Unit H – Applied Genetics in Agriculture

and Agriscience

Sexual Reproduction Processes

• Fertilization – Union of haploid cells in both plants and animals

• Occurs in the ovary of plants and the uterus of animals

• Embyro– A fertilized egg/ovule that will grow to produce new

offspring

• Ovary– Organ responsible for the production of

eggs/ovums in plants and animals.

Sexual Reproduction in Animals

• Fertilization– Occurs internally in most animals – all mammals.

• Some fish and insects are exceptions

• Haploid Cells– Male cells are spermatozoa (sperm), released in

semen to aid in the process of fertilization– Female cells are eggs, produced in the ovary,

fertilized and developed within the uterus• Females release eggs on a cycle (menstrual cycle) that varies

in time length according to species.

Sexual Reproduction in Plants

• Pollination– The transfer of male pollen to the female

reproductive organs• Pollination must occur before fertilization• Removal of the stamen is the first step in

mechanical cross pollination

• Germination– The initial vegetative growth of a seed

Reproductive Parts of Plants

• Male – THE STAMEN– Anther – top of the male part of a flower, contains

pollen– Filament – long slender stock on which the anther

sits• Female – THE PISTIL

– Stigma – the swollen end of the pistil, sticky to receive the pollen

– Style – stalk connecting the stigma to the ovary, pollen on the stigma

– Ovary – produces and stores the ovums (seeds), and protects seeds during development

– 1 ovum = I seed & 1 ovary = 1 fruit

Reproductive Parts of Plants

Types of Flowers in Plants

• Complete – have all the parts of a flower (stamen, pistil, sepals, petals)

• Incomplete – missing any part of the flower

• Perfect – have all the reproductive parts of a flower (stamen and pistil)

• Imperfect – missing any reproductive part of the flower (stamen, pistil, or any part of either)

ASEXUAL REPRODUCTION & CLONING

16.03

Cloning in Agriscience

• Allows rapid production of large numbers of genetically identical organisms. – Agriculturalists can quickly disseminate

outstanding traits.

Cloning in Agriscience

• Most often utilized for the culture of plants – cheaper, easier process, and less political opposition.

• The ability to differentiate is more in plants than animals

• Tissue culture – the production of plants from small amounts of

vegetative material in an invitro environment– an increasingly popular and effective method of

plant production.

Cloning in Agriscience

• Animals are cloned almost exclusively by the division of embryos.

• In recent years, diploid cells have been cloned, but the process is extremely expensive and results in high losses.– Dolly the sheep was produced from mammary

gland cells in a sheep

Cloning in Agriscience

• Clones are genetically identical (the exact same DNA)– Any genetic differences results from environmental

factors• Disease, nutrition, physical injuries, etc.

ASEXUAL PROPAGATION OF PLANTS

16.04 – Demonstrate proper technique in simple asexual propagation of plants

Stem Cuttings

• Section of the stem or a branch is cut, treated with rooting hormone, and placed in soil or water to encourage the development of roots.

• Should always be taken just above a node for best rooting

• Most common method

• Used for both woody and herbaceous plants.

Stem Cuttings

Air Layering

• Section of the stem or branch has the bark removed or slightly damaged and a rooting hormone applied.

• Area is then covered with soil wrapped cellophane until well developed roots can be seen through the plastic

• Branch or stem is cut below the roots only after roots have fully developed.

Air Layering

Tissue Culture

• Common method using extremely small amounts of plant material– Often uses meristem tips

• The tip of a branch where most active growth is occurring

• Tissue is removed from the plant, sterilized and cultured on agar in aseptic conditions

• Meristematic tissue develops shoots, is transferred to another media to develop adventitious roots, is hardened off, and finally transferred to soil.

Division

• Method of plant propagation conducted by physically separating a plant into several smaller plantlets– Often used for grasses and lilies– A variation is the production of non-tunicate bulbs

from scales• Each scale must contain a part of the bottom of the

bulb, the basal plate

Division

Grafting

• Process of removing plant material from one plant for incorporation into another plant– Often used with fruit trees to create dwarf varieties– Two parts

• Scion – top portion of a graft that will form the main part of the plant

• Rootstock – bottom portion of the graft that usually controls growth habit (size of the plant) but produces no vegetation

Grafting

• Budding is related to grafting– Instead of using a scion, exchange of plant material

is accomplished with a single bud

• Scion and rootstock remain genetically distinct even after combination

Grafting

Other Methods

• Leaf Cuttings

• Root Cuttings

TRANSGENIC ORGANISMS

16.05 – Explain methods of gene insertion used in the creation of transgenic organisms

Characteristics

• Can potentially be created using genes from ANY living organism– The trick is finding a method for insertion and

successful expression

• Genetically modified organisms (GMOs) transmit inserted genes at the same rate as naturally occurring genes– Once a gene is inserted, it can be passed on

through sexual reproduction

Steps in Creating a GMO

• Develop a Purpose/Goal– Transmission of genes from one organism to

another is both expensive and potentially dangerous

– Expectations for work should be laid out carefully

• DNA must be extracted from the target organism and the specific gene to be introduced isolated utilizing restriction enzymes

Steps in Creating a GMO

• Vectors are used from the transmission of genes– Viruses make good vectors, as they often insert

DNA into organisms they affect• Plasmids are the viruses most often used as vectors• Plasmids can store large strands of DNA or even

one or more chromosomes– Some vectors can transmit genes simply through

contact with target cells in a liquid solution or by microinjection.

Steps in Creating a GMO

• Isolated DNA is inserted into the new organism by:– Micromanipulation

• Isolated DNA segment is injected into a target cell utilizing a microscopic syringe under high magnification

– Most common – Biolistics

• Uses a gene gun to fire gold plated .22 caliber shells that have been covered with the target gene into a mass of plant cells

– Most often used for plants, as cell mortality is high

Micromanipulation

Biolistics