BI204 Exam 3 (Multiple Choice)

1. Briefly define ncRNA (non‑coding RNA).

ncRNAs are RNA molecules that are transcribed from DNA but do not encode proteins

2. Describe one method by which RNAi works in the cell.

One mechanism: miRNA‑mediated silencing.
miRNAs are processed and loaded into the RISC complex, which binds complementary mRNA and either degrades the mRNA or blocks its translation.

3. Define epigenetics.

Epigenetics refers to heritable changes in gene expression that do NOT involve changes to the DNA sequence

4. Give four examples of differentiated cell types.

• Neuron

• Muscle cell (myocyte)

• Red blood cell

• Hepatocyte (liver cell)

1. How are cancers broadly categorized?

By tissue of origin, such as:

• Carcinomas (epithelial)

• Sarcomas (connective tissue)

• Leukemias/lymphomas (blood/immune)

• CNS cancers (brain/spinal cord)

2. What percentage of mutations found in cancers are hereditary rather than spontaneous?

Roughly 5–10% are hereditary; the rest are spontaneous or environmentally induced.

3. List the two classes of genes mutated in cancers and whether they undergo gain or loss of function.

• Tumor suppressor genes → loss of function

• Proto‑oncogenes → gain of function (become oncogenes)

4. Name two factors that can increase the basic mutation rate.

• UV or ionizing radiation

• Chemical mutagens (e.g., tobacco carcinogens)

5. Describe the six hallmarks of cancer and whether each is loss of tumor suppressor function or gain of proto‑oncogene function.

1. Self‑sufficiency in growth signals — gain of function (proto‑oncogene)

2. Insensitivity to anti‑growth signals — loss of tumor suppressor

3. Evading apoptosis — loss of tumor suppressor

4. Limitless replicative potential — loss of tumor suppressor

5. Sustained angiogenesis — gain of function

6. Tissue invasion & metastasis — loss of tumor suppressor (cell‑adhesion regulators)

1. Name one technology used for creating more DNA.

PCR (Polymerase Chain Reaction)

2. Name one technology used for sequencing DNA.

Illumina sequencing / Sanger sequencing

3. Name one technology used for examining mRNA.

RT‑PCR or RNA‑seq

4. Name one technology used for examining where a protein is located.

Immunofluorescence or GFP‑tagging

5. Name one technology used for confirming that a bacterium has been transformed.

Antibiotic selection on plates or blue‑white screening

6. Name one technology used for fixing mutations in live cells.

CRISPR‑Cas9 genome editing

7. Explain how chromatin reprogramming is required for somatic cell nuclear transfer and stem‑cell cloning.

A somatic nucleus must be reset to an embryonic epigenetic state. This requires:

• Removing somatic epigenetic marks

• Re‑establishing pluripotency‑associated chromatin

• Allowing embryonic genes to be reactivated
  Without this reprogramming, the transferred nucleus cannot support embryonic development.

1. Describe two purposes for Whole Genome / Next‑Generation Sequencing.

• Identifying mutations or variants across the entire genome

• Profiling microbial communities or pathogens

• Detecting structural variants, copy‑number changes, or inherited disease alleles

2. Compare and contrast genomics and genetics in your own words.

• Genetics studies individual genes and how traits are inherited.

• Genomics studies all genes collectively, including interactions, networks, and large‑scale patterns.

3. Explain one use for metagenomics.

Analyzing the microbiome of an environment (soil, gut, ocean) without culturing organisms.

4. What are the three types of associations made with a gene in gene ontology?

• Biological process

• Molecular function

• Cellular component

5. What is the relationship between gene density and organismal complexity?

simple organisms have high gene density, while complex organisms often have large genomes with low density.

6. How does alternative splicing generate extra complexity in the human genome?

A single gene can produce multiple mRNA isoforms, leading to many different proteins from the same DNA sequence, greatly expanding functional diversity.

1. Define allele, genotype, and phenotype.

• Allele — a variant form of a gene

• Genotype — the combination of alleles an organism carries

• Phenotype — the observable traits produced by the genotype and environment

2. What are some common phenotype/trait variations that can’t be seen with the naked eye?

• Blood type

• Enzyme activity levels

• Metabolic rate

• Genetic disease risk alleles

• Hormone levels

3. What is average heterozygosity?

The average proportion of gene loci at which an individual (or population) has two different alleles.

4. What are the costs and benefits of low/high average heterozygosity?

Low heterozygosity:

• Costs: inbreeding depression, reduced adaptability

• Benefits: none biologically, except in controlled breeding for uniform traits

High heterozygosity:

• Benefits: increased genetic diversity, disease resistance, adaptability

• Costs: potential incompatibilities in selective breeding programs

The study of all of an organism’s genes and how they interact with one another is:

Genomics

The Association of a Gene with a term that describes its molecular functions is called:

Gene ontology

The study of all of an organism’s proteins and how they interact with one another is:

Proteomics

A generic term for knockdown of gene expression by RNA

RNAi

The signal that tells a stem cell to become a differentiated cell is called an

Extrinsic Factor

In cancer, a tumor suppressor gene would most likely be effected by a

Weakened Promoter

In cancer, a proto-oncogene would most likely be effected by a

Strengthened Promoter

What percentage of the human genome is made up of protein coding genes

1.5%

Which of the following organisms would have the lowest gene density?

Homo Sapiens

Which of the following organisms would have the highest gene density?

E. coli

Which of the following environments might have high average heterozygosity?

Rich tropical rain forest

Which of the following technologies can be used for making more DNA?

PCR

Which of the following technologies can be used for examining a protein's location?

GFP tagging

Which of the following technologies can be used for examining a mRNA's location?

In Situ Hybridization

Which of the following technologies can be used for fixing a mutation in a live cell?

Crispr-Cas

Which of the following techniques are used to clone identical organisms?

Somatic cell nuclear transfer

Which of the following is a mutation unlikely to be found to cause cancer?

Silent mutation

A version of a specific gene is called a ___.

Allele

Small ncRNAs can carry out RNAi by:

Binding to and chopping up the corresponding mRNA

Hox genes encode

Transcription Factors

The three stages of conventional PCR are

Denaturation, annealing, extension

Cancers are broadly categorized by their ______________

Tissue of Origin

Fully differentiated cells can be dedifferentiated in the lab to make

Induced pluripotent stem cells