control of gene expression Flashcards
what is a zygote
a fertilised egg cell
totipotent meaning and example
has capacity to form all other cells
e.g. zygote
pluripotent meaning and example
can form most cell types- not placental cells
e.g. early embrrryo
multipotent meaning and example
can form all cells of one type
e.g. bone marrow can form all blood cells
unipotent meaning and example
cells that can only form one type of cell
e.g. skin stem cells divide indefinitely
what are the 2 key properties of stem cells?
- they are undifferentiated
- they can divide indefinitely
what is an addition mutation
the addition of one or more nitrogenous base to a DNA sequence
what is a deletion mutation
the removal/ deletion of one or more nitrogenous base from a DNA sequence
what is frame shift
when a base is added or deleted from a DNA sequence, altering all subsequent codons after the mutation
protein totally altered, doesn’t function
what is a substitution mutation
when one or more nitrogenous base is swapped in a DNA sequence
what does degenerate mean
multiple different DNA triplets/ codons code for the same amino acid
what is a silent mutation
a mutation which doesn’t affect the sequence of amino acids / primary structure of polypeptide
what s non-disjunction
when homologous pairs fail to separate during meiosis and the daughter cells have abnormal chromosome combinations
what is translocation
when a set f chromosomes is inserted elsewhere in the same or different chromosome
what is gene expression
translation into a protein
what is inversion of bases
group of bases become separated from DNA sequence and rejoin at same position but in inverse order - back to front
what is translocation of bases
what can it lead to ?
- a group bases become separated from the DNA sequence on one chromosome and become inserted into the sequence of another chromosome
- can lead to abnormal phenotype with increased risk of cancer and reduced fertility
what are mutagenic agents
outside factors which increase mutation rate
examples of mutagenic agents
- high energy ionising radiation disrupts DNA structure
- chemicals (NO2) interfere with transcription or alter DNA structure
- benzopyrene from tobacco smoke deactivates tumour suppressor gene
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pros and cons of mutations
pro- produces genetic diversity which allows for natural selection
con- almost always harmful, making organism less likely to survive
- when occur in body cells instead of gametes, they lead to cancer
examples of stem cell sources
- embryonic stem cells
- umbilical chord
- placenta
- adult stem cells (found in body of foetus through to adult)
what are transcription factors?
Specific molecules which move from cytoplasm to nucleus to switch on genes
Has site which bonds to specific base sequence of DNA in the nucleus
How is
