DNA + RNA Flashcards
condensed form of DNA: DNA + histones
chromatin
core of 8 histone proteins (2x: H2A, H2B, H3, H4) + 2 wraps of DNA
nucleosome core
content of histone core protein
+ charged (able to bind to - charged DNA):
lysine
arginine
charge of DNA
- charge:
negatively charged phosphate groups
histone not in nucleosome core
H1: ties one nucleosome to the next nucleosome
AR: deficiency in UMP synthase
↑orotic acid in urine
megaloblastic anemia (can’t make pyrimidines → no DNA synthesis for rapidly dividing RBCs)
DOESN’T cause ↑ammonia
orotic aciduria
most common causes of megaloblastic anemia
block THF of pyrimidine pathway: vitamin B12 deficiency folate deficiency block UMP part of pyrimidine pathway: orotic aciduria (can't be corrected with B12 or folic acid supplements)
↑ orotic acid + ↑ ammonia
ornithine transcarbamylase deficiency: urea cycle
↑ orotic acid + normal ammonia
orotic aciduria: deficient UMP synthase for pyrimidine synthesis
treatment for orotic aciduria
uridine supplementation to allow for pyrimidine synthesis
X-linked (mainly boys)
deficient in HGPRT used in purine salvage pathway
can’t salvage GMP or AMP → all purines converted to uric acid
Lesch-Nyhan syndrome
HGPRT:
Hyperuricemia
Gout
Pissed off (aggression, self-mutilation “lip-biting”)
Retardation: ID
dysTonia: muscle contractions that distort limbs
Lesch-Nyhan syndrome
treatment of Lesch-Nyhan syndrome
treat gout: allopurinol, febuxostat
adenosine deaminase deficiency can cause
SCID
nucleotide base substitution but final amino acid/polypeptide is unchanged (multiple codons for most amino acids- 3rd base in codon triplet can be variable)
silent DNA mutation
nucleotide base substitution changes amino acid sequence so that polypeptide produce has different structural or functional properties
missense DNA mutation
nucleotide base substitution results in stop (shortens length of polypeptide)
nonsense DNA mutation
nucleotide bases are added or deleted → reading frame is “shifted”
downstream amino acid sequence is completely different
frameshift DNA mutation
missense DNA mutation from GAG (glutamic acid) to GTG (valine) in a gene for hemoblogin
sickle cell disease hemoglobin will polymerize → RBC’s sickle
2 pyrimidines (usually T-T) on same strand of DNA covalently bonded together → kink in DNA backbone
pyrimidine dimer DNA mutation
if a pyrimidine dimer (thymine-thymine) exists in a strand of DNA (and was never repaired) it is susceptible to
UV radiation will damage DNA
types of DNA repair
repair single DNA strand: mismatch repair nucleotide excision repair base excision repair repair double strand: nonhomologus end joining
wrong base added to daughter (C-T) strand during replication
cut daughter strand upstream → remove bases → redo DNA replication
mismatch repair
correct DNA replication but damaged later (UV radiation - pyrimidine dimers)
remove large, BULKY area of nucleotides via endonucleases (cut both sides)→ DNA poly fills gap → DNA ligase join fragments
nucleotide excision repair
remove NONBULKY damage (only 1 base damaged)
glycosylase: recognizes base and removes the base
endonuclease: cuts DNA and removes sugar
DNA poly ß: fills gap
DNA ligase: seals
base excision repair
clean break in both strands of DNA - bring together 2 ends of DNA fragment
nonhomologus end joining
disease with mutation in gene that codes for a mismatch repair protein
hereditary nonpolyposis colorectal cancer
disease with defective nucleotide excision repair: can’t repair pyrimidine dimers due to UV radiation
xeroderma pigmentosum
↑ risk of skin cancer: melanoma, BCC, SqCC
mutation of helicase → defective DNA replication + repair
bloom syndrome
hypersensitive to sunlight
↑ risk of: leukemia, lymphoma, immunodeficiency, infertility
disease due to defective repair of dsDNA breaks
ataxia telangiectasia IgA deficiency cerebellar ataxia poor smooth pursuit ↑AFP >8 mo sensitive to ionizing radiation → can't repair DNA damage
disease due to defective repair of dsDNA breaks
BRCA1 and BRCA2 mutations:
breast cancer + ovarian cancer
RNA copied from DNA template and translated into proteins
mRNA
transfers information from mRNA and brings in amino acids to form polypeptide chain
tRNA
largest type of RNA
mRNA
smallest type of RNA
tRNA
part of ribosome
binds amino acids together
rRNA (ribosomal)
most abundant type of RNA
rRNA
synthesis of mRNA + tRNA
nucleoplasm (liquid part of nucleus)
synthesis of rRNA
nucleolus
first mRNA codon to be translated into an amino acid at the beginning of a polypeptide chain
AUG: start codon
amino acid in eukaryotes: methionine
mRNA stop codons: tells ribosome that polypeptide sequence is done with translation
UGA
UAA
UAG
enzyme that transcribes DNA into mRNA
RNA polymerase
mRNA → amino acids
translation
