Explain the following results using Mendelian genetics (give the genotypes of th

Question

  Explain the following results using Mendelian genetics (give the genotypes of the individuals crossed. No credit for answers that do not include genotype! Also include which law explains the outcome observed (do not simply state the law).

a. A cross of yellow to green peas resulted in all yellow peas.

b. A cross of yellow to green peas resulted in ½ yellow and ½ green peas.

c. A cross of yellow smooth peas to green smooth peas resulted in all yellow peas of which ¼ were wrinkled.

d. A cross between tall round dogs with tall round dogs resulted in a 9/16, 3/16, 3/16, 1/16 ratio.

e. Give the phenotypes of the classes shown above.

Explanation / Answer

a. law of dominance, in this, yellow would be dominant over green that resulting yellow progeny.

YY X yy--------------> Parents (YY-yellow, yy-green )

Yy Yy (Yellow)----------> F1 (Heterozygous express yellow due to dominance)

b. If the parents Yy x yy (test cross)

Yy Yy : yy yy (I/2 yellow and 1/2 green)

c. RrYY x Rryy (RR-round, rr-wrinkle) Yellow/green and smooth/wrinkle will be independently assorted

I/4 is rrYy

d. TtRr x TtRr -------> parents

Here, TTRR : 2TTRr : 4TtRr : 2TtRR : TTrr : ttrr : 2Ttrr : ttRR : 2ttRr (genotypes)

e. Tall round (9): short round (3): tall wrinkle (3): short wrinkle (1)

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