Test: Biology - 10 - MCAT MCQ

Viruses typically consist of genetic material (RNA or DNA) enclosed within a protein capsid. Some viruses may also have an outer lipid envelope derived from the host cell.

Viruses enter host cells through a process called endocytosis, in which the virus is engulfed by the host cell membrane and internalized into the cell.

Viruses are not transmitted through hereditary means (i.e., from parent to offspring). They can be transmitted through inhalation of respiratory droplets, ingestion of contaminated substances, and sexual contact.

The viral envelope, which is derived from the host cell membrane, helps the virus attach to specific receptors on the surface of host cells, enabling infection and entry into the cell.

Human papillomavirus (HPV) infection is strongly linked to the development of cervical cancer in women. Certain strains of HPV can cause persistent infections that can lead to abnormal cell changes and the eventual development of cancer.

Rhinoviruses are the most common viruses responsible for causing the common cold. They are transmitted through respiratory droplets and primarily infect the upper respiratory tract.

Retroviruses, such as HIV, are RNA viruses that use the enzyme reverse transcriptase to convert their RNA genome into DNA, which is then integrated into the host cell's genome. HIV is the causative agent of acquired immunodeficiency syndrome (AIDS).

Transcription factors are proteins that bind to specific DNA sequences, such as enhancers, and regulate the transcription of genes. Enhancers are regulatory DNA sequences that can enhance the activity of promoters and increase gene expression.

Translation is the process in which the information in mRNA is used by ribosomes to synthesize proteins. It involves the decoding of the mRNA sequence into a specific sequence of amino acids.

The spliceosome is a complex of proteins and RNA molecules that removes introns from pre-mRNA during splicing, a process of post-transcriptional gene regulation. Alternative splicing can generate different mRNA isoforms with distinct functions.

Methylation of DNA, particularly at CpG sites, is associated with gene silencing and transcriptional repression. Methylation can prevent the binding of transcription factors and other regulatory proteins, leading to decreased gene expression.

The lac operon is negatively regulated by a repressor protein that binds to the operator region in the absence of lactose. This binding prevents RNA polymerase from transcribing the genes involved in lactose metabolism.

DNA polymerase is the enzyme responsible for synthesizing new DNA strands during DNA replication. It adds nucleotides to the growing DNA chain using the existing template strand as a guide.

Activator proteins bind to enhancer regions in DNA and interact with other transcriptional machinery to enhance the recruitment of RNA polymerase and increase the transcription of the target gene.

RNA decay refers to the process by which RNA molecules are degraded and cleared from the cell. It involves various mechanisms, including exonucleolytic degradation and endonucleolytic cleavage, leading to the removal of unwanted or damaged RNA molecules.