Chapter 7, 8, 9 Applications & Experimentation

Question 1

What are ddNA nucleotides used for?

Answer 1

• used for base sequencing
• lacks -OH on C-3
• in sequencing machine DNA is mixed w/ DNAP, nucleotides, ddNA
• replication is repeated 4 x w/ A, T, C, G
• fragments of DNA separated by gel electrophoresis
• fluorescent markers attached to indicate base sequences

Question 2

What is the promoter’s function in transcription?

Answer 2

• close to start of gene (non-coding)
• RNAP binds to promoter
• repressor proteins can inhibit transcription by bindings to the promoter
• transcription factors bind to the promoter first in eukarytoes

Question 3

Uses of bioinformatics & genomes

Answer 3

• computers store / analyse data
• case sequences are main data
• sequencing initially was only possible w/ individual genes
• now WHOLE genomes sequenced
• locating genes OR searching for conserved sequences in dif. organisms
• evolutionary links

Question 3

Uses of bioinformatics & genomes

Answer 3

• computers store / analyse data
• case sequences are main data
• sequencing initially was only possible w/ individual genes
• now WHOLE genomes sequenced
• locating genes OR searching for conserved sequences in dif. organisms
• evolutionary links

Question 4

Describe the Hershey & Chase Experiment

Answer 4

• aim: determine if DNA OR proteins carry genetic material
• used E coli & bacteriophage virus
• grew bacteriophage in 2 radioactive cultures (either P or S)
• P –> DNA, S –> proteins
• the 2 samples injected their genetic material into E coli cells
• centrifugation used to separate solid + liquid medium
• E coli examined for radioactive material
• only radioactive P, no S detected –> DNA is genetic material

Question 5

Findings of X-Ray diffraction data

Answer 5

• clear images of diffraction patterns produced
• observed cross in centre of DNA –> helical DNA
• angle of cross shape = steepness of angle of helix
• distance b.w horizontal bars = turns of helix are 3.4 nm apart

Question 6

X-Ray Diffraction Mechanisms

Answer 6

• beam of X-ray is directed at material
• some of it is scattered by particles in material = diffraction
• X-ray detector is placed close to sample to collect scattered rays
• sample can be rotated in 3D
• diffraction pattern recorded using X-ray film

Question 6

Epigenetics

Answer 6

• epigenome = pattern of chemical markers in DNA of cell
• env. factors influence gene expression
• fluorescent markers can detect methylation patterns
• cytosine in DNA is converted to methylcytosine by addition of (-CH3)
• catalysed by enzyme + ONLY happens when there is a guanine on 3’ side of cytosine in base sequence
• patterns of methylation established during embryo dev.

Question 7

Tandem Repeats

Answer 7

• regions where adjacent sections of DNA have same base sequence
• # of repeats varies b/w dif individuals in some tandem repeats
• known as variable number tandem repeats
• DNA sample cut by restrictions enzymes into fragments
• amplified at specific gene sites w/ PCR
• fragments separated by gel electrophoresis
• fluorescent label attached to dif tandem repeats
• data from several loci at one time uniquely identify individuals
• simlarities b/w fragment patterns to determine paternity
• DNA profiling based on variable numbers of tandem repeats

Question 8

What did Maurice Wilkins contribute to our understanding of DNA?

Answer 8

he developed a method for producing DNA arrays (orderly arrangement) since it can’t be crystallised

Question 9

What did Rosalind Franklin produce?

Answer 9

She developed a high-resolution detector that produced clear DNA diffracting patterns

Question 10

Radioactive Labelling

Answer 10

• radioisotopes are used
• same chemical structure as other elements but they are radioactive
• e.g. C-14 is used to label organic compounds or CO2 & HCO3- for photosynthesis experiments

Question 11

How can short day plants be induced to flower?

Answer 11

• greenhouses w/ blinds to stimulate chrysanthemums
• when the night is not long enough, they can induce flowering by closing blinds
• extending nights artificially

Question 12

Outline factors affecting germination

Answer 12

• water: rehydrates seeds
• oxygen: cell respiration
• warmth: enzyme activity
• 2 treatments (control w/ all factors, experimental missing 1 factor)

Question 13

Models for Water Flow in Xylem - ADHESIVE PROPERTIES

Answer 13

glass capillary tube (water rises up glass) - mercury is NOT adhesive do doesn’t rise

Question 14

How is respiration rate measured using potometers?

Answer 14

• rate of water uptake is measured using potometer
• plant transpires, water drawn out of capillary tube
• movement of air bubble
• repeated measures of distance moved in 1 minute = transpiration rate

Question 15

Databases & antimalarial drugs (bioinformatics)

Answer 15

• malarial parasite (Plasmodium) resistant to most anti-malarial drugs –> urgent need for new drugs
• huge bioninformatics fatabases onc omputers help to identify chemicals (5655)
• inhibitors found for 6 of 9 enzymes & are not being researched

Question 16

Outline the end product inhibition of threonine dehydratase

Answer 16

• isoleucine (end-product) inhibits threonine dehydratase
• binds to allosteric site
• if there is excess of end product, whole pathway switched off
• intermediates do not build up
• e.g. of non-competitive inhibition

Question 17

Example of competitive inhibition

Answer 17

• O2 = competitive inhibitor
• for Rubisco
• prevents carbon fixation
• blocks active site for CO2

Question 18

Non-competitive Inhibition example

Answer 18

• cyanide ions = non-competitive inhibitor
• for cytochrome c oxidase
• prevents ETC from working

Question 19

Calvin’s Experiment

Answer 19

• aimed to elucidate carboxylation of RuBP
• chlorella sol. in thin glass vessel –> brightly lit
• supplied w/ CO2 & HCO3-
• replaced C-12 w/ C-14 (radioactive)
• took samples at short time intervals
• killed & fixed them w/ hot methanol
• extracted C-compounds, separated by double-way chromatography
• autoradiography –> to determine which compounds had C-14
• indicated order of formation = stages of cycle

Question 20

Outline the chemiosmotic theory.

Answer 20

• most ATP synthesis comes from electrochemical gradient
• across inner membranes of mitochondria
• using energy of NADH & FADH2
• paradigm shift

Question 21

What is electron tomography used for?

Answer 21

• to obtain 3D images of active mitochondria
• revealed that cristae are connected w/ intermembrane space b/w inner & outer membranes via narrow opening
• shape & volume of cristae change when mitochondria are active

Question 22

How is phloem transport rate measured using aphid stylets?

Answer 22

• aphids have long mouthparts = stylets
• push into plant tissue, pierce sieve tube
• high pressure in sieve tube pushes sap out
• C14 supplied to leaf
• time taken for radioactive sucrose to emerge from stylet measured at dif distances from leaf

Question 23

List the benefits of micropropagation.

Answer 23

• new varieties of plants can be bulked faster
• virus-free strains of existing varieties (shoot apex does not have viruses)
• large number of rare plants (e.g. orchids), reduced cost, no need to remove them from natural habitat

Question 24

Outline the steps of micropropagation.

Answer 24

1. small piece of tissue removed from shoot apex of plant being cloned
2. plant tissues & apparatus sterilised
3. tissue placed on sterile nutrient agar
4. w/ high auxin concentration –> cell growth + division
5. lumps of tissue (Callus) grow, can be cut to grow more
6. callus transferred to nutrient agar w/ less auxin, high cytokinin, & gibberellin
7. roots + shoots grow, platelets separated, moved to soil

Question 25

Explain why mutualism in pollination is so important.

Answer 25

• more than 50% of the world’s 250,000 species of flowering plant depend on pollinators for reproduction
• plant obtains nectar (energy) + pollen (protein)
• importance of protecting ecosystems

Question 26

Plant hormone detection

Answer 26

• very tiny amounts of plant hormones in tissue hard to detect
• 5 groups of hormones, chemically diverse, dif extraction methods are needed
• microarrays detect changes in gene expression due to hormones
• hormones bind to proteins (activated)
• bind to promoters –> transcription

Question 27

Models for xylem transport - WATER DRAWN THROUGH CAPILLARIES IN CELL WALL

Answer 27

• use blotting / filter / chromatography paper
• water rises through pores in the paper made of cellulose walls

Question 28

Models for xylem transport - EVAPORATION = TENSION

Answer 28

• porous pot is similar to cell wall, so water adheres, has many narrow pore
• water evaporates from the surface
• water rises up the tube, drawn into pot