8.1 + 8.2 Flashcards
what re 6 types of mutation
- substitution - one or more bases swapped for another
- inversion - a sequence of bases are reversed
- insertion - one or more bases added
- deletion - one or more bases are removed
- duplication - one or more bases are repeated
- translocation - a sequence of bases is moved from one location in the genome to another
why can frame shifts be detrimental
as if changing the number of bases in the DNA code then this can shift all the base triplets that follow so that all the codons after the mutation are changed and the DNA will be transcribed differently
what are the 4 types of stem cells
totipotent stem cells
pluripotent stem cells
multi potent stem cells
unipotent stem cells
describe totipotent stem cells
cells that can differentiate into embryonic tissues, they form from the the embryo and placenta
all genes in nucleus are able to be activated
describe pluripotent stem cells
also found in embryos and vast majority of genes are still able to be activated
describe multipoint stem cells
found in mature mammals, some genes have been switched off but they have the genes for some different cells still available
describe unipotent stem cells
cells that can only form one other type of cell, example is cardiomyocytes that can divide to form other heart muscle cells
what are adult stem cells
obtained from the body tissues found in the bone marrow these are multipotent
what are induced pluripotent stem cells
produced in a lab specialised from adult stem cells to become pluripotent. there cells express a series of transcription factors which are normally expressed by pluripotent stem cells.
good as if from patients own cells there will be no rejection
how is a gene expressed
when is is trancribed into mRNA and then translated into a protein
what are transcription facotrs
proteins which travel into the nucleus and control the rate of transcription by activating or repressing RNA polymerase
how to transcription factors work
bind to the promotor region which is the binding site of RNA polymerase and therefore the starting point for transcription of that gene
how can transcription factors be turned off
by inhibitor molecules. if these bind to the transcription factors it can prevent it from attaching to the promoter region.
how does oestrogen act as a transcription factor
oestrogen binds to a transcription factor called oestrogen receptor forming an oestrogen-oestrogen receptor complex
this complex moves into the nucleus binding to the hormone receptor in the promote region of that gene either activating or repressing transcription
what is iRNA
interfering RNA which are small lengths of non-coding RNA.
what do iRNA do
regulate gene expression by affecting translation, these are double stranded and stop mRNA that have been transcripts already from being translated into a protein
what are the two types of iRNA
siRNA (short interfering) - only in animals
miRNA (micro RNA) - in plants and animals
how do siRNA and miRNA (in plants) work
- double stranded siRNA associates with proteins in the cytoplasm and unwinds
- one of the siRNA strands is chosen and the other breaks down
- Single strand of siRNA binds to the target mRNA
- the proteins associated with the siRNA cut the mRNA into small fragments so it can no longer be translated
- the mRNA fragments then move into a processing body breaking them down
how do miRNA work in mammals
- miRNA precursor folds back in itself held together by hydrogen bonds
- an enzyme called diet moves along the double stranded RNA cutting it into segments
- one strand of each short double-stranded RNA is broken down and the other associates with proteins
- the bound miRNA can base-pair with any target mRNA that is complementary
- the miRNA protein complex prevents gene expression by either breaking down the target mRNA or by blocking its translation
what are the 2 types of genes that control cell division
- proto-oncogenes which cause cancer when turned on
- tumour suppressor genes which cause cancer when turned off
how to proto-oncogenes work
normally help cells grow however if they mutate the can become permanently activated. when this happens cell divide out of control leading to cancer.if it mutates this is called oncogene
how do tumour suppressor genes work
normally help slow down cell division, repair DNA mistakes or tell cell when to die however when they dont work cells can grow out of control
4 differences between benign and malignant tumour
bengin non-cancaours, slow growing, doesn’t metastasise and do have normal shape where malignant are cancerous, fast growing, invade and destroy other tissues through metastasis and may have an abnormal shape
how can oestrogen cause cancer and how increase oestrogen levels
increased oestrogen for an extended period of time is thought to increase chances of breast cancer as it stimulates more breast tissue to divide hence increasing chance of mutation
- taking birth control
- starting menstruation early
- starting menopause late
