Nucleic Acids Flashcards
Nucleotide
A base, sugar, and phosphate
Location of DNA
The nucleus
Nucleoside
Just a base and sugar
Why is DNA so strongly held together?
All pairs have either double or triple hydrogen bonds and the planar bases allow more bonds per volume
DNA backbone
Phosphate backbone linked by phosphodiester bonds
The relatively stronger base pair
Cg, as it has three h bonds
Groovy, man
Minor and major groove. Most DNA contacts made in major groove, where there is more room
Three DNA conformations
B: right handed, normal
A: right handed, more compact, found in DNA RNA hybrids
Z: left handed, found transiently, during transcription
Karyotype
The display of all 46 human chromosomes
Chromosomes can be distinguished by
Size, staining patterns, and fish colour
A gene contains
The DNA sequence that encodes the structural components of a gene product and regulatory elements that control its expression (promoter)
Use of fish
Diagnosing chromosomal conditions
Locus
A specific location on a chromosome
Heterozygous vs homozygous alleles
If two genes functionally differ, they are heterozygous
Homologous chromosomes
Corresponding chromosomes
Conserved synteny
Same genes in the same order, but in different species
Chromatin
A histone DNA complex that contains a large amount of arg and lys, the arg and lys neutralize the negatively charged DNA backbone
Nucleosome
Basic unit of DNA packaging in eukaryotes. Basic unit of chromatin. DNA wound around histones
Histone tails
Regulate histone structure and are subject to covalent modifications. Modified by acetylation and methylation of lysines and by phosphorylation of serines. HATs add histone acetyl groups and loosen up genes for expression. HDACs take off and tighten
HATs
Histone acetyltransferases. Loosen up genes for expression
HDACs
Histone deacetyltransferases. Silence genes by taking off acetyl groups. HDAC inhibitors have uses in anti cancer drugs, by stopping suppression of anti cancer genes.
Histone acetylation
Crucial in destabilizing chromatin structure for replication. Acetyl group removes overall positive charge of lysine. Enzymes that modify are tightly regulated
Euchromatin
Good to go. Open for transcription. Acetylation of tail histones is associated with euchromatin
Heterochromatin
No go. Highly condensed, associated with de-acetylation. Can include HDACs like SIR proteins
RNA
Runs 3’-5’.
Single stranded, but can form secondary and tertiary structures by base pairing upon itself. These looped regions are important for binding proteins and other molecules.
Can act as enzymes as ribozymes
M, r, and t are involved in protein synthesis
mRNA
Messenger, codes for proteins
rRNA
Ribosomal. Forms basic structure of ribosome and catalyzes protein synthesis
tRNA
Transfer. Adapters between mRNA and aas. All have cloverleaf structure. Anti codon site binds to codon on mRNA . Have some modified nucleotides like ribothymidine. 3’ aa attachment site.
snRNA
Small nuclear. Nuclear processes, including splicing of pre mRNA.
snoRNA
Small nucleolar. Process and chemically modify mRNA
scaRNA
Small cajal. Modifiy snoRNA and snRNA
miRNA
Micro. Regulate gene expression by blocking translation of selected mRNA and chromatin formation. Key functions in cell differentiation. Mutations can cause cancer. Similar to siRNA.
siRNA
Small interfering. Turn off gene expression by degrading mRNAs and establishing compact chromatin
Processed mRNA
A 5’ guanosine cap, start codon, stop codon, poly a tail
Ribosomes
Ribonecleoprotein structures on which protein synthesis occurs. Contain rRNA. Many loops and extensive base pairing.
