Home > SAT Test > SAT Reading Practice Tests
See All test questions
Take more free SAT Reading Practice Tests available from cracksat.net.
About eight percent of men of European descentare colorblind, but only about half a percent ofwomen are affected by the same condition. Most ofthese people are "red-green" colorblind, meaning05they cannot see colors related to green or red. Notonly are they unable to tell red and green apart,but yellows and oranges do not appear different,nor do blues and purples. Colorblindness is not"blindness" but is instead an inability to perceive10certain wavelengths of light. A red-green colorblindman looking at a red object can see the object andcan see that it is not white; however, he is unable totell whether the object is red or green, as they bothappear similar to him.15People with normal color vision see colorbecause they have an array of three types ofphotosensitive cells, called cones, on the back oftheir retinas. Each type of cone has a differentpigment that is sensitive to a certain part of the20visible light spectrum. The visible light spectrumruns from smaller wavelengths at the blue end,through medium wavelengths in the green toyellow range, to long wavelengths at the red end.The cones are often referred to as blue, green,25and red cones, based on the wavelength of lightthey absorb most. The blue cones absorb the bluewavelengths of light most, although they alsoabsorb a small amount of the green wavelengths.The green cones have their maximum absorption in30the green wavelengths, but also absorb a bit downinto the blue and up into the yellow wavelengths.The range that the red cones absorb overlaps therange of the green cones quite a bit; the red conemaximum absorption is in the yellow wavelengths,35but red cones also absorb a bit down into thegreen, through the yellow, and up into the redwavelengths.Even though the green and red cones absorbmuch of the same part of the visible spectrum, a40person who lacks the sensitive pigment in eitherred or green cones will have difficulty perceivingeither color, because the brain compares the signalsfrom both to determine exactly which region oflight is being absorbed. With only one set of cones45sending signals, the brain will perceive light fromthe green, yellow, and red wavelengths to be aboutthe same.A person will lack the pigment for either greenor red cones if he or she lacks the gene necessary50to make that pigment. Because genes are inheritedrandomly from our parents, half from each parent,we would expect men and women to have an equalchance of being colorblind. The actual ratio isabout sixteen colorblind men for each colorblind55woman. The reason for this inequality becomesclear once we know that the genes for making thecone pigments are on the X chromosome.Women have two X chromosomes, one fromeach parent. Men only have one X chromosome,60which they get from their mother. A woman canreceive a colorblind gene on an X chromosomefrom one parent, but if the other X chromosomehas a normal cone pigment gene, she will still makenormal pigments and have normal color vision.65The woman would need to receive the colorblindgene from each parent to be colorblind. Since aman only has the one X chromosome, receiving thecolorblind gene from his mother will always causecolorblindness in a man.70Women who have only one copy of thecolorblind gene are referred to as carriers becausethey carry the gene but are not affected by it. Bytracking the affected people in a family, we cancreate a chart, called a pedigree, to determine75which women in the family are carriers. Acolorblind daughter must have had a colorblindfather and either a colorblind or carrier mother,as she must have received a copy of the colorblindgene from each parent. A colorblind son also must80have had either a colorblind or carrier mother, butwhether or not the father was colorblind will notaffect the son.
1. The central idea of the passage is primarily concerned with
2. Which choice provides the best support for the answer to the previous question?
3. In paragraph 6, the author includes details about X chromosomes in order to
4. Based on the passage, which choice best describes what causes red and green to be the two colors that a colorblind person often cannot perceive?
5. Which choice would provide the most support for the author's line of reasoning in paragraph 1?
6. As used in line 19, "sensitive" most nearly means
7. Based on the information in the passage, it can be reasonably inferred that which of the following statements is true?
8. Which choice provides the best evidence for the answer to the previous question?
9. As used in line 73, "affected" most nearly means
10. Based on the information in the passage and the graphic, which of the following statements is true?
* SAT is a registered trademark of the College Board, which was not involved in the production of, and does not endorse, this product.
All content of site and practice tests copyright © 2016 Max.sitemap
contactlink to us