Mutations

What do YOU think? What are mutations? Knowing what you know about DNA, how it replicates, and how it codes for proteins… how might a mutation happen? What might be a result of mutations in DNA?

What are Mutations? Now and then cells make mistakes in copying their own DNA, whether it’s inserting an incorrect base or even skipping a base as the new strand is put together These mistakes are called mutations Mutations are changes in the genetic material

Types of Mutations Point Mutations – mutations involving changes in one or a few nucleotides They’re called point mutations because they occur at a single point in the DNA sequence Point mutations include: substitutions, insertions, and deletions in the DNA sequence If you had to guess, what do you think happens in each of these three types of point mutations? Substitutions? Insertions? Deletions?

Types of Mutations Substitutions A substitution occurs when one base in a DNA sequence is replaced for another Substitutions usually affect no more than one amino acid Why do you think that is?

Types of Mutations Insertions An insertion occurs when a base is added to the DNA sequence The effects of an insertion can be much more dramatic than a substitution. Why do you think that is?

Types of Mutations Deletions A deletion occurs when a base is removed from a DNA sequence How is a deletion similar to an insertion?

Types of Mutations Insertions and deletions can have much more dramatic effects because they are considered frameshift mutations Frameshift mutations shift the “reading frame” of the genetic message Remember: the genetic code is read in codons (sets of three letters), so if a base is added/deleted, all the codons after the mutation are affected because it will shift the groups of three

Types of Mutations By shifting the reading frame, frameshift mutations may change every amino acid that follows the point of the mutation Frameshift mutations can alter a protein so much that it is unable to perform its normal functions

Uncontrolled Cell Replication A normal, healthy cell has 23 pairs of chromosomes (diploid) = total of 46 chromosomes Typically, when your cells divide, you start with one mother cell and end with two exact diploid copies called, daughter cells. This process is called mitosis.

Uncontrolled Cell Replication The only exception to the diploid cells are reproductive cells, called gametes. These cells divide twice in a process to produce gametes, called meiosis Meiosis results in four non-identical gamete cells with 23 chromosomes each (haploid). *This means that every gamete is completely different from another gamete!

Uncontrolled Cell Replication Cell replication, or mitosis, is a closely regulated process in the body. Cancer is uncontrolled cell growth. When cells divide uncontrollably, they form masses of cells called tumors that can damage the surrounding tissues.

Uncontrolled Cell Replication Tumors can be either benign or malignant Benign: the cancer cells stay clumped and the tumor can be removed Malignant: the tumor can metastasize (or break away) and cause other tumors elsewhere What causes this loss of control over growth? It could be environmental (radiation exposure), poor choices (smoking), or genetic predisposition