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From Flashcardlet > 24.6.2013(biochemistry)47 > Flashcards

24.6.2013(biochemistry)47 Flashcards

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0
Q

Other name for template strand

A

Noncoding strand

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1
Q

Interactions responsible for keeping double helix intact

A

Hydrogen bonds
Vanderwaal forces
Hydrophobic interactions

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2
Q

Number of forms of DNA

A

6 forms(A-E,Z)

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3
Q

The form of DNA found under physiological conditions

A

B form(low salt,high degree of hydration)

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4
Q

The distance spanned by one turn of B DNA

A

3.4nm

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5
Q

The width of B DNA

A

2nm

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6
Q

Substance used to lower Tm

A

Formamide

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7
Q

Ribozymes

A

Peptidyl transferase

RNAs involved in splicing

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8
Q

snRNA present in both nucleus and cytoplasm

A

4.5S

7SK

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9
Q

snRNA found in nucleolus

A

U3

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10
Q

snRNA present as perichromatin granules

A

U6

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11
Q

snRNA found in nucleoplasm

A

U1
U2
U4
U5

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12
Q

5’ hydroxyl end cap?

A

7-methyl guanosine triphosphate cap attached to 2’-O-methyl nucleoside

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13
Q

Role of 5’ capping

A

Recognition of mRNA by translation machinery

Prevent from attack by 5’ exonucleases

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14
Q

Length of poly(A) tail

A

20-250 residues

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15
Q

Number of tRNA

A

20

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16
Q

mRNA represents __________% of total eukaryotic cellular RNA

A

2-5

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17
Q

Arms of tRNA

A

Acceptor arm
T psi C arm
D arm
Extra arm

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18
Q

Nucleotide sequence in acceptor arm

A

CCA

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19
Q

tRNA compose ________ % of total cellular RNA

A

20

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20
Q

Ribosomal RNAs constitute _________ % of total RNA content of cell

A

70

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21
Q

Eukaryotic ribosomal RNA

A

80S
60S(5S,5.8S,28S)
40S(18S)

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22
Q

Site of rRNA synthesis

A

Nucleolus

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23
Q

rRNAs are synthesised from

A

45S precursor

Except 5S RNA

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24
Small RNAs constitute _______% of total RNA
Less than 5
25
Length of small RNAs
20-300 nucleotides
26
snRNA involved in intron removal
U1,U2,U4,U5,U6
27
Function U7 snRNA
Production of correct 3' end of histone mRNA(lack polyA tail)
28
Function of 7SK RNA
Forms a ribonucleoprotein complex P-TEFb that regulates mRNA formation by RNA polymerase II
29
RNAs that inhibit gene expression
mi-RNA(microRNA) si-RNA(small interfering RNA) sRNA found in bacteria can induce gene expression too
30
si-RNA mRNA complexes are degraded in
P bodies
31
Mutations occur at frequency of
1 in every 10 to the power 6 divisions
32
Diameter of nucleosomes
10nm
33
Histone octamers
(H3-H4)2 (H2A-H2B)2
34
Covalent modifications of core histones
``` Acetylation Methylation phosphorylation ADP-ribosylation(DNA repair) Monoubiqutilisation Sumoylation(transcription repression) ```
35
Phosphorylation of H1 histone is associated with
Chromosome condensation during replication cycle
36
Acetylation of core histones is associated with
Chromosomal assembly during replication
37
Acetylation of which histones can activate or inactivate gene expression
H3H4
38
DNA winding over histones form supercoils in which direction
Left handed
39
Number of turns of DNA over a histone octamer
1.75
40
Diameter of chromatin fiber
30nm
41
Characteristic of active chromatin
Sensitive to digestion by DNAse 1
42
Transcriptionally active chromatin
Euchromatin,less dense
43
Characteristic of heterochromatin
High 5 methyl deoxycytidine(Mec) content
44
Constitutive heterochromatin
Telomeres | Centromeres
45
Facultative heterochromatin
Inactivated X chromosome
46
Centromere is rich in
A-T
47
Kinetochore
Contains histone H3 variant CENP-A
48
Telomeres are rich in
TTAGGG
49
Packing ratio
Nucleosomes 7-10 Chromatin fibres 40-60 Condensed metaphase chromosomes 8000
50
Number of protein coding genes in DNA
Less than or equal to 25,000
51
Types of moderately repetitive sequences
LINES(long interspersed repeat sequences) | SINES(short interspersed repeat sequences)
52
LINES and SINES are
Retroposons
53
Insertion of Alu sequences causes
Neurofibromatosis Alu sequences belong to SINE family
54
Most common microsatellite repeat
AC
55
Number of mitochondrial tRNA molecules
22
56
Mitochondrial genetic code
AGA,AAG are stop codons | UGA codes for trp
57
mtDNA synthesises how many subunits of respiratory chain
``` 13 of 67 2 of ATP synthase Cytochrome b 3 subunits of cytochrome oxidase 7 subunits of NADH dehydrogenase ```
58
Example of unequal crossing over
Hb lepore
59
Non homologous viral DNA integeration is
Site specific
60
Processed genes are also known as
Pseudogenes They occur as a result of transposition
61
Gene conversion
Elimination of mismatched sequences and homogenisation of sequences between homologous or nonhomologus chromosomes
62
Ori binding protein
dnaA
63
Primosome
Mobile complex btw primase and helicase
64
Processivity
Number of new nucleotides added before the polymerase disengages from template
65
The entire mammalian genome replicates in
9hrs
66
SSB homologue in eukaryotes
Replication protein A
67
Unwinding of DNA
Hexameric proteins MCM(eukaryotes) DNA Beta protein(prokaryotes)
68
RNA template of reverse transcriptase is degraded by
RNase H
69
Mismatch repair is based on
Methyl directed strand cutting by GATC endonuclease
70
Eukaryotic mismatch repair genes
hMSH2 | hMLH1
71
Enzymes involved in base excision repair
N glycosylase | apurinic or apyrimydinic endonuclease
72
Nucleotide excision repair,site of strand cutting
5' btw 21 and 25 | 3' btw 3 and 5
73
Enzymes involved in double strand break repair
Ku | DNA-PK(protein kinase)
74
Diff btw transcription and DNA replication
No proof reading | No primer involved
75
Template strand is read in
3' to 5' direction

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