Mutations

What is a mutation? Changes in the genetic material

Mutations can occur in two different types of Cells: 1. Somatic (body) cells 2. Gamete (sex or germ) cells

Significance of Mutations Most mutations are neutral, meaning they have little or no effect on the expression or function of the proteins they code for Those that cause dramatic changes produce defective proteins that disrupt biological activities However, mutations are the source of genetic variability in a species, which can be highly beneficial

Harmful Mutations Causes Genetic disorders ex: sickle cell anemia, cystic fibrosis, hemophilia, muscular dystrophy and down syndrome (or trisomy twenty one) Causes different Types of cancer

Kinds of Mutations I. Gene Mutations- II. Chromosomal Mutations- produce changes in a single gene II. Chromosomal Mutations- produce changes in the whole chromosome

I. Gene Mutations Point Mutation- changes in one or a few nucleotides within the DNA sequence Substitutions-one base is changed to another Frameshift Mutation- A single nitrogen base is deleted or inserted from the DNA sequence causing a shift in the “reading frame” of the genetic message. Insertions-one base is inserted Deletions-one base is deleted

Gene mutations continued Example: substitution THE FAT CAT ATE THE RAT THE FAT CAT ATE THE HAT Example: insertion THE YFA TCA TAT ETH ERA Example: deletion TEF ATC ATA TET HER

Point Mutations: Small Scale Mutations usually effect no more than one amino acid THE FAT CAT ATE THE RAT THE FAT CAT ATE THE HAT

Frameshift Mutation Frameshift is usually more dramatic May change every amino acid that follows the point of insertion or deletion THE FAT CAT ATE THE RAT TEF ATC ATA TET HER AT

Review What are the three parts of a nucleotide? What are the four bases? How many bases code for an amino acid? What is made by joining amino acids? What are genes? Where are genes?

The effects of insertions or deletions Which one usually effect no more than a single amino acid? substitutions What happens if a nucleotide is added or deleted? the “reading frame” or code is shifted from that point on which is a frameshift mutuation. Which one alters a protein so much that it is not able to perform its normal function? frameshift

Kinds of Mutations I. Gene Mutations- II. Chromosomal Mutations- produce changes in a single gene II. Chromosomal Mutations- Involve changes in the number or structure of chromosomes which change the location of genes or the number of copies of genes

Two Types of Mutations 2. Chromosomal Mutations 1. Gene Mutations A. Point Mutations B. Frameshift Mutations A. Deletion B. Duplication C. Inversion D. Translocation E. Non-disjunction

Ex: original chromosome A B C * D E F Deletion: A B * D E F Duplication: A B B C * D E F Inversion: A E D * C B F Translocation: A B C * J K L G H * I D E F

Chromosomal Mutations Deletion- loss of all or part of a chromosome Duplication-production of extra copies of parts of the chromosome Inversion- reverses the direction of parts of a chromosome Translocation- part of one chromosome breaks off and attaches to another chromosome Non-disjunction- means “not coming apart”. When homologous chromosomes fail to separate properly during meiosis (cell division producing gametes)

Non-disjunction- Chromosomal mutation A karyotype generally has two chromosomes at each position (23 pairs) Trisomy (3) means a person has an extra chromosome Monosomy (1) means a person is missing a copy of a chromosome.

Trisomy 21- Down Syndrome Karyotype (47XY)

Klinefelter’s Karyotype (47XXY)

What is Klinefelter syndrome? Klinefelter syndrome is a chromosomal condition that affects male physical and cognitive development. Its signs and symptoms vary among affected individuals. Affected individuals typically have small testes that do not produce as much testosterone as usual. Testosterone is the hormone that directs male sexual development before birth and during puberty. A shortage of testosterone can lead to delayed or incomplete puberty, breast enlargement (gynecomastia), reduced facial and body hair, and an inability to have biological children (infertility). Older children and adults with Klinefelter syndrome tend to be taller than their peers. Children with Klinefelter syndrome may have learning disabilities and delayed speech and language development. They tend to be quiet, sensitive, and unassertive, but personality characteristics vary among affected individuals.

Turner’s Syndrome Karyotype (45XO)

What is Turner’s Syndrome? Turner syndrome is a chromosomal condition that affects development in females. The most common feature of Turner syndrome is short stature, which becomes evident by about age 5. An early loss of ovarian function (ovarian hypofunction or premature ovarian failure) is also very common. The ovaries develop normally at first, but egg cells (oocytes) usually die prematurely and most ovarian tissue degenerates before birth. Many affected girls do not undergo puberty unless they receive hormone therapy, and most are unable to conceive (infertile). A small percentage of females with Turner syndrome retain normal ovarian function through young adulthood.

Mutations and Natural Selection Examine the diagram Does natural selection work on the genotype or phenotype? Natural selection leads to a change in the “population” NOT the individual.

Beneficial Mutations Produce proteins with new and altered activities that are useful in changing environments (gene resistant) Plant and animal breeders take advantage of these mutations (genetically altered) Polyploid plants- produced when chromosomes fail to separate during meiosis. Result in triploid (3N) and tetraploid (4N) organisms. Polyploid plants are often larger and stronger than diploid plants.