3.5 Genetic modifications

Question 1

Explain PCR

Answer 1

PCR: multiply the copies of a desired DNA fragment by artificial replication

1. Dentauration
2. Annealing
3. Elongation

Question 2

Explain gel electrophoresis

Answer 2

Gel electrophoresis allows to sepratae proteins/DNA fragments depending on their mass/size

1. Samples are prepared to carry charge: proteins in appropriate buffers, DNA negative, stained - placed in gel
2. Electric current is applied - causes samples move trhough gel - largets move the least, smallest - the most
3. Using a mixture of known mass fragments - determine the mass of samples

Question 3

Explain DNA profiling

Answer 3

DNA profile is unique - non-coding satellite DNA STR - PCR - gel electrophoresis - compare

• paternity tests
• forensic investigations

Question 4

Explain gene trasnfer

Answer 4

DNA - universal code - organism can express foreign genes if incorporated

Transfer of genes between species - genetic modification - organism - transgenic (ex bacteria producing human insulin)

Steps:

• gene and vector isolated nad multiplied - centrifugation - PCR
• restriction endonucleases cutting needed places in gene and vector - create sticky ends for inserting
• gene incorporated into vector by DNA ligase - fuse sugar-phosphate backbones - recombinant construct
• vector trasnfer into organism
• selecting the successful transgenic organisms - antibiotics - purification of expressed gene - protein

Question 5

Sticky ends vs blunt ends

Answer 5

When restriction endonucleases cut vectors and DNA samples - in cloning leave sticky ends - more safe gene insertion into vector

Question 6

Benefits vs risks of GMOs

Answer 6

Question 7

Example of GMO in rela life and problems with it

Answer 7

Bt corn is GMO - incorporated insecticide gene - better harvest BUT harm monarch butterflies - pollen from Bt corn transferred to milkweeds - butterfly larvae feed - lower chances of survival BUT another study found no relationship

Question 8

Define clones

Answer 8

CLONES: a group of organisms which are genetically identical (asexually produce clones, sexually - rarely but identical twins)

Question 9

Explain somatic cell nuclear transfer

Answer 9

INn somatic cell nuclear transfer cloned embryos can be produced using differentiated adult cells

• somatic adult cells taken - cultured
• nucleus of unfertilised egg destroyed with UV - removed - enucleated egg cell - nucleus from somatic cell replaced
• electric current applied to stimulate division - development into embryo - implanted into uterus

Sheep Dolly

Question 10

Natural cloning methods

Answer 10

1. Binary fission
2. Budding (yeast)
3. Fragmentation (new oegnaisms grwo from separated fragments of parent organisms - starfish)
4. Parthenogenesis (embryos form from unfertilised egg (diploid by female - insects, fish, reptiles)

Question 11

Explain method for plant cloning

Answer 11

Vegetative propagation - ability to grow seprate organisms independently from a piece of another organism (plant roots, shoots)

• strawberries form runners
• micropropagation

Question 12

Human cloning methods

Answer 12

If the zygote randomly splits into two - monozygotic twins (share 100%)

or

If egg cell divides before fertilisation - dizygotic - on-identical twins (share 50%)

Question 13

Reproductive vs therapeutic cloning

Answer 13

Question 14

Explain cloning via embryonic division

Answer 14

• embryos separated while still pluripotent - form cloned organisms - implanted into uterus - grow to form several fetuses

Problem: the orginal embryo is formed in sexual reproduction - genetics not controlled but can produce identical organisms

Question 15

Explain stem cutting

Answer 15

Stem cutting: separated portion of a plant stem which can regrow into an independent clone

• all stems possess nodes - meristem cells - planted in soil with upper nodes out - new plant propagated (roses, grapes)

Factors that influence success:

• position of cutting
• growth medium
• conc of growth hormones
• growth conditions (temperature, sun, water, pH)

Question 16

Explain micropropagation

Answer 16