If one egg is fertilised by two sperm, it results in three sets of chromosomes, rather than the standard two – one from the mother and two from the father. And, according to researchers, three sets of chromosomes are “typically incompatible with life and embryos do not usually survive”.

Mitochondria are special because they have their own ribosomes and DNA floating in the matrix. There are also structures called granules which may control concentrations of ions. Cell biologists are still exploring the activity of granules.

Mitochondria have a double membrane structure, with an inner layer with many folds to create a high surface area. This provides more space for more metabolising proteins and therefor they are able to create more energy at one time.

Chloroplasts and mitochondria are double membrane bound organelles. Characteristics of Mitochondria (i) The mitochondria are sausage-shaped or cylindrical having a diameter of 0.2-1.0 µm and average 0.5 µm and length 1.0-4.1 µm. (ii) Each mitochondrion is a double membrane bound structure.

“Maternal inheritance” of mtDNA in mammals is of interest to reproductive biologists; as in almost all species the entire sperm, including the midpiece mitochondrial sheath, enters the egg at fertilization. Subsequently, tail and midpiece structures can be traced for several division cycles (9, 10).

It is possible for twins to have different fathers in a phenomenon called heteropaternal superfecundation, which occurs when two of a woman’s eggs are fertilized by sperm from two different men. Identical twins occur if that fertilized egg divides into two separate eggs, early in the pregnancy.

Superfecundation twins: When a woman has intercourse with two different men in a short period of time while ovulating, it’s possible for both men to impregnate her separately. In this case, two different sperm impregnate two different eggs.

Once the sperm have entered the uterus, contractions propel the sperm upward into the fallopian tubes. The first sperm enter the tubes minutes after ejaculation. The first sperm, however, are likely not the fertilizing sperm. Motile sperm can survive in the female reproductive tract for up to 5 days.

Try some of these tips:

1. Don’t smoke or use illicit drugs, especially anabolic steroids.
2. Avoid contact with toxins such as pesticides and heavy metals.
3. Limit how much alcohol you drink.
4. Eat a healthy diet and keep your weight under control.
5. Keep your scrotum cool, because heat slows down the making of sperm.

While it’s extremely unlikely, the simple answer is yes. Women are not able to conceive whilst on their period, but sperm survives within the female reproductive system for up to five days. This means that a tiny fraction of women do have a small chance of becoming pregnant from unprotected sex during their period.