IGCSE Biology Paper-2: Specimen Questions with Answers 157 - 158 of 203

Question 157

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Question

MCQ▾

Which combination of chromosomes from egg and sperm cells will produce a boy?

Choices

Choice (4)
a.Egg-X, Sperm-X
b.Egg-Y, Sperm- X
c.Egg-Y, Sperm- Y
d.Egg-X, Sperm- Y

Answer

d.

Explanation

  • XY and XX system – eg. Most of the fishes, Amphibians, Reptiles and Mammals.
  • In such cases, the Y-chromosome is male determining, and the absence of Y-chromosome determines the femaleness. Moreover, the male sex is heterogametichomogametic (producing two types of sperms – X-containing and Y-containing) while female is (producing one type of eggs/ova – all X-containing). The X-containing sperm and Y-containing sperms can also be called as Gymnosperm and Andros perm respectively.
  • In human also, it is the genetic make -up of sperms that determines the sex of the child and it is very unfortunate that women are blamed for producing female children (daughters) and even ill-treated for this false notion.
XY and XX system

XY and XX System

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Question 158

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Question

MCQ▾

Which blood vessel, if it becomes blocked, could lead directly to a heart attack?

Choices

Choice (4)
a.Coronary Artery
b.Hepatic Portal Vein
c.Vena Cava
d.Pulmonary Artery

Answer

a.

Explanation

  • Atherosclerosis plaques, is the most common form of arteriosclerosis (hardening of the arteries) and, through its contribution to heart disease and stroke, is responsible for about 50 % of the deaths in the United States, Europe, and Japan. In atherosclerosis, localized or atheromas, protrude into the lumen of the artery and thus reduce blood flow.
  • The atheromas additionally serve as sites for thrombus (blood clot) formation, which can further occlude the blood supply to an organ. It is currently believed that the process of atherosclerosis begins because of damage, or “insult, ” to the endothelium. Such insults are produced by smoking, hypertension (high blood pressure), high blood cholesterol, and diabetes.
  • The first anatomically recognized change is the appearance of fatty streaks, which are gray-white areas that protrude into the lumen of arteries, particularly at arterial branch points. These are aggregations of lipid-filled macrophages and lymphocytes within the tunica internal.
  • They are present to a small degree in the aorta and coronary arteries of children aged 10 to 14, but progress to more advanced stages at different rates in different people. In the intermediate stage, the area contains layers of macrophages and smooth muscle cells.
Coronary Artery

Coronary Artery

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