Chromosomes - Anita

• Chromosomes are tiny structures inside cells made from DNA, RNA, and protein. The information inside chromosomes act like a recipe that tells cells how to function and replicate. Every form of life has its own unique set of instructions, including you. Your chromosomes describe what color eyes you have, how tall you are, and whether you're a boy or a girl.
• When we talk about a gene we are referring to a section of DNA. One example of this would be the gene that determines the color of your hair. When we talk about the specific sequence of a gene (like the sequence that gives you black hair versus the sequence that gives you blonde hair), this is called an allele. So everyone has a gene that determines their hair color, only blondes have the allele that makes the hair blonde. 
• As we mentioned above, humans have 23 different pairs of chromosomes for a total of 46 chromosomes. We all get 23 chromosomes from our mother and 23 from our father. Scientists number these pairs from 1 to 22 and then an extra pair called the "X/Y" pair. The X/Y pair determines if you are a boy or a girl. Girls have two X chromosomes called the XX, while boys have an X and a Y chromosome called the XY.
• Within each chromosome are specific sections of DNA called genes. Each gene contains the code or recipe to make a specific protein. These proteins determine how we grow and what traits we inherit from our parents. The gene is sometimes called a unit of heredity.
• When a cell is not dividing (called the interphase of the cell cycle), the chromosome is in its chromatin form. In this form it is a long, very thin, strand. When the cell begins to divide, that strand replicates itself and winds up into shorter tubes. Before the split, the two tubes are pinched together at a point called the centromere. The shorter arms of the tubes are called the "p arms" and the longer arms are called the "q arms."

Baby Boy Chromosomes
 

Baby Girl Chromosomes