Genes and quantitative characters

1. GENES AND QUANTITATIVE
CHARACTERS
PRESENTED BY:-
VAGHELA BHAVUBHA A
MSc SEM-1 (BOTANY)
PAPER :- CBO-403
DEPARTMENT OF LIFE SCIENCES,
H.N.G.U., PATAN

2. CONTENT
 INTRODUCTION
 TYPES OF QUANTITATIVE TRAITS
 REFERENCES

3. INTRODUCTION
 We know that the heredity units are genes.
 The separate forms of a gene that mendel
called factors = alleles
 If an offspring carring 2 dominant or one
dominant and one recessive allele, the
offspring will appear to have the dominant
trait.
 If an offspring carries 2 recessive allels, it will
appear to have the ressesive trait.

5. TYPES OF QUANTITATIVE
TRAITS
 Quantitative traits are of the following
three main types:-
(1) Continuous Traits
(2) Meristic Traits
(3) Thresold Traits

6. (1) CONTINUOUS TRAITS
 Most phenotypic variation in populations is
not manifested in a few easily distinguished
categories.
 Instead, the traits vary continuously from one
phenotypic extreme to the other, with no
clear-cut breakes in between.
 Human height is a prime example of such a
trait.

8.  Other examples milk production in cattle,
growth rate in poultry, yield in corn and
blood pressure in human beings.
 Such traits are called continuous traits
because there is a continuous gradation
from one phenotype to the next.

9. YIELD IN CORN

10. (2) MERISTEMIC TRAITS
 In such type of quantitative traits, the
phenotype is determined by counting.
 Some examples are number of skin
ridges forming the fingerprints, number
of kernels on an ear of corn, number of
eggs laid by a hen, number of bristles
on the abdomen of a fly and number of
puppies in a litter.

12.  An examples of a meristic traits is the
number of ears on a stalk of corn, which
typically has a value 1,2,3 or 4 ears on a
given stalk.

13. (3) THRESOLD TRAITS
 These are those quantitative traits that have
only two, or a few, phenotypic classes, but
their inheritance is determined by effects of
multiple genes together with the environment.
 Examples of thresold include twinning in
cattle as well as parthenogenesis (i.e.,
development of unfertilized eggs ) in turkeys.

14. TWINNING IN CATTLE

15.  In many thresold traits disorders, the
phenotypic classes are “affected” versus
“not affected”.
 Examples of thresold traits disorders in
human beings include adult diabetes,
schizophrenia and many congenital
abnormalities such as spina bifida.

16. REFERENCES
 https :// en.wikipedia.org/wiki/genes
 www.google.com –for images
 Genetics – Gupta p.k