DNA and chromosomes

The P5 kiddos in my P5 Science classes have just completed the topic on Cells during the school holidays.
I have shared with them some information on DNA and chromosomes that is beyond the syllabus.

(1) What is DNA?
DNA stands for deoxyribonucleic acid. It is found primarily in the nucleus of cells. It is the material that transfers genetic characteristics from one generation to another in living organisms.

A DNA molecule is made up of a series of nucleotides arranged in 2 strands that resemble a ladder and twist to form a double helix.

Nucleotides are made up of a base, a sugar and phosphate. The 4 bases are adenine (A), guanine (G), cytosine (C) and thymine (T). The 4 bases pair with each other (A with T and G with C). How they are
ordered or sequenced provides information needed for the growth and development of our bodies.

(2) What are chromosomes?
It is a structure within the cell nucleus. It is made up of a single coiled piece of DNA. Human cells have 23 pairs of chromosomes. 23 chromosomes come from our mother while 23 chromosomes come from our father.

(3) Sex chromosomes determine our gender
What sex / gender a baby will be is decided when the egg and sperm unite. Each egg and each sperm have one sex chromosome.

There are two kinds of sex chromosomes - X and Y. Eggs carry only an X and sperm carry either an X or a Y

X+X means the cell will develop into a baby girl.
X+Y means that it will develop into a boy.

Image: How sex chromosomes determine our gender