control of gene expression Flashcards
how are cells able to control their metabolic activities
by regulating transcription + translation of a gene
define mutation
any change in amount or structure
of DNA of an organism
how do mutations occur
spontaneously during DNA replication
how can mutations be passed on
if the mutation occurs in the gametes
what are the different types of gene mutation
addition, deletion, substitution, inversion, duplication and translocation of bases.
how is the mutation rate increased
using mutagenic agents, such as carcinogens
what can mutations result in
change in amino acid sequence of the polypeptide
which changes the primary structure, then the secondary then the 3D tertiary structure of the protein
why do some mutations not change the amino acid
due to the degenerate nature of the genetic code
more than one triplet can code for the same amino acid
what can base additiondo
cause a frame shift to the right
what is a base deletion called
point mutation
what is the inversion of bases
DNA breaks off + reinserted at same position
but is now inverted
what is translocation + its consequences
group of bases break off
+ get reinserted on another chromosome
can also cause cancer + reduced fertility
what is totipotency
ability of embryonic stem cells to divide into any type of cell
totipotent cells ; where, what
occur for only a limited time in early mammalian embryo
can divide into any type of body cell
can be used to treat disease
what causes cell differentiation
during development, totipotent cells translate only part of their DNA
pluripotent; where, what
found in embryos, in blastocyst
can divide into almost any type of cell except placenta cell
multipotent; where, what
mature mammals
can divide to form a limited no of cell types
unipotent; where, what
mature mammals, made in adult tissue
can only differentiate into a single type of cell
what are iPS (induced pluripotent stem) cells for and how are they produced
can be produced from adult somatic cells using appropriate protein transcription factors
how can a gene be expressed
transcription the gene can be stimulated
when specific transcriptional factors move
from cytoplasm into nucleus
structure of a transcription factor
has a DNA binding site
and a receptor
how does the transcription factor stimulate transcription
transcription factor binds to DNA
at DNA binding site which is specific to a certain gene
to the correct, complementary gene
what happens when the gene isn’t being expressed
inhibitor molecule binds to transcriptional factor at
DNA binding site
blocking it, preventing it from binding to DNA + starting transcription
explain and describe the role of oestrogen in gene expression
can influence transcriptional factors
- diffuses across membrane as its lipid soluble
- combines with transcriptional factor at receptor site
- hormone changes shape of transcriptional factor causing inhibitor molecule to be released
- so DNA binding site is exposed, factor can go into nucleus + bind to DNA
what is epigenetics
heritable changes in gene function
without changes to base sequence of DNA
what causes these heritable changes
changes in the environment by inhibiting transcription
how do changes in the environment inhibit transcription
increased methylation of DNA
or
decreased acetylation of associated histones
