Cellular Control Flashcards
Where is mRNA made?
mRNA is made in the nucleus
What bases does mRNA contain?
Adenine, guanine, uracil and cytosine
What does universal mean when referring to properties of the genetic code?
The same codons code for the same amino acids in all organisms
What does degenerate mean when referring to the properties of the genetic code?
Most amino acids have more than one codon that code for them
What does non-overlapping mean when referring to properties of the genetic code?
Each base is only read once
What are the 4 types of genes?
Structural genes
Regulatory genes
Housekeeping genes
Tissue specific genes
What are structural genes?
Genes that code for a protein that has a function within a cell.
Eg. Genes coding for enzymes, membrane carriers, hormones etc.
What are regulatory genes?
Genes that code for proteins (or various forms of RNA) that control the expression of structural genes
Eg. Genes coding for transcription factors
What are housekeeping genes?
Genes that code for proteins that are constantly required
Eg. Genes that code for enzymes necessary for reactions in respiration
What are tissue specific genes?
Genes that code for proteins that are only required at certain times to carry out a short-lived response
Eg. Genes coding for hormones used for growth and repair
What are the 4 different ways genes can be regulated?
Transcriptional
Post-transcriptional
Translation
Post-translational
How are genes regulated at transcriptional level?
Genes are able to be turned on/off
How are genes regulated at post-transcriptional level?
mRNA can be modified, which regulates translation and the types of proteins produced
How can genes be regulated at translational level?
Translation can be stopped or started
How can genes be regulated at post-translational level?
Protein can be modified after synthesis, which changes their function
What are heterochromatin?
Tightly wound DNA —> Chromosomes are visible under a microscope
What are Euchromatin?
Loosely wound DNA —> Not visible under a microscope
Transcription isn’t possible when DNA is tightly wound (heterochromatin). Why?
Because RNA polymerase can’t attach and move along the DNA
During what part of the cell cycle does protein synthesis take place?
During the interphase because there is euchromatin, making genes more accessible to RNA polymerase
What charge does DNA have?
DNA has a negative charge
What charge do histone proteins have?
A positive charge
What happens at acetylation and phosphorylation?
•Reduce charge on histone
•Histones now become more negative
•Causing DNA to coil less tightly
•Genes are now more accessible
What happens during methylation of histone proteins?
• Involved adding a hydrocarbon
• Histones now more hydrophobic
• The histone bind tighter together
• DNA coils tighter as a result
• This prevents transcription of genes
What are epigenetics?
Heritable changes in gene function that don’t change the base sequence of DNA
What are examples of epigenetics?
Acetylation
Phosphorylation
Methylation
Which part of the gene do transcription factors bind to?
The promoter region
What are activators?
The binding of the transcription factor aids RNA polymerase binding to DNA, starting transcription
What are repressors?
The binding of the transcription factor blocks RNA polymerase from binding to DNA, stopping transcription
What are tumour suppressor genes?
Genes that inhibit proliferation and tumour development.
They stop cells from dividing too quickly
What are protooncogenes?
Genes involved in normal cell growth, which if mutated, it may become an oncogene which can cause cancer
What is a transcription factor?
Proteins that bind to DNA and control which genes in a cell are turned on and off
Where do transcription factors bind in eukaryotic gene expression?
They bind to the promoter region
What is an operon?
A group of genes under the same regulatory mechanism that are expressed at the same time
E. Cool prefer glucose as a respiratory substrate. If this is in short supply what do they use instead? And what are the drawbacks?
If glucose is unavailable they will use lactose. However different enzymes are required to metabolise lactose
What protein does the gene Lac Z in E. coli code for?
Lac Z codes for the protein B- galactosidase.
The function of beta galactosidase is to hydrolyse lactose to glucose and galactose
What protein does the gene Lac Y in E. coli code for?
Lac Y coded for the protein lactose permease which facilitates the crossing of lactose across the cell membrane
What is the role of Lac I?
Lac I is a regulatory gene located near the operon.
Lac I codes for a depressor protein that is constantly being made and prevents the transcription of Lac Z and Lac Y in the absence of lactose
What is a phosphodiester bond?
The covalent bond between the sugar of one nucleotide and the phosphate of the next nucleotide
What is a mutation?
The change in a sequence of bases in DNA
What are the 3 types of mutation?
Substitution
Deletion
Insertion
What is a substitution mutation and what are they also known as?
A substitution mutation is when one nucleotide is substituted for another
Also known as point mutations
What are the 3 types of point mutation?
Silent mutation - different codon but same amino acid
Missense mutation - different amino acid
Nonsense mutation - stop codon
What is an insertion mutation?
An insertion mutation is when an extra nucleotide is added
What is a deletion mutation?
A mutation when a nucleotide is removed
What are insertion and deletion mutations know as?
Frame shift mutations
These are generally worse than substitution mutations
What is a neutral effect of a mutation?
Normal functioning protein is still synthesised - phenotype of organism is unchanged
What is a harmful effect of a mutation?
The protein is not synthesised or is non-functional.
The phenotype of the organism is negatively impacted
What is a beneficial effect of a mutation?
The protein is synthesised with a new and useful characteristic in the phenotype
What are the 4 types of chromosome mutations?
Deletion - section breaks off
Duplication - section duplicated
Translocation- section breaks off and rejoins another non-homologous chromosome
Inversion- section breaks off, is reversed and joins back on
What is a body plan?
The structure of an organism
Name the genes that control the development of a body plan
Homeobox genes
Why is development of body plans similar for plants, animals and fungi?
It is controlled by similar homeobox genes in each type of organism.
The homeobox genes have highly conserved region called the homeobox
What are homeotic genes?
Genes that regulate morphogenesis (the process that causes an organism to form its shape)
What is a homeobox gene?
A subset of homeotic genes which contain a homeobox sequence
What is a homeobox sequence?
A sequence of 180 base pairs found within homeobox genes which are involved in regulating anotomical development in plants and fungi.
It is highly conserved
What is a homeodomain sequence?
60 amino acids found in all homeobox protein (encoded by the homeobox sequence)
It is part of the protein that binds to DNA, allowing the protein to act as a TF to activate or repress genes.
What are hox genes?
A subset of homeobox genes found only in animals. It is involved in the formation of anatomical features in the correct location of the body plan.
They code for homeodomain proteins
Give examples of how genes controlling development of a particular segment of the body plan?
Hox genes in the head control the development of mouth parts.
Hox genes in the thorax control the development of wings, limbs, ribs
What are diploblastic animals?
Animals that have 2 primary tissue layers in the developing embryo
Eg. Jellyfish, corals, sea anemones
What are triploblastic animals?
Animals that have 3 primary tissue layers in the developing embryo
Eg. More complex animals from worms to humans
What is colinearity?
The order in which genes appear along the chromosomes is which their effects are expressed in an organism
What do hox genes regulate?
The development of embryos along the anterior —> posterior axis (head —> tail) and they are responsible for correct positioning of body parts
What does highly conserved mean?
Meaning the sequence is kept through evolution and is the same for many different organisms
What is morphogenesis?
The regulation of the pattern of anatomical development
What is apoptosis?
Programmed cell death. It is regulate by hox genes and is deliberate and controlled
What is apoptosis?
Programmed cell death. It is regulate by box genes and is deliberate and controlled
What are internal stimuli that result in apoptosis?
Damage to DNA - prevents uncontrolled cell division
Release of hormones
Psychological stress
What are external stimuli that can cause apoptosis?
Changes in light intensity
Disease
Lack of nutrients
Effects of drugs eg. Thalidomide
What are the stages of apoptosis?
1) enzymes break down cell cytoskeleton
2) the cytoplasm becomes densely packed with organelles. The cell surface membrane changes and ‘blebs’ form
3) chromatin condenses, the nuclear envelope breaks down, and DNA breaks into fragments
4) The cell breaks into vesicles that are then ingested by phagocytes so that cell debris doesn’t damage other cells or tissue
