Answer:
Genetic drift
Explanation:
Genetic drift is defined as the random change in allelic frequencies from one generation to the other.
Genetic drift is an evolutionary mechanism in which the allelic frequencies in a population change through many generations. Its effects are harder in a small-sized population, meaning that this effect is inversely proportional to the population size. Genetic drift results in some alleles loss, even those that are beneficial for the population, and the fixation of some other alleles by an increase in their frequencies. The final consequence is to <u>randomly</u> fixate one of the alleles. Low-frequency alleles are the most likely to be lost. Genetic drift results in a loss of genetic variability within a population.
Genetic drift has important effects on a population when this last one reduces its size dramatically because of a disaster -bottleneck effect- or because of a population split -founder effect-.
People with two copies of the sickle cell gene have the disease. People who carry only one copy of the sickle cell gene do not have the disease, but may pass the gene on to their children. Abnormal hemoglobin, called hemoglobin S, causes sickle cell disease (SCD). The problem in hemoglobin S is caused by a small defect in the gene that directs the production of the beta globin part of hemoglobin. This small defect in the beta globin gene causes a problem in the beta globin part of hemoglobin, changing the way that hemoglobin works.
Explanation:
After repeated stimulation by antigen, B cells can make antibodies that bind their antigen with much higher affinity a process called affinity maturation. ... Thus, antigen stimulation greatly increases the antibody arsenal. Antibodies are proteins, and proteins are encoded by genes.
Answer:
chemical change.
Explanation:
There are two types of changes in matter: physical change and chemical change.
physical change- it is a change in matter that alters only its physical properties or its physical appearance. This type of change is reversible. For example- freezing of water, the water turns into solid ice and it can be reversed by melting the ice.
chemical change- it is a change in matter that alter its chemical and thus its physical properties. Most chemical changes are irreversible. for example- burning of paper, results in black soot and ashes- Thus changing both physical and chemical properties.
