Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
145 Cards in this Set
- Front
- Back
|
where is the genetic information in living organism contained?
|
nucleic acids
|
|
|
what is the most common genetic information?
|
DNA but RNA may be used by viruses
|
|
|
what does the information in the DNA allows the cell to do?
|
allows the cell to control its internal metabolism and chemistry.
|
|
|
what is a chromosome
|
it is an organized piece of DNA that contains genetic instructions.
|
|
|
what are the genetic instructions called and what do they do
|
called genes and they direct organismal development and function.
|
|
|
what is a gene?
|
a genetic unit of heredity that contains info needed to make a specific protein
|
|
|
the proteins that are made by genes do what?
|
they act as enzymes that carry out a specific bit of chemistry.
|
|
|
what is the genome?
|
its the collection of genes found in a given organism
|
|
|
what is the phenotype?
|
the physical appearance of a characteristic. EX: blue eye color, or a bacteria being antibiotic resistant to penicillin.
|
|
|
what is the genotype
|
refers to the specific genetic makeup of the organism.
|
|
|
how many genes do human have for everything
|
two-one then a back up, but they do not have to be the same. Ex. you could have a gene for blue eyes or brown eyes. The dominant trait will be the phenotype
|
|
|
bacteria have a single circular chromosome. T/F
|
true.
|
|
|
what does a cell do when it divides?
|
DNA Replication-it makes copies of all the chromosomes so the new cell will have a full set of instructions
|
|
|
what is the first thing DNA does in replication?
|
they transcribe their info into RNA segments.
|
|
|
when info in transcribed what is the next step?
|
they need to make sense of the RNA sequence and then translate the info into directions for assembly of amino acids into a functional protein.
|
|
|
what is the double helix
|
two parallel chains of DNA that are ladder-like, and twisted into a spiral
|
|
|
what are the nitrogen base pairs in DNA?
|
A & T (adenine and thymine)
G & C (guanine and cytosine) |
|
|
are the nitrogen base pairs strong bonds?
|
they are not because they are hydrogen bonds which means they are susceptible to separation under the right conditions.
|
|
|
how does DNA replication start?
|
starts by the separation of the double helix (the two strands) by the use of helicase & each strand is used as a template to make a new strand.
|
|
|
what do you need to make a new strand of DNA
|
Semiconservative Replication- you need the proper nucleotides (A, T, C, or G) in the proper pairing position.
|
|
|
what is DNA gyrase
|
its an enzyme that unwinds the strands without making a big know of the double helix.
|
|
|
how does DNA synthesis start?
|
it starts with the insertion of a small premade piece of nucleic acid called a primer, it is inserted by the enzyme primase.
|
|
|
after the primer is inserted, what is the next step?
|
its to insert the proper nucleotides the the new strand opposite the one on the old strand by DNA polymerase (it only makes an error 1 in 10 billion times)
|
|
|
after DNA polymerase inserts the proper nucleotides in place & the sequence is complete, what is next?
|
the enzyme ligase comes in and seals up the ends of the new strands to make a complete molecule.
|
|
|
what do bacterial chromosomes present problems?
|
they are round rather then linear, so replication begins at one point and proceeds in the opposite direction around the circle. Both replication will meet at the other end of the circle & the 2 chromosomes will need to be seperated
|
|
|
where does DNA replication take place on the chromosome?
|
on the Origin of Replication (ori site)
|
|
|
what is needed in order for transcription to take place
|
it will need a working copy of the genetic info, & you dont need the whole chromosome, just the gene of interest
|
|
|
when a new copy of a gene is made it makes a new strand out of what in transcription?
|
makes a new strand of genetic info out of RNA (not DNA). It specifically makes a messenger RNA (mRNA) copy of the DNA sequence
|
|
|
When making mRNA, what are changes that occure
|
T is replaced by Uracil (U). U will never be in DNA.& a different enzyme is used to do the copying.
|
|
|
In transcription you make RNA so what enzyme is used?
|
RNA polymerase
|
|
|
once transcription is started at the appropriate place it proceeds until when?
|
until a termination period is reached & at this point copying stops.
|
|
|
what happens in the last step of genetic coding, translation?
|
the genetic info encoded in the mRNA is decoded into instructions for building a protein (specific sequence of amino acids).
|
|
|
the letter sequence in the mRNA is read in 3 groups called what?
|
codon which represents a specific amino acid.
|
|
|
the code is made up of 4 letters (A,U,C,& G) in groups of 3 so that gives us 64 possibilities, what is the problem?
|
There are only 20 common amino acids. Which means that multiple codes will be used or each amino acid.
|
|
|
what is the start codon in translation and what does it code for
|
its AUG and its codes for the amino acid Methionine
|
|
|
what are the three stop codons?
|
UAA, UAG, UGA-translation is stopped once one of these is reached.
|
|
|
what does that translation process involve?
|
ribosomes, mRNA, & tRNA.
|
|
|
what are ribosomes
|
they are the factories of protein production. they are made up of two halves that sandwhich an mRNA between them.
|
|
|
how does tRNA get into a ribosome?
|
they squeeze through one of the many holes in a ribosome. the most important openings are the A site and P site
|
|
|
what is tRNA (transfer RNA)
|
its an RNA molecule that has different amino acids attached on one end.The other end has a sequence of 3 nucleotides called the anti-codon.
|
|
|
what can the anti-codon do?
|
it can base pair with the codon which helps place the amino acids in the proper position.
|
|
|
translation step 1
|
the process begins w/ the assembly of the two ribosome halves that cover the mRNA. The ribosomes set up on the first AUG sequence it finds. Then 2 appropriate tRNA molecules settle in the P site (the 1st tRNA sits) & A site (2nd codon of mRNA pairs w/ a tRNA carrying the second amino acid) sites **the codon must match the anti-codon of the proper tRNA.
|
|
|
translation step 2
|
once the 2 tRNA's are settle in, the 2 amino acids are in the proper orientation to for a peptide bond. the 1st amino acid releases from its tRNA, the empty tRNA is released and floats away to be reused.
|
|
|
translation step 3
|
after the 1st tRNA is released the ribosome complex moves one codon to the right. This exposes the next codon in the open A site and a new tRNA can settle in and it allows amino acid 2 to peptide bond w/ amino acid 3. The 2ns amino acid (leu) releases and its tRNA floats away. process continues until a stop codon is reached.
|
|
|
translation step 4
|
once a stop codon is reached, the process will stop. Since there is no tRNA for the stop codon, the ribosome stalls. Eventually the whole complex comes apart and can be used again to make another protein..
|
|
|
difference between eucaryotic cells and prokaryotic cells with transcription & translation
|
eukaryotic cells conduct both in different locations. prokaryotic (bacterial) do not have a nucleus so both occur simultaneously.
|
|
|
what if the polymerase makes a mistake in copying DNA
|
errors in the protein sequence are introduced and it will be passed on every time the cell is replicated. They occur once for every million genes copied.
|
|
|
what happens with an error in the production of mRNA
|
it affects the proteins made using that mRNA.
|
|
|
what are mutations
|
when something goes wrong in the transcription process, and something is changed in proteins. It can be either a good thing or bad. They are not all permanent.
|
|
|
what is point mutation (3 different kinds of mutations)
|
mutations that form when a single nucleotide is changed into something different. It affects the protein being produced in 3 ways-neutral, missense, an nonsense.
|
|
|
what is a nonsense mutation
|
its the most serious mutation. Ex: Glycine codon GGA could change to UGA which is a stop codon, so now protein synthesis immediately stops, whether the protein is finished or not.
|
|
|
what is neutral mutation?
|
a change in the DNA still codes for the same amino acid, the exact same protein is built. EX: Ex. If a codon is GGA and a mutation changes it to GGG, it still means a ribosome should use glycine
|
|
|
what is a more severe problem in mutations-Missense Mutation
|
If glycine codon (GGA) was mutated to GAA. now the codon no longer codes for Glycine it codes for Glutamine, a different amino acid, & now the resulting protein is different. Disease ex:sickle Cell Anemia.
|
|
|
frameshift mutations
|
loss or gain of nucleotides, rather than change. If one/two nucleotides are gained/lost it will throw off the reading frame of the ribosome. We read codons in 3s, so if one is messed up it messes up the whole line. Ex: See the cat and the bat eat the rat (insert the letter Z)=See thZ eca tan dth era tea tth eba t
|
|
|
mutations can be caused by external influences such as:
|
cosmic rays from outer space, x-ray radiation can cause birth defects, going out into the sun can cause formation of Thymine Dimers.
|
|
|
what do Thymine Dimers do
|
they bend DNA and lead to Frameshift mutations.
|
|
|
what are thymine dimers
|
they are adjacent T nucleotides that bind to each other instead of binding to the A nucleotides on the opposite strand. If not repaired they are removed leading to frameshift & in skin cell it leads to melanoma.
|
|
|
chemicals that cause mutations
|
they look a bit like normal DNA nucleotides but dont follow the normal pairing rules.
|
|
|
Base analogs
|
incorporated into the DNA as say a T. The next time the DNA replicated, the DNA polymerase becomes confused by the base analog and it decides to insert a G instead of the proper A.
|
|
|
How does the AIDS drug AZT work
|
it makes the HIV virus mutate its DNA and hopefully kill it but it also mutates human cells
|
|
|
aflatoxin
|
carcinogen that is commonly found in peanut buter and it also causes frameshift mutation. **FDA requires testing before any new chemical is used in food.
|
|
|
Ames test
|
a simple test that can be performed to test for the mutagenic property of a chemical using bacteria as a test organism. The trick is to look for a change in the phenotype of an organism.
|
|
|
what strain is used in the ames test
|
salmonella that cannot produce Histidine, a required nutrient. such strains are called His-. The gene for His- production has a point mutation, the gene is busted & if exposed they will randomly change things. It could turn the broken His gene back into its normal state.
|
|
|
How many plates are made in the Ames experiment?
|
2. one plate includes the chemical being tested for mutagenicity, the other control plate contains no chemical. Both contain a small amount of histidine-this allows the organisms to behin dividing & allow the mutagen (if its really a mutagen) to have it's effect. eventually the histidine will run out nd only those that mutate will be able to produce more and survive.
|
|
|
chemicals being carcinogenic
|
there is 90% correlation between mutagens and carcinogens. A positive AMES test helps determince if its worth doing further animal testing.
|
|
|
when an organism acquires a new capability it...
|
comes from either a mutation in an existing gene which gives an advantage or they "steal" a gene from somewhere else.
|
|
|
recombination
|
occurs when an organism incorporates some DNA from another source. So 2 pieces of DNA merge to become one. The new DNA is called a Recombinant.
|
|
|
bacteria in transformation
|
bacteria have a need for nucleic acids so they have the ability to absorb naked DNA, normally this DNa would be broken down and reused by the cell. Sometimes the bit of DNA gets incorporated into the bacterial chromosome. EX: the non capsule producing strain acquired the capsule gene from the dead cells & used it to start producing a capsule.
|
|
|
why are capsules difficult on the immune system?
|
makes it difficult for the immune system to fight off an infection.
|
|
|
transduction
|
this is another method that allows genes to be transfered from one bacterial cell to another. A virus accidently transfers the genes.
|
|
|
bacteriophage (AKA phage)
|
is a bacterial virus
|
|
|
viruses cant replicate on their own so what do they do?
|
they infect a host cell and take over the replicating machinery of the cll to make baby viruses. Once the viral DNA replication process is done, the parts of the virus are assembled & the virus particles are released & they go on to infect other cells
|
|
|
what are 2 things that are produced when viruses replicate?
|
genetic info is duplicated and protein parts needed for the shell of the virus.
|
|
|
conjugation
|
last process/most complicated/most specialized.
|
|
|
plasmids
|
extra bits of DNA found in circular form. They have been described as containing genes like antibiotic resistance genes, genes for degredative enzymes, special metabolism, and pathogenic factors like the production of a capsule.
|
|
|
what do plasmids have that bacterial chromosomes also have?
|
they have an ori site, which means they get replicated each time the chromosomes does before cell division.
|
|
|
Fertility or F Plasmid
|
cells that have it are called F+ cells & F- if they dont. It contains genes that allows for the formation of sex pili that are used for conjugation. F+ cell extends a tubule that attaches to another cell.
|
|
|
What does the double strand of a plasmid do?
|
it passes through the tunnel where it serves a s template that is used to synthesize the other strand. The process is the same as DNA replication & now the F- cell becomes F+
|
|
|
High Frequency recombinant (Hfr)
|
when the fertility plasmid inserts itselft into the bacterial chromosome and becomes recombinant.
|
|
|
breeding program
|
manipulating genetics of living organisms, fruits, veggies, and others. Modern civilization would not exist unless out ancestors developed effective farming techniques.
|
|
|
Gregor Mendel
|
experienced w/ pea plants that allowed him to observe certain patterns of inheritance that allowed him to put forth some rules on inherritance. He deduced how things work when parents pass on traits to offspring to make hybrid organism, also chromosomes were responsible for heredity
|
|
|
biotechnology industry
|
was born out of war-Germans/Britains using fermentation to mass produce acetone & glycerol used in high explosives.
|
|
|
Fleming
|
discovered Penicillin, the 1st antibiotic, but it was too expensive to mass produce years earlier & was not widely used. But the war funded having it mass produced & saved thousands of lives.
|
|
|
Watson and Crick
|
gained fame & nobel prizes, after the war, by describing the structure of DNA. They jump started the genetics revolution.
|
|
|
Genetically Modified Organisms
|
have characteristics of both organisms used to modify it. It takes DNA from 2 organism to form a recombinant DNA molecule that is place into one organism. Its an efficient way to gain new functions w/out losing any of the old ones.
|
|
|
Examples of selectively altering genes in an organism to change it's phenotype:
|
1. increase antibiotic production
2. produce medically useful proteins (hormones) 3. fix or repair defective genes in ppl 4. make disease and drought resistant plants 5. identify genetic material to help solve crimes 6. clean the environment of toxic spills (Exxon Valdez) |
|
|
DNA tools:
|
1. Annealing
2. Restriction endonucleases 3. Electrophoresis 4. Oligonucleotides 5. Polymerase chain reaction 6. Gene probes 7. Hybridization 8. Sequencing |
|
|
Recombinant DNA Technology:
|
1. Gene isolation
2. Gene splicing 3. Cloning vectors 4. Cloning hosts 5. Product expression and isolation 6. Gene libraries |
|
|
Recombinant Products:
|
1. Hormones/drugs
2. Enzymes 3. Pesticides 4. Probes 5. Vaccines |
|
|
Transgenic Organism Microbes:
|
1. Frost-free bacteria
2. Bacteria with insecticide 3. Viral vaccines 4. n2-fixing bacteria |
|
|
Transgenic Organism Plants:
|
1. Engineered w/ Agrobacterium
2. Pesticide resistance 3. Disease resistance 4. Improved fruits & vegetables |
|
|
Transgenic Organism Animals:
|
1. Recombinant embryos
2. Animal models of human disease 3. Mammals engineered for protein production 4. Improvements in animal husbandry |
|
|
Genetic Treatments
|
1. Gene therapy
2. Antisense DNA & RNA 3. Triplex DNA |
|
|
Genetic Analysis:
|
1. Gene mapping & sequencing
2. Junk DNA 3. Genetic screening 4. DNA fingerprints |
|
|
Tools-Restriction Enzymes
|
cut jagged at very specific sites on DNA that contain particular sequence of nucleotides, usually 6-10 bases. It produces 2 sticky ends, 2 ends can meet & base pair if they were both cut by the same restriction enzyme
|
|
|
Ligase in the use w/ restriction enzymes
|
used to seal up the breaks of the 2 DNA fragments and for a recombinant DNA.
|
|
|
Tools: Vector
|
used to introduce recombinant DNA into a host cell to insert desired traits.
|
|
|
Vector Creation
|
the first step is to create the plasmid vector. 2 things are needed: an appropriate plasmid & the gene to be transfered. Each item is cut using a restriction enzyme.
|
|
|
what is the problem with vector creation?
|
theres a problem of finding the one instance where the right gene got placed into the plasmid at the right place.
|
|
|
How to find the one cell out of hundreds that worked out right?
|
This is when its important to have used the right plasmid, one that will detect the presence of a gene by looking for changes in phenotype.
|
|
|
By a cell having a plasmid, what can we tell?
|
it has new characteristics and new genes.
|
|
|
we need two traits in vector creation, what are they
|
the presence of one trait will tell us the cell has a plasmid but the absence of the other will tell us that some other DNA has been inserted in the plasmid.
|
|
|
steps for a successful attempt to have the DNA bits come together to form a new plasmid.
|
1. Vector such as plasmid is isolated
2. DNA containing gene of interest is cleaved by an enzyme into fragments 3. the gene is inserted into plasmid (Recombinant DNA) 4. Plasmid is taken up by a cell such as bacterium (recombinant bacterium) |
|
|
The steps when putting bacteria on a plate w/ Ampicillin and another gene?
|
1. Plasmid DNA and foreign DNA are both cut with the same restriction enzyme
2. Foreign DNA, the gene of interest, is inserted into the r. plasmid, where it inactivates the lacZ gene. 3. The r. plasmid is introduced into a bacterium, which becomes ampicillin-resistant 4. All treated bacteria are spread on an agar plate containing ampicillin and B-galactosidase substrate, & incubated 5. White colonies that appear must contain foreign DNA. Blue colonies dont contain foreign DNA **the white cells are the ones we want & they mess up color change cuz they have an intact gene. |
|
|
After the plasmid vector is placed back into the cell what are the steps that follows?
|
1. choose appropriate cells & grow in high #s.
|
|
|
bacteria produce what that is normally only found in the bloodstream?
|
human proteins such as insulin or growth hormone.
|
|
|
the new & improved form of insulin, what is it & how does it work?
|
humulin & its absorbed better via injection due to an inversion of two amino acids in the sequence.
|
|
|
what is interferon used for?
|
its used to boost the immune system of those with autoimmune diseases. Many new vaccines are produced in this manner.
|
|
|
what do we do with all the cells that have been produced/cloned & now all have the gene of interest?
|
they can be used in a gene library or can be inserted into other organism to make Genetically Modified Organisms (GMO's).
|
|
|
What is Agrobacterium tumefaciens
|
a bacteria that has a plasmid that naturally inserts DNA into a plant cell. It causes plant tumors and is considered a big problem in agriculture. working w/ plants is an obvious application of genetic engineering.
|
|
|
what do we do to help reduce a. tumefaciens
|
we build a vector using the natural bacterial system & insert a gene of interest into a plasmid & grow the plant cell into a mature plant that will now contain the gene of interest.
|
|
|
monsanto & round up (how are they related?
|
monsanto produces a soy bean that is very resistant to RoundUp which is used to kill weeds.
|
|
|
Bacillus thuringiensis?
|
a microbe that produces a toxin (Bt toxin) that kills insects. Its used to spray fields to kill crop destroying insects but now its possible to insert the bacteria into a corn plant so the insects that eat it will die.
|
|
|
Polymerase Chain Reaction (PCR)
|
artificially mimics the process of DNA replication when their are not enough DNA present to work with
|
|
|
How does PCR work
|
DNA is heated and 2 strands will seperate, it cools and Polymerase is added and the copying begins. To make more strands the sample is heated again to separate the strands and a new set of replication can take place. It continues until a sufficient amount of identical DNA strands are produced.
|
|
|
what can go wrong with heating Polymerase?
|
the enzymes are destroyed by the heat so a new set of DNA polymerases are needed for each cycle, which becomes expensive.
|
|
|
what is a way to get around the expensive ways of heating Polymerase?
|
we look to a ready made Polymerase that can take high temps, such as those thermophillic organisms that have adapted enzymes that can function at high temps. Ex: bacterium thermus aquaticus (hot water) has provided a thermophillic DNA polymerase (Taq).
|
|
|
who shot the said to be last mountain lion in Happy Valley & in what year
|
Samuel Brush in 1856.
|
|
|
Human Genome Project
|
a massive undertaking to sequence and locate all of the genes found in humans
|
|
|
how does the process of electrophoresis work?
|
DNA fragments of differeing size are placed into a slab of agarose immersed in a fluid. Electrical current is used to make the negatively charged DNA move towards the positive electrode. SMaller DNA pieces migrate faster than larger pieces.
|
|
|
how does the DNA sequencing process start for electrophoresis?
|
begins by using PCR to create large amounts of given DNA segment. This sample is seperated into 4 piles. Each pile is made up of the DNA segment that's then cut up into different sized pieces. Each piece in each segment ends in the same letter
|
|
|
how does the diagram look for 4 separate DNA piles & their letters?
|
set #1 has 3 segments that end in A
set #2 has 4 segments that end in T set #3 has 2 segments that end in G set #4 has 2 segments that end in C |
|
|
where would the smalles piece of DNA be located in the tube of gel?
|
its found at the bottom & is apart of the set that ends in T. The next shortest is in the set that ends with A.The third is again in T. So far its TAT. the sequence looks like this : TATCATGGATC. This is only for 11 nucleotides. It can be done for hundreds of nucleotides.
|
|
|
what would be a more sensitive method used in DNA fingerprinting?
|
use a radioactive probe that will attach to the DNA fragments. When exposed to an Xray film the bands are visible.
|
|
|
As the HUman Genome Project Progresses more info is coming to light regarding the function of genes in disease, what?
|
Its possible to do tests to determine the genotype of an individual. Ex: Test for breast cancer that indicates affected individuals run an increased risk of developing this type of cancer. Early treatment can lead to a 90% survival rate, knowing early on lead to more checkups.
|
|
|
Genetic screening
|
can be used to maybe one day get a complete genetic profile of all known genetic diseases and predispositions. It may lead to issues with insurance & life insurance, because of risk.
|
|
|
Gene therapy
|
involves the insertion of genes that correct the function of mutated ones. Ex: Diabetes, you could insert a functional gene that produces the proper proteins that would produce insulin & control sugar metabolism
|
|
|
Results of Gene therapy:
|
there have been many unsuccessful human trials. If this technology is perfected it has the potential to be revolutionary where we could manipulate physical characteristics at the genetic level.
|
|
|
what is a gene gun?
|
a gene gun is a device that's used to introduce DNA into a cell. CAn be used to prevent allergies. It delivers functional genes to replace defective ones.
|
|
|
how does the gene gun?
|
using a blast of helium, it accelerates tiny gold or tungsten nano particles which can be coated w/ DNA which are then shot into a cell.
|
|
|
Why the interest in GMO's
|
1. agriculture
|
|
|
what is the problem with the agriculture/food production.
|
food production has been stable for the last 30 yrs (since the Green Revolution of the 60s gave in increase in seed varieties). But the population of the world is increasing and that means it will get harder to feed the worlds population.
|
|
|
what is the early ex. of genetic transfer into plants
|
insertion of a gene from a firefly. The luciferase gene allows an organism to "glow". The result was a transgenic plant that was able to light up by itself.
|
|
|
how does the Bt toxin kill insects?
|
1. insect ingest Bt toxin
2. the toxin binds to receptors on the gut & causes the insect to stop eating 3. the toxin then breaks open the lining of the gut and toxin gets into the other tissues. 4. the insect dies. |
|
|
what are problems w/ Bt
|
1. Bt corn is not approved by the FDA for consumption in humans.
2. The problems it causes for other insects that are'nt harming the crops. |
|
|
what is the corn variety that caused problems in 2003?
|
starlink, which contains a protein known as Cry9C, and it is not easily digestable (its approved for use in animal feed). Taco shells from Taco Bell tested + for the protein because the corn was being produced for cows and somehow got to the factory that made the shells.
|
|
|
concert with Bt and milkweed?
|
monarch butterfly feeds on milkweed and the gene from corn to milkweed would kill of the monarch population
|
|
|
what was the 1st genetically modified food
|
the Flavr Savr tomato in 1994-company wanted a tomato that stayed ripe even when it was off the vine.
|
|
|
what is the new scoop w/ genetically modified tomatoes in recent yrs?
|
a tomato has been developed that resist salt & this allows farmers to use the 25 mil. acres of farmland thats lost each year when it gets to salty.
|
|
|
who was golden rice created by?
|
Peter Beyer & Ingo Potrykus. They published results in Science journal in 2000.
|
|
|
what was golden rice?
|
rice that got a gene for beta carotene production which was transfered from a daffodil into a rice plant. Its a precursor for the production of Vitamin A, which deficiency affects a # of women and children. Rice is the most widely eaten food.
|
|
|
Golden Rice 2?
|
It has 20x the beta carotene of the original golden rice.
|
|
|
gene doping, what is it?
|
a term used to refer to the abuse of legitimate medical gene therapy treatments that modify a persons genetic makeup.
|
|
|
what is Erythropoetin?
|
a hormone that controls the production of Red Blood Cells. More RBCs the more O2 which means muscles wont tire as easily. Growth factor hormones control the rate of muscle cell division.
|
|
|
Myostatin?
|
myostatin controls how big a muscle can get. The Belgian Blue Bull has a defect in the Myostatin gene so they are VERY muscular.
|
