15. To study various syndromes and their karyotypes in human
beings.
Date: / /20
Aim:- To study the various syndromes and their karyotypes.
Principle:-
Karyotype is the name given to the whole group of
characteristics that allow the identification of particular chromosome set. It
includes the number and size of chromosomes that are constant for a species.
Chromosomes are arranged in a series of their decreasing lengths representing
what is called idiogram. The characteristics of chromosome in making idiogram
are the number, length, position of centromere, secondary constrictions, length
of chromosome arms, arm ratio, banding pattern, etc.
The position of centromere is different in different
chromosomes but it is always constant
for a particular chromosome. You have already studied four
different shapes of chromosomes based on the position of centromere.
The idiogram is arrangement of chromosomes according to their
decreasing size, keeping position of centromeres aligned. The sex chromosomes
are always shown at the end.
Figure:-
Procedure :-
A normal human being shows 46 chromosomes (23 pairs) out of
which first 44 chromosomes i.e. 22 pairs are of autosomes and the last 2
chromosomes i.e. 23rd pair represents sex chromosomes. The first 22 pairs are
arranged according to their size in desending order. In humans, chromosomes are
classified into 7 groups viz. A, B, C, D, E, F and G. Sex chromosomes are
placed at the end on the right side of group 'G'. Human karyotype is
represented in the above diagram.
The karyotype is advantageous to study and dignose different
types of syndromes. Syndromes are structural or numerical abnormalities of
human chromosomes
Observe the given idiograms and comment on syndrome.
A normal human being shows 46 chromosomes (23 pairs) out of
which first 44 chromosomes i.e. 22 pairs are of autosomes and the last 2
chromosomes i.e. 23rd pair represents sex chromosomes. The first 22 pairs are
arranged according to their size in desending order. In humans, chromosomes are
classified into 7 groups viz. A, B, C, D, E, F and G. Sex chromosomes are
placed at the end on the right side of group 'G'. Human karyotype is
represented in the above diagram.
The karyotype is advantageous to study and dignose different
types of syndromes. Syndromes are structural or numerical abnormalities of
human chromosomes
Observe the given idiograms and comment on syndrome.
Chromosomal condition or syndrome (if any): Turner's syndrome
in male.
Symptoms: Short stature (Height) and webbed neck,
lower posterior Hair line,
Broad sheild shaped chest
poorly developed ovaries and breast
low intelligence.
Chromosomal condition or syndrome (if any): 'Klinefelter's
syndrome'
Symptoms :
Harsh voice,
under developed testis
Tall with long arms,
development of breast(Gynaecomestia)
Sterile.
Chromosomal condition or syndrome (if any): 21 Trisomy
(Down's syndrome)
Symptoms:
Flattened face, Protruding tongue
Small head, Short neck, Short height
Upward slanting eye lids (palpebral fissures)
Unusually shaped or small ears
Tiny white spots on the colored part (iris) of the eye called
Brushfield's spots Poor muscle tone
Broad, short hands with a single crease in the palm
Relatively short fingers and small hands and feet
Questions
1. What is trisomy?
Answer- A condition in which an extra copy of chromosome is present
in the nucleus of cell causing developmental abnormalities. e.g. 21. Trisomy
(Down's syndrome).
St
2. What is autosome?
Answer- The chromosomes which control the somatic characters are
known as autosomes.
3. Define monosomy and mention how does it differ from
trisomy.
Answer- Monosomy- Absence of one chromosome from pair of chromosome.
In trisomy condition extra chromosome is present in diploid chromosomal
condition by which three chrosomes are present instead of two chromosomes.
4. What is non-disjuction of chromosomes?
Answer- Non-disjunction is the failure of homologous chromosomes to
separate properly during cell division.
5. Explain the karyotype.
Answer- Karyotyping is the process of pairing and ordering all the chromosomes of an organism.
Multiple Choice Questions
1. Down's syndrome is due to -----------------------
a. crossing over
b. linkage
c. sex linked inheritance
d. non-disjunction of chromosomes
Answer- d. non-disjunction of chromosomes
2. Ovum producing Klinfelter's syndrome shall have chromosome
number -----------------------
a. 21
b. 22
c. 23
d. 24
Answer- d. 24
3. Chromosome number of Down's syndrome or Mongolism is 47
a. 46
b. 44
c. 48
d. 47
Answer- d. 47
4. Chromosomes were first seen by -----------------------
a. Strassburger
b. Hofmeister
c. Flemming
d. Waldeyer
Answer- d. Waldeyer
5. In human beings, single X /XO abnormality causes ----------------------
a. Down's syndrome
b. Klinfelter's syndrome
c. Turner's syndrome
d. Patau's syndrome
Answer- c. Turner's syndrome
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