An exceptional adult-clutch-embryo association and its implications for dinosaur reproduction

Reproductive cloning is the process of producing a genetically identical copy—a clone—of an entire organism. While clones can be produced by splitting an early embryo—similar to what happens naturally with identical twins—cloning of adult animals is usually done by a process called somatic cell nuclear transfer (SCNT).
Somatic Cell Nuclear Transfer
In SCNT, an egg cell is taken from an animal and its nucleus is removed, creating an enucleated egg. Then a somatic...

Comparative Development of Embryos Did you know that the embryos of fish, birds, and humans all look surprisingly similar in their early stages? This is because many animals share common ancestors, and these similarities during development provide important evidence for evolution. By studying how embryos of different species develop, scientists can see patterns that show how living things are connected, even if they look very different as adults.Comparative embryology helps explain how species...

The first successfully cloned mammal was Dolly, a sheep, born on 5th July 1996 at Roslin Institute, Scotland. The cloned sheep was named after the American singer Dolly Parton. Dolly lived for seven years and died of respiratory complications, which is speculated to be due to the actual age of her DNA. Because the DNA in cloned cells belongs to an older individual,  the cloned individual’s life expectancy may be affected. Indeed, analysis of Dolly’s DNA revealed shorter...

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This produces daughter cells with abnormal chromosome numbers.  Nondisjunction is common during anaphase I or anaphase II of meiosis.  Mutations in synaptonemal complex proteins that attach homologous chromosomes increase the chances of nondisjunction in anaphase I of meiosis I. In contrast, mutations in topoisomerases and condensins that hold...

Mammal ReproductionMammals have specialized reproductive strategies that set them apart from other vertebrates. Most mammals give birth to live young (except monotremes like the platypus and echidna, which lay eggs) and provide care for their offspring. One key feature of mammals is that mothers produce milk to feed their young through mammary glands. Mammals also show various parental care behaviors that increase the survival chances of their young, such as protecting, feeding, and teaching...

During fertilization, an egg and sperm cell fuse to create a new diploid structure. In humans, the process occurs once the egg has been released from the ovary, and travels into the fallopian tubes. The process requires several key steps: 1) sperm present in the genital tract must locate the egg; 2) once there, sperm need to release enzymes to help them burrow through the protective zona pellucida of the egg; and 3) the membranes of a single sperm cell and egg must fuse, with the sperm...