week 24 Flashcards
what are pedigrees
a diagram of a family relationship using symbols to represent people and lines to represent genetic relationships. they are used to determine modes of inheritance.
what can pedigrees be used for in terms of position of a gene
to determine if the gene for a given trait is on an autosome or a sex chromosome
how are autosomal traits passed
from parents to offspring, independent of the X and Y chromosomes.
what are the four different modes of inheritence
autosomal recessive
autosomal dominant
X-linked recessive
X-linked dominant
how do you label pedigrees
dominant genes- positive symbol
recessive genes- negative symbol
male-male transmission cannot occur via X chromosome, true or false?
true. so X-linked inheritance is excluded
what is somatic embryogenesis
process of regenerating whole plants from a somatic (non-reproductive) single cell in culture rather than a fertilised zygote.
why are plants great systems for experiments
no issues of animal ethics
many plants we know all their genes and have tools to study what their proteins do
somatic embryogenesis- regenerating whole plants from single cells in culture
plant cells show totipotency
easy to introduce new genes into plants
direct genetic manipulation to improve
what are some goals of crop improvement
disease resistance
stress tolerance (cold, drought, etc.)
altered composition of harvested products
what is genetic transformation of plants
direct introduction of new genetic info. these are called transgenic plants
what is agrobacterium tumefaciens
a bacterium that can transfer part of its DNA into plant cells, a powerful tool in plant biotechnology. causes crown galls (tumours of proliferating cells) to be produced on plants.
motile and swims towards would sites on plants
what is T-DNA
transfer DNA, a region on tumour tumour-inducing (Ti) plasmid, which is transferred to the plant cell nucleus. the T-DNA region of the Ti plasmid is copied and coated with proteins before transfer to the plant cell.
how does agrobacerium tumefaciens infection work
Agrobacterium enters the wound site
binds to plant cell wall
T-DNA is copied from Ti plasmid
T-DNA enters plant cell
T-DNA integrates into chromosomal DNA
what are auxin and cytokinin
plant proteins which cause abnormal cell division and tumour formation. they are natural plant cells however T-DNA causes overproduction.
what are opines in agrobacterium
agrobacterium encodes enzymes for opine biosynthesis. opines are amll molecules used by agrobacterium for growth.
how can T-DNA be modified to introduce foreign genes into plants
delete existing genes
insert new genes
Introduce selectable marker gene
what is a selectable marker gene
an antibiotic resistance gene provides a selectable marker gene: it encodes an enzyme that inactivates an antibiotic. transformed plants survive in the presence of the antibiotic, non-transformed plants die.
what is a disadvantage of agrobacterium
it doesnt efficiently infect several of the worlds major crop plants (wheat, maize, rice).
what is used to insert DNA into plant cells when agrobacterium is ineffective
shooting DNA into plants- DNA-coated microscopic metal particles accelerated into plant tissues or biolistic gun.
transformed cells are recognised if new gene encodes an enzyme that produces a coloured product.
what is a solution for many major crop plants being difficult to regenerate in culture
regeneration of embryos
what does plants being sedentary mean
they are planted in one place (cannot move) so need to cope with diverse environmental stresses to survive e.g. frost, drought. they need to optimise growth to maximise light capture.
what does the carrot totipotency experiment show
any cell in the individual plant has the genetic info needed to produce the whole plant.
what does differential gene expression mean
only a fraction of the genetic info present in a particular cell is expressed at any one time. different genes are turned on or off in different cells.
what does constitutive gene expression mean
genes which are continuously active, expressed all the time in all cells.
