BioE002- Fundamentals of Molecular Biology Chapter 4

DNA

Where instructions for cellular functions are stored

Nucleotide

A monomer created by adding nucleosides (nitrogenous bases/sugar) + phosphates

Purines

2-carbon nitrogen ring bases (Adenine + Guanine)

Pyrimidines

1-carbon nitrogen ring bases (Cytosine + Thymine/Uracil)

Nucleotide

Building block of DNA and RNA, the nucleic acids that carry genetic information in cells

Nucleoside

base + sugar

Nucleotide base

ACGT

Phosphodiester bond

The formation of this is involved in the polymerization of nucleotides to form nucleic acids

James Watson and Francis Crick

Discovered DNA double helix structure

1953

Year DNA double helix was discovered

Advantages of DNA structure

• Allows DNA to be packed in chromosomes

• Facilitates proper self-replication

• Facilitates proper transcription to mRNA

• Makes DNA stable

• Prevents rapid mutation of DNA structure

• Makes DNA water soluble in nature

Chromatin

Mixture of DNA and proteins that form chromosomes found in human cells

Histones

Proteins that package massive amount of DNA in genomes into highly compact form that fits into the cell nucleus.

Nucleosome

Basic repeating subunit of chromatin packed inside nucleus. A single nucleosome consists of ~150 DNA base pairs wrapped around core of histone proteins (8 proteins)

Heterochromatin

closed, gene-poor, densely packed chromatin where transcription can’t occur

Euchromatin

Loosely packed, gene-rich chromatin where transcription can occur

Telomere

Repeated DNA sequences at ends of chromosome. A long stretch of DNA sequences repeated hundreds of times. Protects the chromosome ends from becoming frayed or destroyed. When a cell divides, telomeres become slightly shorter. The cell dies when it can’t keep dividing.

T-Loop

Knot at the end of the telomere that keeps chromosome ends from sticking together

Telomerase

An enzyme that adds repeated portions of telomere back so it doesn’t get too short

Karyotype

An individual’s complete set of chromosomes

Trisomy

Down syndrome where an individual has an extra copy of chromosomes in their cells.

Klinefelter syndrome

Male born with an extra X chromosome. Intersex

Protein coding DNA

Goes through transcription process and produces mRNA.

mRNA

goes through translation process and produces proteins

Non-coding DNA

Goes through process and produces non coding RNA. Can function as RNA as no translation is required.

Eukaryotic Cell cycle

Gap Stage 1, synthesis, gap stage 2, mitosis

Gap Stage 1

G1. Cell grows and carries out metabolism; organelles duplicate

Synthesis

S. DNA replication and chromosome duplication. Has RNA transcription and protein synthesis greatly reduced with the exception of histone proteins. Highly mitotic cells possess telomerase

Gap Stage 2

G2. Cells grow and prepare for mitosis. Marked by significant protein synthesis in preparation for mitosis.

Mitosis phase

M. Prophase→ Prometaphase→ Metaphase→ Anaphase→ Telophase→ Cytokinesis.

Eukaryotic Cell Cycle

A series of stages that a cell goes through to divide into two daughter cells. Checkpoint surveillance mechanisms guarantee each step is completed correctly before the next step is initiated.

Prophase

The first stage of cell division in mitosis and meiosis. During prophase, DNA condenses into visible chromosomes, and the mitotic spindle begins to form. 

Prometaphase

Second stage of mitosis. A stage of cell division that occurs during mitosis, when the nuclear membrane breaks down and chromosomes begin to move toward the center of the cell. 

Metaphase

Third phase of mitosis. A stage of cell division, mitosis or meiosis, where chromosomes condense and align in the middle of a cell

Anaphase

The fourth and shortest phase of mitosis. The stage of mitosis when sister chromatids separate and move to opposite ends of a cell.

Telophase

The fifth stage of mitosis. The replicated chromosomes reach opposite poles of the cell, a new nuclear membrane forms around each set of chromosomes

Cytokinesis

the final stage of cell division where the cytoplasm of a single cell is physically divided into two separate daughter cells,

Mitosis

Cells reproduce by process of cell division. This process leads to cells that are genetically identical to the parent and is the basis for making new cells.

Meiosis

Production of cells with half of parent genetic content and is the basis for producing new sexually reproducing organisms.

Interphase

The period between M-phases(G1→G2)

Permanent cells

Cells such as neuronal, muscle, red blood, are highly specialized and lack the ability to divide

Differentiated cells

Cells that normally don’t divide but can be induced to begin DNA synthesis and divide when given appropriate stimulus. Ex: Liver cells and lymphocytes

Dividing Cells

Cells that normally possess a relatively high level of mitotic activity. Ex: Hematopoietic stem cells

Asymmetric cell division

A process of stem cells where daughter cells have different fates. Generates cellular diversity.