Unit 6 (Regulation and Mutations)

Mutations

Changes in the genetic material of a cell that can alter phenotypes

• Primary source of genetic variation

• Normal function and production of cellular products are essential

• Any disruption can cause new phenotypes

• large-scale changes: chromosomal changes

• small-scale changes: nucleotide substitutions, insertions, or deletions

Small scale mutations

• Point mutations: change a single nucleotide pair of a gene

• Substitution: replacement of one nucleotide and its partner with another pair of nucleotides

  • Silent: Change still codes for the same amino acid (redundancy)

  • Missense: change results in a different amino acid

  • Nonsense: change results in a stop codon

Frameshift mutation

• When the reading frame of the genetic information is altered

• Leads to disastrous effects:

  • Insertion: a nucleotide is inserted

  • Deletion: a nucleotide is removed

Large Scale Mutations

• Occurs in chromosomes

• Nondisjunction: when chromosomes do not separate properly in meiosis

  • Results in the incorrect number of chromosomes (ex. Down syndrome - trisomy 21)

• Translocation: a segment of one chromosome moves to another

• Inversions: a segment is reversed

• Duplications: a segment is repeated

• Deletions: a segment is lost

Natural Selection

Any time mutations occur, they are subject to natural selection

• Genetic changes can sometimes enhance the survival and reproduction of an organism

Increasing Genetic Variation

• Prokaryotes can exchange genetic material through horizontal gene transfer

• If there is a mutation that is beneficial to survival and reproduction of the prokaryote, then it can be transformed

  • Transformation: up-taking of DNA from a nearby cell

  • Transduction: viral transmission of genetic material

  • Conjugation: cell to cell transfer of DNA

  • Transposition: movement of DNA segments within and between DNA molecules

Biotechnology

• Both DNA and RNA can be manipulated through genetic engineering

Gel electrophoresis

A technique used to separate DNA fragments by size

• DNA is loaded into wells on one end of a gel and electric current is applied

• DNA fragments are negatively charged so they move towards the positive electrode

Polymerase Chain Reaction (PCR)

A method used in molecular biology to make several copies of a specific DNA segment

• Segments of DNA are amplified

• Results can be analyzed using gel electrophoresis

DNA sequencing

The process of determining the order of nucleotides in DNA