p2: gene expression Flashcards
state all the different types of mutations that can occur and explain what happens in each mutation
- substitution: when one base is changed for a different base
- addition: when one or more bases is inserted into the DNA base sequence and causes a frame shift.
- deletion: when one or more bases is removed from the DNA base sequence and causes a frame shift.
- inversion: a group of bases becomes separated from the DNA base sequence and re-join at the same position but in the inverse order.
- duplication: one or more bases are repeated so a frame shift is caused
- translocation: a group of bases become separated from the DNA base sequence on one chromosome become inserted into the DNA sequence of a different chromosome and causes a frame shift.
describe the two features in a stem cell
stem cells are undifferentiated and can keep dividing and can differentiate into specialised cells.
define the terms totipotent, pluripotent, multipotent, and unipotent and name at what point in life are they present.
- totipotent: cells which divide and differentiate into any cell type and are present during early life in mammalian embryos
- pluripotent: cells which divide and differentiate into most cell types and are found later in mammalian embryo life
- multipotent: divide and differentiate into a limited number of different cell types and are found in mature mammals
- unipotent: divide and differentiate into only one cell type and is found in mature mammals e.g. cardiomyocytes in the heart muscle.
explain how stem cell transplants can be used in treatment of diseases.
stem cells are transplanted into the body so they can divide and differentiate to produce healthy cells to replace the damaged cells.
evaluate the use of embryoic stem cells vs. adult stem cells in the treatment of disease
adult stem cells:
+ no ethical issues
+ less chnace of rejection as sam/ similar DNA
- multipotent cells: can divide and differentiate into a limited number of cell types
- difficult to isolate
embryonic stem cells:
+ pluripotent: can divide and differentiate into most cell types
+ easy to isolate as uses embryos from IVF
- ethical issues
- high chnage of rejection
describe what induced pluripotent stem cells are and give the advantages of using them in medicine
-iPS cells are nomrla cells removed from a patient and factors are added t make the cell pluripotent so it can divide and differentiate into the desird cell type and can be transplanted back into the patien.
advantages:
- no ehtical issues as using own cells
- can differentiate into almost all cell types
- less chnce of rejection
describe how growth factors can be used in vintro to produce whole plants from plant tissue samples. what feature of plant cells makes this possible
- by adding certain factors and giving ight conditions plant cells can develop into new organisms or plant organs
- totipotent plant cells are grown in sterile condiitions to produce a calllus
- the callus is then placed in a growth medium when the callus of undifferentiated cells so they differentiate into specific plant tissues
describe the steps by which transcription factors control the expression of target genes
- trannscription factors are proteins
- in eukaryotes transcription factrs move from the cytoplasm inot the nucleus
- the bind a promoter of a gene
- this stimulates/ inhibits RNA polymerase to transcribe the gene and produce mRNA
describe the steps by which oestrogen initiates transcription
- oestrogen is a lipid sp is lipid soluble so crosses the phospholipid bilayer by diffusion
- oestrogen binds to a potein receptor in the cytoplasm
- receptor/oestrogen complex is a transcription factor and binds to a promoter
- this stimulates RNA polmerase to transcribe the gene and produce mRNA
describe the steps by which siRNA controls genne expression by RNA interference
- siRNA has a specific complimentary base sequence to target mRNA
- siRNA binds to a protein which acts as an enzyme
- one of the siRNA strands is removed to make it single stranded
- the siRNA now binds to mRNA molecules by complimentary base pairing
- mRNA is destroyed
- the mRNA can no longger be used in translation and is broken dowwn by enzymes
decribe the difference between siRNA and miRNA
microRNA is not fully complimentary and not specific to one mRNA so can target more than one type of mRNA
define epiggenetics
heriitable chnages in gene function cause by chnages in the environment without changes to the DNA base sequence
explain how methylation affects the expression of genes
- methyl groups are added to the DNA
- this mmeans ranscription factors cnnot bind the promoter
- therefore gene is not transcribed
explain how acetylation affects the expression of genes
-the addition of acetyl groups to histone proteins makes the chromatin less condensed
- tanscription factors can bind the promoter
- transcription does occur
describe the difference between benign and melignant tumours
melignant tumours have cells which can break off annd sread to other arts of the body (metastasise) wherease benign tumours do not spread to other parts of the body.
