IB Biology HL - Unit D1.3: Mutation and Gene Editing

What are gene mutations?

Mutations that occur within genes, affecting 1 or a few nucleotides.

What are chromosomal mutations?

Mutations that occur on chromosomes, potentially affecting more than 1 gene.

Why are chromosomal mutations considered serious?

They often result in the death of the individual or large-scale issues.

What is a duplication mutation?

A chromosomal mutation where part of the chromosome is duplicated.

What is a deletion mutation?

A chromosomal mutation where part of the chromosome is deleted.

What is an insertion mutation?

A chromosomal mutation where part of one chromosome breaks off and inserts into another chromosome.

What is an inversion mutation?

A chromosomal mutation where part of the chromosome is removed, inverted, and replaced.

What is a translocation mutation?

A chromosomal mutation where parts of two separate chromosomes are exchanged.

What are point mutations?

Gene mutations that occur at the molecular level, changing a single nucleotide.

What are frameshift mutations?

Gene mutations where 1 or a few nucleotides are added or deleted, shifting the codons of mRNA.

What is a single nucleotide polymorphism (SNP)?

A variation in the DNA sequence at a specific position in the genome occurring in at least 1% of the population.

What are the consequences of mutations in non-coding regions?

Often no effect, but may impact promoter activity or splicing signals.

What is a same-sense (silent) mutation?

A point mutation where the substituted base does not change the resulting amino acid.

What is a mis-sense mutation?

A point mutation that causes a change in the amino acid coded for by the mRNA codon.

What is a non-sense mutation?

A point mutation that changes the mRNA codon to a stop codon, leading to premature termination of translation.

What causes sickle cell disease?

A mutation in the hemoglobin protein due to a point mutation in the HBB gene.

What is the normal allele for hemoglobin?

HbA.

What is the mutant allele for hemoglobin in sickle cell disease?

HbS.

What is the impact of frameshift mutations?

They change every codon downstream, often leading to a nonfunctional protein.

What are mutagens?

External agents that cause mutations and increase the mutation rate.

What are some examples of chemical mutagens?

Nitrous acid, benzene, chemicals from cigarette smoke, and alkylating agents.

What historical events highlight the impact of radiation as a mutagen?

The Hiroshima bombing in WWII and the Chernobyl nuclear accident.

What are germ cell mutations?

Mutations that occur in reproductive cells and can be passed to offspring.

What are somatic cell mutations?

Mutations that affect only some cells and cannot be passed to offspring.

What is a common somatic cell mutation associated with cancer?

Mutations in the TP53 gene, a tumor suppressor gene.

What is the role of the p53 protein?

The p53 protein prevents tumor formation by activating DNA repair mechanisms, arresting damaged cells in the cell cycle, and triggering apoptosis if the damage is irreparable.

What is the significance of gene mutations in evolution?

Gene mutations are the original source of all genetic variation, which is essential for evolution by natural selection, despite many mutations being harmful or neutral.

What is gene knockout?

Gene knockout is a method used to determine the function of a gene by removing or inactivating it and observing the resulting phenotype.

What is the first step in the gene knockout process?

The first step is identifying the target gene.

What is CRISPR-Cas9?

CRISPR-Cas9 is a method for making precise, targeted changes in DNA.

What is the role of guide RNA (gRNA) in CRISPR-Cas9?

The gRNA is designed to match a specific DNA sequence and pairs with the Cas9 enzyme to form a complex that binds to the target DNA.

What happens when Cas9 cuts the DNA?

Cas9 cuts both DNA strands at the target site, activating the cell's natural repair mechanisms to either disable the gene or insert a new sequence.

What are some applications of CRISPR-Cas9?

Applications include gene knockout for studying gene function, gene therapy for correcting inherited diseases, and agriculture for producing disease-resistant crops.

How can CRISPR-Cas9 be used in agriculture?

CRISPR-Cas9 can be used to knockout genes that pathogens use to infect crops, thereby producing disease-resistant plants.

What ethical issues are associated with CRISPR technology?

Ethical issues include the need for regulation and oversight of genome editing technologies, as well as concerns about potential misuse.

What is a conserved sequence in genetics?

A conserved sequence is a DNA sequence that remains very similar or identical across different species or within a species over long evolutionary time.

What is a highly conserved sequence?

A highly conserved sequence shows extremely little variation due to strong selective pressures and typically codes for essential proteins.

What does the Negative (Purifying) Selection Hypothesis suggest?

It suggests that mutations in conserved sequences are extremely harmful and are selected against in the process of natural selection.

What does the Slower Mutation Rate Hypothesis propose?

It proposes that conserved sequences are more structurally stable and have a naturally lower rate of mutation, likely due to more efficient repair mechanisms.

What is the purpose of the International Summit on Human Gene Editing?

The summit aims to address ethical issues and harmonize regulations regarding genome editing technologies like CRISPR.

How does CRISPR-Cas9 contribute to biomedical research?

It allows for the development of animal models of human diseases by editing genomes to mimic genetic mutations found in humans.

What is the significance of the World Health Organization's guidelines on gene editing?

The WHO published guidelines and established an international registry for human genome editing trials to ensure ethical practices.

What is the potential impact of CRISPR on vector-borne diseases?

CRISPR can be used to modify mosquito genomes to reduce malaria transmission by targeting genes essential for female fertility or blocking the parasite's life cycle.

What is the role of CRISPR in treating sickle cell disease?

CRISPR was used to knockout a gene that suppresses fetal hemoglobin production, allowing for its production to alleviate disease symptoms.

What is the main advantage of using knockout organisms in research?

Knockout organisms allow scientists to infer the role of a missing gene by comparing their phenotypes to wild-type organisms.

What are SNPs in the context of genetic research?

Single Nucleotide Polymorphisms (SNPs) are variations in a single nucleotide that can be introduced into animal embryos for research purposes.

What is the outcome of knocking out genes in mosquitoes?

Knocking out genes essential for female mosquitoes' fertility can lead to population collapse and reduced disease transmission.

What is the significance of the CRISPR-Cas9 system in genetic engineering?

It allows for precise editing of DNA, enabling deletion, insertion, or modification of genes with high accuracy.

What is the importance of studying conserved sequences?

Studying conserved sequences helps understand essential biological functions and evolutionary processes across species.