Question 1: Why was it important to start with true-breeding plants? Question 2: What phenotypic ratios did Mendel observe in the F2 generation of a dihybrid cross? Question 4: Would Mendel predict that you would get the same or different results from the cross of white males x scarlet females compared to its reciprocal? Solution Gregor Mendel wanted to know how parental traits are passed to the offspring. To get a clear concluding result without any mixed unexpected outcome or unexplained phenomenon Mendel wisely decided to start with pure breed i.e. known true breeding homozygous (pure dominant/recessive) pea plants (when selfed it produces same trait every time). In 1865 Mendel crossed two equal type of heterozygous pea plants with two characteristics to see outcome of dihybrid cross and discovered law of independent assortment. First he took pea plant of homozygous and dominant round (RR) yellow (YY) seeds and crossed with homozygous and recessive for wrinkled (rr) and green (yy) seeds and produced RrYy genotype heterozygous plants expressing dominant trait i.e. round and yellow seeds (F1 generation). Then he crossed two F1 plants (dihybrid cross: RrYy x RrYy). Phenotypic ratios did Mendel observed in his F2 generation of the dihybrid cross was 9:3:3:1::round & yellow: round & green: wrinkled & yellow: wrinkled & green. This is how he discovered parental trails sorted independently to next generation (linkage was not found). Mendel had not predicted that we would get the different results from the cross of white males x scarlet (Red eyed: Scarlet is a brilliant red colour with a tinge of orange) females compared to its reciprocal. Because the dominant scarlet colour of drosophila is a sex linked inheritance (present in sex chromosome) and the phenotypical output of a cross will arise differently as mended predicted. There is one X and one Y-chromosome in males while females have two X- chromosomes. In female only the dominant gene will produce red eye even if the individual is heterozygous for white allele..

1. Question 1: Why was it important to start with true-breeding plants?
Question 2: What phenotypic ratios did Mendel observe in the F2 generation of a
dihybrid cross?
Question 4: Would Mendel predict that you would get the same or different results from the
cross of white males x scarlet females compared to its reciprocal?
Solution
Gregor Mendel wanted to know how parental traits are passed to the offspring. To get a clear
concluding result without any mixed unexpected outcome or unexplained phenomenon Mendel
wisely decided to start with pure breed i.e. known true breeding homozygous (pure
dominant/recessive) pea plants (when selfed it produces same trait every time).
In 1865 Mendel crossed two equal type of heterozygous pea plants with two characteristics to
see outcome of dihybrid cross and discovered law of independent assortment. First he took pea
plant of homozygous and dominant round (RR) yellow (YY) seeds and crossed with
homozygous and recessive for wrinkled (rr) and green (yy) seeds and produced RrYy genotype
heterozygous plants expressing dominant trait i.e. round and yellow seeds (F1 generation). Then
he crossed two F1 plants (dihybrid cross: RrYy x RrYy).
Phenotypic ratios did Mendel observed in his F2 generation of the dihybrid cross was
9:3:3:1::round & yellow: round & green: wrinkled & yellow: wrinkled & green. This is how he
discovered parental trails sorted independently to next generation (linkage was not found).
Mendel had not predicted that we would get the different results from the cross of white males x
scarlet (Red eyed: Scarlet is a brilliant red colour with a tinge of orange) females compared to its
reciprocal. Because the dominant scarlet colour of drosophila is a sex linked inheritance (present
in sex chromosome) and the phenotypical output of a cross will arise differently as mended
predicted. There is one X and one Y-chromosome in males while females have two X-
chromosomes. In female only the dominant gene will produce red eye even if the individual is
heterozygous for white allele.