Question

please answer two question below

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e) 9; 9 3. In another plant species, the presence and type of hairs on the plant are controlled by epistatic interaction between two independently assorting genes. Gene C determines whether the plant has hairs (dominant) or not (recessive); Rene D determines whether the hairs are straight (dominant) or curly (recessive). In a cross between a straight-haired plant and a curly- haired plant, 1/4 of the offspring have no hairs. 3/8 have straight hairs, and 3/8 have curly hairs. Using capital letters to designate the dominant alleles and small letters to designate the recessive alleles, the genotypes of the two parent plants must have been: a) CC DD; cc dd b) Cc Dd; Cc Dd c) Cc Dd; Cc dd d) cc Dd; Cc dd e) cannot tell from the information given 4. In a different plant species, flower color and fruit color are controlled by two independently assorting genes, both of which have two alleles that exhibit incomplete dominance. In both cases, the homozygous phenotypes are red and yellow and the heterozygous phenotype is orange. If two plants with orange flowers and orange fruits are crossed with one another, what proportion of the offspring will have orange flowers and orange fruits? a) 1/16 b) 1/8 c) 1/4 d) 3/4 e) All

Answer 1

3 . Since the gene interaction here is epistatic, one gene would suppress the expression of other gene. Gene C determines presence or absence of hair and gene D determination straight or curly hair. When the organism is homozygous recessive for gene C, there would be no hair and so no expression of gene D.

The genotype of the offsprings would be:

1/4 = cc _ _ ( _ used for alleles of gene D which are not expressed)

3/8 = C_ Dd

3/8 = C_dd

(_ represents either dominant or recessive allele of the gene)

The phenotype of parents are straight haired plant and curly hair plant. Since bothe have hair but the 1/4 of the obtained offsprings are without hair, the trait due to recessive allele, parents are supposed to be heterozygous for gene C. One of the parent is having curly hair so it is homozygous recessive for gene D and because the obtained offsprings have both curly and straight hair, it is possible only when the other parent is heterozygous for gene D.

From above explanation, the genotype of two parents must have been: CcDd ; Ccdd ( option 3)

4. The proportion can be calculated by writing punnett square considering gene A for flower and gene B for fruit. The offsprings would have orange flower and orange fruits only if they are in heterozygous condition for both the genes. Out of 16 offsprings, 4 are heterozygous for both the genes, so the proportion is 4/16 = 1/4

Another way is multiplying the probability of heterozygous condition for individual genes.

If Aa is selfed then 2/4 of the offsprings would be Aa

If Bb is selfed then 2/4 of the offsprings would be Bb

Multiplying the proportion in both the conditions, the proportion of offsprings with genotype AaBb would be = 2/4×2/4= 4/16 = 1/4.

Cc Dd x Cold : cc-- no hair :C.D. straight hair C-dd Curly hair

На ВЬx A4 Bь Б) В Ab ав ab AA BB AA Bь Аав Aa Bb АРВЬ АА Бь На ВЬ Aabb А ВЗ АВЬ a a BB a a Bb Aa Bb Aabb a abb a abb