Answer:
(b) Tt and Tt let's use Mendel's
cross of tall and dwarf pea plants as an example.
The plants of
genotype Tt are self-pollinated.(both tall (T) but with dwarf (t) alleles).
The letters T and t are used to
represent the alleles of the gene that determine plant height by conventions.
The upper case letter (T) represents the dominant allele and the recessive
allele (t) is represented by the same letter in lower case.
Thus, the tall parents plants
having heterozygous alleles, results in off springs which comprises of both
tall and dwarf plants.
For the parental cross, both the
parents are true breeding plants, the tall plant is homozygous for the tall
allele T, while the dwarf plant is homozygous for the dwarf allele 't'. Mendel
tracked each trait through two generations.
When true breeding plants were
crossed to each other, this is called a parental cross and offspring comprise
the first filial or F1 - generation. When the members of theF1 -
generation were crossed, this produced the F2-generation or second
filial generation.
A cross between true breeding
tall and dwarf plants of the parent generation yield phenotypically tall
plants.
The cross between TT and Tt is
called back cross, which results into two homozygous and two heterozygous
dominant gametes. The cross between Tt and tt is called testcross which results
into 1:1 ratio of gametes.
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