocation)?

Back 39

unbalanced gametes and affected children

Front 40

what is an unbalanced chromosomal rearrangement? Are these individuals usually phenotypically affected?

Back 40

when rearrangement causes loss or gain of chromosomal material; yes - severly

Front 41

what are reciprocal translocations?

Back 41

breakage of nonhomologous chromosomes with reciprocal exchange of chromosome material

Front 42

what are terminal chromosome deletions?

Back 42

single breaks leading to loss of chromosome material distal to the breakpoint

Front 43

what are interstitial chromosome deletions?

Back 43

where two breaks in chromosome occur and DNA between breaks is lost

Front 44

what is the phenotype for 'cri du chat' syndrome? Is this most commonly due to a de novo deletion or it is inherited from translocation parents?

Back 44

terminal deletion of 5p; due mostely to de novo terminal deletion

Front 45

What is the phenotype of Prader-Willi syndrome (PWS)? Which disease has a very similar phenotype?

Back 45

interstitial deletion in proximal 15q; Angelmann syndrome (AS)

Front 46

what is the main difference in the etiology of Prader-Willi and Angelmann syndromes?

Back 46

PWS is mostly due to microdeletion in paternal 15q whilc AS is mostly due to microdeletion in maternal 15q

Front 47

why is 15q particularly prone to interstitial deletions?

Back 47

due to presence of repeated sequences flanking the deleted region and unequal crossing over mediated by these sequences during meiosis

Front 48

what is the name for 45,X anomaly?

Back 48

Turner syndrome

Front 49

what is the name for the inactivation of the only active X chromosome in a cell?

Back 49

nullisomy

Front 50

from where is the extra X chromosome derived in 47,XXY?

Back 50

maternally

Front 51

what is the etiology of 47,XXX?

Back 51

materal nondisjunction

Front 52

is 47,XYY a result of maternal nondisjunction? Does it increase with advanced maternal age?

Back 52

no; no

Front 53

what is the main reason that 49,XXXXX patients survive?

Back 53

X-inactivation

Front 54

how many Barr bodies are present in a 49,XXXXX patient?

Back 54

4

Front 55

why do patients with increased or decreased number of X chromosomes have abnormalities despite X-inactivation?

Back 55

not all genes undergo inactivation and the genes on 'inactivated' chromosomes that remain active lead to altered phenotypes

Front 56

at which location of the X and Y chromosomes does pairing occur in males during meiosis? What is the name for this region?

Back 56

distal tips of X and Y chromosomes; pseudoautosomal region

Front 57

what can occur at the pseudoautosomal region on X and Y chromosomes?

Back 57

crossing over

Front 58

which genes of the X chromosomes escape X-inactivation?

Back 58

genes in the pseudoautosomal region (they are expressed in Y chromosomes)

Front 59

which factor is responsible for male differentiation in humans?

Back 59

testis-determining factor (TDF)

Front 60

how do XX males occur?

Back 60

crossing over of sex determining gene on Y (SRY) just below pseudoautosomal region to X transfers male characteristics to X chromosome

Front 61

what is the relationship between cytogenetic changes and malignancy?

Back 61

many cytogenetic changes are specific to a certain type of malignancy and are used as a routine part of diagnosis