Genetic Mutations Quiz

Mutation Overview

• Mutations are changes in the DNA sequence of bases.
• Mutations are not always harmful; some are beneficial and essential for evolution.
• Most people have dozens to hundreds of mutations in their DNA.
• Mutations are the ultimate source of new genetic material, creating new alleles in a species.

Types of Mutations

• Germline mutations: Occur in gametes (sex cells). Transmitted to offspring, and every cell in the offspring will have the mutation.
• Somatic mutations: Occur in other cells of the body. May have little effect on the organism as they are confined to one cell and its daughter cells. They cannot be passed to offspring.

Causes of Mutations

• Errors in DNA Replication: DNA polymerase occasionally incorporates a non-complementary base, potentially leading to a mutation during the next round of replication. This is rare as exonuclease functions as proofreading mechanism.
• Errors in DNA Recombination: DNA rearranges itself through recombination via various mechanisms. Occasionally DNA is lost during replication, causing a mutation.
• Radiation: UV radiation (sunlight, tanning beds), X-rays (medical, dental, security screening).
• Chemicals: Cigarette smoke (contains many mutagenic chemicals), benzoyl peroxide (common in acne products), nitrates and nitrites (preservatives in processed meats).
• Infectious Agents: Human Papillomavirus (HPV), Helicobacter pylori.

Gene Mutation

• A change to a gene's DNA sequence.
• Creates a permanent change to that gene's DNA sequence causing a different product.

Chromosomal Aberrations

• A disorder characterized by morphological or numerical alterations in one or more chromosomes; affecting autosomes, sex chromosomes, or both.
• Different types of structural abnormalities include: translocation, deletion, inversion, isochromosome, and ring chromosome.

Types of Gene Mutation

• Point Mutations: Changes in a single nucleotide.
  • Silent Mutation: No change in the resulting amino acid.
  • Missense Mutation: Change in the resulting amino acid.
  • Nonsense Mutation: Change in the amino acid to a stop codon resulting in a shorter, possibly non-functional protein.
  • Frameshift Mutation: Addition or deletion of one or two nucleotides, disrupting the reading frame.

Chromosomal Mutations

• Numerical Instability: Small-scale gains (like trisomy), small-scale losses (like monosomy) or large-scale gains (like polyploidy).
• Structural Instability: Deletions, duplications, inversions, and translocations.

Deletion

• Loss of one or more base pairs from the DNA.
• If one or two bases are deleted, the translational frame is altered, resulting in a garbled message and non-functional protein product.

Cystic Fibrosis

• A hereditary disorder marked by lung congestion and infection, malabsorption of nutrients by the pancreas.

Cri Du Chat Syndrome

• Characteristics include a high-pitched cry, small head, and flattened bridge of the nose.

Duplications

• A region of a chromosome is repeated causing an increased in gene dosage in that region.
• Occurs when a stretch of one or more nucleotides in a gene is copied and repeated next to the original DNA sequence.

Charcot-Marie-Tooth Disease

• One of a group of disorders that cause damage to the peripheral nerves.

Inversions

• One region of a chromosome is flipped and reinserted.
• An inversion changes more than one nucleotide, replacing the original sequence with the same sequence in reverse order.

Opitz-Kaveggia Syndrome

• X-linked recessive mental retardation. Characterized by dysmorphic features, relative macrocephaly, hypertelorism, downslanted palpebral fissures, prominent forehead, upsweep of frontal hair, and broad thumbs and halluces.

Translocations

• A region from one chromosome is aberrantly attached to another chromosome.

Substitutions

• Replace one DNA building block (nucleotide) with another.
  • Missense: Change in the amino acid specified.
  • Nonsense: Change in the amino acid to a stop codon.

Non-sense Mutation

• A type of substitution where the altered DNA sequence signals a premature stop of protein building.

Sickle-Cell Anemia

• A disorder of hemoglobin in red blood cells, resulting in abnormal shape and function leading to various health complications.

Insertion

• Insertion of additional base pairs.
• Can lead to frameshifts, depending if multiples of three bases are inserted.

Thalassemia

• Disruption in the production of hemoglobin in red blood cells resulting in symptoms such as anemia.

Types of Chromosomal Aberrations

• A broad set of changes to chromosomes, including altered numbers (aneuploidy, polyploidy) and structural changes.

Abnormal Karyotype

• Analysis of chromosomes reveals changes in chromosome number (e.g. Trisomy 21, Down Syndrome), or structural changes. (e.g. Deletions, duplications, inversions, translocations).

Trisomy 18

• Presence of three copies of chromosome 18. A variety of health problems.

Klinefelter's Syndrome

• Male has an extra X chromosome, leading to underdeveloped testes and physical traits.

Patau's Syndrome

• Trisomy 13. Results in numerous birth defects and developmental issues.

Aneuploidy vs Polyploidy

• Aneuploidy is an abnormal number of individual chromosomes. Polyploidy is an abnormal number of sets of chromosomes.

Polypoid

• Cells having three or more sets of chromosomes.

Chromosome Duplication

• Repeated copies of a DNA segment from a chromosome (which can be small section or large segment).

Chromosome Inversion

• A segment of a chromosome breaks off, reattaches within the same chromosome but in a reversed orientation.

Sex Chromosome Aberrations

• Disorders affecting the number or structure of X and Y chromosomes. Common examples include monosomy X (Turner syndrome) or structural abnormalities, such as isochromosome Xq.

Turner Syndrome

• Missing an X chromosome (XO). Has a variety of physical and developmental consequences.

Effects of Mutations on Plants

• Mutations can change foliage, flowers, fruit, or stem appearance.

Effects of Mutations in Animals/Humans

• Mutations in animals and humans can result in various physical abnormalities and health issues.

Albinism

• Mutation in the melanin-producing gene resulting in no or reduced melanin. Leads to reduced pigmentation in skin, hair, and eyes.

Eight-Legged Goat

• A goat born with extra legs due to a probable genetic phenomenon during development within the mother.

Plant Mutations

• Mutations in plants can alter their physical appearance and/or features.

Beneficial Mutation

• Change in a DNA sequence that enhances or helps the species in some way over time.

Trichromatic Vision

• The ability of some organisms to see different colours, involving the interaction of three color-sensing cone cells.

Lactose Tolerance

• Single point mutation in the DNA near the lactase gene converting cytosine(C) to thymine (T), resulting in lactose tolerance.

Mutation and Cancer

• Uncontrolled, abnormal growth of cells.
• Mutations are associated with the development, progression, and spread of cancer.
• Mutation to specific genes like p53 may be at the origin of the abnormal cell development and spread seen in cancer.

p53 Gene

• A gene responsible for controlling cell division and death in certain cells.
• Mutations in this gene can lead to cancer cell growth and spread.