6.1 cellular control Flashcards
define mutation
random change to genetic material
name the types of mutations
substitution (point)
insertion and deletion (indel)
name the types of point (substitution) mutations
silent
missense
nonsense
explain what a substitution mutation is
nucleotide/ base is swapped for another
explain what is meant by silent mutations
a point mutation/ substitution occurs but the triplet still codes for the same amino acid
explain what is meant by missense mutations
a different amino acid is coded for and may have significant impacts on the protein coded for
explain what is meant by a nonsense mutation
a point mutation that alters the base triplet may result in a stop codon / terminator
explain what is meant by frame shift
base is inserted or deleted from the gene
leading to the subsequent base triplets being altered
explain the effects of mutations
beneficial - drive evolution through natural selection, as different alleles are produced, eg. new protein synthesised
harmful - proteins are not synthesised
neutral - normal functioning protein produced
causes of mutation
can occur naturally
x-rays
high energy radiation
chemicals
UV light
viruses
define mutagen
increase the chances of mutations occuring
role of regulatory mechanisms
ensure the correct genes are expressed in the correct cell at the correct time
name the 3 types of regulatory mechanisms and when they occur
transcriptional level - during transcription
post transcriptional level - after transcription
post translational level - after translation
what is a structural gene
codes for a protein that has a function within a cell
what is a regulatory cell
codes for proteins that control the expression of structural genes
explain Lac Operon as a transcriptional level mechanism in prokaryotes
controls the production of lactase enzyme and other structural enzymes
only synthesised when lactose is present
define operon
cluster of genes that are controlled by the same promoter
describe the structure of the Lac Operon
regulatory gene - promoter - operator - structural genes
explain how the Lac Operon mechanism works
lactose not present = regulatory gene transcribed to produce repressor protein = binds to the operator = RNA polymerase is unable to bind to the promoter region as its blocked by the protein = transcription cannot take place = lactase not synthesised
lactose present = binds to the 2nd binding site of the repressor protein = distorts the shape = doesn’t bind to operator site = RNA polymerase can bind to the promoter region = transcription takes place = lactase produced
define transcription factor
protein/ non coding RNA that binds to specific site on the length of DNA to inhibit or activate transcription
explain how transcription factors work as a transcriptional level mechanism in eukaryotes
t.f bind to specific promoter regions
either allows or inhibits the binding of RNA polymerase to the DNA
activates or supresses transcription of a gene
explain the difference between an activator or repressor
activators = start transcription
repressors = stop transcription
explain the post transcriptional level mechanism
editing of primary RNA to produce mature RNA
introns are removed by splicing to leave exons which fuse together to form a continuous mRNA strand
define intron
non coding regions of DNA
