Mutations Flashcards
Mutation
Permanent change to a gene or chromosome leading to a new characteristic in an organism, Can be caused by changing base sequences in a section of DNA which changes the proteins that will be synthesised by the body, Advantageous or disadvantageous
Mutant
Organism with a characteristic resulting from a mutation
Mutagens
Agents known to increase the rate at which mutations occur, Eg UV light, X-rays, radiation, chemicals such as sulfur dioxide or antibiotics
Somatic mutation
Mutation in a body cell, reproductive cells aren’t affected and once the organism dies, the mutation is lost
Germline mutation
Mutation in the gametes, individual isn’t usually affected however they produce gametes with changed DNA
Gene mutations
When there is a change in a single gene, Occur during DNA replication before cell division, If DNA copies are incorrectly changed, changed DNA continues to be copied in all future divisions, If a single base is changed in a gene the DNA may code for a new amino acid and thus a different protein or causing a protein to not be created at all however there may be no change
Point mutation
Change in just one base
Albinism
Point mutation, Results from a missing protein, Protein responsible for the pigment of hair, skin and eyes is missing
Duchenne muscular dystophy
Point mutation (deletion), Caused by missing the protein dystrophin, Results in wasting of the leg muscles and later the arms, shoulders and chest, Individuals generally experience muscle weakness as the ages of 3-5 years, Eventually death occurs due to failure of respiratory muscles, Boys who contract the disease don’t live past 25 years
Frameshift mutation
When a single base is added or deleted from DNA which shifts the reading of codons by one base
Cystic fibrosis
Results from changes to DNA of the CFTR gene resulting in different amino acids in the CFTR protein, CFTR protein regulates the development of the chloride channels in the cell membrane, Without the CFTR protein a person cannot transport chloride ions and the movement of water into and out of cells, Without the correct version of the CFTR protein the person suffers from salty tasting skin, persistent ocughing, wheezing and digestive problems
Lethal recessive
When a recessive mutation isn’t masked by a dominant (normal) allele, Can occur if both partners carried the same recessive mutation, Cause the death of the embryo or foetus by miscarriage or abortion
Chromosomal mutations
Occur when there is a change in the whole or part of a chromosome causing a change in a few nucleotide bases, Can affect genes
Aneuploidy
Change in the chromosome numbers
Causes of chromosomal mutations (5)
Deletion where part of a chromosome is loss, Duplication where a section of a chromosome occurs twice, Inversion when a break occurs in the chromosome and the broken piece joins back in but inverted (the wrong way around), Translocation when part of a chromosome breaks off and is re-joined to the wrong chromosome, Non-disjunction- during meiosis when a chromosome pair doesn’t separate meaning one daughter cell has one less chromosome (monosomy) and on has one extra (trisomy, down syndrome)
Diseases caused by non-disjunction monosomy
Cri-du-chat syndrome is caused by a missing portion of chromosome 5, often causes problems with infants larynx and nervous systems, Turners syndrome is due to a missing sex chromosome, born female but are short in stature, lack secondary sex characteristics and are infertile
Diseases caused by non-disjunction trisomy
Down syndrome occurs when an individual has an extra chromosome 21, Pataus syndrome occurs when an individual has an extra chromosome 13, individuals often have a small head, mental problems, extra fringe on each hand, cleft palate and malformations of the eyes and ears, Klinefelter syndrome occurs when an individual has an extra x chromosome
Causes of mutations
Errors in replication, During cell division, Damage caused by mutagens
Problems that occur during DNA replication
Wrong bases pair up, DNA can be removed (deleted), DNA can be duplicated (insertion), DNA can become unreadable or be an incomplete code (frameshift), Problems can affect the gene or the whole chromosome and can affect a somatic cell or a gamete
Problems that occur during cell division
Genetic material is swapped during cross over, Segments of chromosome can be reversed (inversion), Sections of chromosomes can be attached to each other (translocation), Extra chromosomes can be added or deleted (aneuploidy/non-disjunction), Causes gametes produced to have an incorrect number of chromosomes, Affects the chromosome or parts of a chromosome, Affects the gametes (germline mutation)
Damages from mutagens
Resemble proteins and can be incorporated into DNA, Cause: Trigger DNA replication errors, DNA breakages or lengthening, Block DNA replication, Damage DNA structure, Chemically react and modify DNA, Damaged DNA then multiply, Affects one gene or the whole chromosome, Affects a somatic cell or a gamete
