Phys 3 Flashcards

Which structures form the backbone of DNA?

A. Deoxyribose and phosphate

B. Nitrogenous bases

C. Purines and pyrimidines

D. Ribose and phosphate

What connects the two sugar-phosphate backbones of double-stranded DNA?

A. Water molecules

B. Paired nitrogenous bases

C. Deoxyribose molecules

D. Phosphate bridges

Which pair contains only purine bases?

A. Adenine and thymine

B. Cytosine and thymine

C. Cytosine and guanine

D. Adenine and guanine

Which pair contains only pyrimidine bases in DNA?

A. Adenine and guanine

B. Adenine and thymine

C. Cytosine and thymine

D. Guanine and cytosine

How many hydrogen bonds connect A–T and G–C base pairs?

A phosphate, deoxyribose, and nitrogenous base together form a:

A. Nucleotide

B. Nucleoside

C. Polypeptide

D. Phospholipid

What process copies information from DNA into RNA?

A. Replication

B. Translation

C. Transcription

D. Transduction

In a human cell, where does transcription occur, and what are 3-base mRNA sequences called?

A. Cytoplasm; anticodons

B. Nucleus; codons

C. Rough ER; introns

D. Golgi; exons

Compared with deoxyribose, ribose contains an additional:

A. Methyl group

B. Amino group

C. Phosphate group

D. Hydroxyl group

Which enzyme synthesizes RNA during transcription?

A. RNA polymerase

B. DNA polymerase

C. RNA ligase

D. Topoisomerase

Which DNA region allows RNA polymerase to begin transcription?

A. Poly-A signal

B. Terminator

C. Promoter

D. Intron

What does RNA polymerase do after binding the promoter?

A. Removes introns

B. Unwinds the DNA helix

C. Joins Okazaki fragments

D. Attaches a ribosome

What provides energy for adding an RNA nucleotide to the growing RNA strand?

A. Hydrogen bond formation

B. Ribose hydrolysis

C. ATP synthesis

D. Removal of terminal phosphates

What initially aligns an RNA nucleotide with its complementary DNA base?

A. Hydrogen bonding

B. Ionic bonding

C. Covalent bonding

D. Peptide bonding

A mutation in a transcription termination sequence would most directly impair:

A. Transcription initiation

B. DNA unwinding

C. Transcript release

D. RNA splicing

Why does newly synthesized RNA separate from its DNA template?

A. RNA binds ribosomes immediately

B. RNA becomes methylated

C. DNA loses its phosphates

D. DNA strands re-anneal

After transcription, newly synthesized RNA is initially released into the:

A. ER lumen

B. Nucleoplasm

C. Mitochondrial matrix

D. Golgi apparatus

What is the initial RNA transcript that will be processed into mature mRNA?

A. tRNA

B. rRNA

C. Pre-mRNA

D. snRNA

During pre-mRNA processing, what happens to introns and exons?

A. Introns removed; exons retained

B. Introns retained; exons removed

C. Both are removed

D. Both remain unchanged

A defect in small nuclear RNA would most directly impair which process?

A. Promoter binding

B. mRNA export

C. rRNA synthesis

D. Pre-mRNA splicing

Which RNA carries the genetic code from the nucleus to the cytoplasm for protein synthesis?

A. tRNA

B. mRNA

C. rRNA

D. miRNA

Which feature best describes mature mRNA?

A. Double-stranded RNA

B. Ribosomal structural RNA

C. Short regulatory RNA

D. Long single strand with codons

What happens if an amino acid cannot attach to the 3′ end of tRNA?

A. tRNA cannot carry amino acids

B. Ribosomes cannot form

C. DNA cannot be transcribed

D. miRNA cannot bind mRNA

Which RNA uses an anticodon to recognize an mRNA codon and deliver an amino acid?

A. mRNA

B. rRNA

C. tRNA

D. miRNA

What are the three-base sequences on mRNA and tRNA called, respectively?

A. Anticodon; codon

B. Codon; anticodon

C. Codon; codon

D. Anticodon; anticodon

Which RNA provides the information that determines the amino acid sequence of a protein?

A. mRNA

B. tRNA

C. rRNA

D. miRNA

What major process occurs in the nucleolus?

A. DNA replication

B. mRNA splicing

C. tRNA charging

D. rRNA processing and ribosome assembly

Why does most protein synthesis occur in the cytoplasm rather than the nucleus?

A. DNA cannot function in nucleus

B. Mature ribosomes function in cytoplasm

C. RNA cannot enter nucleus

D. Nuclear pores block proteins

How do newly formed ribosomal subunits leave the nucleus?

A. Through nuclear pores

B. Through rough ER

C. By membrane diffusion

D. Through Golgi vesicles

A short, nontranslated RNA of about 22 nucleotides regulates gene expression. What is it?

A. mRNA

B. tRNA

C. miRNA

D. rRNA

How are microRNAs best classified?

A. Protein-coding RNAs

B. Ribosomal RNAs

C. Amino acid carriers

D. Noncoding regulatory RNAs

How is a mature miRNA produced?

A. Processing of a pri-miRNA

B. Translation of an mRNA

C. Cleavage of rRNA

D. Charging of tRNA

A miRNA binds a complementary mRNA. What is the usual effect?

A. Increased transcription

B. Decreased gene expression

C. Increased DNA replication

D. Increased mRNA splicing

A tumor secretes what type of factors?

A. Adhesion factors

B. Antioxidant factors

C. Angiogenic factors

D. Antimetabolic factors

How can a rapidly growing tumor contribute to “nutritive death” of normal tissues?

A. Stops all mitosis

B. Blocks every artery

C. Destroys all ribosomes

D. Consumes available nutrients

Which codon usually starts translation in eukaryotic cells?

A. AUG

B. UGA

C. UAA

D. UAG

Which set contains only stop codons?

A. AUG, UAA, UGA

B. UGA, UGG, UAG

C. UAA, UAG, UGA

D. UAA, UAC, UAG

What happens when a miRNA binds strongly to a complementary mRNA?

A. Stabilizes mRNA and increases translation

B. Prevents mRNA degradation

C. Promotes mRNA degradation and inhibits translation

D. Increases translation

Abnormal microRNA regulation has been strongly linked to which diseases?

A. Hemophilia and PKU

B. Gout and osteoarthritis

C. Cancer and heart disease

D. Achondroplasia and cystic fibrosis

Short double-stranded RNAs used to silence specific genes are called:

A. snRNAs

B. siRNAs

C. mRNAs

D. tRNAs

Why are siRNAs potentially useful as therapies?

A. Increase all miRNA production

B. Convert RNA into DNA

C. Can silence specific known genes

D. Delete genes permanently

After entering the cytoplasm, a synthetic siRNA silences genes by activating:

A. RISC

B. TFIID

C. RNA polymerase II

D. Ribosomes

What sequence signals the beginning of translation in these notes?

A. Chain-initiating codon

B. Shine-Dalgarno sequence

C. TATA box

D. Stop codon

Multiple ribosomes translating the same mRNA form a:

A. Rough ER

B. Polyribosome

C. Spliceosome

D. Nucleosome

Which statement about ribosomes is correct?

A. Each ribosome makes one protein only

B. Each mRNA needs a unique ribosome

C. Ribosomes cannot translate secretory proteins

D. Any ribosome can translate a given mRNA

What happens when a stop codon enters the ribosome?

A. Translation continues

B. A water-carrying tRNA binds

C. The completed protein is released

D. DNA is degraded

What does the signal sequence of a secreted protein cause?

A. Ribosome binds the ER

B. mRNA returns to nucleus

C. Translation stops

D. Protein enters mitochondria

What gives rough ER its granular appearance?

A. Glycogen

B. Attached ribosomes

C. Lipid droplets

D. Lysosomes

Most proteins released directly into the cytosol function as:

A. Secreted hormones

B. Lysosomal enzymes

C. Membrane receptors

D. Enzymes and structural proteins

Which cells commonly package large amounts of protein into secretory vesicles?

A. Neurons

B. Skeletal muscle cells

C. Renal epithelial cells

D. Glandular secretory cells

Which activity directly forms peptide bonds during translation?

A. Peptidyl transferase

B. Aminoacyl-tRNA synthetase

C. RNA polymerase

D. Helicase

During peptide bond formation, which groups form water?

A. Carboxyl carbon and amino nitrogen

B. OH from COOH and H from NH2

C. Entire amino group

D. Entire carboxyl group

The sequence TATAAAA in a basal promoter is called the:

A. Initiator sequence

B. CAAT box

C. Poly-A signal

D. TATA box

What is the main role of the basal promoter?

A. Functions only in stress genes

B. Recruits transcription machinery

C. Controls RNA splicing

D. Encodes miRNA

What is the upstream promoter region?

A. Region after the start site

B. Ribosome-binding site

C. miRNA-coding region

D. Regulatory region with transcription-factor sites

Why can different tissues express different genes despite having the same DNA?

A. Genetic code changes

B. Exons are deleted

C. Transcription factors regulate promoters differently

D. Enhancers are removed

Which regulatory DNA regions can act far from a gene and still increase transcription?

A. Enhancers

B. Silencers

C. Basal promoters

D. Introns

Which DNA elements prevent enhancers from activating nearby unrelated genes?

A. Enhancers

B. Silencers

C. Insulators

D. Basal promoters

Where do many regulatory proteins bind to control gene transcription?

A. Coding exons

B. Promoter regions

C. Introns

D. Telomeres

Which statement about regulatory proteins is correct?

A. Each activates only one gene

B. Repressors never activate genes

C. One protein can activate or repress

D. Activators bind only RNA

Gene expression can also be regulated after transcription during which processes?

A. DNA replication

B. Promoter binding

C. Chromatin remodeling

D. RNA splicing or translation

Highly condensed DNA structures visible during cell division are called:

A. Chromosomes

B. Centrosomes

C. Nucleoli

D. Spliceosomes

Which proteins help compact DNA and can reduce transcription when tightly associated with it?

A. Tubulins

B. Cohesins

C. Histones

D. Dyneins

During ATP depletion, which molecule activates glycogen phosphorylase according to these notes?

A. ADP

B. Pi

C. cGMP

D. cAMP

How are purine and pyrimidine synthesis reciprocally regulated according to these notes?

A. Each stimulates the other and inhibits itself

B. Both stimulate themselves

C. Both inhibit each other

D. Each affects only itself

Most of a dividing cell's life cycle is spent in which phase?

A. G0

B. Mitosis

C. Interphase

D. S phase

What distinguishes DNA replication from transcription?

A. Only one DNA strand is copied

B. Only genes are copied

C. RNA nucleotides are used

D. Both DNA strands are copied

Which pairing correctly matches DNA replication enzymes with their functions?

A. Polymerase elongates; ligase seals DNA

B. Ligase unwinds; polymerase cuts DNA

C. Polymerase methylates; ligase unwinds

D. Ligase proofreads; polymerase joins

Which enzyme joins newly synthesized DNA fragments into a continuous strand?

A. Helicase

B. Topoisomerase

C. DNA ligase

D. DNA glycosylase

What type of bonds hold complementary DNA strands together?

A. Disulfide bonds

B. Ionic bonds

C. Peptide bonds

D. Hydrogen bonds

Chronic oxidative stress can do what?

A. Telomere erosion

B. Telomerase activation

C. Telomere extension

D. Chromosomal translocation

Which normal cell type has high telomerase activity?

A. Skeletal muscle cell

B. Hematopoietic stem cell

C. Adult hepatocyte

D. Mature neuron

What eventually happens to most somatic cells because they lack significant telomerase activity?

A. Divide indefinitely

B. Maintain stable telomeres

C. Enter senescence

D. Repair all telomeres

Why does increased telomerase activity benefit cancer cells?

A. Improves DNA proofreading

B. Reduces mutations

C. Blocks growth signals

D. Allows indefinite replication

Why can telomere shortening help protect against cancer?

A. Limits excessive cell divisions

B. Activates oncogenes

C. Prevents DNA repair

D. Extends cell lifespan

Colchicine can produce large polyploid cells because:

A. RNA synthesis stops

B. DNA replicates without mitosis

C. Mitosis occurs without DNA replication

D. Protein synthesis stops

Which drug prevents formation of the mitotic spindle according to these notes?

A. Paclitaxel

B. Vincristine

C. Colchicine

D. Doxorubicin

Why can colchicine-treated cells become unusually large?

A. Increased lipid storage

B. Reduced lysosomal activity

C. Loss of mitochondria

D. Increased RNA and protein synthesis

What process allows cells with the same genome to develop different functions?

A. Differentiation

B. Necrosis

C. Senescence

D. Translocation

How can differentiation permanently reduce expression of certain genes?

A. Deletes all promoters

B. Selectively represses promoters

C. Activates every gene

D. Removes all histones

If DNA remains tightly wound around histones, what happens to those genes?

A. Become highly active

B. Move to cytoplasm

C. Remain transcriptionally inactive

D. Replicate continuously

The optic vesicle induces nearby ectoderm to form which structure?

A. Lens

B. Retina

C. Optic nerve

D. Vitreous body

A cell shrinks and is removed without causing inflammation. What type of cell death is this?

A. Necrosis

B. Apoptosis

C. Pyroptosis

D. Autophagy

A cell swells, ruptures, and causes inflammation. What type of cell death is this?

A. Apoptosis

B. Senescence

C. Necrosis

D. Differentiation

Which enzymes form the proteolytic cascade responsible for apoptosis?

A. Kinases

B. Cyclins

C. Phosphatases

D. Caspases

Abnormal regulation of apoptosis is associated with which disease in these notes?

A. Alzheimer disease

B. Cystic fibrosis

C. Hemophilia A

D. Myasthenia gravis

Cancer fundamentally results from abnormalities in genes controlling:

A. Protein folding

B. Cell growth and division

C. Mitochondrial replication

D. Membrane transport

What do normal proto-oncogenes commonly regulate?

A. Telomere repair

B. Protein secretion

C. Cell adhesion, growth, division

D. Hemoglobin production

Loss of an anti-oncogene can lead to:

A. Better DNA repair

B. Stronger cell adhesion

C. Permanent cell-cycle arrest

D. Unopposed oncogene activity

How do carcinogens in cigarette smoke primarily promote cancer?

A. Activate all telomerase

B. Cause DNA mutations

C. Block all mitosis

D. Increase all methylation

How can ionizing radiation increase cancer risk?

A. Extends telomeres

B. Improves DNA repair

C. Causes DNA breaks and mutations

D. Stops mitochondrial growth

Why can chronic tissue irritation increase mutation risk according to these notes?

A. Slows all mitosis

B. Prevents DNA replication

C. Decreases cell replacement

D. Increases mitotic activity

Why do some families have increased inherited cancer risk?

A. One cancer-related mutation is inherited

B. Telomeres are always long

C. Mitosis is permanently slow

D. DNA repair is perfect

Which enzyme allows retroviruses to make DNA from RNA?

A. DNA ligase

B. Reverse transcriptase

C. Primase

D. Topoisomerase

Why does reduced adhesion between malignant cells promote cancer spread?

A. Prevents primary tumors

B. Blocks angiogenesis

C. Promotes metastasis

D. Increases immune clearance

What does gene expression ultimately involve?

A. DNA replication

B. Mitosis and cytokinesis

C. Chromosome condensation

D. Transcription and translation

What is the immature RNA transcript that is processed into mature mRNA?

A. Pre-mRNA

B. siRNA

C. rRNA

D. tRNA

What normally happens to introns and exons during mRNA processing?

A. Introns retained; exons removed

B. Introns removed; exons retained

C. Both are removed

D. Both remain

A defect in snRNA would most directly impair which process?

A. DNA replication

B. mRNA export

C. Pre-mRNA splicing

D. Protein translation

What are ribosomes primarily made of?

A. mRNA and translation factors

B. rRNA and about 75 proteins

C. tRNA and membrane lipids

D. DNA and helicases

Where are newly synthesized rRNA and ribosomal proteins assembled?

A. Nuclear pores

B. Nuclear lamina

C. Nucleolus

D. Cytoplasm

Which RNA is a short noncoding molecule that regulates gene expression?

A. mRNA

B. tRNA

C. snRNA

D. miRNA

What happens just before miRNA is loaded into RISC?

A. Dicer cleaves pre-miRNA

B. miRNA is translated

C. Telomerase extends miRNA

D. Ribosomes bind miRNA

Most proteins synthesized by ribosomes are released directly into the:

A. Cytosol

B. Golgi

C. Lysosome

D. Mitochondria

Protein synthesis is best described as:

A. Energy independent

B. A major energy-consuming process

C. Minimally energy demanding

D. Using no GTP

What is the main function of DNA insulators?

A. Repair DNA breaks

B. Increase all transcription

C. Separate regulatory gene domains

D. Splice introns

When pyrimidine levels are high, what happens according to these notes?

A. Pyrimidine synthesis is inhibited while purine synthesis is stimulated

B. Both pathways are inhibited

C. Both pathways are stimulated

D. Purine synthesis alone is inhibited

After DNA replication, the two identical chromosome copies joined at the centromere are called:

A. Chromatin fibers

B. Sister chromatids

C. Kinetochores

D. Spindle fibers

During metaphase, chromosomes align at the center of the cell along the:

A. Cleavage furrow

B. Polar spindle

C. Equatorial plate

D. Nuclear lamina

Which proteins form the contractile ring during cytokinesis?

A. Tubulin and dynein

B. Keratin and vimentin

C. Actin and myosin

According to these notes, what primarily limits the maximum size of a cell?

A. Amount of functioning DNA

B. Number of mitochondria

C. Histone concentration

D. Nuclear calcium

Compared with normal cells, cancer cells generally have:

A. Increased adhesion

B. Reduced cell-cell adhesion

C. Identical adhesion

D. Complete inability to detach

What stage of mitosis is described below?

While the spindle is forming, the chromosomes of the nucleus become condensed into well-defined chromosomes.

What stage of mitosis is described below?

The growing microtubular spines of the aster fragment the nuclear envelope.

At the same time, multiple microtubules from the aster attach to the chromatids at the centromeres, where the paired chromatids are still bound to each other.

The tubules then pull one chromatid of each pair toward one cellular pole and its partner toward the opposite pole.

What stage of mitosis is described below?

The two asters of the mitotic apparatus are pushed farther apart.

The microtubular spines from the two asters, where they interdigitate with each other to form the mitotic spindle, actually push each other away.

Minute contractile protein molecules called “molecular motors,” which are composed of actin, extend between the respective spines and actively slide the spines in a reverse direction along each other.

The chromatids are pulled tightly by their attached microtubules to the center of the cell, lining up to form the equatorial plate of the mitotic spindle.

What stage of mitosis is described below?

The two chromatids of each chromosome are pulled apart at the centromere.

All 46 pairs of chromatids are separated, forming two separate sets of 46 daughter chromosomes.

One of these sets is pulled toward one mitotic aster and the other is pulled toward the other aster as the two respective poles of the dividing cell are pushed still farther apart

What phase of mitosis is described below?

The two sets of daughter chromosomes are pushed completely apart.

he mitotic apparatus dissolutes and a new nuclear membrane develops around each set of chromosomes. This membrane is formed from portions of the endoplasmic reticulum is present in the cytoplasm.

The cell pinches in two, midway between the two nuclei.

What is a region of repetitive nucleotide sequences located at each end of a chromatid and serve as protective caps that prevent the chromosome from deterioration during cell division?