1. Chromosomal Gene Mutations
What if it’s NOT just the number?

2. Gene Mutations
Damaged Chromosomes – sometimes a portion of a gene or chromosome is lost or damaged during meiosis
Gene mutation – a mutation that affects the gene
Insertion – one or more nucleotides are added within the DNA sequence
Deletion – one or more nucleotides are removed (lost) from the DNA sequence
Substitution (point mutation) – an event in which a single nucleotide is replaced with a different nucleotide

3. Mutations Type Definition Example Insertion A new nucleotide is added
…TAGCCAGATA…
…TAGCGCAGATA…
Deletion
A nucleotide is removed (lost)
…TAGCAGATA…
Substitution (aka Point Mutation)
A single nucleotide is replaced with a different nucleotide
…TAGCCAGTTA…

4. Chromosomal Mutation - Deletion
Chromosomal mutation – a mutation that affects multiple genes on a chromosome
Chromosomal deletion – an event in which a piece of the chromosome is deleted
Can remove one or more genes from chromosome

5. Chromosomal Mutation - Amplification
Amplification – a large piece of the chromosome is repeated/duplicated
Causes two or more copies of one or more genes

6. Chromosomal Mutation - Inversion
Inversion –one or more nucleotides break off and are flipped over before being reinserted/ reattached
Reverses orientation

7. Chromosomal Mutation - Translocation
Translocation is when segments of DNA (nucleotides) move from one chromosome to another chromosome
Translocation – one piece of a chromosome is incorrectly inserted into a different chromosome OR when two pieces of different chromosomes are interchanged

8. Translocation

9. Effect of Mutations Mutations are ANY change in the DNA sequence!
Change to the nucleotide sequence may cause an incorrect polypeptide (protein) to be made
Incorrect polypeptide means the protein may not function properly
Incorrect sequence = incorrect shape
Incorrect shape = incorrect function

10. Substitution Mutations - Silent
Substitution mutations can affect genes in multiple ways
Different nucleotide does not always change amino acid used…
Silent mutation – a mutation in which there is no effect on the polypeptide chain created
No visible affect

11. Substitution Mutations – Missense Insertion
Different nucleotide does not always change amino acid used
“Wobble” base! (I’ll explain later!)
Missense mutation – a mutation that results in the insertion of a different amino acid
May change proteins created

12. Substitution Mutations - Nonsense
Different nucleotide may cause the ribosome to read the codon message incorrectly
Nonsense mutation – a mutation in which a “stop codon” is expressed early, creating a shorter polypeptide chain
Greatly affects protein created

13. What the heck is a “codon” anyway?
Remember this?
Pls txt whn you get a sec
Hnd the wrk out ltr
Stp whn dun

14. Frameshift Mutations – VERY BAD!
Codons are read “three” nucleotides in a row
Insertions and deletions cause frameshift mutations in the reading frame
Frameshift mutation – a mutation in which the codon reading frame is changed, potentially changing ALL codons following
Since Codons are read in groups of three nucleotides, addition or removal of a nucleotide changes the entire reading frame
Different polypeptides produced

15. Good, Bad or Nothing?
Mutations may have an effect on “fitness” (chance of survival)
Beneficial mutations – a mutation that increases an organism’s chance of survival (fitness)
Fur color may allow organism to better blend into the environment, avoiding predators
Harmful mutation – a mutation that decreases an organism’s fitness
May make protein used to carry oxygen less efficient
Neutral mutation – a mutation that does not affect an organism’s fitness
No change in proteins
All silent mutations are neutral mutations