Question

3. Round shells is incompletely dominant to square shells, the heterozygous combination is a pointed shell. Smelly

shell's is an X-linked trait and recessive. A pointed shell smelly shelled male is crossed with a round
heterozygous non-smelly shelled female. What's the phenotype of their offspring?

Answer 1

2/16 rounded not smelly females, RRX+X-

2/16 pointed not smelly females, RrX+X-

2/16 rounded smelly females, RRX-X-

2/16 pointed smelly females, RrX-X-

2/16 rounded not smelly males, RRX+Y

2/16 pointed not smelly males, RrX+Y

2/16 rounded smelly males, RRX-Y

2/16 pointed smelly males, RrX-Y

Step-by-step explanation:

Available data:

• RR round shell
• rr square shell
• Rr Pointed shell
• X+ is dominant and codes for not smelly
• X- is recessive and codes for Smelly

Cross: A pointed smelly shelled male with a round heterozygous non-smelly female

Parentals) Rr X-Y x RRX+X-

Gametes) RX-, RY, rX-, rY

RX+, RX+, RX-, RX-

Punnett square) RX- rX- RY rY

RX+ RRX+X- RrX+X- RRX+Y RrX+Y

RX+ RRX+X- RrX+X- RRX+Y RrX+Y

RX- RRX-X- RrX-X- RRX-Y RrX-Y

RX- RRX-X- RrX-X- RRX-Y RrX-Y

F1) 2/16 bivalves are expected to be rounded not smelly females, RRX+X-

2/16 bivalves are expected to be pointed not smelly females, RrX+X-

2/16 bivalves are expected to be rounded smelly females, RRX-X-

2/16 bivalves are expected to be pointed smelly females, RrX-X-

2/16 bivalves are expected to be rounded not smelly males, RRX+Y

2/16 bivalves are expected to be pointed not smelly males, RrX+Y

2/16 bivalves are expected to be rounded smelly males, RRX-Y

2/16 bivalves are expected to be pointed smelly males, RrX-Y