Mutations and Chromosomal Abnormalities Flashcards

Vocabulary flashcards covering types of mutations, structural and numerical chromosomal abnormalities, genetic syndromes, and causes and impacts of mutations.

Mutation

A sudden and permanent change of DNA.

Gene mutations

Changes in the base sequence of the DNA in a gene, typically occurring during DNA replication, which serve as the main way new alleles are produced in a population.

Chromosome mutations

A change in the structure or total number of chromosomes.

Base substitution

A gene mutation where one base in the DNA template strand is replaced, altering one triplet code which may change a single amino acid, specify a stop signal, or have no effect.

Base inversion

A gene mutation where the order of bases in a gene segment is reversed, which alters a triplet code and may result in a different amino acid.

Sickle-cell anaemia

A disorder caused by a base substitution that changes the amino acid glutamic acid to valine, causing abnormal haemoglobin to form long fibres under low oxygen levels and making red blood cells sickle-shaped.

Reading frame shift

The shifting of the reading frame caused by deleting or inserting base(s), altering the entire amino acid sequence after the point of mutation and usually resulting in a non-functional protein.

Chromosome structural deletion

A structural chromosome mutation involving the loss of a gene segment from a chromosome.

Chromosome duplication

A structural chromosome mutation involving the gain of extra genes on a chromosome.

Chromosome structural inversion

A structural chromosome mutation where the order of genes on a chromosome is reversed.

Chromosome translocation

A structural chromosome mutation involving the exchange of gene segments between non-homologous chromosomes.

Crossing over

A process occurring during Prophase I of meiosis where homologous chromosomes exchange segments at the chiasma, producing recombinant chromosomes and increasing genetic variation.

Non-disjunction

The failure of homologous chromosomes or sister chromatids to separate during gamete formation in meiotic cell division.

Non-disjunction at Meiosis I

The failure of homologous chromosomes to separate, producing gametes that either have an extra chromosome ($n+1$) or are missing a chromosome ($n-1$).

Non-disjunction at Meiosis II

The failure of sister chromatids to separate, producing gametes with an extra chromosome ($n+1$), a missing chromosome ($n-1$), or a normal chromosome number ($n$).

Down syndrome

A disorder caused by non-disjunction resulting in an extra chromosome 21 ($47$ total chromosomes), characterized by shorter stature, a distinctive round face, smaller ears, and some degree of mental retardation.

Turner's syndrome

A condition in females who have one missing X chromosome ($XO$), resulting in little development of secondary sexual characteristics, lack of ovaries, and infertility.

Klinefelter's syndrome

A condition in males who have an extra X chromosome ($XXY$), resulting in some breast development and underdeveloped testes causing infertility.

Spontaneous mutations

Mutations that occur naturally and randomly at a very low rate.

Induced mutations

Mutations caused by external environmental agents called mutagens.

Mutagens

Chemical or physical agents (such as nitrous acid, tar, asbestos, mustard gas, UV light, X-rays, and gamma rays) that increase the rate of mutation.

Free radicals

Highly reactive molecules formed when high-energy radiation ionizes water or other molecules, which can damage DNA molecules.

Somatic cell mutations

Mutations occurring in non-reproductive body cells that are not passed on to offspring and are lost when the individual dies.

Gamete mutations

Mutations occurring in gametes or gamete-producing cells that are inheritable, providing a source of population variation essential for natural selection and evolution.