chapter 20 - gene expression Flashcards
What is a gene mutation
It is where there is a change in quantity or the structure of DNA. And if there is any change to one or more nucleotide bases, or rearrangement of bases in the DNA this is known as a gene mutation.
What is a nonsense mutation
It is where there is a formation of one of the three stop codons that mark the end of a polypeptide chain. As a result the production of the polypeptide coded for by the section of DNA would be stopped. The final Protein would be significantly different then the protein cannot perform its normal function.
what is a misense mutation
It is why a codon codes for a different amino acid. Meaning that the structure of a polypeptide chain produced will differ in a single amino acid therefore the protein may not function properly. For example if it’s an enzyme it’s active so it may no longer fit the substrate and therefore the reaction will not be catalyzed.
Give an example of a misense mutation
Sickle cell Amenia. Where one amino acid is substituted for another.
What is a silent Mutation
It is where the formation of a different codon produces the same amino acid as before. This is because the genetic code is degenerate. So most amino acids have more than one codon. The mutation has no effect on the polypeptide produced and therefore the mutation will have no effect.
What is deletion of a base
Where one or more nucleotide pairs are deleted from the sequence this causes a frame shift to the left. the gene is read differently. possibly lead to the production of a non functional protein.
how does deletion differ if The base was deleted at the start of the sequence compared to the end of the sequence
If the base was deleted at the start of the sequence this could alter every triplet in the sequence. Whereas if the base is deleted at the end of the sequence this is likely to have a small impact but can still have a consequence.
What is incision/addition of a base
It is why one or more nucleotide pairs are inserted into the sequence. This causes a frame shift to the right.
What is duplication of bases
It is where one or more bases are repeated. This produces a frame shift to the right
What is inversion of bases
It is where a group of bases become separated from the DNA sequence and re-join at the same position but in the inverse order. [Back to front]. The base sequence of this portion is then reversed and this affects the amino acid sequence that follows.
What is translocation of bases
It is where a group of bases become separated from the DNA sequence on one chromosome and are inserted into the DNA sequence of a different chromosome. Translocations often have a significant effects on gene expression, leading to an abnormal phenotype.
Give some examples of the effects from translocation of basis.
It can include the development of certain forms of cancer and also reduce fertility.
List two ways in which mutagenic agents can increase the likelihood of a mutation via an outside factor.
From high energy ionizing radiation - For example alpha and beta particles as well as short wave length radiation such as x-rays and ultraviolet lights. These forms of radiation come disrupt the structure of DNA.
Chemicals - Such as nitrogen dioxide may alter the structure of DNA or interfere with transcription. Benzopyrene, a constituent of tobacco smoke, is a powerful musician that inactivates a tumor suppressor gene leading to cancer.
What can happen when other chemicals add groups to nucleotides.
Benzopyrene is a chemical found in tobacco smoke. It can add a large group to guanine that makes it unable to bind with cytisine. When DNA polymerase reaches the affected guanine it’s inserts any of the other bases.
What can happen when certain chemicals remove groups from nucleotide bases
Nitrous acid come remove an email group from cytisine in DNA changing it to your cell. different bases bind coordinarily
what type of mutation is caused by benzopyrene
Ionizing radiation such as x-rays come produce highly reactive agents called free radicals. These free radicals can alter the shape of the bases in DNA so DNA polymerase can no longer act on them.
Suggest one genetic affect of DNA polymerase being unable to act on DNA
The replication of DNA requires DNA polymerase therefore replication cannot continue
What is cell differentiation
It is where cells are specialized to perform specific functions. The process by which each cell develops into a special structure suited to the role that it will carry out is known as cell differentiation.
Why are differentiated cells different from each other
This is mainly because they each produce different proteins. The proteins a cell produces are coded for by the genes it possesses [more accurately, by the genes that are expressed [switched on]].
What is a totipotent cell
come from a single fertilized egg. They can mature into any type of cell. The early cells that are derived from the fertilized egg are also totipotent. These later differentiate to become specialized.
Give two ways in which genes are prevented from expressing themselves include:
Preventing transcription and preventing the production of mRNA.
Preventing translation
What are stem cells
in mature mammals, only a few cells retain the ability to differentiate into other cells. These are called stem cells.
Stem cells are undifferentiated dividing cells that occur in adult animal tissues and need to be constantly replaced. They have the ability to divide to form an individual copy of themselves in a process called self renewal.
What are embryonic stem cells [mammals]
they Come from embryos in the early stages of development. They can differentiate into any type of cell in the initial stages of development.
What are unbiblical cord blood stem cells [mammals]
They are derived from umbilical chord blood and are similar to adult stem cells.
What are placental stem cells [mammals]
They are found in the placenta and develop into specific types of cells
What are adult stem cells [Mammals]
They are found in the body tissues of the fetus through to the adults. They are specific to a particular tissue or organ within which they produce the cells to maintain and repair tissues throughout an organisms life.
What are totipotent stem cells
They are found in the early embryo and can differentiate into any type of cell. Since all body cells are formed from a zygote, it’s follows that the zygote is totipotent.
They can further differentiates/develop into slightly more specialized cells called pluripotent stem cells.
What are pluripotent stem cells
They are found in embryos and can differentiates into almost any type of cell. However they cannot differentiate into placenta cells. Examples of pluripotent stem cells are embryonic and fetal stem cells.
What are multipotent stem cells
They are found an adult and can differentiate into a limited number of stem cells. They usually develop into cells of a particular type for example stem cells in the bone marrow can produce any type of blood cell. examples of multipotent cells all adult stem cells and umbilical cord blood stem cells and placenta cells.
What are unipotent stem cells
They can only differentiate into a single type of cell. They are derived from multipotent stem cells and I made an adult tissue.
What is IPS [overall]
Induced pluripotent stem cells
What is IPS in detail
Induced pluripotent stem cells [IPS cells] are a type of pluripotent cell that is produced from Unipotent stem cells. These body cells are generally altered in a laboratory to make them acquire characteristics of embryonic stem cells [a type of pluripotent cell] to make the unipotent cell acquire new characteristics.
To make the unipotent cell acquire new characteristics this involves inducing genes and transcriptional factors within the cell to express themselves. To turn on genes that were otherwise turned off. The fact that these genes are capable of being reactivated shows that adult cells retain the same genetic information that was present in the embryo.
How do you IPS cells differ to embryonic stem cells
IPS cells have a feature called self renewal. This means that they can potentially divide infinitely to provide a limitless supply. This Can lead to only a single sample needed to be taken as IPS cells replicate
What are the advantages of IPS cells
They are very similar to embryonic cells
They do not cause destruction to an embryo
The adults giving the body cells can give permission
What are pluripotent cells used for
They are used to treat human disorders. The stem cells could be used to regrow damage cells in humans. Such as, replace burnt skin cells, Replace beta cells [type one diabetes],Or neurons in Parkinson’s disease.
What are the disadvantages of using pluripotent cells for treating human disorders
Sometimes the treatment doesn’t work [could be rejection]
Pluripotent cells can continually divide sometimes forming a tumor [cancer]
Ethically, There is a debate on whether it is right to make a therapeutic clone of yourself to obtain stem cells. as the embryo will be destroyed
What type of cells are found in bone marrow
adult stem cells such as bone marrow Can produce different cells to replace those in a particular Organ/tissue.
They are multipotent
Describe the process of in vitro culturing of human embryonic stem cells
The early embryo is cultured in a nutrient medium
The outer layer collapses on the inner layer [cell mass] is freed from the embryo.
Chemicals are added to break up the cell mass into smaller groups.
Colonies of embryonic stem cells exist and each group grows into a colony
Special differentiation factors are added to colonies in separate containers.
differentiation occurs.
Differentiated cells are transferred to damaged tissues
Describe growth of plant tissue cultures
Mature plants have many totipotent cells. Under the right conditions many plant cells can develop into any type of cell. For example if we take a cell from the root of a carrot, place it in a suitable nutrient medium and give it certain chemicals stimuli at the right time we can develop a completely new carrot plant.
root cells of carrot plant placed in growth medium single cell to multiple via cell division young plant adult plant
Give three features of plant growth factors and how they are involved in the growth and development of plants issues
They have a wide range /effect on plants tissues
The effects on a particular tissue depend upon the concentration of growth factor
The same concentration affects different tissues in different ways
what are the general principles involved in controlling the expression of a gene by controlling transcription
Transcription factors move from the cytoplasm into the nucleus. These molecules switch on the gene allowing transcription to begin.
Each transcription factor has a site that binds to a specific base sequence of DNA in the nucleus
When it binds it causes the region of DNA to begin the process of transcription.
Messenger RNA is produced on the information it carries is in translated into a polypeptide.
What a gene is not being expressed [switched off] the site on the transcription factor that binds to DNA is not active.
As the site is inactive it cannot cause transcription and polypeptide synthesis.
What does oesteogen do
it can switch on a gene. and it’s a steroid hormone. It starts transcription by combining with a receptor sites on the transcription factor. This activates the DNA binding site by causing it to change shape.
