Inheritance

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Question 23

In mammals, males have two different sex chromosomes ( $X$ and $Y$ ) and females have two similar sex chromosomes ( $X$ and $X$ ).

However, in many insects (such as certain species of grasshoppers), females have two of the same sex chromosomes ( $X$ and $X$ ), while males have only one sex chromosome, which is represented as $X O$ (the $O$ denotes the absence of a second sex chromosome).

Complete the genetic diagram to show how sex is inherited in these grasshoppers.

Genotype of male parent: $‾\underline{\qquad\qquad}$
Genotype of female parent: $‾\underline{\qquad\qquad}$
Gametes from male parent: $‾\underline{\qquad\qquad}$
Gametes from female parent: $‾\underline{\qquad\qquad}$
Genotypes of offspring: $‾\underline{\qquad\qquad}$
Sex of offspring: $‾\underline{\qquad\qquad}$

[4]

Insect eggs contain nutrients that the growing embryo needs to develop outside the mother's body.

(i) Suggest one food molecule (major nutrient) present in the yolk of an insect egg and describe the role of this molecule in the growth and development of the embryo.

(ii) Suggest one advantage of the egg being enclosed in a tough, waterproof outer shell (chorion).

(iii) Egg yolks are also a source of iron. Give another source of iron in the human diet and describe the function of iron in humans.

[4]

The number of chromosomes in the gametes (sperm and egg) of grasshoppers is less than the number of chromosomes in their body cells. Explain how the correct number of chromosomes is maintained in the offspring across generations.

[3]

Inheritance

Question 23

Inheritance Questions

Inheritance

Question 23

Inheritance Questions