Topic 7 DNA Flashcards
Transcription
Transcription factors- are proteins that bind to the DNA in the nucleus and affect the process of transcribing the genetic material. could help rna polymerase bind more easily or less easily
transcription factors bind to the DNA’s promotor region, which is found upstream of the gene.
Enhancer sequence: When transcription binds here, it changes the structure of chromatin (the wound-up DNA), making it more or less available to RNA polymerase and, therefore, controlling gene expression.
Epigenetics
genetic control by factors other than DNA sequence.
the environment can influence cell bio chemistry altering these epigenetic factors and therefore the development of specialised cells.
DNA methylation
DNA methylation silences a gene or
sequence of genes
methyl group (positive) attach to the cytosine base of DNA. this results in DNA not being transcribed transcription factors cannot bind.
acetyl group are negative like DNA, they end up repelling each other and so DNA doesn’t tightly coil, leaves DNA loose so transcription factors can still bind
very important in embryonic development. DNA demthylation is also important, when you remove the methyl group you activate the DNA again so it can be transcribed.
Cell differentiation
As an organism grows the cells differentiate to become specialised cells.
the change in epigenetic factors can be in response to internal stimuli within the cell or external factors in the environment for the cell.
what are stem cells
stem cells are undifferentiaated cells that continue to divide and become specialsed
Types of stem cells
Totipotent
pluripotent
multipotent
unipotent
Totipotent (in morula)-. differentiate into any cell
and then the blastocyst
forms inner mass cell (pluripotent) make fetus cant divide to form placenta- could treat human disorders could replace beta cells that are not making insulin
multipotent and unipotent stem cells found in mature mammals and ca divide to form limited number of different cell types.
unipotents can only differentiate into one type of cell eg skin cells can only differentiate into skin cells
induced pulripotent stem cells
iPS are created from adult unipotent cells. These cells, which can be from almost any body cell, are altered in the lab to return to state of pluripotentency.
to do this genes that were switched off to make the cells specialed must be switched back on.
this is done by transcription factors.
they are very similar to embryonic puripotent stem cells, but do not cause the destruction of an embryo and the adult can give permission
environment causes these hertiable change in gene function not mutation. these changes are caused by the environment and inhibit transcription
transcription
transcription factors can bind to different base sequences that they are complementary in shape to
Analyse the graph to explain why DNA methylation is involved in the development of an
embryo.
level of DNA methylation increases after the blastocyst stage
because genese are switched off cannot be transcribed
causing cells to become specialised
DNA methylation of cytosine at CpG sites
* Methylations adds a CH3
* DNA methylation causes silencing of genes
* by preventing transcription
* epigenetic modifications are {inherited
Explain how a bone marrow stem cell differentiates into either a
common myeloid progenitor cell or a common lymphoid progenitor cell
by epigenetic modification (1)
* for example by {DNA methylation / histone methylation / histone
acetylation} (1)
* {house-keeping genes / genes needed in both cell types} remain
switched on (1)
* genes needed in {common lymphoid progenitor / lymphoid} cells
become (permanently) switched off (1)
* causing {proteins / named protein} to be made that are specific to
the {cell type / named cell}
dna methylation siliences genes causing cells to be specialised
induced pluripotent cells vs pluripotent
Ethical Approval: Since iPSCs are derived from adult somatic cells (e.g., skin or blood cells), they don’t raise the same ethical questions as ESCs, making them more widely acceptable for research and clinical use.
why are genes switched on
Bacteria turn on genes for lactose metabolism only when lactose is present.
what are the roles of transcription
Transcription factors (TFs) are proteins that regulate gene expression by binding to specific DNA sequences and controlling the transcription of genes. They play a crucial role in turning genes on or off in response to cellular signals, environmental changes, and developmental cues.
Describe how soya bean plants can be genetically modified to produce large
numbers of GM soya bean plants.
use oof restriction enzyme to cut gene
use ligase to insert DNA
use vector
use plasmid
PCR
- Heated to break apart the DNA strands. 2. Cooled to allow primers to bind. 3. Heated again to activate DNA polymerase and allow free nucleotides to join. 4. New DNA acts as template for next cycle.
recombinant DNA there are two ways
Usig restriction endonucelases to cut out DNA
or using reverse transcriptase MRNA-DNA (introns are spliced out and exons are spliced together using a splicesome)
- inserting the gene in a vector as a carrier and plasmids DNA is cut with the same endonucleases as before this leaves complementary sticky ends that re joined by ligase enzyme.
3.
knockout mice
embryonic stem cells taken from mouse are modified eg inactivating gene then inserted in another embryo containing a mix or normal and modified genes then injected into a female uterus carying this modified embryo and producing chimeric mice some will have knockout and ortehr will not then reproduce with normal mice someone will have knockout gene (inactive) the ones with knockout are reproduced together to produce a line of knockout mice
Only one of the two tissues shown in the photographs A and B is totipotent.
Describe how you could use a plant tissue culture technique to show which of the
two tissues is totipotent.
ref to {sample / explants} from both (tissues)
;
2. ref to aseptic conditions / named example ;
3. grow cells into a callus / eq ;
4. ref to growth regulators / eq ;
5. ref to {cells / tissue} can differentiate / cells can
become {whole plants / eq} ;
6. ref to details of procedure e.g. agar / leave
for a suitable length of time / suitable
controlled variable ;
DNA methylation can prevent transcription factors from binding to the promotor regions. In inhibiting transcription from occurring. Therefore silencing a gene
