A-band

Examples of A-band in the following topics:

• Sliding Filament Model of Contraction

  • The I-band is spanned by the titin molecule connecting the Z-line with a myosin filament.
  • The region between two neighboring, parallel I-bands is known as the A-band and contains the entire length of single myosin myofilaments.
  • Within the A-band is a region known as the H-band, which is the region not superimposed by actin myofilaments.
  • The myofilaments themselves do not contract or expand and so the A-band remains constant.
  • The A-band remains constant throughout as the length of the myosin myofilaments does not change.

• Superphylum Lophotrochozoa

  • The Lophotrochozoa are protostomes possessing a blastopore, an early form of a mouth; they include the trochozoans and the lophophorata.
  • This layer multiplies into a band which then splits internally to form the coelom; this protostomic coelom is termed schizocoelom.
  • Trochophore larvae are characterized by two bands of cilia around the body.
  • However, they show a number of important differences.
  • The Caribbean Reef Squid or Sepioteuthis sepioidea is a complex lophotrochozoan.

• Basics of DNA Replication

  • At the point, the molecules stopped sedimenting and formed a stable band.
  • DNA from cells grown exclusively in 15N produced a lower band than DNA from cells grown exclusively in 14N.
  • The DNA harvested from cells grown for two generations in 14N formed two bands: one DNA band was at the intermediate position between 15N and 14N and the other corresponded to the band of exclusively 14N DNA.
  • Dispersive replication would have resulted in exclusively a single band in each new generation, with the band slowly moving up closer to the height of the 14N DNA band.
  • DNA grown in 15N (red band) is heavier than DNA grown in 14N (orange band) and sediments to a lower level in the cesium chloride density gradient in an ultracentrifuge.

• Identification of Chromosomes and Karyotypes

  • In a given species, chromosomes can be identified by their number, size, centromere position, and banding pattern.
  • Giemsa staining results in approximately 400–800 bands (of tightly coiled DNA and condensed proteins) arranged along all of the 23 chromosome pairs.
  • An experienced geneticist can identify each chromosome based on its characteristic banding pattern.
  • In addition to the banding patterns, chromosomes are further identified on the basis of size and centromere location.
  • Notice that homologous chromosomes are the same size, and have the same centromere positions and banding patterns.

• Types of Energy

  • A wrecking ball can perform a large amount of damage, even when moving slowly.
  • What if that same motionless wrecking ball is lifted two stories above a car with a crane?
  • A spring on the ground has potential energy if it is compressed, as does a rubber band that is pulled taut.
  • This energy is transformed into kinetic energy that allows a car to race on a racetrack.
  • Moving water, such as in a waterfall or a rapidly flowing river, has kinetic energy.

• Phylum Annelida

  • The clitellum is a reproductive structure that generates mucus that aids in sperm transfer and gives rise to a cocoon within which fertilization occurs; it appears as a fused band in the anterior third of the animal .
  • A well-developed and complete digestive system is present in earthworms (oligochaetes) with a mouth, muscular pharynx, esophagus, crop, and gizzard being present.
  • Each segment is limited by a membranous septum that divides the coelomic cavity into a series of compartments.
  • Excretion is facilitated by a pair of metanephridia (a type of primitive "kidney" that consists of a convoluted tubule and an open, ciliated funnel) that is present in every segment towards the ventral side.
  • It can be seen in this image as the enlarged band around the animal.

• Genetic Maps

  • Although individuals of a given species are genetically similar, they are not identical; every individual has a unique set of traits.
  • The DNA of every individual will give rise to a unique pattern of bands when cut with a particular set of restriction endonucleases; this is sometimes referred to as an individual's DNA "fingerprint."
  • Certain regions of the chromosome that are subject to polymorphism will lead to the generation of the unique banding pattern.
  • SNPs are variations in a single nucleotide.
  • Recombination between genes A and B is more frequent than recombination between genes B and C because genes A and B are farther apart; a crossover is, therefore, more likely to occur between them.

• Strategies Used in Sequencing Projects

  • The chain termination method involves DNA replication of a single-stranded template with the use of a primer and a regular deoxynucleotide (dNTP), which is a monomer, or a single unit, of DNA.
  • Because the ddNTPs are fluorescently labeled, each band on the gel reflects the size of the DNA strand and the ddNTP that terminated the reaction.
  • Reading the gel on the basis of the color of each band on the ladder produces the sequence of the template strand .
  • In a larger piece, you see that the same mountain is behind a lake.
  • The DNA is separated on the basis of size, and these bands, based on the size of the fragments, can be read.

• Population Size and Density

  • For example, a larger population may be more stable than a smaller population.
  • Individuals in a low-density population are thinly dispersed; hence, they may have more difficulty finding a mate compared to individuals in a higher-density population.
  • A quadrat is a square that encloses an area within a habitat.
  • With this method, researchers capture animals and mark them with tags, bands, paint, body markings, or some other sign.
  • With the mark and recapture method, researchers capture animals and mark them with tags, bands, paint, body markings or some other sign.

• Muscle Tissues and Nervous Tissues

  • They differ by the presence or absence of striations or bands, the number and location of nuclei, whether they are voluntarily or involuntarily controlled, and their location within the body.
  • Smooth muscle cells have a single, centrally-located nucleus and are spindle shaped.
  • Smooth muscle tissue is also called non-striated as it lacks the banded appearance of skeletal and cardiac muscle .
  • A nerve consists of a neuron and glial cells.
  • There is a large structure with a central nucleus: the cell body (or soma) of the neuron.