Identify the scientists credited with discovering the double helix structure of DNA, and the function of a gene. Explain the properties of stem cells and sex determination in humans. Finally, explain

1.1.1
D. Crick and Watson.
James Watson and Francis Crick are credited with discovering the double helix structure of DNA and the base pairing rules.

1.1.2
D. a protein.
A gene is a segment of DNA that contains the instructions for making a specific protein.

1.1.3
D. They can be stimulated to form any type of cell needed.
Stem cells are undifferentiated cells that have the ability to differentiate into various specialized cell types, a property known as potency.

1.1.4
B. 50%
In humans, the sex of a child is determined by the sperm. There is an approximately equal chance (50%) of a sperm carrying an X chromosome (resulting in a female, XX) or a Y chromosome (resulting in a male, XY).

1.1.5
A. The allele for colour-blindness is recessive and located on the X-chromosome.
Colour blindness is an X-linked recessive trait. Males have only one X chromosome, so if they inherit the recessive allele on that X, they will express the trait. Females have two X chromosomes, so they need two copies of the recessive allele to be colour-blind, making it less common in females.