Plants: Molecular Genetics

Front 1

What is somatic embryogenesis?

Back 1

Regenerating whole organisms from a single cell in culture

Front 2

What are some goals of crop improvement?

Back 2

Disease resistance

Stress tolerance

Altered composition of harvested product

Front 3

What is genetic transformation?

Back 3

Direct introduction of new genetic information

Front 4

What are genetically modified plants called?

Back 4

Transgenic plants

Front 5

How is new genetic information introduced into plants?

Back 5

Employ an organism that genetically modifies plants - agrobacterium tumefaciens

Front 6

What does agrobacterium infection cause?

Back 6

Crown galls to be produced on plants - tumours of proliferating cells

Front 7

How ith the plant infected by agrobacterium?

Back 7

Tumour inducing plasmid contains a region call Transfer-DNA which transferred to the plant cell nucleus

The T-DNA region of the Ti plasmid is copied + coated with proteins before transfer to the plant cell

Front 8

Give a summary of the agrobacterium infection

Back 8

AB enters at wound site

AB binds to plant cell wall

T-DNA copied from Ti plasmid

T-DNA enters plant cell

T-DNA integrated into chromosomal DNA

Front 9

What are the genes on T-DNA?

Back 9

Encoded enzymes for auxin + cytokinin biosynthesis

Encoded enzymes for opine biosynthesis

Front 10

What do auxin + cytokinin cause?

Back 10

Abnormal cell division - tumour formation

Front 11

What are opines?

Back 11

Small molecules used by agrobacterium for growth

Front 12

How do yo modify T-DNA to introduce a foreign gene into plants?

Back 12

Delete existing genes

Insert new gene

Introduce selectable marker gene

Front 13

What is a selectable marker?

Back 13

It encodes an enzyme that inactivates an antibiotic

Front 14

Where does a selectable marker come from?

Back 14

An antibiotic resistant gene

Front 15

What type of plants survive the presence of the antibiotic?

Back 15

Transformed plants

Front 16

What is the problem with agrobacterium?

Back 16

It does not effectively infect several of the worlds major crop plants (wheat, maize, rice)

Front 17

What is a solution to the problems of agrobacterium?

Back 17

Shoot DNA into plants

Front 18

What will plants need to be able to do due to their sedentary nature?

Back 18

Cope with diverse environmental stresses to survive

Front 19

What is the order of gene expression?

Back 19

Gene -> mRNA -> Protein

Front 20

How is a gene turned into mRNA?

Back 20

By transcription

Front 21

How is mRNA turned into protein?

Back 21

BY translation

Front 22

What do genes in average plant encode?

Back 22

For about 12-15,000 different proteins

Front 23

What are some examples of protein function?

Back 23

Enzymes

Electron carriers

Ion channels

Structural components

Receptors

Transcription factors

Front 24

How do cells differ in protein composition?

Back 24

Differential gene expression

Constitutive gene expression

Front 25

What is differential gene expression?

Back 25

Only a fraction of the genetic information present in a particular cell is expressed at any one time

Front 26

What is constructive gene expression?

Back 26

Expression in all cells all the time

Front 27

How can gene expression be studied?

Back 27

Looking at proteins

Detect specific mRNAs

Visualising transcription

Front 28

What is the environmental regulation of gene expression?

Back 28

Light-induced genes

Stress-induced genes

Touch-induced genes

Front 29

What makes an altered phenotype?

Back 29

Mutant gene -> mutant protein -> altered phenotype

Front 30

What is the forward genetic approach?

Back 30

Isolated mutant in selected process -> identify gene that has become mutated

Draw conclusions on gene function

Front 31

What is the best plant for molecular genetic research?

Back 31

Arabidopsis thaliana

Front 32

What are the advantages of arabidopsis for genetics?

Back 32

Small + easy to grow

Rapid generation (6 weeks seed-seed)

Hundreds of seeds per plant

Self-fertile + can be crossed

Easy to produce mutants

Front 33

What is the mutagen in seed mutagenesis?

Back 33

Seeds

Front 34

What are characteristics of M generation plants?

Back 34

Arabidopsis is diploid

Has 5 homologous pairs of chromosomes

Very high probability that a given gene will only be mutated on one of the chromosomes

M1 plants are heterozygous for mutant genes

Front 35

What are the advantages of arabidopsis for molecular biology?

Back 35

Small genome

Easy to genetically transform using Agrobacterium floral dip

Genes corresponding to mutants can be isolated

Front 36

What is the advantage of a small genome for microbiology?

Back 36

Enables full genome sequence to be obtained + helps gene isolation

Front 37

What is the advantage of genes corresponding to mutants being isolated to microbiology?

Back 37

Need to relate position of mutated gene in genome to DNA sequence

Front 38

What genes caused epidermal cells to develop into particular cell types?

Back 38

Mutants altered in trichome formation

The glabra1 mutant was used to isolatethe wild-type GL1 geneGL1 encodes a transcription factor.Switches on other genes required tomake a trichome

Front 39

How do plants develop in light?

Back 39

Short hypocotyl

Expanded cotyledons

Chlorophyll

Front 40

How do plants develop in darkness?

Back 40

Long hypocotyl

Unexpanded cotyledons

No chlorophyll

Front 41

How many genes in a genome are regulated by light in seedlings?

Back 41

About 1/3 of genes

Front 42

What provides information on the regulation of transcription in transgenic plants?

Back 42

Expression of promoter-reporter gene fusions in transgenic plants

Front 43

How can we monitor temporal changes in gene transcription?

Back 43

Using luciferase

Front 44

In relation to light, what can plants detect?

Back 44

Light presence/absence

Light quantity

Light spectral quality

Light direction

Light duration

Front 45

What are the regulatory photoreceptors?

Back 45

Phytochromes (red light)

Cryptochromes/Phototropins (UV-A + blue light)

UV-B photoreceptor UVR8

Front 46

What does a photoreceptor comprise of?

Back 46

Apoprotein

Chromophore

Front 47

What is apoprotein?

Back 47

The photoreceptor protein

Front 48

What is chromophore?

Back 48

Attached to the apoprotein

A small organic molecule that absorbs light

Front 49

What does the phytochrome apoprotein bind?

Back 49

A linear tetrapyrrole chromophore

Front 50

What regulates CAB gene transcription?

Back 50

Phytochrome

Front 51

What binds flavin + pterin?

Back 51

Cryptochromes

Front 52

What do flavin + pterin do?

Back 52

Absorb UV-A + blue light

Front 53

What are cryptochromes?

Back 53

Involved in controlling processes such as stem extension, gene expression + flowering time

Front 54

What are phototropins?

Back 54

Control several important plant responses, including phototropism

Front 55

What binds flavin chromophores?

Back 55

Phototropins

Front 56

What do flavin chromophores do?

Back 56

Absorb mainly UV-A + blue ligth

Front 57

What dont plants sunburn?

Back 57

Due to flavonoids in the epidermis