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Biochemistry - Molecular
Terms in this set (29)
Condensed DNA (found in nucleus). There are two types.
Linker Histones (H1 and H5)
Highly alkaline proteins made of arginine and lysine found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes
Structure made of -ve charged DNA that loops twice around a +ve charged histone octamer.
HighlyCondensed form of chromatin strand. Appears dark on electron microscopy. It is transcriptionally INACTIVE. Only 8% of the genome is of this type.
Both centromeres and telomeres are heterochromatic, as is the Barr body of the second, inactivated X-chromosome in a female.
Less condensed form of chromatin strand. Appears light on electron microscopy. Transcriptional ACTIVE. 92% of the genome is of this type.
DNA methylation at CpG island
Process that irreversibly stops transcription by adding a methyl group to a gene DNA strand, making the gene inaccessible for transcription. Plays an important role in epigenetics as well as X-chromosome inactivation, aging and carcinogenesis.
A region of DNA with at least 200 base pairs, and a GC (cytosine and guanine) percentage that is greater than 50%.
Process that reversibly stops transcription.
Process that relaxes DNA coiling, promoting transcription.
Base + (deoxy)Ribose
Base + (deoxy)Ribose + phosphate
The phosphate is linked by a 3'-5' phosphodiester bond
"PUR(rines) are PURe As Gold"
Type of nucleotide: Adenine and Guanine. They are structurally made of 2 rings.
"CUT the PY (pie)"
Type of nucleotide: Cytosine, Uracil and Thymine. They are structurally made of 1 ring.
Chemical note: deamination of Cytosine makes Uracil
Structural note: Uracil (RNA) vs. Thymine (DNA)
Pyrimidines are Cytosine (CMP), Uracil (UMP) and Thymine (TMP)
The pyrimidine ring is synthesized before the ribose 5-phosphate molecule is supplied by 5-phosphoribosyl 1-pyrophosphate (PRPP).
(Asp, aspartate; CPS II, carbamoyl phosphate synthetase II; Gln, glutamine; Glu, glutamate)
Clinical note on pyrimidine synthesis
Some immunosuppressive, antineoplastic and antibiotic drugs interfere with pyrimidine synthesis:
Leflunomide: inhibits dihydroorotate dehydrogenase
Methotrexate (MTX) + Trimethoprim (TMP) + Pyrimethamine: inhibit dihydrofolate
5-fluorouracil (5-FU): inhibits thymidylate synthase
Adenine (AMP) and Guanine (GMP)
The purine ring is assembled on a ribose 5-phosphate molecule supplied by 5-phosphoribosyl 1-pyrophosphate (PRPP).
Clinical note of purine synthesis
Some immunosuppressive, antineoplastic and antibiotic drugs interfere with purine synthesis:
6-mercaptopurine (6-MP): inhibits de novo synthesis
Mycophenolate and Ribavirin: inhibit inosine monophosphate dehydrogenase
Enzyme involved in the synthesis of nucleotides that converts ribose 5-phosphate into phosphoribosyl pyrophosphate (PRPP). PRPP synthetase is involved in some X-linked recessive diseases. Mutations that lead to super-activity result in purine and uric acid overproduction. Super-activity symptoms include gout, sensorineural hearing loss, hypotonia, impaired muscle coordination (ataxia), hereditary peripheral neuropathy, and neurodevelopment disorder.
X-linked recessive condition that is caused by absent HGPRT, an enzyme that converts guanine into GMP. This results in excessive uric acid production and is manifested by the following symptoms:
Pissed off (aggression)
Retardation (neurodevelopment disorder)
Treatment: allopurinol + febuxostat
Adenosine deaminase deficiency
This condition leads to increased dATP which is toxic to lymphocytes. It is one of the major causes of autosomal recessive Severe Combined ImmunoDeficiency (SCID).
Enzyme required for adenosine and deoxyadenosine degradation and removal from the body into urine.
AT-rich DNA sequence
Promoter region at the origin of DNA replication
Replication where each strand of the original DNA molecule serves as a template for the production of its counterpart.
Y-shaped region along the DNA template where leading and lagging strands are synthethised.
DNA replication direction
DNA is always synthesized in the 5' to 3' direction!
Leading DNA strand
The strand of nascent DNA which is being synthesized in the same direction as the growing replication fork. A polymerase "reads" this strand's template and adds complementary nucleotides to the nascent leading strand on a continuous basis. On this strand, the replication route is continuous.
Lagging DNA strand
The strand of nascent DNA whose direction of synthesis is opposite to the direction of the growing replication fork. On this strand the new DNA is made in installments (Okazaki fragments), which are later joined together by a DNA ligase enzyme. This is because the enzymes that synthesise the new DNA can only work in one direction along the parent DNA molecule. On this strand, the replication route is discontinuous.
They are short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication. They are complementary to the lagging template strand, together forming short double-stranded DNA sections. Contain between 1000 and 2000 nucleotides in prokaryotes (e.g. E. coli) and roughly 100 to 200 nucleotides in eukaryotes.
Genetic material (DNA/RNA) replication enzymes
THIS SET IS OFTEN IN FOLDERS WITH...
Biochemistry - Nutrition
Biochemistry - Metabolism
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