Functions and dysfunction in genomic regulation Flashcards
which amino acids make up a histone
the basic aa lysine and arginine
how is the pairing of A-T and G-C different?
A-T pairs contain 2 hydrogen bonds and G-C contains three
what is the exclusive carrier of information from DNA to protein?
RNA (mRNA)
When can RNA be transcribed into DNA?
though an RNA virus (HIV) by using reverse transcriptase
which is an RNA-dependent DNA polymerase
which part of DNA is the structural backbone?
sugar-phosphates; and give DNA its negative charge
which basic residue of histone proteins is the target for posttranslational modifications?
lysine
why are mitotic chromosomes condenses 500 times when compared with interphase chromosomes?
to prevent physical damage to the DNA as chromosomes are separated and passed on to daughter cells
what is the basic unit of chromosome packing?
nucleosomes
how many histone proteins make up the core particle of a nucleosome?
8
what are the DNA binding proteins that are involved in forming chromosomes?
histones and non-histone chromosomal proteins
what type of bonds are formed between DNA and the histone octamer in each necleosome
hydrogen bonds
what type of chromatin is highly concentrated at the centromers and telomers of a chromosome?
heterochromatin
euchromatin
refers to the transcriptionally active areas of the genome in which histone association with the DNA has been reduced
what effect does heterochromatin have on actively expressed, nearby genes?
they will be silenced if relocated near heterochromatin
where are long terminal repeats found and how are the formed?
at either end of retrotransposons (proviral DNA) and they are formed by reverse transcription of retroviral DNA
what effect does histone deacetylase (HDAC) have on gene expression?
HDAC removes the acetate group from histones, thereby allowing histones to reassociate with DNAactively represses gene expression – deactylated chromatin is compact and transcriptionally repressed– aka: turns gene off
function of histone acetyl transferase (HAT)
actively PROMOTES gene expression- mediated by binding of transcription factors - acetylated chromatin is open and transcriptionally active
HAT will acetylate lysine side chains on histones, which reduces the charge attraction between histones and DNA-
often associated with transcription factors that bind to the region of DNA that needs to be transcribed, facilitating the removal of histones from the DNA and binding of the transcription apparatus
effect of methylation on PTM
represses gene transcription – the greater the extent of methylation, the less readily a gene is transcribed
ex: CpG islands within a promoter - cysteine gets hypermethylated at 5’ position – transcriptional silencing
