Living Environment - June 2010

16 Even though identical twins have the same genetic material, they may develop slightly different characteristics because

(1) each twin receives different chromosomes from the egg
(2) one twin may only have genes from the father
(3) gene expression may be influenced by factors that switch genes on and off
(4) a gene mutation may have occurred before the zygote divided

17 What normally happens immediately after fertilization in sexual reproduction?

(1) specialization of cells to form a fetus from an egg
(2) production of daughter cells having twice the number of chromosomes as the parent cell
(3) production of daughter cells having half the number of chromosomes as the parent cell
(4) division of cells resulting in the development of an embryo from a zygote

18 The human female reproductive system is rep resented in the diagram below.

Production of gametes and support of the fetus normally occur in structures

(1) 1 and 2     (3) 3 and 5
(2) 2 and 4     (4) 4 and 5

19 Essential materials needed for development are transported to a human fetus through the

(1) reproductive hormones
(2) egg cell
(3) placenta
(4) ovaries

20 The failure to regulate the pH of the blood can affect the activity of

(1) enzymes that clot blood
(2) red blood cells that make antibodies
(3) chlorophyll that carries oxygen in the blood
(4) DNA that controls starch digestion in the blood

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