لراغبى الامتياز ف الmolecular biology ان شاء الله

بدون اى مقدمات عشان مفيش وقت؛ دى أسئلة ع ال Molecular Biology بس دى أسئلة ع الحاجات اللى مش متوقعة يعنى اللى معظمنا مش بياخد باله منها أو بيستهتر بيها ومابيركزش عليها
عامة أنا عرضت الأسئلة دى على د/أمل منصور وقالتلى انها كويسة جدا
وياريت يا جماعة محدش يستهتر بسؤال م الأسئلة دى عشان محدش ضامن د/هانى حليم ناوى على ايه ف الامتحان الجاى ده
و فى معظم الأسئلة دى ان شاء الله مش هتحتاجو انكو ترجعو للكتاب لأن الاختيارات هتسهلكو الاجابة ماعدا بعض الأسئلة هتضطروا فيها انكو ترجعوا للكتاب عشان تشوفوا حاجات تانية بنفسكو
أسيبكو دلوقتى مع الأسئلة عشان مطولش عليكو أكتر من كدة؛




Questions:-

1-concerning the deoxynucleotide , the pentose sugar is.......... at its..........
a)dehydrated , carbon3 .
b)oxygenated , carbon2 .
c)dehydrated , carbon3 .
d)deoxygenated , carbon2 .


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2-guanine & Thymine are present in 2 forms :- ..........&............ but the ............ form is the predominant .
a)imino & amino ,amino .
b)enol & keto ,keto .
c)imino & amino , imino .
d)enol & keto , enol .

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3-pyrimidines are attached to carbon ......... of the pentose sugar through its ............ , while purines are attached to it through ...............both by ............bond .
a)one , N1 , N9 n-glycosidic bond .
b)three , N9 , N1 , hydrogen bond .
c)one , N1 , N9 hydrogen bond .
d)two , N1 , N9 , N-glycosidic bond .

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4- people suffering from gout can be treated by :-
a)xanthine oxidase .
b)allopurinol .
c)hypoxanthine .
d)dideoxyinosine .

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5-according to Watson & crick double helix model (B-form) , each turn is .........in legnth & ...........in width .
a)3.4 nm - 1.9 um (micrometer) .
b)4.3 nm - 9.1 nm .
c)3.4 nm - 1.9 nm .
d)3.4 nm - 9.1 um .

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6- A-form of Double helix is :-
a)dehydrated B-form .
b)dehydrated z-form .
c)hydrated B-form .
d)hydrated z-form .

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7-all the follwing are stabilizing factors of the DNA helix Except :-
a)Hydrophobic interactions .
b)intrachain hydrogen bonds .
c)Van der waals forces .
d)interchain hydrogen bonds .

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8-the more "G-C" base pairs existing in aDNA molecule , the .......... Tm is .
a)lower .
b)higher .
c)Tm is constant (not affected) .
d)there is no relationship .

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9-mitochondria :-
a)has a double stranded linear DNA molecule .
b)has a double stranded circular DNA molecule .
c)has a single stranded linear DNA molecule .
d)has a single stranded circular DNA molecule .
e)has no DNA molecules .


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10-the structure of chromatin is determined & stabilized by :-
a)histones Pts. (proteins).
b)non-histones Pts. .
c)both a & b .
d)neither a nor b .

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11-the non-coding nucleic acid sequences :-
a)are involved in the control of gene expression .
b)can be translated into polypeptide .
c)act as an evolutionary buffer able to withstand nucleotide mutation without disrupting the integrity of the organism .
d)both a & c .

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12-the pre-priming complex is produced by joining of :-
a)DnaA , SSB Pts. .
b)SSB Pts. , DNA helicases .
c)DnaA , SSB Pts . & DNA helicases .
d)DnaA Pts. & DNA helicases .

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13-............does not require ATP to reseal the DNA strand :-
A)topoisomerase I .
b)topoisomerase II .
c)both of them require ATP .
d)both of them do not require ATP .

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14-DNA gyrase:-
A)is a type I of topoisomerase found in bacteria & plants .
b)is a type II of topoisomerase found in bacteria & plants .
c)introduces (forms) negative supercoils which neutralize the positive supercoils during opening of the double helix .
d)both b & c .

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15-primosome complex is formed of :-
a)pre-priming complex(DnaA, SSB Pts. & DNA helicases)+primase .
b)DnaA & SSB Pts. + primase .
c)DNA helicases + primase .
d)DnaA Pts. + SSB Pts. only .

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16-in humans telomeric DNA , the ........strand is longer than the.........strand .
a)AC -TG .
b)TG -AC .
c)AG - TC .
d)AT -GC .

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17-nucleotide-excision repair mechanism can correct thymine dimer in bacteria:-
a)as it is the main mechanism in bacteria .
b)it helps the direct repair mechanism .
c)it is the main mschanism in absence of visible light that activate the direct repair .
d)it cannot crrect thymine dimer in bacteria absolutely .

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18-Mut Pts. (S,H,L) form a complex which identify the mispaired nucleotide(s) on the unmethylated...........strand .
a)ATGC .
b)GATC .
c)TACG .
d)CATG .

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19-hereditary nonpolypois clorectal cancer(HNPCC)is the result of defects in:-
a)direct repair .
b)nucleotide-excision repair .
c)base-excision repair .
d)methyl directed repair (mismatch repair) .

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20-mRNA make up(comprises)about.........of the total cellular RNA,while rRNA comprises about........& tRNA constitutes about.........of the total cellular RNA .
a)80% - 15% - 5% .
b)15% - 80% - 5% .
c)5% - 80% - 15% .
d)80% - 5% - 15% .
e)15% - 5% - 15% .

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21-heterogenous nuclear RNA (hnRNA)is a precursor molecule for :-
a)mRNA .
b) rRNA .
c)tRNA .
d)all the above .

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22-in humans , the cellular DNA contains all genes ,but the region which contain the active gene would be:-
a)methylated-acetylated .
b)methylated-deacetylated .
c)demethylated-acetylated .
d)demethylated-deacetylated .

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23-methylation of the DNA occurs at:-
a)the As that precede Ts .
b)the Cs that precede Gs .
c)the Ts that precede Gs .
d)the As that precede Cs .

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24-promotors are present :-
a)on the sense strand of DNA .
b)on the non-sense strand of DNA .
c)on both the sense & non-sense strands of DNA .
d)are not present on DNA .

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25-promoters & operators are considered :-
a)trans-acting factors .
b)cis-acting elements .
c)regulatory proteins .
d)regulatory sequence(s) .
e)both b & d .

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26-nonsense codon is :-
a)a start codon .
b)termination codon .
c)untranslated codon .
d)both b & c .

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27-transversions point mutation :-
a)are changes from purine into the other purine or from pyrimidine into the other pyrimidine .
b)are changes from purine into one of pyrimidines or from pyrimidine into one of purines .
c)all the above .
d)none of the above .

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28-truncated protein is produced as aresult of :-
a)silent mutation .
b)missense mutation .
c)nonsense mutation .
d)frame-shift mutation(premature termination) .
e)both c & d .


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29-CF(cystic fibrosis) disease caused by deletion of 3 nucleotides fromthe codung region of a gene resulting in loss of .......... in the protein encoded by that gene .
a)tyrosine .
b)phenylalanine .
c)glutamine .
d)alanine .

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30-the amino acid bind the convenient tRNA through its ........by a/an..........bond .
a)carboxyl group , hydrogen bond .
b)amino group , peptide bond .
c)carboxyl group , peptide bond .
d)amino group , ester bond .
e)carboxyl group , ester bond .

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31-which of the following has a proofreading acivity:-
a)DNA polymerase I .
b)DNA polymerase III .
c)aminoacyl-tRNA synthetase .
d)all the above .

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32 -the hydrolysis of the bond linking the polypeptide chain to the last tRNA occurs :-
a)at the A site .
b)at the P site .
c)at the E site .
d)at the cytoplasm .(after the dissociation of the whole complex) .

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33-glycosylation of a protein occurs :-
a)in the cytoplasm .
b)in the nucleus .
c)in the endoplasmic reticulum & the golgi complex .
d)none of the above .







-Answers :-


1-d
2-b
3-a
4-b
5-c
6-a
7-b
8-b
9-b
10-c (both are DNA-binding Pts. & differ from the SSB Pts.).
11-d
12-c
13-a
14-d
15-a
16-b
17-c
18-b
19-d (as aresult of a mutation to the Pts. involved in this mechanis, in humans & about 5% of all colon cancer is the result of these defects) .
20-c
21-a
22-c
23-b
24-b (the template strand).
25-e
26-d
27-b
28-e
29-b
30-e
31-d
32-a
33-c