Search Results

Chronology of leptin research (A history of leptin research)

By: HWC, Views: 4954

In 1950. researchers at Jackson Laboratories noticed that one of their mice had become extremely obese—it had an insatiable appetite. Intrigued, they bred a strain of mice showing this characteristic. In the late 1960s, researchers surgically connected the bloodstreams of a normal mouse and a...

Amniocentesis and CVS Animation

By: HWC, Views: 4775

Amniocentesis and chorionic villus sampling (CVS) are prenatal diagnostic tools. In amniocentesis, which can be performed as early as 14 weeks into the gestation period. A syringe needle is inserted through the abdominal and uterine walls to withdraw some amniotic fluid. The fluid contains...

X chromosome inactivation in calico cats

By: HWC, Views: 4825

X chromosome inactivation causes a mosaic tissue effect in calico cats. what makes this female calico cat "calico." Like all mammals, this cat began her life as a single cell. That cell had two X chromosomes, one from each parent. One of the chromosomes carried a dominant allele for the ...

Mechanisms for chromosome movement Animation

By: HWC, Views: 4876

At mitotic metaphase, the fully-formed spindle is composed of many microtubules that extend from the poles. Some of these, the kinetochore microtubules, are attached to the kinetochores of each chromosome. Kinetochores are located at the centromeres. At anaphase, sister chromatids separate and...

Genetic distance between human groups

By: HWC, Views: 4747

One proposed family tree for modern humans. This family tree is based on nucleic-add hybridization studies of many genes and immuno-logical comparisons. Branch points show presumed genetic divergences. This data indicates that the greatest genetic distance separates humans native to Afri...

Inflammatory response Animation

By: HWC, Views: 4422

Any tissue damage or bacterial invasion can bring about inflammation. The inflammatory response can be triggered by an invasion of bacteria, or by a cut or other physical damage to cells. Chemicals, such as histamine, released by the bacteria or damaged cells. accumulate in the tissue. Thes...

Primate Evolutionary Tree Animation

By: HWC, Views: 4040

Presumed evolutionary branchings in the primate family tree. The first primates arose between 85 and 65 million years ago. The common ancestor of apes and hominids branched off from Old World monkeys about 23 million years ago. The hominid lineage, which includes humans and earlier humanlik...

Cell mediated immune response to a viral infection Animation

By: HWC, Views: 3903

Intracellular pathogens are the targets of cell-mediated immune response. The process begins when a virus infects a macrophage. Another macrophage engulfs the same virus or an antigen from it. In both cells, enzymes cleave the viral antigens into small bits. The fragments move to the cell sur...

Chromosome structural organization/ Mechanisms for chromosome movement Animation

By: HWC, Views: 4046

How the chromosome is organized. At metaphase, the chromosomes are duplicated and are at their most condensed. In each chromosome, two identical sister chromatids are held together at a constricted region called the centromere. When a chromosome is condensed, interactions among chromosomal ...