Notes in MtM IV (DNA and the genome)

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Published	11/11/2024	{{c1::Nucleotides}} are the {{c1::monomers that make up nucleic acids (DNA or RNA)}}. The sugar could either by {{c1::ribose}} (in RNA) or {{c1::deoxy…
Published	11/11/2024	The structure of a nucleotide consists of {{c1::a pentose sugar}} attached to a {{c1::nitrogen base}} and {{c1::a phosphate group}}.
Published	11/11/2024	{{c2::Adenine and Guanine}} are {{c1::purines}} and {{c2::Cytosine and Thymine}} are {{c1::Pyrimidines}}.
Published	11/11/2024	DNA is a {{c1::double-helical}} structure composed of {{c1::two long strands}} of {{c1::nucleotides}} joined together by {{c1::hydrogen bonds}}.
Published	11/11/2024	Each of the two DNA strands is created by the formation of {{c1::phosphodiester}} bonds between {{c1::consecutive nucleotides}}.
Published	11/11/2024	The {{c2::series of phosphodiester bonds which form an entire DNA strand}} are known as the {{c1::sugar-phosphate backbone}}.
Published	11/11/2024	Each DNA strand has a {{c1::5’}} end and a {{c1::3’}} end. The two strands in DNA run in an {{c1::anti-parallel}} direction.
Published	11/11/2024	A {{c2::chromosome}} is a {{c1::highly condensed DNA molecule}}. In human cells, there are {{c1::23}} pairs of chromosomes.
Published	11/11/2024	Of the 23 pairs of human chromosomes, {{c1::22}} are {{c2::somatic}} and {{c1::1}} is {{c2::sex}}.
Published	11/11/2024	Different chromosome pairs can be identified by {{c1::differing sizes}}, {{c1::fluorescent dyes of different colours}} that {{c1::bind to a specific p…
Published	11/11/2024	A {{c1::gene}} is a {{c1::specific length of DNA that codes for an RNA strand}}.
Published	11/11/2024	A newly formed RNA stand is either {{c1::translated by ribosomes to form a protein}} or {{c1::stays as a RNA strand}}.
Published	11/11/2024	{{c1::r}}RNA and {{c1::t}}RNA are involved in {{c2::the translation of mRNA}}.
Published	11/11/2024	{{c1::sn}}RNA and {{c1::sno}}RNA {{c2::modify other RNA molecules}}.
Published	11/11/2024	{{c1::mi}}RNA {{c2::binds to and inhibits translation of mRNA}}.
Published	11/11/2024	Within genes, there are other non-protein coding regions such as {{c1::introns}} (which are {{c2::not expressed}}) and {{c1::promotor}} and {{c1::regu…
Published	11/11/2024	In chromosomes but outside genes, there are many repeated sequences ({{c1::satellites}}) which are {{c1::non-protein coding but have other functi…
Published	11/11/2024	{{c2::Centromeres}} are the site of  {{c1::attachment of protein fibres}} during {{c1::cell division}}.
Published	11/11/2024	Telomeres marks {{c1::the ends of chromosomes}} to ensure {{c1::full replication of DNA}}. They also serve as {{c1::protective caps}} for {{c1::chromo…
Published	11/11/2024	{{c2::Replication sites}} are {{c1::the site where DNA replication begins}}.
Published	11/11/2024	Repeated units of DNA can cause problems during replication by leading to {{c1::mispairing}} of {{c1::non-homologous chromosomes}}.&nbs…
Published	11/11/2024	The packaging and condensation of DNA into chromosomes involves the association of DNA to a {{c1::histone core}} composed of {{c1::8 histone proteins}…
Published	11/11/2024	The {{c1::complex of DNA and histones}} is called a {{c1::chromatin}}.
Published	11/11/2024	{{c1::One unit of DNA bound to a histone core}} is known as a {{c2::nucleosome}}.
Published	11/11/2024	Chromatin exists in two forms during interphase, which are {{c1::euchromatin}} and {{c1::heterochromatin}}.
Published	11/11/2024	{{c2::Euchromatin}} are a {{c1::less compact}} type of chromatin, so {{c1::it is easier to transcribe}}. It is found mainly in {{c1::gene-rich areas}}…
Published	11/11/2024	{{c2::Heterochromatin}} is a {{c1::highly condensed type}} of chromatin, so {{c1::it cannot be transcribed}} and so therefore {{c1::proteins cannot ac…
Published	11/11/2024	DNA replication is a {{c1::semi-conservative}} process, where {{c1::each strand acts as a template for the synthesis of a new strand}}.
Published	11/11/2024	DNA replication begins at {{c1::replication origins}}, which are usually rich in {{c1::A-T}} base pairs, as they are weaker than {{c1::C-G}} base pair…
Published	11/11/2024	At the start of DNA replication, an {{c1::initiator protein}} attaches to DNA at each {{c1::replication origin}}, {{c2::opening up the double helix an…
Published	11/11/2024	The {{c2::replication fork}} is a region where {{c1::a cell's DNA double helix}} has been {{c1::unwound and seperated}} by {{c1::helicases}}.&nbs…
Published	11/11/2024	A {{c1::primer}} is a {{c2::short length of RNA}} that is complimentary to the {{c2::template DNA}} strand. It is synthesised by {{c2::primase}} enzym…
Published	11/11/2024	{{c1::Free nucleotides}} begin to form {{c2::hydrogen bonds}} with the {{c2::exposed bases on template strands}}, following complementary base-pairing…
Published	11/11/2024	{{c1::DNA polymerase}} {{c2::proofreads the replicated strand}} to ensure that the {{c2::correct bases has been added}}, before it moves on to the nex…
Published	11/11/2024	DNA polymerase can only add nucleotides in a {{c1::5’}} to {{c1::3’}} direction. Therefore, the opposite direction (also called {{c1::lagging}}) stran…
Published	11/11/2024	{{c2::Okazaki fragments}} are short sequences of {{c1::DNA nucleotides }} which are synthesized {{c1::discontinuously}} and later …
Published	11/11/2024	{{c2::DNA mismatch repair}} is a system for {{c1::recognizing}} and {{c1::repairing erroneous insertion}}, {{c1::deletion}}, and {{c1::mis-incorp…
Published	11/11/2024	The 3 main ways of DNA damage outside of replication are {{c1::depurination}} (which is the {{c2::spontaneous removal of a purine}}, leading to a {{c2…
Published	11/11/2024	This damage to DNA is repaired by the action of {{c1::nucleases}}, {{c1::DNA repair polymerase}}, and {{c1::DNA ligase}}.
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