Genetics: Overview

Genetics: Overview

Each individual is unique, with a personalized print found in his or her DNA.

DNA Facts

  • DNA has the following 4 basic building blocks:

    -C, Cytosine

    -G, Guanine

    -A, Adenine

    -T, Thymine

  • The DNA building blocks link into a spiral staircase, called a double helix, to create chromosomes.
  • Humans have 23 distinct pairs of chromosomes.
  • One pair of chromosomes comes from the father and the other from the mother.
  • One of these pairs of chromosomes is the sex chromosomes (XX, female; XY, male).
  • The remaining 22 non-sex chromosomes are called autosomes.
  • Each chromosome has hundreds of genes, which are passed from generation to generation.


All in the Family

  • DNA explains why family members look alike.
  • DNA explains why some families are more susceptible to certain diseases, including breast cancer.


Breast Cancer Genetics

  • There are many defective genes that predispose someone to breast cancer.

    Most of these defective genes are on autosomes, or non-sex chromosomes, which means that breast cancer genes can be passed down from your mother or father. So, when it comes to breast cancer genetics, your father’s family history is just as important as your mother’s family history.

  • The most common breast cancer gene defects are:

    -BRCA1 gene

    -BRCA2 gene

  • However, there are other defective genes that can also predispose you to developing breast cancer.
  • Knowing as much as you can about your family history can help your physicians determine if you may carry a defective gene that puts you at risk of breast cancer.


Genetics loads the gun, but environment pulls the trigger.

  • Not everyone with a defective breast cancer gene will develop cancer.
  • Additional factors that can increase one’s risk for developing breast cancer include being overweight, prolonged use of hormone replacement therapy, and previous radiation therapy (such as in treatment for Hodgkin’s lymphoma).

Keep in mind: Family matters—know your history. Ask your doctor to help determine your breast cancer risk.