Given a scientific passage and an answer, generate a question for the given answer.

Q: Passage: Fats may be either saturated or unsaturated. A saturated fat is a fat that consists of triglycerides whose carbon chains consist entirely of carbon-carbon single bonds. Therefore, the carbon chains are saturated with the maximum number of hydrogen atoms possible. An unsaturated fat is a fat that consists of triglycerides whose carbon chains contain one or more carbon-carbon double bonds . A fat with one double bond is called monounsaturated, while a fat with multiple double bonds is called polyunsaturated (see Figure below ). Answer: saturated and unsaturated

A: What are the two types of fats?
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Q: Passage: For example, remember that for the height gene in pea plants there are two possible factors. These factors are alleles. There is a dominant allele for tallness (T) and a recessive allele for shortness (t) . Answer: alleles

A: What factors determine the effect of a gene?
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Q: Passage: The skin consists of two distinct layers, an outer layer called the epidermis and an inner layer called the dermis. The epidermis is constantly being renewed as dead cells on the surface are shed. This layer contains melanin-producing melanocytes. The dermis contains blood vessels, nerve endings, hair follicles, and sebaceous and sweat glands. Answer: epidermis

A:
Shedding of dead cells ensures constant renewal of what outer layer of the skin?
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