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biology 0610printed 233 · PDF 233
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Genetic diagram of inheriting sex chromosome
GENES
Segments of DNA ,on which genetic information is stored are called genes.
These genes determine your traits as they contain code for production of specific
proteins which allow only specific traits to develop.
Alleles are different types of version of the same gene.
If the alleles of a particular gene are identical in chromosome then it is known as
homologous chromosome
If the alleles of a particular gene are not identical in chromosome then it is known as
heterozygous chromosome.
Genotype is the genetic makeup of the organism in terms of allele.
Phenotype is the physical appearance of an organism.
Alleles
Alleles are different types of version of the same gene.
Allele can be of 2 types:
1.Dominant Allele:
Allele that gives an expression when it is present.Often shown
by capital alphabet e.g “G”
2.Recessive allele:
Allele that only gives an expression when no dominant allele is present or both
the alleles present are recessive.Often shown by small alphabet e.g “g”.
Example Question
Q. In a species of animal, the allele for brown eyes is dominant and the allele for
green eyes is recessive.
Write down the suitable symbols for these 2 alleles
ANS.) Brown eyes= B
Gametes
X
Y
X
XX
XY
Y
XY
YY