Except for a few viruses whose genetic material is RNA, the genetic material of most organisms is DNA.

Prokaryotic "chromosomes" are composed of a circular DNA molecule and a small amount of protein

Eukaryotic chromosomes are composed of DNA and approximately equal amounts of protein

The first carbon atom forms a glycosidic bond with the base - nucleoside

The four atoms of the sugar ring are in the same plane, and the protruding atoms are biased towards the C-5' side - internal formula (on the contrary - external formula)

RNA Main Cytosine C Uracil U

DNA contains cytosine thymine T

Both contain adenine A and guanine G

Modified pyrimidines (trace bases/rare bases)

isomer

3',5'-phosphodiester bond

X-ray diffraction data

Base pairing (Chargaff's law)

DNA titration curve

Complementary relationship between bases (base pairing)

The Π electron cloud between the paired base planes forms the base stacking force—propeller twisting

Narrow angles form minor grooves Wide angles form major grooves - specificity and protein interaction

Further twisted into supercoiled DNA (covalently closed circular DNA)

One strand breaks to form open circular DNA

Negatively supercoiled DNA

significance

Nucleosome (nuclear particle): a double-helical DNA molecule coiled with histones

Autosomes: The less compressed genetic material in the interphase nucleus and higher transcriptional activity

heterochromosome: vice versa

Non-histone proteins (sequence-specific DNA binding proteins): high mobility proteins, transcription factors, DNA polymerases, chromosome skeleton proteins - involved in the regulation of DNA replication and gene expression

Messenger RNA (mRNA): guides protein synthesis

Ribosomal RNA (rRNA)

Spacer sequences: There are some sequences between genes that neither transcribe RNA nor regulate gene expression.

Operator: Genes with the same function are often strung together and controlled by common regulatory elements and transcribed into the same mRNA molecule, which can guide the synthesis of multiple proteins.

Positive strand virus: After RNA enters the host cell, it can directly guide protein synthesis.

Negative strand virus: After entering the host cell, it must first synthesize RNA that is complementary to its base sequence before it can synthesize the corresponding protein.

Bipartite virus: After entering the host cell, it uses the negative strand of the double-stranded RNA as a template to synthesize positive-stranded RNA to guide protein synthesis, and then synthesizes the negative-stranded RNA to form a double-stranded RNA and assemble it with the protein to form a new virus.

Retrovirus: After entering the host cell, it needs to synthesize DNA complementary to its base sequence under the action of reverse transcriptase, which is called complementary DNA. The cDNA is then transcribed into mRNA to guide protein synthesis.

Overlapping genes: A nucleic acid sequence can encode multiple peptide chains

Plasmid: small circular DNA contained in bacteria

The genome is larger

No operator substructure exists

There are a lot of repetitive sequences

There is a broken gene

Accounting for 15% of the total

Transport amino acids to the corresponding location in the ribosome-mRNA complex for protein synthesis

Clover secondary structure/four-ring four-arm structure

Three-level structure inverted L shape

Accounting for 80% of the total

mRNA accounts for 3-5% of the total amount

The precursor is synthesized in the nucleus, and the entire gene, including introns and exons, is transcribed to form nuclear heterogeneous RNA (hnRNA) with extremely heterogeneous molecular sizes.

small nuclear RNA (snRNA)

small nucleolar RNA (snoRNA)

Antisense RNA (asRNA)

RNA interference (RNAi)

by function

within the cell

size

physical properties

sexual dissociation properties

Denaturation, renaturation, color increase and decrease effects, molecular hybridity

melting temperature

centrifugation

Sequence determination

The substrate on which the enzyme acts

hydrolysis site

non-specific nuclease

Determine the base composition of RNA or remove RNA impurities in solution

Color enhancement effect

The same DNA has different absorption properties max=260

Bases act as absorbers

hydrogen bonding between base pairs

base stacking force

Positive ions in the environment

Denaturation of double-stranded nucleic acids

Melting temperature Tm

After denaturation, biological functions are lost, UV absorption increases, solution viscosity decreases, and buoyant density increases.

Restoration

annealing

subtractive color effect

Influencing factors

molecular hybridization

probe

Southern blotting/Southern hybridization

Northern blotting/Northern hybridization

DNA chip technology/DNA microarray

F.Sanger proposed the chain termination method

Newly developed high-throughput sequencing technology (PCR)/polymerase chain reaction