Structure and Organization of Nucleic Acids Flashcards
What are 4 noncoding DNA Sequences?
- spacer sequences
- Introns
- genes encoding non-coding RNA
- repetitious DNA
Where is most of satellite dna confined?
teleomeres and centromeres
What is the most abundant class of repetitious DNA? What percentage? What does it consist of?
interspersed repeats; account for about 45% of DNA..
transposons and retrotransposons
What are spliced out of primary RNA?
introns
The DNA sequence that is transcribed to yield a protein or a functional RNA is called a what?
gene
Gene families arise from what?
gene duplications
What is a pseudogene?
when mutations inactivate the duplicate created when a gene family is made
The B-globin gene is an example of what?
gene families clustered at one chromosomal locus
DNA + histone = ?
chromatin
Explain the 3 levels of condensation in a chromosome.
Dna is wrapped around histone proteins to form an 11 nm wide fiber (H2A, H2B, H3, H4)
The histones with DNA wrapped around them are called nucleosomes. a fifth histone H1 attaches to the nucleosomes and seals the structure.
Nucleosomes associated to form a 30 nm wide fiber
30 nm wide fibers forms a 300 nm wide loop domain
What phases does each chromosome consist of two identical DNA strands called chromatids?
G2 and M
What are the 3 types of molecules that must be actively transported into the nucleus?
mRNA, proteins, and ribosomal subunits
What 2 proteins assist in the important and export of molecules into and out of the nucleus?
importin or exportion
Ran-GTP
What are the key points to DNA replication?
- semi-conservative
- replication is initiated at specific origins (multiple ones are found on each chromosome)
- replication origins are activated in clusters
- replication is bidirectional from each origin
- nucleosomes are also replicated
What are 4 properties of DNA polymerases?
- RNA primers are required
- template directed
- 5’ –> 3’
- dATP, dGTP, dCTP, and dTTp are nucleotide donors
DNA replication steps.
- DNA helicases unwind DNA.
- single-stranded binding proteins bind to expose DNA strand
- super-coiling results and topoisomerases received to relieve strain
- DNA poly alpha synthesizes short RNA primer and generates a primase with a free 3=OH
- DNA poly alpha switches to DNA poly delta
- accessory proteins are loaded adjacent to the primer to allow the enzyme to synthesize more DNA before falling off
- 5 prime to 3 prime direction; leading strand synthesized and lagging strand is synthesized and generates an Okazaki fragment
- RNA primers removed by specific rubonucleases and gaps filled in by DNA polymerase
What is TTAGGG?
telomere sequence
What is the telomere sequence?
TTAGGG
What are the 3 components of a nucleotide?
- pentose sugar (ribose or 2’ deoxyribose)
- phosphate group
- purine/pyrimidine base
How would you find the amount of a nucleotide?
Adenine = Thymine Guanine = Cytosine
Purine = Pyrimidine
So if Adenine is equal to 20%, that means
T= 20. So, A+T = 40% and G+T must equal 60%
How many hydrogen bonds from between g and c?
3
The helical structures of DNA are stabilized by what 3 things?
- hydrogen bonding
- hydrophobic and stakcing interactions between the bps in teh center
- interactions of polyanionic backbone with cations
How many hydrogen bonds between A and T?
2
How are base pairs assembled on top of each other?
stacked on top of each other like rungs on a ladder
