Although all sperm may look the same to a casual observer in fact human ejaculates are very heterogeneous, and subpopulations of sperm with distinct biochemical and physiological characteristics can be identified in every sample.
Each sperm cell contains half the father's DNA. But it's not identical from sperm to sperm because each man is a mixture of the genetic material from his parents, and each time a slightly different assortment of that full DNA set gets divided to go into a sperm.
As it turns out, the sperm from different species of animals have different shapes—and new research shows that those shapes can be used to figure out who's who among closely related rodents.
So, what does sperm look like? A normal human sperm's head is egg-shaped. Its edges are smooth and its width and length are 2 microns and 4 microns respectively. Its acrosome does not contain vacuoles.
Morphologic sperm traits, including the shape of the head and the length of the flagellum, are diverse in mammals. In general, the width and length of the sperm head vary due to variations in the size and organization of the acrosome and nuclei [1].
Dog sperm looks similar to human sperm, but unlike the human version, dog sperm isn't ready to fertilize an egg right away. That's because dog sperm has a coating of cholesterol that covers its head, where the DNA information is kept.
Ethical considerations preclude definitive research on the subject, but it's safe to say that human DNA has become so different from that of other animals that interbreeding would likely be impossible.
While there is no definite age at which male ejaculation ceases, it has been suggested that it may happen when a man reaches his late 40s or early 50s. It is important to note, however, that this is not a universal rule and some men may continue to ejaculate at a later age.
Healthy semen is a cloudy white color with a jelly consistency similar to a raw egg. Slight changes in semen color, texture, and even smell might be normal and should no pose concern. In some cases, semen color changes could be a sign of an underlying issue.
Unhealthy sperm can look very different from healthy sperm in terms of color, shape, and size. Normal healthy sperm ranges in color from a transparent to a grayish white, while unhealthy sperm can often appear yellow-green or off-white.
There is ample evidence to show that as millions of human sperm cells swim towards a waiting ovum or egg, only one gets to fertilize it. Now, a new study shows that even though the fastest and most capable sperms reach the ovum first, it is the egg that has the final say on which sperm fertilizes it.
If two sperm fertilize one egg which is a very rare occurrence in 1% of the case the embryo can't survive. So, two sperm cannot fertilize the same egg.
There is a chance that two different sperm cells will fertilize both eggs. A woman gives birth to twins in this case. Fraternal twins or non-identical twins are the terms used to describe these types of twins.
Like your genome, each gamete is unique, which explains why siblings from the same parents do not look the same. Following fusion of the egg and sperm, another type of cell division called mitosis occurs, producing two identical cells from one.
Combining two sperm wouldn't work. There just isn't enough in a sperm to sustain an embryo early on. What about removing the DNA from an egg, and adding two sperm to that? Theoretically you'd end up with a child with the DNA of both dads, and just a bit of the donor's DNA.
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".
As men get older it is also usual for their semen to become slightly thinner with less volume being produced at ejaculation. It is therefore quite normal if there appear to be clumps of jelly-like globules in your semen and there is nothing to worry about here.
There is no specific frequency with which a man should ejaculate. There is no solid evidence that failure to ejaculate causes health problems. However, ejaculating frequently can reduce the man's risk of getting prostate cancer. Ejacu-lation can be through having sex or masturbating a few times a day.
Some studies suggest that moderate ejaculation (2–4 times per week) is associated with a lower prostate cancer risk. However, ejaculating more often doesn't mean your cancer risk drops even more.
People who choose not to ejaculate are unlikely to experience harmful side effects. The body breaks down unused sperm, which does not build up to trigger further problems. Over time, not ejaculating can trigger psychological problems.
Due to the much larger evolutionary distance between humans and monkeys versus humans and chimpanzees, it is considered unlikely that true human-monkey hybrids could be brought to term.
You're right, humans and dogs can't reproduce. So you won't get anything like Barf the Mog from Spaceballs. A half man/half dog wouldn't get very far past a single cell (assuming the egg and sperm could even come together!). This is because dogs and people have very different sets of instructions in their DNA.
In fact, such human-animal hybrids are often referred to as “chimeras”.