karyotyping Flashcards
- Humans have a diploid number (2n) of ___
chromosome
46
The gametes contain only _ copy of each pair of
chromosome
one
Each chromosome contains a region
called the ___, which
divides the chromosome into two
arms
centromere
Chromosomes can be classified
according to the location of the
__
centromere
metacentric
submetacentric
acrocentric - near the end
telocentric - at the end
metacentric
submetacentric
acrocentric - near the end
telocentric - at the end
Human males and females have one pair of sex
chromosomes that are not completely
__
homologous
Females have two homologous ___chromosomes
X
Males have a nonhomologous pair, consisting of __chromosome
one X and one Y
Chromosomes other than sex chromosomes are
called __
autosomes
The autosomes are numbered 1-22
in __ order of length
descending
The sex chromosomes are labelled
as __
X and Y
On the basis of size and centromere
placement, human autosomal
chromosomes are divided into
seven groups
A (1-3), B (4-5), C, (6-12), D (13-15), E (16-18), F (19-20), and G (21-22)
Karyotype
The chromosomes are usually
studied and photographed while
they are in __ of mitosis
metaphase
They are arranged in pairs according
to size and centromere location to
form a __
karyotype
Chromosome ___ are
used to identify specific regions on each
chromosome
banding patterns
The short arm of each chromosome is
designated the _, and the long arm
the ___
p arm; q arm
Each arm is subdivided into numbered
__ beginning at the centromere
regions
Within each region, the bands are
identified by ___
number
This address consists of the
____
chromosome number (1), the
arm (q), the region (2), and
the band (4)
Karyotypes are constructed by using ___ from a number of sources
cells
One of the most common methods of preparing cells begins with a ___ sample
blood
Few drops of blood are added to a flask containing a ___ growth medium
nutrient
A mitosis-inducing chemical such as ___ is added to the flask
phytohemagglutinin
the cells are grown for __ days at body temperature in an incubator
2 or 3
A drug such as ___ is added to stop dividing cells at metaphase
Colcemid
Over a period of about 2 hours of treatment, all cells entering mitosis are arrested in
___
metaphase
The blood cells are concentrated by ___
centrifugation
A ___ solution is added to break open and destroy the RBCs and swell the lymphocytes
salt
Fixation in a mixture of ___
methanol and acetic acid
The swollen __ are dropped onto a microscope slide
lymphocytes
- The fragile cells will break open, spreading )___ chromosomes onto the slide
metaphase
The preparation is partially digested with __
trypsin
After staining, the preparation is examined with a microscope and a cluster of metaphase
chromosome is located
true or falsw
true
___ are prepared from the cluster of metaphase
chromosomes
Computer generated karyotypes
___ are used to produce a pattern of bands that is specific to each chromosome
Stains and dyes
The most common method is ___, in which
chromosomes are first treated with an enzyme (trypsin) that
partially digest chromosomal proteins and then are stained
with Giemsa stain
G-banding
The resulting pattern of bands is used to identify individual
chromosomes in cytogenetic analysis
true or false
true
Metaphase chromosomes have a total of about __ band
550
treat metaphase spreads with the chemical quinacrine mustard. Observe fluorescent banding pattern with a special ultraviolet light microscope
q banding
heat metaphase spreads at high temperature to achieve partial denaturation of DNA. Stain with Giemsa stain. Observe with light microscope
R banding
chemically treat metaphase spreads to extract DNA from the arms but not the centromeric regions of chromosomes. Stain with Giemsa stain ad obserce with light microscope
c banding
pattern is the reverse of the G bandig
R banding
darkly stained c band centromeric region of the chromosome corresponds to region of constitutive heterochromatin
c banding
A karyotype provides several kinds of information
- The number of chromosomes
- Sex chromosome content
- Presence or absence of individual chromosomes
- Nature and extent of any large structural abnormality
Almost any cell with a nucleus can be used to make a __
karyotype
In adults, ___ are used routinely
lymphocytes, skin cells (fibroblasts), and cells from biopsies or surgically
removed tumor cells
Chromosomal abnormalities can be detected before birth by using ___ sampling to collect cells from embryos and fetuses
amniocentesis and
chorionic villus
A technique used routinely to collect fetal cells for analysis
Amniocentesis
The fetus and placenta are located by ultrasound, and a needle is inserted through the abdominal and uterine walls (avoiding the placenta and fetus) into the amniotic sac
surrounding the fetus
Amniocentesis
Amniocentesis
Approximately___ of fluid is withdrawn by syringe
10-30
The fluid is mostly fetal urine containing cells shed from the skin, respiratory tract, and
urinary tract of the fetus
true or false
true
Amniocentesis
Cells are isolated from the fluid by ___
centrifugation
Karyotype analysis makes it possible to diagnose the sex of the fetus
t or f
t
Amniocentesis is not performed until the ___ week of pregnancy
16th
Before the 16th week, there is very little amniotic fluid and contamination of the sample with maternal
cells is often a problem
t or f
t
Amniotic cells can be analyzed to detect ____
biochemical disorders or chromosome abnormalities
Advance maternal age – risk of having children with chromosome abnormalities increases dramatically after
age _
35
The procedure is normally used under certain condition
- Advance maternal age – risk of having children with
chromosome abnormalities increases dramatically after
age 35
* 2. Previous child with a chromosomal aberration
* 3. A parent with a chromosome rearrangement
* 4. X-
CVS retrieves fetal tissue from the __
placenta
This has several advantages over amniocentesis
Chorionic Villus Sampling
It can be performed earlier in pregnancy (8 to 10 weeks)
orionic Villus Sampling
Because placental cells are already dividing and do not have to be induced to
begin mitosis, karyotypes are available within a few hours or a few days
t or f
t
his procedure, a flexible catheter is inserted through the vagina or
abdomen into the uterus, guided by ultrasound images
Chorionic Villus Sampling
Some chorionic villi are removed by ___
suction
__ is used less often than amniocentesis
CVS
It offers early diagnosis of genetic diseases, and if termination of pregnancy ___9 to 12 weeks than at 16 week
is elected, maternal risks are lower at
