This document discusses genes and quantitative traits. It begins by introducing genes and alleles, noting that quantitative traits are influenced by multiple genes. It then describes the three main types of quantitative traits: continuous traits which vary gradually, like human height; meristic traits which are counted, like the number of kernels on an ear of corn; and threshold traits which have few phenotypic classes determined by multiple genes and environment, like twinning in cattle. Examples of each type of quantitative trait are provided.

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