Std12th Bio Pract Part B Spotting No 10
Date ; / /202
Introduction:
A pedigree is a list of ancesteors showing genetic relationships between members of a family.
A record of inheritance of certain genetic traits for two or more generations presented in the form of family tree or a diagram, is called pedigree chart. Study of pedigree chart provides a strong tool, which is used to trace the inheritance of a specific trait, abnormality or disease in a family. In a pedigree charts specific symbols that are used, are indicated below:
Aim : To Study
the prepared pedigree charts of genetic traits such as rolling of widow's peak,
blood groups and colour blindness.
Requirements : Prepared
pedigree charts of genetic traits.
Procedure:
Observe the given pedigree chart
and write comments on it.
1. Inability to roll
the tongue :
The rolling of tongue is the
ability of a person to roll the tongue inwards in ' U' shaped as shown in the
following figure. The inability to roll the tongue, is caused by autosomal
recessive allele 'a'. Both homozygous dominants (AA) and heterozygous (Ao)
individuals are able to roll the tongue while homozygous recessive (aa)
individuals are unable to roll the tongue.
Comment on the given pedigree chart with respect to
1. Inheritance of trait
Rolling of the tongue.
2. Number of normal, carriers and affected progeny
normal-9
carriers-5
affected 2
3. Linkage - sex linked or autosomal
autosomal recessive allelic linkage.
2. Widow's Peak
Widow's peak is a V.- shaped hair
line across the forehead. It is a dominant autosomal trait. The gene responsible
for widow's peak is dominant 'W'. Therefore, both homozygous ominant (WW) and heterozygous
( Ww) individuals have widow's peak, while homozygous recessive (ww) individuals
have straight hair line. This feature is observed with both men and women.
Comment on the given pedigree chart with respect to:
1. Inheritance of trait
Widow's Peak
2. Number of normal, carriers and affected progeny
normal - 5,
carriers-0
affected-6
3. Linkage - sex linked or autosomal
dominant autosomal trait
3. Human
blood groups:
1. The blood
groups in human beings are described as per ABO system of classification.
2. The gene I
(isoagglutinogen) controls the ABO blood groups.
3. It has three
alleles; I, I, and i (recessive).
4. The alleles I and I produce a
slightly different form of antigen and allele i (recessive), does not produce
any surface antigen on R.B.Cs.
5. Each individual
possesses only two alleles out of three.
6. Alleles I^ and I are co-
dominant. Individually they are completely dominant over allele i.
7. There are six different
genotypes and four different phenotypes with blood groups which are seen as
follows:-
|
Phenotype |
Genotype |
|
Blood Group A |
I^I^ or I^i |
|
Blood Group B |
Por ti |
|
Blood Group AB |
IA |
|
Blood Group O |
ii |
Comment on the given pedigree
chart and give the genotypes of the blood groups of individuals marked in blank
box numbers 2, 4, 8, 9, 12, 13. :-
2-1Ai
4-Bi
8-1Ai
9-Bi
12-ii
13- JAB
Comment on the given pedigree chart with respect to :
1. Inheritance of trait
Colour blindness
2. Number of normal, carrier (!nd affected progeny
normal - 6
carrier - 4
affected- 1
3. Linkage - sex linked or auto
omal
X sex linked recessive disorder
of humans.
Questions
1. What is pedigree?
A pedigree is a list of ancestors showing genetic
relationships between members of a family.
2. Why x-linked disorder are more common in male than in the
female?
This is because the X chromosome is large and contains many
more genes than the smaller Y chromosome. In a sex-linked disease, it is
usually males who are affected because they have a single copy of X chromosome
that carries the mutation
3. What are holandric traits?
These are the genes that are carried on the Y chromosome.
They mainly code for testes, which secrete testosterone and are responsible for
making an organism male. There are only a handful of genes on the Y chromosome;
holandric traits can only be passed from father to son, and holandric diseases
are rare
4. Give an example of autosomal recesssive disorder in
humans.
Examples of autosomal recessive disorders include cystic
fibrosis, sickle cell anemia, and Tay-Sachs disease.
Q. 5. Explain the concept of co-dominance with respect to
ABO system in humans.
Codominance means that neither allele can mask the expression of the other allele. An example in humans. would be the ABO blood group, where alleles A and alleles B are both expressed. So if an individual inherits allele A from their mother and allele B from their father, they have blood type AB
4. Study of flowers adapted to pollination by differentpollinating agencies (Wind and Insects)
PART B Question No 04 Spotting Practical Experiment No 3
5. Study of V. S. of anatropus ovule through a permanent slide/ relevant chart.
7. Study of meiosis in onion flower bud with the help of permanent slides.
6. Study of T. S. testis, T. S. ovary and V. S. of blastula, through permanent slides.
Please do not enter any spam link in the comment box. ConversionConversion EmoticonEmoticon