Final answer:
Humans have approximately 20,000 to 22,000 genes. To make a person, an egg cell from the mom and a sperm cell from the dad combine. The types of earlobes you have are determined by your genes. There are four chemicals that make up DNA: adenine, thymine, cytosine, and guanine. A female horse combined with a male donkey produces a mule. Chromosomes are paired, but genes are not. Mutations of genes can sometimes help, but often hinder, animals in surviving in nature.
Step-by-step explanation:
Humans have an estimated 20,000 to 22,000 genes. Each human cell has 23 pairs of chromosomes, one set inherited from each parent. To make a person, you need a cell from your mom called an egg and a cell from your dad called a sperm. These cells join together during fertilization to form a new cell called a zygote, which eventually develops into a person. The types of earlobes you have are determined by your genes. There are four base chemicals that make up DNA: adenine (A), thymine (T), cytosine (C), and guanine (G). When a female horse is combined with a male donkey, you get a mule. Chromosomes are paired, but genes are not. Mutations of genes can sometimes help, but often hinder, animals in surviving in nature.