week 8 Flashcards
what is the autosomal recessive mode of inheritance
trait appears in both sexes equally, often skips generations, two heterozygous carriers can have affected children eg cystic fibrosis and sickle cell anaemia
what is the autosomal dominant mode of inheritance
trait appears in every generation, affected individuals have at least one affected parent, equal occurrence in males and female eg Huntingdon’s disease
explain X linked recessive mode of inheritance
more common in males as they only have one X chromosome
affected fathers do not pass traits on to their sons, carrier females may have affected sons
eg haemophilia
explain x linked dominant mode of inhertiance
appears in every generation, affected fathers pass it to all daughters but not sons
affected mothers can pass it to both sons and daughters
how can you interpret a pedigree mode of inheritance
if both sexes affected equally, likely autosomal, if more male affected possibly x linked recessive
skips generations? yes = likely recessive no = likely dominant
2 unaffected parents with an unaffected child = likely autosomal recessive
affected fathers pass the trait to all daughters but not sons = likely X linked dominant
why are plants such good experimental systems
rapid growth and ease of cultivation
regeneration capability
large populations and genetic diversity
availability of model species eg arabidopsis
reproducible responses to environmental conditions
no issues of animal experimentation
describe how agrobacterium works and is used to introduce foreign genes to plants
agrobacterium enters at wound site
binds to plant cell wall
tDNA copied from Ti plasmid
tDNA enters plant cell
tDNA integrates into chromosomal DNA
what is gene expression in plants
the regulation of transcription and translation, resulting in the production of specific proteins. Many genes are expressed at different times during development, in different tissues and in response to environmental stimuli
why is gene expression important in plant growth
Specific patterns of gene expression dictate the formation of organs (leaves, roots, flowers) and the timing of developmental transitions, such as seed germination and flowering.
it helps develop understanding of how plants grow and develop to understand gene expression
how do plants differ their gene expression in response to the environment
they continuously adjust gene expression in accordance to their environment enabling them to adapt to the changing conditions
name some methods of introducing new genes to plants
agrobacterium tumefaciens, DNA shooting for several of the worlds major crop plants (maize, wheat, rice)
for these crops you can also regenerate embryos as they are hard to regenerate in culture
what absorbs light in plants and what is the result
pigments that absorb blue light known as blue-light photoreceptors, and initiate a variety of responses including phototropism which is the opening of stomata
phytochromes absorrb red and far-red light
What are the main aims of crop improvement
disease resistance, stress tolerance and altered composition of harvested product
how is a gene of choice transferred into a plant gene using agrobacterium
gene of choice is introduced to the tDNA, which then enters the is put into a tDNA plasmid and put back into the agrobacteria
define differential and constitutive gene epression
differential - onyla fraction of the genetic info in a cell is expressed at any one time
constitutive - expression in all cell all the time so many proteins will be differentially expressed
name 3 ways we can study gene expression
- look at proteins using gel electrophoresis
- detect specific mRNA’s using transcriptome sequencing
- visualise transcription using reporter genes like a simple colour assay
name 3 kind of genes gthat can be controlled environmentally that affect gene expression
light induced genes
stress induced genes - when plant exposed to cold 100s of genes switched on
touch induced genes - expressed rapidly after a mechanical stimulation
list advantages of using arabidopsis for genetics
- small and easy to grow
- rapid generation time
- hundreds of seed per plany
- self fertile and can be crossed
- easy to produce mutants
how can mutants give insight into gene function
mutant genes create mutant proteins which lead to an altered phenotype, allowing you to draw conclusions on gene function
list advantages of arabidopsis for molecular biology
- small genome enables full genome sequencing and helps gene isolation
2/. has little repetitive dna and non-coding dna in nucleus - has a lot of protein encoding genes - higher proportion than normal
- easily genetically transformed using agrobacterium floral dip
why is the genetic approach using arabidopsis so successfull
it allows researchers to dissect gene function. These methods help in linking specific genes to developmental processes and stress responses by observing changes in phenotype.
