Chromosomal Mutations

Genetic Code The information to make proteins is found inside of genes. Genes are sections of DNA which carry the blueprint for proteins according the sequence of nitrogen bases.

three nucleotides long, they are also called nucleotide triplets. Genetic Code Each set of 3 nucleotides is known as a codon. The sequence of bases in the codon determines the amino acid in the protein. Because codons are three nucleotides long, they are also called nucleotide triplets.

If there is a change to a nucleotide triplet, there could be a change to the sequence of amino acids! Whenever there is any change to the sequence of DNA, it is called a mutation.

When an insertion or deletion of nucleotides occurs that is not divisible by 3, it causes a shift in the reading frame. This mutation is called a frame shift, and it can lead to severe changes in the protein.

Substitutions are also called point mutations because they involve changing a single base pair, and there is a wide range of consequences that happen as the result of a base pair substitution.

Point Mutations Missense mutations are when the identity of one amino acid is changed. Nonsense mutations occur when a point mutations results in the formation of a STOP codon. Silent mutations occur when the point mutation causes NO CHANGE to the amino acids.

Chromosomes DNA is not found in many little pieces. Instead, large amounts of DNA are packaged together into chromosomes. Human cells hold 46 chromosomes that contain thousands of genes. Human Chromosomes Chromosome The complete set of chromosomes with all of an organism’s DNA is known as its genome.

Chromosomes If you uncoiled all of the DNA in ONE human cell, it would be almost 2 meters long. There is enough DNA in all your cells to make it to the Sun and back! The reason it can fit inside a tiny nucleus is because it is tightly coiled around special proteins.

Chromosomes In eukaryotic cells chromosomes are organized in pairs. Each pair contains a chromosome from the mother and the father.

Chromosomes A picture of the complete set of chromosomes organized into pairs is called a karyotype. The chromosomes are also stained with dyes so that they can be identified and studied.

Mutations Mutations can occur on a large scale within cells and affect entire chromosomes. These chromosomal mutations most often occur during the production of gamete cells.

Males produce a gamete cell known as sperm and females produce a gamete cell known as an egg or ovum. During the production of gamete cells, chromosomes recombine to create unique chromosomes with new combinations of genes.

Mutations sperm egg Only mutations that occur in gamete cells are passed on to the organism’s offspring.

Chromosomal Mutations Both insertions and deletions can occur on a large scale. Instead of just a few nucleotides, these chromosomal changes often involve thousands.

Chromosomal Mutations An inversion occurs when a region of the chromosome is detached, then accidentally flipped before it is reattached. The region of DNA becomes inverted.

Chromosomal Mutations A duplication is exactly what it sounds like. A region of the chromosome is copied and that portion of the chromosome is doubled.

Chromosomal Mutations A translocation occurs when non-homologous chromosomes cross over and recombine. This means chromosomes which are NOT alike trade sections. This should not happen, and it creates a chromosome with an abnormal collection of genes.

Nondisjunction Nondisjunction occurs when chromosomes do not pair correctly when gamete cells are made. This results in the three chromosomes (trisomy) or only one chromosome (monosomy) when there should be two. These abnormalities usually result in very serious complications. Turner’s Syndrome