Genetic Mutations

Autosomal Recessive

A type of Mendelian inheritance where two copies of an altered gene must be present for the trait to be expressed.

Autosomal Dominant

A type of Mendelian inheritance where only one copy of an altered gene is needed for the trait to be expressed.

X-linked

A type of inheritance where genes are located on the X chromosome, affecting males and females differently.

Polymorphisms

Genetic alterations that are harmless and present in more than 1% of the population.

Mutations

Harmful alterations in the nucleotide sequence of a gene.

Chromosomal aberrations

Alterations involving the absence of a chromosome or large portions of one, or the presence of extra chromosomes.

Loss-of-function

A mutation resulting in an absent or dysfunctional protein, which is more common.

Gain-of-function

A mutation that results in a protein with enhanced function, which is less common.

Missense mutation

A point mutation that results in a different amino acid being incorporated into a protein.

Silent mutation

A point mutation that does not change the amino acid sequence of a protein.

Nonsense mutation

A point mutation that creates a premature stop codon in the protein sequence.

Frameshift mutations

Mutations caused by insertions or deletions that shift the reading frame of the genetic code.

Deletions

Mutations involving the loss of a segment of DNA.

Insertions

Mutations involving the addition of extra DNA segments.

Inversions

Mutations where a segment of DNA is reversed within the chromosome.

Xeroderma pigmentosum

A disease resulting from DNA damage and mutation, characterized by extreme sensitivity to sunlight.

Ataxia telangiectasia

A disease caused by DNA damage and mutation, leading to neurological problems and increased cancer risk.

Environmental mutagens

Agents or substances that can cause permanent alterations to DNA, such as chemical mutagens, radiation, and sunlight.

Germline mutations

Mutations in germline cells that can be passed to subsequent generations, responsible for hereditary diseases.

Phenotype

The observable physical or biochemical characteristics of an organism, determined by both genetic makeup and environmental influences.

Mimicry in DNA replication

The mechanism by which some mutagens mimic correct nucleotide bases but fail to base pair correctly during DNA replication.

Free radicals

Highly dangerous and a highly reactive molecule that attacks the DNA molecule and alters it in many ways.

Ultraviolet radiation

Contains ultraviolet radiation (the component that causes a suntan).

Cross link formation

When UV light is absorbed by the DNA, it causes a cross link to form between certain adjacent bases.

Unrepaired dimers

Occasionally unrepaired dimers develop and cause the replicating system to skip over the mistake leaving a gap.

Skin cancer risk

Unprotected exposure to UV radiation by the human skin can cause serious damage and may lead to skin cancer and extensive skin tumors.

Covalent link of thymines

Exposure to UV light can cause adjacent thymines to covalently link.

Distortion of DNA

Distorts the DNA molecule and breaks the hydrogen bond with adenine.

Isomer

Sometimes DNA nucleotides shift without warning to a different chemical form known as an isomer.

Conservative mutation

May change the amino acid sequence, but the amino acid change has similar biochemical properties as the original; hence, the function may not be significantly affected.

Nonconservative mutations

Substitution of a biochemically different amino acid which changes the biochemical nature of the protein.

Point mutation

An alteration of one nucleotide base.

Silent mutations

DNA mutations that do not result in a change of the amino acid sequence of a protein.

Nonsense mutations

A point mutation that results in a premature stop codon, or a nonsense codon in the transcribed mRNA.

DNA expression mutations

A type of mutation that does not change the protein itself but where and how much of a protein is made.

Altered protein function

Some mutations result in proteins that do not function normally, and may end up causing disease.

Protein production issues

Result in proteins being made at the wrong time, proteins made in the wrong cell type, too much protein made, or too little protein made.

Sickle cell anemia

An altered protein in red blood cells alters the shape of the red blood cell, causing the cell to become stuck in blood vessels and prevents cells from carrying sufficient oxygen to the rest of the body.

Hemophilia

Mutation results in the absence of a protein that causes blood to clot, resulting in uncontrolled bleeding in response to injury.

Development of some cancers

A protein that prevents additional mutations from building up can become turned off, leading to the accumulation of mutations and increasing cancerous behavior in cells.

DNA damage

Common occurrence in cells, which leads to the necessity of various DNA repair mechanisms.

Damage reversal

Mechanisms including photoreactivation and ligation of single strand breaks.

Damage removal

Includes base excision repair, mismatch repair, and nucleotide excision repair.

Damage tolerance

Mechanisms such as recombination repair and mutagenic repair.

X-rays and peroxides

Can cause breaks in the backbone of DNA.

DNA ligase

Rapidly repairs simple breaks in one strand of DNA.

Bulky DNA damage

Damage that blocks DNA replication and transcription, such as UV-induced dimers and certain chemical adducts.

Endonucleases

Cleavage of the DNA strand containing damage occurs by these enzymes on either side of the damage.

Exonuclease

Removes a short segment containing the damaged region after endonuclease cleavage.

DNA polymerase

Fills in the gap that results from the removal of the damaged DNA segment.

NER mutants

Lower organisms that are UV-sensitive and have elevated levels of mutation and recombination induced by UV.

Autosomal recessive hereditary disease

Xeroderma pigmentosum is classified as this type of genetic disorder.

AT patients

Cells show abnormalities including spontaneous and radiation-induced chromosome breaks and sensitivity to killing by X-rays.

Cell cycle checkpoint

A decision point that governs progression through the next phase of the cell cycle.

Uncontrolled cell growth

Can result from mutations in checkpoint genes, leading to cancer.

Frequency of heterozygotes

Estimated to be about 1% in the population for one AT mutation.

Cancer risk in AT heterozygotes

Higher cancer risk and intermediate radiation sensitivity compared to the general population.

Screening by X-ray methods

May increase the chances of an AT heterozygote developing cancer.

Types of DNA mutations

Various types occur, affecting the function and stability of genes.

Effects of mutations

Can lead to various health issues, including genetic disorders and increased cancer susceptibility.

Types of repair mechanisms

Cells have several mechanisms to repair DNA damage, ensuring genomic stability.

Diseases from repair mechanism failure

Certain diseases occur when DNA repair mechanisms do not function properly.