NOTES ON GENETICS
Q.SHORT NOTE:-
5 Marks
Q.1 KARYOTYPING
ANS.1
1.
It is a Basic
tool of Cytogeneticist
2.
Karyotype is a
photographic representation in which chromosomes are arranged in order of
decreasing length
3.
Giemsa stain (G
banding) technique—each chromosome can be seen to possess a distinctive pattern
of alternating light and dark bands of variable widths
4.
Shorthand of
Cytogenetics:
5.
Short arm denoted as p, long arm denoted
q.
6.
Each arm divided
into numbered regions from the centromere onwards.
7.
Each region numerically arranged into bands.
8.
For e.g., 5p24
would denote chromosome 5, short arm, region 2 and band 4.
9.
Cytogenetic
disorders may result from structural or numeric abnormalities of chromosomes.
10.
It may affect
autosomes or sex chromosomes.
11.
Applied ;-Cytogenetic
Disorders involving Autosomes
a)
Trisomy 21/Down’s
syndrome most common chromosomal disorder.
b)
Down syndrome is
a chromosomal abnormality characterized by the presence of an extra copy of
genetic material on the 21st chromosome
c)
Trisomy 21 is
caused by a meiotic nondisjunction event.
d)
With
nondisjunction, a gamete (i.e., a sperm or egg cell) is produced with an
extra copy of chromosome 21; the gamete thus has 24 chromosomes
e)
When combined
with a normal gamete from the other parent, the embryo now has 47 chromosomes,
with three copies of chromosome 21.
f)
About 4% of
cases are due to Robertsonian translocations.
g)
Maternal age has
a strong influence.
g:\anatomy pdf\notes\short notes
karyotyping notes .docx
ONE OR TWO SENTENCES.
2
MARKS.
Q1.WHAT IS GENETICS?
ANS. A BRANCH OF BIOLOGICAL
SCIENCE CONCERNED WITH THE STUDY OF THE CAUSE & NATURE OF SIMILARITY &
DISSIMILARITY OF THE INDIVIDUALS RELATED BY COMMON ANCESTRY(HEREDITARY).
