bio flashcards - genes/genetics

Gene Mutations, Effect of the Environment on Gene Expression, Selective Breeding, Genetic Engineering, Cloning

cloning

cloning

process of making a genetically identical organism

enucleated

when the nucleus is removed from the cell

why do scientists clone animals?

• All the cloned organisms would have the desired trait(s)

• makes copies of organs and tissues for transplants

• animal models of disease (diabetes, muscular dystrophy, etc)

• Production of human therapeutic proteins (hormones, clotting factors, etc)

• Saving endangered species

disadvantages of cloning

• same sex, so could not mate with one another

• cloned organisms may have a genetic flaw;  does it cause early aging/death???

• since the group of cloned organisms are the same genetically, entire group could be lost to disease (no resistance to the pathogen)

how was Dolly cloned?

• Wilmut (scientist) and his colleagues transplanted a nucleus from a mammary gland cell of a sheep into the enucleated egg of a blackface ewe (type of sheep).

• The nucleus-egg combination was stimulated with electricity to fuse the two and to stimulate cell division.

• The new cell divided and was placed in the uterus of a blackface ewe to develop.

gene mutations can lead to…

• beneficial mutations can lead to adaptations and evolution

• harmful mutations can lead to genetic disorders

• some can possibly have no effects!

Sickle Cell Anemia

caused by a mutation in the gene that codes for the production of hemoglobin. Instead of red blood cells being smooth, round, and able to glide through blood vessels, red blood cells are abnormal and stick to one another which builds up and blocks blood vessels (causing pain, bacterial infections, and organ damage)

point mutations

mutations that involve a change in one or two nucleotides that occur at a single point in the nucleotide sequence

substitution mutation

• one nucleotide is different

• changes the codon for one amino acid

• can result in a protein that doesn’t function normally

frameshift mutations

(deletion and addition mutations are examples of this)

• Shift the “reading frame” of the codons

• all of the codons after the point of the mutation are affected

• Usually results in a protein that does not function

• Can result in a serious genetic disorder

silent mutations

a type of mutation that is altered but does not affect the amino acid used (i.e, if CUC was altered to CUA, there would be no effects as they both fall under Leucine)

somatic cell

body cells (all cells that AREN’T sex cells)

where can gene mutations occur?

can occasionally form in all cells of the body, and sometimes result in cancerous cells forming

mutations are passed to offspring if…

if the gene mutations are in sex cells (sperm and egg)

selective breeding

• accomplished by crossing two members of the same species which possess genes for particular traits

• when they are crossed they will produce at least some offspring that will have these desirable characteristics

• also called artificial selection

inbreeding

offspring produced by artificial selection are mated with one another to reinforce those desirable traits (used in plants)

hybridization

crossing two individuals with different desirable traits to produce offspring with a combination of both desirable traits.

examples of hybridization

• Brahman cattle: Good resistance to heat but poor beef.

• English shorthorn cattle: Good beef but poor heat resistance.

• Santa Gertrudis cattle: Formed by crossing Brahman and English shorthorns; has good heat resistance and beef.

what effect does the environment have on gene expression?

The nucleotide sequence of the DNA remains the same, but some environmental factors can change the expression of the gene (whether the gene is turned on or off)

• Some environmental factors include temperature, humidity, nutrient availability or stress.

examples of the environment affecting gene expression

the arctic fox

• When the outside temperature is warm the hair is made with dark pigment

• When it is cold the hair is made with no pigment (gene is turned off)

identical twin studies

• The environment molds your personality, but your genes determine what kind of environment you seek

• Since the early 1960s, several twin studies have reported that identical twins reared apart are actually more alike than those raised in the same home  (i.e, the Jim twins)

• By examining how twins (especially twins raised apart) are different, a study may determine the degree that a particular trait is influenced by genes or the environment.

Recombinant DNA

• DNA from two or more species is incorporated into a single recombinant molecule

• one method is to use small circular pieces of DNA called plasmids

• the plasmid and the foreign gene are both cut with the same restriction enzyme

• both DNA strands have complementary "sticky ends”

• the opened plasmid and the gene of interest are mixed with DNA ligase, which “glues” the strands together

• All offspring of the bacteria would also contain the inserted gene (bacteria reproduce asexually)

plasmids

molecules of DNA that are found in bacteria separate from the bacterial chromosome. They are small and usually carry only a few genes

restriction enzymes

(“molecular scissors”) found in bacteria, they restrict the growth of invading viruses by cutting up the DNA of the virus.

• recognize a particular sequence of DNA nucleotides and cuts the DNA at that point

what is recombinant DNA used for?

bacterial clones can be made to produce many important things for us, and the gene product can be purified and used to treat human disorders

• examples include insulin, growth hormone, clotting factor for hemophiliacs & the hepatitis B vaccine

benefits of genetically modified products

• Crops

  • Increased growth rate

  • Increased nutrients & crop yields

  • Improved resistance to disease, pests, and herbicides

  • New products

• Animals

  • Increased resistance, productivity, hardiness, and feed efficiency

  • Better yields of meat, eggs, and milk

  • Improved animal health and diagnostic methods

controversies of genetically modified products

• Safety

  • Potential human health impacts, including allergens, unknown effects

  • Potential environmental impacts, including: unintended transfer of transgenes through cross-pollination, unknown effects on other organisms, and loss of biodiversity

• Ethics

  • Tampering with nature by mixing genes among species

  • Objections to consuming animal genes in plants and vice versa

genetic engineering

altering an organism’s DNA (incorporating a gene into the DNA)