lesson 3

• This blueprint is referred to as DNA, which, as established, consists of sequenced nitrogen bases, phosphate groups, and sugar backbones.
• DNA - Histone - Nucleosome - Chromatin fiber - chromatid - chromosome
• The cell cycle is the ordered series of events involving cell growth and division to produce new cells (daughter cells).
• An overview of the cell cycle shows two (2) major phases: interphase and mitotic phase.
• This phase is dedicated to the growth, preparations, DNA synthesis, and replication. Interphase
• G0 This phase is where the cell spends the longest amount of time. It is the normal state of the cell where it undergoes standard levels of growth, metabolism, and no active division.
• The second-longest phase of the Cell cycle. Although visually similar to G0, the biochemical aspect of the cell is much more active. Proteins, building blocks for DNA, and energy are being accumulated. G1
• Once the cell has accumulated enough building blocks and energy, it beings the process of replicating DNA. Genetic material is normally observed as semicondensed chromatids. S
• Significant changes to the organelles and cell structure occur during this phase. The cytoskeleton is dismantled, organelles are duplicated, proteins needed to separate chromosomes are synthesized, and large amounts of energy are stored. G2
• After the preparations done during interphase are completed, the mitotic phase starts where the cell begins the process of aligning genetic material, separating them, dividing the cell, and forming the two (2) new daughter cells.
• DNA replication has ended at this point and is being condensed into chromosomes. Protein structures called centrioles begin to form and migrate toward opposite ends of the cell. Prophase
• The disintegration of the nuclear envelope signifies the late phase of prophase and the transition to metaphase known as prometaphase
• the phase After the nuclear envelope is removed, the microtubules attach to the kinetochore of the chromosomes. Metaphase
• Once the microtubules have pulled all the chromosomes, they will align at an imaginary equator known as the metaphase plate.
• This phase is the shortest, most crucial, and visually active phases of the M phase. The initiation of anaphase starts with the removal of cohesion proteins (responsible for the presence of the centromere).
• The telophase is initiated once the separated chromosomes are clearly located on opposite poles of the cell. Microtubules and centrioles disassemble to construct the new cytoskeleton of the daughter cells. A nuclear envelope will form around the chromosomes.
• The telophase is initiated once the separated chromosomes are clearly located on opposite poles of the cell. Microtubules and centrioles disassemble to construct the new cytoskeleton of the daughter cells. A nuclear envelope will form around the chromosomes.
• Once the chromatids have been separated, the microtubule spindle will form an actin ring in between the two (2) new daughter cells. For animal cells, this is known as a cleavage furrow, while in plant cells it is known as the cell plate. Cytokinesis
• The G1 checkpoint therefore evaluates if the necessary conditions for DNA replication have been met.
• asses the cell size and protein reserves of the cell. However, the main feature of G2 checkpoint is that it evaluates the DNA replicated.
• The M Checkpoint is also referred to as the spindle checkpoint. It checks if all sister chromatids are attached to their corresponding microtubules
• Mitosis is focused on cell division and producing daughter cells that are the same as the mother cell. This similarity is due to the same number of chromosomes present in the daughter cells as in the mother cell
• The main goal of meiosis is to take a diploid cell, reduce its chromosome number to produce haploid daughter cells.
• Cancer - caused by changes (mutations) to the DNA within cells. Cells divide uncontrollably and spread into surrounding tissue to make tumours (abnormal cells).
• Down Syndrome - a genetic condition where a person is born with an extra copy of chromosome 21 (type error: nondisjunction - the failure of separation of sister chromatids). It is not inherited.
• Klinefelter Syndrome (XXY) - where boys and men are born with an extra X chromosome. Men have low testosterone, causing some feminine features.
• Trisomy X - presence of an additional X chromosome in each of a female's cell (XXX). Have no life expectancy.
• Turner syndrome, a condition that affects only females, results when one of the X chromosomes (sex chromosomes) is missing or partially missing.