The immune system<span> is made up of a network of cells, tissues, and organs that work together to protect the body. One of the important cells involved are white blood cells, also called leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.</span>
Answer: The drug abuse is influenced by the environment and exerts influence on the gene expressions.
Explanation:
The genetic make up of the person is decides, which genes will be expressed and develop a trait in an individual. But this genetic expression can be influenced by the environmental factors like food, exposure to sunlight, and others. This study which relate environment with the genetic make up is called epigenetics. No person is drug addict by birth but the consumption of drug can influence the genetic make up and traits in a abuser. So here, the environment is influencing the genetic basis of a abuser.
Cell-tissue-organ-organ system-organism
The answer is 50 percent.
Parent plant of genotype Rr will in meiosis produce haploid gametes which will carry either R allele or r allele. Since there are only two possibilities R or r, the probability that seed will get r gene is 1 of 2. This can be presented as 1/2, which is 50%.
Organs or skeletal elements of animals and organisms
