Mutations Essential knowledge 3 C 1 Changes in

Mutations

Essential knowledge 3. C. 1. Changes in genotype can result in changes in phenotype a. Alterations in a DNA sequence can lead to changes in the type or amount of the protein produced and the consequent phenotype. [See also 3. A. 1] Evidence of student learning is a demonstrated understanding of the following: 1. DNA mutations can be positive, negative or neutral based on the effect or the lack of effect they have on the resulting nucleic acid or protein and the phenotypes that are conferred by the protein. b. Errors in DNA replication or DNA repair mechanisms, and external factors, including radiation and reactive chemicals, can cause random changes, e. g. , mutations in the DNA. Evidence of student learning is a demonstrated understanding of the following: 1. Whether or not a mutation is detrimental, beneficial or neutral depends on the environmental context. Mutations are the primary source of genetic variation. c. Errors in mitosis or meiosis can result in changes in phenotype. Evidence of student learning is a demonstrated understanding of each of the following: 1. Changes in chromosome number often result in new phenotypes, including sterility caused by triploidy and increased vigor of other polyploids. [See also 3. A. 2] 2. Changes in chromosome number often result in human disorders with developmental limitations, including Trisomy 21 (Down syndrome) and XO (Turner syndrome). [See also 3. A. 2, 3. A. 3]

MUTATIONS = change in the genetic code Can be due to : Errors in DNA replication or repair ___________________ External factors ___________________ such as X-rays, UV-radiation, or carcinogens (cigarette smoke) GENE MUTATIONS = change in a single gene POINT Change in just a few nucleotides in the ____DNA sequence Image from: https: //evolution. berkeley. edu/evolibrary/article/%3 C? %20 echo%20$base. URL; %20? %3 E/mutations_03

Images from: https: //evolution. berkeley. edu/evolibrary/article/%3 C? %20 echo%20$base. URL; %20? %3 E/mutations_03 SUBSTITUTION DELETION INSERTION DUPLICATION

If change codes for same amino acid = SILENT mutation _____ GGC and GGA BOTH code for glycine = ”WOBBLE” If change codes for a different amino acid = _________ mutation MISSENSE May change function of protein EX: Sickle cell mutation: A → T If change codes for a STOP instead of an amino acid NONSENSE = ________ mutation Protein sequence will be terminated early (shorter) and NONFUNCTIONAL.

Images from: https: //evolution. berkeley. edu/evolibrary/article/%3 C? %20 echo%20$base. URL; %20? %3 E/mutations_03 Because messages are read in groups of 3 (CODONS) insertions/deletions can cause a _________. FRAMESHIFT A shift in the reading frame changes every codon after the mutation. Can result in NONSENSE or MISSENSE mutations. Frameshift mutations at beginning of a gene change more of the code than at the end

CHROMOSOMAL MUTATIONS – changes in number or structure of whole chromosomes deletions & duplications inversions & translocations

POLYPLOIDY ________________ LETHAL in humans rare in most animals Beneficial in plants Image from: https: //upload. wikimedia. org/wikipedia/commons/thumb/a/aa/Haploid%2 C_diploid_%2 Ctriploid_and_tetraploid. svg/1200 px. Haploid%2 C_diploid_%2 Ctriploid_and_tetraploid. svg. png