Introduction to GeneticIntroduction to Genetic ExpressionExpression

Father sperm gamete Mother egg gamete

22 autosomes +1 sex chromsome (X or Y) =23 total chromosomes(1N)

22 autosomes +1 sex chromosome (X) =23 total chromosomes(1N)

46 chromosomes(2N)

Common Name

Genus and Species

Diploid ChromosomeNumber

Buffalo Bison bison 60

Cat Felis catus 38

CattleBos taurus, B. indicus

60

DogCanis familiaris

78

Donkey E. asinus 62

Goat Capra hircus 60

HorseEquus caballus

64

Human Homo sapiens 46

Pig Sus scrofa 38

Sheep Ovis aries 54

The record for minimum number of chromosomes is held by Myrmecia pilosulaa species of ant. Females have 2 chromosomes per cell while males have only one chromosome.

The record for maximum Number of chromosomes.

Ophioglossum reticulatum a type of fern, has 1260 chromosomes per cell!!!

These 46 chromosomes can be arranged by number in a procedure known asa karyotype. The father’s sperm determine the gender of the baby. Sons receive a Y sex chromosome from their father. Daughters receive an Xfrom their father. Mother’s only give X sex chromosomes. What is this baby???

After careful staining, one will find distinct banding patterns on chromosomes. These banding patterns can be used to not only identify pairs, but also to specify the location of particular gene sites on each chromosome. Diagrams like these are used for gene mapping.

A gene is a string of bases(ACTGs) that code(genotype) for a protein that functions within the chemistry of an organism to eventually be expressed as a particular physical manifestation(phenotype). Gene mapping is performed in amanner that is universal so research scientists and geneticists can share their studies of genes and their variations(alleles) across the globe.

ALD?On the surface of peroxisomes, there is a transport protein that brings an enzyme into the peroxisome to break down very long chain fatty acids. ALD is a result in a mutation in this protein that prevents it from functioning properly.

The white matter of the brain, including myelin, depends on the perfect blend of lipids(fats) and protein to be constructed properly. It is still not entirely understood how excessive VLCFA(very long chain fatty acids) affect this white matter, but all the symptoms point to the imbalance as the cause of the disorder.

The Code is DeoxyriboNucleicAcid and RiboNucleicAcidOf these two main types combined, there are only five uniquenucleotides(code letters) and all of them are made of the elements: carbon, nitrogen, hydrogen, oxygen, phosphorous

Phosphate group

Sugar backbone of double helix

Nitrogenous Base

Determines the actual code letterof the moleculeA C T G or U

amino acids

Alleles are variations in the code at a particular gene. These variations arise in the form of base differences in the DNA. These changes affectchemistry by changing specific amino acids in the protein that is being constructed. A different amino acid sequence results in a change in the shape of the protein…which affects its function. In most cases, the origin of various alleles are mutations.

Mutation Types

The quick brown fox jumps over the lazy dog.

The quick brown ssox jumps over the lazy dog.

The quick brown fox jumps ccove rth elaz ydo gove rth elaz ydo g.

The quick brown fox overt hela zyd ogovert hela zyd og.

The quick brown fox jumps gody zal ehtr evogody zal ehtr evo.

point

original

insertion

deletion

inversion

Whether or not an allele is beneficial depends on environmental factors. Every organism is 100% genetic and 100% environmental. Even identical twins are unique!Adaptation is how an individual organism’s genetics interacts with the environment within its lifespan.Evolution is the process where variations within the gene pool of a population are selected by the environment.

100%

+

100%

So how does genetics interact with the Environment?

PROTEINS

The order of amino acidsdictates how a polypeptide(protein) will fold up on itself.

Different amino acids are attracted to and repulsed from one another in varyingdegrees.

This extremely complicated and dynamic interactionresults in a very specific three dimensional shape for each protein.

Just like there is only one shape of key thatwill open this lock, for each chemical reactionin a living creature there is a specific proteinthat will catalyze(unlock) it.

Enzymes as keys

Most enzymes end with the suffix –ase. The rest of theirname is usually reflected in the substrate on which they act. LactoseLactase ATP created ATP synthetase etc.

Alleles and mutations are modifications in the shape ofthese catalytic enzymes…some convey an advantageand others do not. Much of the potential benefit dependsdirectly on environmental conditions. Malaria and its relationship with sickle cell is an example of one suchcondition.

sickle cell(defense)

plasmodium(disease causingprotozoan)

nasty mosquito(vector/carrier)

An interesting trend was discovered where the gene frequency of the sickle cell allele was correlated with the distribution of malaria.Subsequently it was found that some individuals with the sickle cell allele were more apt to survive infection. This advantage was mostprofound in young children(6-18months). At its root, the environment has selected for the frequency of the sickle allele to increase since survivors are able to pass on their genes to offspring.

Sickle cell is a result of a change At the sixth amino acid of the betaChain protein subunit of hemoglobin.Normal cells have:

glutamic acid = GAA or GAG

Sickle cells have:

Valine = GUA / GUG / GUU / GUC

This seemingly simple change has large effects on blood cells.

Homozygous dominant - HbSSThese people have normal blood cell function and do not have theenvironmental advantage against malaria.

Heterozygous - HbSsThese individuals have one allele for the normal form of the proteinand one for the sickle form. These are the individuals who have anadvantage in an environment with malaria present.

Homozygous recessive - HbssWithout a normal form of the protein, these people acquire sickleCell disease. This disease shortens lifespan drastically and resultsIn a host of problems from kidney failure to hypoxia during exertion.

Pedigree: Sickle Cell Disease (autosomal)

= male

= female

Pedigree: X-linked Red/Green Colorblindness

= male

= female

It is important to remember that the environment is not sentient. It does not think about what is best, nor does it orchestrate these manipulations with the least bit of logic or rational thought. The principle is quite simple. If an organism survives long enough to reach reproductive age, finds a mate, and successfully procreates,nature has selected that organism’s traits for at least one more generation.