اختبار ذاتي التصحيح عن تركيب الحمض النووي - جامعة قطر

اختبار الفصل 11 - التفاعلات الجزيئية

اختبار شامل ومتكامل مع تصحيح تلقائي وتغذية راجعة فورية

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Section 1: Identification & Structure of Genetic Material (تحديد المادة الوراثية وتركيبها)

سؤال 1

Which of the following is NOT one of the four criteria necessary for genetic material?

A. Information B. Transmission C. Variation D. Translation

سؤال 2

In Griffith’s experiment, which injection resulted in the death of the mouse?

A. Living type R bacteria B. Heat-killed type S bacteria C. Living type R + Heat-killed type S bacteria D. Heat-killed type R bacteria

سؤال 3

What term describes the process where genetic material is transferred from dead bacteria to living bacteria, changing their traits?

A. Replication B. Transformation C. Transmission D. Transcription

سؤال 4

Which component is attached to the 5’ carbon of the pentose sugar in a nucleotide?

A. Nitrogenous base B. Phosphate group C. Hydroxyl group D. Hydrogen bond

سؤال 5

Which of the following bases are classified as Purines (double ring structure)?

A. Cytosine and Thymine B. Adenine and Guanine C. Thymine and Uracil D. Cytosine and Guanine

سؤال 6

In a DNA double helix, the two strands are held together by hydrogen bonds according to which rule?

A. Chargaff’s rule (A with G, C with T) B. Chargaff’s rule (A with T, G with C) C. Pauli’s exclusion principle D. Watson’s rule (A with C, G with T)

سؤال 7

The DNA double helix strands are described as ________ because one runs 5’ to 3’ and the other 3’ to 5’.

A. Parallel B. Antiparallel C. Dispersive D. Conservative

Section 2: DNA Replication Overview (نظرة عامة على التضاعف)

سؤال 8

Which model of DNA replication suggests that the new double helix contains one parental strand and one newly made daughter strand?

A. Conservative model B. Dispersive model C. Semiconservative model D. Discontinuous model

سؤال 9

The Meselson and Stahl experiment used isotopes of which element to distinguish between parental and daughter DNA strands?

A. Carbon (¹²C/¹⁴C) B. Nitrogen (¹⁴N/¹⁵N) C. Phosphorus (³²P) D. Oxygen (¹⁶O)

Section 3: Molecular Mechanism & Enzymes (الآلية الجزيئية والإنزيمات)

سؤال 10

Which enzyme is responsible for separating the DNA strands and moving the replication fork forward?

A. DNA Primase B. DNA Ligase C. DNA Helicase D. DNA Topoisomerase

سؤال 11

What is the function of single-strand binding proteins?

A. To synthesize the primer B. To connect Okazaki fragments C. To prevent the separated DNA strands from re-forming a double helix D. To alleviate coiling ahead of the fork

سؤال 12

DNA polymerase cannot start synthesis on a bare strand; it requires a short segment of RNA called a:

A. Promoter B. Primer C. Telomere D. Okazaki fragment

سؤال 13

In which direction does DNA polymerase synthesize the new DNA strand?

A. 3’ to 5’ B. 5’ to 3’ C. 5’ to 5’ D. Randomly

سؤال 14

Which strand is synthesized continuously in the direction of the replication fork?

A. Lagging strand B. Leading strand C. Template strand D. Parental strand

سؤال 15

The lagging strand is synthesized discontinuously in small segments known as:

A. Watson fragments B. Okazaki fragments C. Griffith fragments D. Primase fragments

سؤال 16

Which enzyme is responsible for removing RNA primers and replacing them with DNA in *E. coli*?

A. DNA Polymerase III B. DNA Polymerase I C. DNA Ligase D. DNA Helicase

سؤال 17

What is the role of DNA Ligase?

A. It unwinds the double helix. B. It synthesizes RNA primers. C. It joins adjacent DNA fragments (Okazaki fragments) covalently. D. It proofreads the DNA.

سؤال 18

Which DNA polymerase in *E. coli* is responsible for the majority of DNA replication?

A. DNA Polymerase I B. DNA Polymerase II C. DNA Polymerase III D. DNA Polymerase V

Section 4: Telomeres (التيلوميرات)

سؤال 19

What is the "3’ overhang" problem in eukaryotic replication?

A. DNA polymerase cannot copy the tip of the strand with a 3’ end. B. The DNA becomes too long to fit in the nucleus. C. Helicase cannot unwind the end of the chromosome. D. RNA primers cannot be removed.

سؤال 20

Which enzyme prevents the shortening of chromosomes by attaching repeat sequences to the ends?

A. Topoisomerase B. Ligase C. Telomerase D. Primase

سؤال 21

High levels of telomerase activity are typically found in:

A. Normal somatic cells B. Senescent (aging) cells C. Human cancer cells D. Bacteria

Section 5: Eukaryotic Chromosome Structure (تركيب كروموسوم حقيقيات النوى)

سؤال 22

The complex of DNA and proteins that makes up eukaryotic chromosomes is called:

A. Genome B. Chromatin C. Centromere D. Telomere

سؤال 23

What is the repeating structural unit of eukaryotic chromatin, consisting of DNA wrapped around histones?

A. Nucleosome B. Ribosome C. 30-nm fiber D. Radial loop

سؤال 24

A nucleosome consists of DNA wrapped around an octamer of which proteins?

A. Polymerases B. Ligases C. Histones D. Primases

سؤال 25

Which histone protein is responsible for the formation of the 30-nm fiber (zigzag structure)?

A. H2A B. H3 C. H4 D. H1

سؤال 26

The third level of compaction involves the formation of _________ by interaction with the nuclear matrix.

A. Double helix B. Nucleosomes C. Radial loop domains D. Okazaki fragments

سؤال 27

Which type of chromatin is less compacted and transcriptionally active?

A. Heterochromatin B. Euchromatin C. Metaphase chromatin D. Centromeric chromatin

سؤال 28

Heterochromatin is characterized by being:

A. Highly compacted and transcriptionally inactive B. Loosely packed and transcriptionally active C. Found only in bacteria D. Made of RNA only

سؤال 29

When are chromosomes most compacted?

A. During Interphase B. During Metaphase C. During Replication D. During Transcription

سؤال 30

How many DNA polymerases have been identified in humans?

A. Only 1 B. 5 C. 12 or more D. None

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