Lesson # 16Mutations

MutationsProduction of new alleles

Positive aspects and negative aspects

Mutations do not always cause damage. Thanks to them, there is a greatergenetic variability amongst individuals in a population. Different alleles forthe same gene usually exist due to a mutation.

Blue eyes

Sometimes a mutation can result in an allele or version of a gene whichproduces a genetic disorder.

Colorblindness (Recessive sex-linked disorder)

Albinism (Recessive autosomal disorder)

Haemophilia (Recessive sex-linked chromosome)

Sickle Cell anemia (Incomplete dominance)

Achondroplasia (Dominant autosomal disorder)

Types of mutations

Gene mutations: new alleles are created for the same gene when there is a mistake

produced during the DNA replication during the S phase.

Types of mutations

Chromosome structure mutations: when the structure of the chromosome is

not the correct one. This happens due to a mistake in the crossing over

which occurs in the formation of gametes (Prophase I of meiosis).

Types of mutations

Numerical mutations: An alteration in the number of chromosomes.

Trisomy 13 Patau syndrome

Trisomy 18 Edwards syndrome

Trisomy 21 Down syndrome

X0 Turner’s Syndrome

XXY Klinefelters síndrome

Normally due to a mistake in Anaphase I during meiosis (formation of a

gamet).

Types of mutations

Therefore, there are 3 main types of alterations in the genetic information of

an indivual due to a mutation

Causes of mutations

Mutagens: agent which produces or facilitates a mutation to occur.

Types of mutagens

Physical mutagen: radiation (X-rays or UV)

Chemical mutagens: some subtances can cause changes in genes. Like forexample pollutants, substances in tobacco. Risk of mutations increase with the

increased exposure.

Biological mutagens: some viruses can increase the frequency of genetic

mutations

Some mutations result in the appearance of cancer cells.