Genetics and Evolution (Module 6) Flashcards
What is a mutation?
A random or spontaneous change to the sequence of bases in DNA
What are the different types of mutation?
Substitution, deletion and insertion
What are substitution mutations?
When one or more nucleotides are substituted, which causes a change in codon, therefore amino acid sequence and primary structure of a protein
What is degenerate code?
When, in substitution mutations, when the codon changes it still codes for the same amino acid; so does not change the primary shape of the protein
What are insertion mutations?
When one or more nucleotides are inserted into a DNA base sequence
What are deletion mutations?
When one or more nucleotides are deleted from a DNA base sequence
What do deletion and insertion mutations cause?
Frameshifts, which has much worse effects as some genes are unfinished as codons are always 3 bases. Lots of bases also change amino acid formation
What are the three outcomes of mutations?
No outcome, damaging outcome, beneficial outcome
Name some mutagens (chemical, physical or biological agent that increases likelihood of mutation)?
Ionizing radiation, deaminating agents, alkylating agents, base analogs, viruses
What are the different types of chromosomal mutations?
Deletion, duplication, translocation, inversion
Why are chromosomal mutations worse than other mutations?
Because there are more genes condensed than are effected
What is the difference in gene expression between eukaryotes and prokaryotes?
The stimuli that trigger transcriptional enzymes to be activated
What are the different ways gene expression can be controlled?
Transcriptional, post-transcriptional, translational, post-translational
What are genes regulated by?
Protein based hormones
What are some transcriptional control mechanisms?
Chromatin remodeling, Lac Operon, Histone modification
What is chromatin remodeling in transcriptional control?
When DNA is either tightly wound into heterochromatin (so it cannot be accessed by RNA polymerase to be transcribed from) or loosely wound into euchromatin (so DNA can be accessed by RNA polymerase for transcription)
What is histone modification in transcriptional control?
DNA (negatively charged) is wrapped around positively charger histones. Acetyl or phosphate groups can be added to DNA to make the histones less positive so the DNA is wound less tight (for access for transcription), or methyl groups can be added to make the histones more positive, so DNA is bound tighter (less access for transcription)
What is Lac Operon?
A form of gene expression where a repressor protein binds to a promoter region, which prevents the binding of RNA polymerase so transcription cannot ensue. If glucose/lactose is present, it binds to the repressor- causing it to change shape and so cannot bind to the promoter region; RNA polymerase can bind for transcription.
What is the role of cyclic AMP? (cAMP)
Catalysing the lac operon mechanism to speed it up, when glucose is present, forms ATP instead to inhibits lac operon.
What are introns and exons?
Introns are non-coding DNA and exons are coding DNA
What happens during pre-translational control?
Introns are removed from pre-mRNA (splicing) and modified nucleotides are provides at both ends (5’ and 3’) to form ‘caps’ and ‘tails’.
Why does mRNA need ‘caps’ and ‘tails’?
To help stabilise the molecule and prevent degradation in the cytoplasm
What is RNA editing in pre-translational control?
When mRNA molecules have addition, deletion or substitution (point) mutations to increase the range of proteins that can be made from a single RNA molecule.
What mechanisms control protein synthesis? (transcriptional control)
Degradation of mRNA, binding of inhibitory proteins to mRNA, activation of initiation factors (aid binding of mRNA to ribosomes)
What are some mechanisms for post-translational control?
Addition of non-protein groups (carbohydrates, phosphate, lipids), modifying amino acids/formation of bonds, folding/shortening proteins, modification of cAMP
What are body plans?
A small group of genes that regulate anatomical development
What are hox genes?
A subset of homeobox genes that regulate ONLY animal anatomical development
What are homeobox genes?
A sequence of 180 bases that are involved in regulating anatomical development in animals, plants and fungi