Mitochondrial and Nuclear Genome and Human Mitochondrial DNA Haplogroup
Mitochondrial and Nuclear Genome
- The mitochondrial genome is inherited solely from the mother (a biological female).
- Fathers (biological males) do not transmit their mitochondrial genome to their offspring.
The nuclear genome represents an amalgamation of DNA sequences inherited from each parent.
Male & Female Chromosomes
Biological sex is typically* determined by the combination of sex chromosomes inherited from both parents.
Females typically* have two X chromosomes (XX), and males typically have one X and one Y chromosome (XY).
It is the contribution of the male during fertilization that determines the genetic sex of the offspring.
- If a sperm carrying an X chromosome fertilizes an egg, the resulting combination is XX, leading to a female offspring.
- If a sperm carrying a Y chromosome fertilizes an egg, the combination is XY, resulting in a male offspring.**
* Girls with Swyer syndrome (1 in 80 thousand) have an XY chromosomal makeup (as boys normally do) instead of an XX chromosomal makeup (as girls normally do). Despite having the XY chromosomal makeup, girls with Swyer syndrome look female and have functional female genitalia and structures including a vagina, uterus and fallopian tubes.
** History has something to say about this: Henry's (8th) driving desire for a male heir was to lead him to divorce two wives and have two wives beheaded: it led to religious revolution and the creation of the Church of England, the Dissolution of the Monasteries and the Reformation. The decisions that Henry made during his reign were to shape modern Britain.
source: basic science and history
Human Mitochondrial DNA Haplogroup
In human genetics, a human mitochondrial DNA haplogroup is a haplogroup defined by differences in human mitochondrial DNA. Haplogroups are used to represent the major branch points on the mitochondrial phylogenetic tree. Understanding the evolutionary path of the female lineage has helped population geneticists trace the matrilineal inheritance of modern humans back to human origins in Africa and the subsequent spread around the globe.
The letter names of the haplogroups (not just mitochondrial DNA haplogroups) run from A to Z. As haplogroups were named in the order of their discovery, the alphabetical ordering does not have any meaning in terms of actual genetic relationships.
The hypothetical woman at the root of all these groups (meaning just the mitochondrial DNA haplogroups) is the matrilineal most recent common ancestor (MRCA) for all currently living humans. She is commonly called Mitochondrial Eve.
The rate at which mitochondrial DNA mutates is known as the mitochondrial molecular clock. It is an area of ongoing research with one study reporting one mutation per 8000 years. source: Wikipedia
