Unit 6 - Genetics of living systems Flashcards
Characteristics of genetic code
Universal
Triplet code
Degenerate
Non-overlapping
Properties of DNA
Introns
Exons
Introns
Sections of DNA that do not code for a polypeptide
Regulatory sequences
Acts as a buffer for mutations
Regulatory sequences
Promoter regions
Terminator regions
Operator regions (prokaryotes)
Exons
Sections of DNA that code for polypeptides
Regulatory or structural genes
Regulatory genes
Genes that code for proteins used in DNA regulation
Structural genes
Genes that code for regular proteins
Mutagens
Chemical, physical, or biological agents which cause mutations e.g. viruses (viral DNA inserts itself into the genome), radiation (Breaks one or both DNA strands)
Where can genes be turned on or off
Transcriptional
Post-transcriptional
Translational
Post-translational
When does up/down regulation occur
Post trasncriptional
Translational
Post translational
Either increases/ decreases rate of protein synthesis
When are proteins modified
Translational
Post translational
Where are ribosomes assembled
Nucleolus
Why is there a ribosomal groove
So mRNA can be read for transcription
Types of mutations
Genes
Chromosomal
Point mutations
Mutations that occur at a spp point
Insertion
Substitution
Deletion
Effects of point mutations of proteins
Silent
Missense
Nonsense
Insertion mutations
Addn. of one or more nucleotide base pairs into a DNA sequence
Substitution mutation
Occurs when a base pair is substituted for another
Deletion mutation
Occurs when a base pair is deleted from the DNA sequence
Frameshift
A mutation caused by the addn. or deln. of a base pair(s) resulting in the translation of the genetic code from an unnatural reading frame from the point mutation to the end of the gene
Silent mutations
Change in the DNA sequence that results to the change in nucleotide base pairs having no subsequent effect on on the amino acid produced
May have occurrred in introns
Missense mutations
A single nucleotide change leads to a different codon and therefore a different AA
Nonsense mutations
Change in nucleotide sequence that leads to one of codons being converted to a terminator codon so the protein produced is truncated
Class of mutations
Beneficial - depends on environment
Neutral - No effect on chances of survival
Disadvantageous - Causes genetic diseases, lessens chances of survival
Histones
Basic proteins that associate w/ DNA in the nucleus and help to condense the DNA into a smaller volume
Little balls in which DNA wraps around
Chromatin
Complex of DNA and proteins that condense to form chromosomes within the nucleus of eukaryotic cells
Euchromatin
Lightly packaged DNA; RNA polymerase can access the bases to transcribe the genes –> genes can be turned on
Heterochromatin
Tightly packaged DNA; RNA polymerase cannot access the bases to transcribe the genes so they are turned off
Promoter regions
Region of DNA that acts as the binding site for RNA polymerase to start transcription
Intron
Usually upstream
Operator regions
Short region of DNA that is close to the promoter region
Interacts w/ regulatory proteins that controls the transcription of operons
Downstream
To the right
Upstream
To the left