Biochem PART III Flashcards
(21 cards)
QUESTION 49: What is a nucleosome?
-It is the structural unit of what?
-What does it consist of?
-What does it help do?
-Chromatin
-DNA wrapped around a core of 8 histone proteins
-package DNA
QUESTION 50: What is meant by a dyad?
-It is the what?
the central point of symmetry around which the histone proteins are arranged in a nucleosome
QUESTION 50: What is meant by a dyad?
-It acts as what?
the axis of symmetry for the nucleosome structure
QUESTION 51: How many different kinds of proteins comprise a nucleosome?
-How many types and what are they?
-4
-H2A, H2B, H3, and H4
QUESTION 52: How many proteins comprise a nucleosome?
8; 2 copies each of H2A, H2B, H3, and H4
QUESTION 53: What happens to DNA on the nucleosome?
-It wraps around what how many times?
-What does this form?
-the histone protein core; 1.75 times
-the outer edge of the nucleosome
QUESTION 54: What is meant by a superhelix?
-It is a ____-handed what?
-it is formed when there is what?
-right-handed double helix
-there is over- or under-winding of the DNA
QUESTION 55: What roles do cationic and anionic amino acids play in the nucleosome?
-Cationic amino acids have what kind of charge?
-What do they interact with?
-What do they help do?
-positive charge
-negatively charged phosphate backbone of DNA
-organize & stabilize the nucleosome
QUESTION 55: What roles do cationic and anionic amino acids play in the nucleosome?
-Anionic amino acids have what kind of charge?
-They help maintain what?
-negative charge
-the 3D structure of the nucleosome
QUESTION 56: What is chromatin?
-It is the assembly of what?
-What does it do?
-DNA, RNA, and proteins
-packages DNA into compact, dense structures
QUESTION 56: What is chromatin?
-What is open chromatin involved in?
-Close chromatin is (tightly/loosely) packed and (more/less) accessible for transcription
-active transcription
-tightly; less
QUESTION 57: How does the spacing of nucleosomes affect chromatin structure?
-It makes it more or less what?
-What does linker DNA separate? What does it control?
-The ____ and ___ of linker DNA determine the ____ and ___ of nucleosomes
-compact
-nucleosomes; their arrangement
-length and twist; displacement and orientation
QUESTION 58: What are euchromatin & heterochromatin? How might they be related to the positions of nucleosomes on DNA?
-Euchromatin is ____ packed chromatin
-What is it associated with?
-loosely
-active gene expression
QUESTION 58: What are euchromatin & heterochromatin? How might they be related to the positions of nucleosomes on DNA?
-Heterochromatin is ____ packed chromatin
-What is it associated with?
-densely
-inactive gene repression
QUESTION 58: What are euchromatin & heterochromatin? How might they be related to the positions of nucleosomes on DNA?
-The nucelosomes in euchromatin are (more/less) spaced out
-In hetereochromatin, they are (loosely/tightly) packed
-more
-tightly
QUESTION 59: What is formaldehyde crosslinking & how much information does it provide about the genome?
-It chemically links what two things together?
-What does it provide insights into?
-What does it help map?
-DNA and proteins
-higher-order chromatin compaction
-chromatin loops & binding sites
QUESTION 60: How does RNA differ from DNA at the level of chemical structure?
-RNA has what? What does it use? Describe its strand
-DNA has what? Describe its strand and what it forms.
-ribose; U instead of T; single stranded
-deoxyribose; double-stranded & forms a double helix
QUESTION 61: What influence does the 2’-hydroxyl group have on the properties of RNA?
-2’-OH groups in RNA can attack what? What does this lead to?
-This is more likely if the RNA is what?
-phophorus; self-cleavage or hydrolysis
-single-stranded
QUESTION 62: Why is RNA primarily single-stranded?
-it is single stranded during what?
-This is so that it allows what two things?
-Transcription
-flexibility & the ability to fold back on itself for base pairing
QUESTION 63: What happens when new DNA is copied from a double helical molecule?
-What are the 5 steps?
- Unwinding of the double helix at the replication fork
- RNA primers are formed to initiate DNA replication
- Complementary base pairing occurs (A with T, C with G)
- Leading and lagging strands are formed
- Primer removal and ligation result in two identical daughter DNA molecules
QUESTION 64: What is the name of the process during which new DNA is copied from a double-helical molecule?
replication
