Nucleic acids and chromatin

what is the structure of DNA?

double helix

built up from nucleotides

strands are antiparallel

the backbone is formed from phosphodiester bonds between adjacent nucleotides

what are some useful roles of junk DNA?

regulatory roles

DNA methylation

histone modifications

non-coding RNAs

what is epigenetic memory?

how cells remember their identity

what are some features of chromosomes?

centromere- kinetochore attach to centromere for chromosome segregation

a short and long arm

telomere- end of chromosomes, repetitive DNA sequences

what is the Hayflick limit?

the number of times normal somatic cells can divide before the cell stops dividing

what is chromatin?

a complex of proteins and DNA which packages genetic material inside the nucleus of eukaryotc cells 

what are the two forms of chromatin?

euchromatin- less condensed, can be transcribed

heterochromatin- highly condensed, typically not transcribed

what is a histone?

a basic protein that DNA wraps around to form nucleosomes

what is a nucleosome?

DNA wrapped around a histone octamer, the fundamental subunit of chromatin

what is a chromatosome?

a histone H1 and a nucleosome

what is chromatin remodelling?

a dynamic modification to control DNA accessibility for transcription, replication and repair

what is the importance in being able to control how DNA is used?

different cells in an animal have different functions

an animal has different needs throughout its life

animals need to adapt to different environments

how can histone tails be chemically modified?

acetylation, methylation, phosphorylation

where does DNA methylation occur?

in CpG sites

what is a CpG site?

where C is followed by G in 5’-3’ direction

what is a CpG island?

regions of DNA rich in C-G sequences

often near gene promoters

what is the result of DNA methylation?

gene silencing

what are epigenetic effects?

they influence the phenotypic changes by changing gene activity without altering the genotype

what are the major mechanisms of epigenetic effects?

DNA methylation

histone methylation/acetylation/phosphorylation

chromatin remodelling

when are epigenetic effects inherited?

during cell division