Notes, abstracts, papers, exams and problems of Biology

DNA Replication

The process of DNA duplication, which allows identical genetic information to be shared between cellular daughters, consists of the following:

• The two strands of the double helix are separated.
• Free nucleotides can join the DNA nucleotides through their complementary bases. Only the nucleotides A can be combined with T, and C with G.
• The new nucleotides bind and form new DNA chains.
• Each of the two DNA chains serves as a template to create new strands.

Protein Synthesis

Proteins are formed by the joining of smaller molecules called amino acids. There are over 20 types of amino acids in different proteins. The order in which amino acids bind determines the type of protein.

Each cell produces thousands of proteins in its ribosomes, using... Continue reading "DNA Replication, Protein Synthesis, and Gene Therapy" »

Special Types of Cell Division

• Budding: Casts asymmetric cytoplasmic material; the daughter cell emerges as a bud from one side of the mother, such as in yeast or sponges.
• Sporulation: Several successive mitoses occur without cytokinesis; multinucleate cells are formed, for example, in fungi and protozoa.

Meiosis

To condense, look better.

Meiosis I

Stages of Prophase I

It is the most complex stage, with five sub-phases:

1. Leptotene: Chromosomes condense to become visible by light microscopy. Each is composed of two chromatids.
2. Zygotene: Homologous chromosomes pair up until they are completely aligned along their length. This pairing is called synapsis and occurs through a protein structure called the synaptonemal complex.
3. Pachytene: Crossover (chromatid