Answer:
The need for continental time zones stemmed directly from the problems of moving passengers and freight over the thousands of miles of rail line that covered North America by the 1880s. Since human beings had first begun keeping track of time, they set their clocks to the local movement of the sun.
Answer:
The answer is A. Invented SCUBA
Explanation:
- Emile Gagnan and Jacques Cousteau were engineers who invented the first SCUBA device, the Aqua-Lung.
- Gagnan's most important contribution to this discovery was his theory that a valve commonly used in gas generator engines would be useful in regulating air supply under water in varying pressures.
Answer:
A
Explanation:
Because there are two DNA strands in the DNA molecule and they both rotate around each other in a helix formation. So two helixes = double helix.
Answer: Option C
Explanation:
Color blindness is a common hereditary condition which means it usually passes from parents. Red green color blindness is passed on from the mother to the son.
The chromosome number 23 is the sex chromosome also responsible for colorblindness. As it is sex linked the son can receive the recessive allele from the mother.
The mother of the child had a recessive allele which she transferred into her son. As it is sex inherited disease the son is affected by gene carried from mother.
Answer:
Mitochondrial DNA.
Explanation:
Mitochondria is known as the power house of the cell and one of the important organelle responsible for the production of energy. Mitochondria contains its own DNA.
To understand the maternal ancestor history, the mitochondria DNA must be studied. The mitochondria is solely obtained from the mother as the egg contains large amount of cytoplasm that contains mitochondria. The mitochondria can never be inherited from paternal origin as the sperm contains few amount of cytoplasm and mitochondria.
Thus, the answer is mitochondrial DNA.
