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The genetics of dog hair colour is much more complicated than most people might think. There are many different genes, each themselves with sometimes three or four alleles, whose combination leads to the hundreds if not thousands of different coat varieties seen in canids both domestic and wild. Many people tend to think of genetics as working in the traditional Mendelian fashion of basic dominance and recessiveness of genes controlled by a single allele (say A/a), but dog hair colour is one of many examples where the answer is not that simple. The introduction of more than two alleles whose dominance over one another varies leads to many more possible combinations of traits and is why the pattern, colour, length and curliness of dog hair varies so widely across the family Canidae. One gene that plays a key role in coat colour is the agouti gene that encodes for a signalling molecule which disrupts the pathway in fur melanocytes (specialized pigment-producing cells) that leads to eumelanin production, these being darker brown and black pigment molecules. As a result, dogs that express the aguoti gene at high levels instead produce lighter phaeomelanin pigments that result in yellow, gold and even red coat colours. It's still not that simple however because the agouti gene has four alleles (a, aw ,at , ay ) each leading to varying levels of expression and different patterns of light and dark colours seen across the Canidae family.
Speciation is the process by which one lineage splits into two separate species as a result of selective pressures as well as due to evolution by natural selection. This process can occur under two broad categories of allopatric or sympatric, each leading to the outcome of speciation through two distinct mechanisms. Allopatric speciation occurs as a result of the geographic splitting of one species traditional range whether it be by a river, mountain range, canyon or human development like highways and canals. Sympatric speciation occurs when two different species arise within the same habitat with no geographical separation between the two. This process can occur as a result of the presence of an unfulfilled ecological niche which once filled leads to a split in the behaviour and breeding habits within one species, eventually leading to two new species through genetic isolation of the two populations.
The genetics of dog hair colour is much more complicated than most people might think. There are many different genes, each themselves with sometimes three or four alleles, whose combination leads to the hundreds if not thousands of different coat varieties seen in canids both domestic and wild. Many people tend to think of genetics as working in the traditional Mendelian fashion of basic dominance and recessiveness of genes but dog hair colour is one of just many examples where the answer is not that simple. The introduction of more than two alleles whose dominance over one another varies leads to many more possible combinations of traits and is why the pattern, colour, length and curliness of dog hair varies so widely across the family Canidae.
Mammalian teeth come in many different forms and differ from the teeth of reptiles in that mammals have evolved heterodonty which is the condition of having specialised teeth for different functions. Reptiles have uniform teeth that do not differ in form or function, the condition known as homodonty. Mammalian teeth fall into four different categories, each with different form and function. At the front of the mouth are incisors, behind which is a pair of canines which may or may not be present, followed by premolars and molars. Apart from canine teeth of which there is always only one or none on each side, the number of each tooth type varies by species. Us humans have in total (usually) 32 teeth, of which eight are incisors, four are canines, and eight premolars and molars.
Traditionally, the methods used to test a mother’s growing fetus for abnormalities are highly invasive and pose a serious risk to the developing child. Due to advances in genetics in recent years, newer far less invasive procedures are now available to expecting mothers that offer equally valid, and in some cases, possibly more reliable results without the need to put the child at risk. Non-invasive prenatal screening involves taking a simple blood sample from a mother who is at least 10 weeks along in her gestation period. The blood is centrifuged to separate the blood plasma from the denser red blood cells, and what's left is a solution containing just cell-free DNA (cfDNA) fragments from both the fetus and the mother. The majority of the cfDNA will be from the mother, but for reliable results in this test, a percentage of just 4% fetal DNA is adequate. The analysis is done by looking at the proportions of fragments found from each of the child’s 23 chromosomes and looking for higher or lower than expected proportions of certain chromosomal fragments that could indicate a trisomy or chromosomal deletion. For example, finding a higher proportion of cell-free DNA (cfDNA) fragments from chromosome 21 of the fetus suggests the child is at a higher risk of being born with Down Syndrome. All this has only recently become possible thanks to advances in the speed and efficiency at which genetic sequencing can be performed. The samples of multiple patients may be sequenced at once leading to a much faster and cost-efficient way of analyzing DNA.
In 1869 Thomas Huxley proposed the theory that birds descended from dinosaurs. For a long time, however, the idea was widely unaccepted and it wasn't until the discovery of many specimens of feathered theropod dinosaurs such as Archaeopteryx and other like it which lived in the late Jurassic and thereafter that pushed the idea into the spotlight and allowed it to gain traction and support. The idea is now widely accepted and new fossil finds are providing insight into how small flightless feathered raptors became the incredibly diverse array of birds that share the Earth with us today.
As early as the mid-1800’s the theory that birds had descended from dinosaurs had been proposed but was widely unaccepted for some time. It was the discovery of feathered theropod dinosaurs like Archaeopteryx that pushed the idea into the spotlight and allowed it to gain traction. Now the idea is widely accepted and new fossil finds are providing insight into how small flightless feathered raptors became the incredibly diverse array of birds that share the Earth with us.
The family Canidae contains all species of living and extinct quadrupedal carnivores resembling the domestic dog. This includes domestic dogs themselves, coyotes, wolves, foxes, dingoes and many others. Some interbreeding can occur between coyotes and dogs, as well as dogs and wolves and wolves and coyotes. The offspring of these pairings are fully viable and usually fertile, begging the question are these three varieties of canines really separate species. The wolf, Canis Lupis, is the largest of these three species and has overlapping ranges with the coyote, Canis latrans. These ranges also unsurprisingly overlap with human settlement, meaning there is the potential for both of these species to interbreed with a person pet dog or a stray domestic dog, the species Canis familiaris. What separates these three as different species is their tendency under ideal circumstances to avoid breeding with members of the other species. Although interbreeding is possible, in a proper habitat with adequate resources and fertile mates available it will not occur. These rare hybrids only occur when there is a shortage of healthy and viable mates of the same species.
Inside of a small plastic container is a single beige larva about one centimeter in length. Its body is a mixture of light beige and darker shades of brown interspersed through out with a distinct brown line running the length of the back of its abdomen. At the front the body narrows to from what appear to be a small pair of mandibles. The rear of the larva is much wider and flatter than the head and has two dark brown spots that look remarkably like a pair of eyes. The animals body is broken into individual segments, 12 in total, each of which is defined by a ring around the animal.