Structure and Organization of Nucleic Acids Flashcards
List 4 types of non-coding DNA
1) spacer sequences
2) introns
3) genes encoding non-protein coding RNAs
4) repetitious DNA sequences
What’s the difference between exons and introns?
exons - translates into proteins
introns - do not translate into proteins, gets spliced out
What’s the characteristics of genes within a gene family? How does it occur?
- similar nucleotide sequences and similar proteins, not identical (most likely isozymes)
- arise from gene duplication events
What’s a pseudogene?
duplicated genes that over time become inactivated
What’s a chromatin?
DNA and its associated proteins (1/3 DNA and 2/3 proteins)
When do condensation of DNA occur?
between cell division
What are the three levels of condensation?
1) DNA wraps around histone proteins to form a 11nm wide fiber, known as nucleosomes
2) nucleosomes are associated to form a 30nm wide solenoid fiber
3) 30nm fiber forms a 300nm wide loop domains
Number of chromosomes found in diploid human cell
46 chromosomes
Number of chromosomes found in haploid cell
23 chromosomes
How does mitochondrial genome differ from nuclear genome?
- structurally, mitochondrial genome is circular
- mitochondrial genome has a very high gene density
- mitochondrial genome are not extensively associated with proteins like nuclear genome
heterochromatin
- darker in stains
- transcriptionally inactive
euchromatin
- lighter in stains
- transcriptionally active
- decondensed DNA
What process occurs in nucleolus?
ribosome assembly
What are some features of nuclear pore complex?
1) functions to regulate traffic between nucleus and cytoplasm
2) proteins are transported into and out of the nucleus in energy-dependent mechanism
3) small molecules can enter easily (metabollites, ATP, GTP, etc)
What are the three main types of molecules that are being transported in and out of the nucleus?
mRNA
proteins
ribosomal subunits
Describe how ribosomal subunits are transported and when
ribosomal subunits are synthesized in cytoplasm but assembled in nucleolus, and functions outside the nucleus
1) transport into the nucleus to be assembled
2) transport out to its final destination
The energy to drive both import and export mechanisms comes from what?
cytoplasmic hydrolysis of Ran-bound GTP
GTP is loaded onto Ran in the nucleus, then once it goes out to the cytoplasm it gets hydrolyzed
What drug acts as a topoisomerase II inhbitor and is used as an anti-cancer agent
doxorubicin
What two drugs are bacterial topoismerase II inhibitors that as antibiotics?
nalidixic acid and ciprofloxacin
What are the nucleotide donors for DNA synthesis?
dATP, dGTP, dCTP, dTTP
What enzyme is this? ATP-dependent enzymes that use free energy from hydrolysis of ATP to power unwinding of DNA double helix
DNA helicase
What is enzyme is this? relieves the supercoiling caused by the unwinding
topoisomerase
What enzyme synthesize RNA primers?
primase activity of polymerases
Which end of the DNA strand does DNA polymerase work at?
3’ end in the direction of 5’ to 3’
the strand of DNA being synthesized continuously in the direction of 5’ to 3’
What strand is this? What is the direction of parent strand?
leading strand, parent strand is 3’ to 5’
What are Okazaki fragments?
pieces of DNA segments synthesized from the lagging strand
What enzymes joins Okazaki fragments together?
DNA ligase
What enzyme removes RNA primers?
ribnucleases
What is the formula used to calculate number of nucleotide bases?
[adenine]=[thymine] and [guanine]=[cytosine]
[purine]=[pyrimidine]
What the name of the class of molecules that fit exactly in between base pairs with the helix, distorting the structure of the double helix?
DNA intercalating agents
- they often cause insertions and deletions
Which type of topoisomerase manipulate 2 double helices at the same time, relieving the supercoiling effect?
Topoisomerase II
What is the action of topoisomerases?
nick and re-ligate DNA strands
What are acridine dyes, ethidium bromide and doxorubicin examples of?
DNA intercalating agents
