A child carries a combination of DNA from both parents. Half of the child's DNA comes from the mother, and half comes from the father. This is achieved through the combination of the mother's egg and the father's sperm, each contributing one half of a complete set of chromosomes.
How DNA is Inherited
- Chromosomes: Humans have 23 pairs of chromosomes. Each parent contributes one chromosome from each pair.
- Eggs and Sperm: The egg from the mother and the sperm from the father each contain 23 chromosomes. Upon fertilization, these combine to create a zygote with a complete set of 46 chromosomes (23 pairs).
- Mitochondrial DNA: It's important to note that a small amount of DNA, called mitochondrial DNA, is inherited solely from the mother through the egg. This DNA is separate from the DNA found in the cell's nucleus.
Specific Examples
- Autosomal DNA: 50% of a child's autosomal DNA (DNA found in the chromosomes other than sex chromosomes) originates from each parent.
- Sex Chromosomes: The sex of the child is determined by the combination of sex chromosomes. Females have two X chromosomes (XX), receiving one X from each parent. Males have one X and one Y chromosome (XY), receiving the X from the mother and the Y from the father.
- Gestational Surrogacy: In gestational surrogacy, the surrogate mother provides only the environment for fetal development. The baby's DNA is solely from the intended parents (egg and sperm donors). The surrogate mother does not contribute any DNA.
Clarification on Surrogacy
Multiple sources explicitly state that in gestational surrogacy, the surrogate mother does not share DNA with the baby. The baby's genetic material comes exclusively from the egg and sperm provided by the intended parents. The surrogate only provides the womb for the fetus to grow.
