central dogma

• A gene is a segment of DNA that contains the instructions for building and maintaining an organism and is the basic unit of heredity.
• Closely related species will have a higher percentage of similarity in their DNA base order, for instance, humans and chimps share around 98%.
• The study of genes helps researchers understand the evolutionary history and relatedness of different species.
• A gene consists of specific sequences of nucleotides, the building blocks of DNA, which provide the code for creating proteins needed for determining the various traits and characteristics of an individual.
• Transcription factors mediate the binding of RNA polymerase II to the promoter, forming a transcription initiation complex.
• Promoters signal the initiation of RNA synthesis, with a promoter called the TATA box being the promoter in eukaryotes.
• A eukaryotic promoter includes a TATA box.
• Several transcription factors must bind to the DNA before RNA polymerase II can do so.
• Additional transcription factors bind to the DNA along with RNA polymerase II, forming the transcription initiation complex.
• Alleles are different forms of the same gene, and in every gene, you can have two of the same allele (AA) or two different alleles (Aa).
• A chromosome is a thread-like structure made of DNA and proteins found in the nucleus of a cell.
• Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).
• DNA consists of two molecules arranged into a ladder-like structure called a Double Helix.
• A molecule of DNA is made up of millions of tiny subunits called Nucleotides.
• Each nucleotide consists of a Phosphate group, a Pentose sugar, and a Nitrogenous base.
• Adenine (A) and Guanine (G) are PURINES, which have a TWO ring structure.
• Thymine (T) and Cytosine (C) are PYRIMIDINES, which have a ONE ring structure.
• A TWO ring purine always pairs with a ONE ring pyrimidine due to complementary base pairing.
• Strands of DNA are different, they are oriented in opposite directions to each other and are Antiparallel.
• The order of the bases in one strand determines the order of the bases in the other strand due to complementary base pairing.
• RNA (Ribonucleic Acid) is single stranded with Uracil instead of Thymine and contains ribose sugars rather than deoxyribose sugars, which makes RNA more unstable and more prone to degradation.
• Transcription initiation complex is the starting point of transcription.
• Each end of a pre-mRNA molecule is modified in a particular way: poly-A tail.
• Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that lie between coding regions, these noncoding regions are called intervening sequences, or introns.
• Paternal ( n ) + Maternal ( n ) are prone to mutations and contain more variations, more differences.
• Usually Nuclear DNA regions + Mitochondrial / Chloroplast DNA regions are used to produce a highly resolved phylogenetic trees.
• A gene can be transcribed simultaneously by several RNA polymerases.
• RNA transcript is the product of transcription.
• RNA polymerase II transcribes genetic information into RNA.
• The other regions are called exons because they are eventually expressed, usually translated into amino acid sequences.
• In animals, Nuclear + Mitochondrial DNA regions are used, but most papers use only Mitochondrial DNA.
• Transcription factors regulate the transcription process.
• Molecules of tRNA are not identical: each carries a specific amino acid on one end and an anticodon on the other end; the anticodon base-pairs with a complementary codon on mRNA.
• In plants, Nuclear + Chloroplast regions are used, but for prokaryotes, usually the whole genome is used (because their genome is smaller).
• A cell translates an mRNA message into protein with the help of transfer RNA ( tRNA).
• Depends on the taxa you are studying, some favor only one region, some favor multiple regions (up to 10 regions!).
• These modifications share several functions: they facilitate the export of mRNA and protect mRNA from hydrolytic enzymes.
• In prokaryotes, the polymerase stops transcription at the end of the terminator.
• mRNA is translated in codons (3 nucleotides).
• Transcription progresses at a rate of 40 nucleotides per second in eukaryotes.