Biology Test - 67

A polygenic trait is a characteristic, sometimes we call them phenotypes, that are affected by many, many different genes. A classic example of this would be height.. Skin color is another trait that is very obvious in humans that is controlled by many, many different genes.

Mitosis, Meiosis, and Fertilization. A regular human cell has 46 chromosomes: 44 autosomes, which come in pairs, and 2 sex chromosomes, which specify whether someone is male (usually XY) or female (usually XX). The pairs of autosomes are called "homologous chromosomes."

Each chromosome at the anaphase stage of a bone marrow cell in our body has only one chromatid. Solution: Lampbrush chromosomes are a special form of chromosomes that are found in the growing oocytes (immature eggs) of most animals, except mammals.

In an organism that has 44 chromosomes i.e. 22 homologous pairs; at the end of first meiotic division the daughter cell will have; 22 chromosomes.

On the Origin of Species (or, more completely, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life), published on 24 November 1859, is a work of scientific literature by Charles Darwin which is considered to be the foundation of evolutionary biology.

The two bones of the lower leg, the large tibia and the smaller fibula, come together at the ankle joint to form a very stable structure known as a mortise and tenon joint.

The centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids (a dyad). During mitosis, spindle fibers attach to the centromere via the kinetochore. Centromeres were first thought to be genetic loci that direct the behavior of chromosomes.

Polytene chromosomes were first discovered in the 1880s in insects (Balbiani 1881). One of the earliest published examples of polytene chromosomes is of Chironimus salivary gland chromosomes found in Walther Flemming's 1882 book, Zellsubstanz, Kern, und Zelltheilung (Flemming 1882).

Balbiani rings (BR) in principle are giant puffs in the polytene chromosomes of the salivary gland cells of larvae of Chironomus tentans, as first described in 1881 by Balbiani. The typical morphological chromosome structure forming the Balbiani rings is the result of the very high transcription rate of these genes.