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V
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They produce sex cells or gametes which fuse to form a new
organism
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Every gene controls one or several particular characteristic features
in living organisms
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The process is done by genes, which define the characters the
organism
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His work laid the foundation of modern genetics
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Dominant traits
The traits that express themselves in an organism in every possible
combination and can be seen are called Dominant traits
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Therefore, the tall trait of the plant is said to be dominant over the
short trait
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So, recessive character/trait is present in an organism but cannot be
seen if a dominant allele exists
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The ratio of characters, arising out of this cross, at F2 generation is
called monohybrid ratio
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g
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So, 3:1 is monohybrid ratio
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Dihybrid cross
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When two characters are considered while crossing two organisms,
then such a cross is known as a dihybrid cross
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E
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, If a plant with round and green pea is crossed with a plant with
wrinkled and yellow pea,
The first generation plants would all have round and green pea
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Thus, 9:3:3:1 is the dihybrid ratio
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Laws of Mendel

Law of Dominance says that a gene has two contrasting alleles and one
always expresses itself in the organism
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Law of Segregation says that traits get segregated completely during the
formation of gametes without any mixing of alleles
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Sex determination
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The process of determining the sex of an individual based on the
composition of the genetic material is called sex determination
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In humans, sex determination happens on the basis of the presence
or absence of Y chromosome
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An Ovum, upon fusion with Y containing sperm, gives rise to a male
child and upon fusion with X containing sperm gives rise to a girl
child

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