BIOL 115 Exam 2 Flashcards
Base substitution- what are the two types and how do they work?
Changes the base of a single DNA nucleotide
Two types:
- Transitions
-Transversions
Replaced with different bases
Pyrine (T replaced with Purine (A) and Purine (A) replaced with Pyrine (T)
Transition
Replaced by the same base
(Pyrine (T) to Pyrine (C) and a Purine (A) to a Purine (G)
Transversions
Replaced with different bases
Pyrine (T replaced with Purine (A) and Purine (A) replaced with Pyrine (T)
3 major types of mutations?
Base substation, Insertions and Deletions, and Expanding Nucleotide Repeats
Insertion
Extra base or bases is added to the DNA strand causing a frameshift
Deletion
Base or bases are removed from DNA strand causing a frame shift
Frameshift Mutation
Caused by insertion or deletion that alters the reading frame of a gene (can be bad which affects amino acids and mRNA)
In-Frame Insertions and Deletions
caused by insertions and deletions of a multiple of 3 nucleotides (this leaves frame intact even though there was an insertion or deletion which effects the phenotype) but does NOT alter the reading frame
Expanding Nucleotide Repeats - what is it and what if there is too many?
Repeated sequence of a set of nucleautides casing number of copies of the sequence to increase
If too many…
Causes a disease to form
What mutation effects phenotypes?
Forward Muation and Reverse Mutation
Forward Mutation
Changes wild-type phenotype to a phenotype that is ‘mutant’
Reverse Mutation
Changes a ‘mutant’ phenotype back to the ‘wild type’ phenotype
Wild type phenotype
An individual having the normal phenotype; that is, the phenotype generally found in a natural population of organisms
Mutant Phenotype
An individual has a phenotype that differs from the normal phenotype. Occurs by natural selection or crossing over with a different species of the same gene
What mutations effect the Protein Structure?
Missense mutation, nonsense mutation, and silent mutation
Missense Mutation- what causes it and what are the different conditions?
Overall: caused by Transition and transversion from base substitution
1) When a single nucleotide base in a DNA sequence is swapped for another one, resulting in a different codon and, therefore, a different amino acid.
ex: TTC-> TCC (Pyrine to Pyrine) TRANSITION
causing Protein to be: Conservative
2) If the amino acid substitution involves two amino acids with very different chemical properties which causes changes in protein:
ex: TTC-> TGC (Pyine to Purine) TRANSEVERSION
causing protein to be: Non-conservative
Protein Changes:
Conservative - Protein is functional
Non-conservative - Protein is not functional
Nonsence
The amino acid is replaced with a stop codon (seen in mRNA) which signals the ribosome to stop building a protein
ex: TAG -> UAG
Examples of STOP codons: UAA, UAG, and UGA
Silent Mutation
The substitution doesn’t change the amino acid that the codon codes for
ex: AAA-> AAA
Neutral Mutation
Changes the amino acid sequence of a protein without altering its ability to function
Loss-of-function Mutation
Causes a complete or partial loss of function
Affects; structure of protein, transcription and translation
Gain-of-function Mutation
Causes the appearance of a new trait or function
or
causes the appearance of a trait in inappropriate tissue or at an inappropriate time
Lethal Mutation
Causes premature death
Conditional Mutation
Expressed only under certain mutations that affect phenotype at elevated temperatures
Suppressor Mutation and what are the two classes?
Suppresses the effect of an earlier mutation at a different site
2 classes of suppressor mutation:
Intragenic and Intergenic
Intragenic Supressor Mutation
Suppresses the effect of an earlier mutation within the SAME gene
ex: can suppress a frameshift mutation
Intergenic Suppressor Mutation
Suppresses the effect of an earlier mutation in a DIFFERENT gene
ex: translation can occur even with a stop codon
Genotype
Organisms Genetic Information (alles passed by the parent)
ex: BB, Bb, or bb
Phenotype
The appearance of a character (Observable traits)
- It is influenced by the genotype
ex: purple, white, wrinkled, round…
Locus
Stripe on the chromosomes ( specific physical location of a gene)
ex: Each chromosome has an allele (one white flower and the other for the purple flower)
Heterozygote
Inherit a different version of a gene from each parent. They do not match
ex: Bb and bB
Homozygote
Inherit the same version of the gene from each parent, so you have two matching genes
ex: BB and bb
Diploid
Two copies of each chromosome (most organisms)
ex: in a pair (2-2-2)
Haploid
One copy of each chromosome (in most gametes like sperm or eggs)
ex: single (1-1-1)
Characteristic
Feature of an organism
Ex: Seed shape
Allele
Only one of two or more alternative forms of a gene
ex: R (dominant) and r (recessive)
