What statement is true about lethal alleles? a. they cannot be maintained in a gene pool because they are always dominant. b. they cannot be maintained in a gene pool because the individuals with them never survive. c. they can be maintained in a gene pool if they are expressed before reproductive age. d. they can be maintained in a gene pool by heterozygous carriers.

Hello!

If you were to infer that non-lethal alleles are dominant, and lethal alleles are recessive, then let's assign A as the dominant allele, and a as the recessive allele.

Dominant homozygous (AA) or heterozygous (Aa) individual are not affected by the lethality of this allele because dominant alleles (A) are... dominant!

You are affected by the lethal alleles if and only if you are homozygous (aa) recessive.

So, if you were heterozygous (Aa), you wouldn't be affected by the lethal gene, because you have the dominant allele (A), but the recessive allele (a) would be in the next generation's gene pool.

Therefore, the answer is choice D, they can be maintained in a gene pool by heterozygous carriers.

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.

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