Biology

Archibald Gerrod speculated that alkaptonuria, a hereditary disease, was caused by the absence of an enzyme that breaks down a specific substrate, alkapton.

RNA is chemically similar to DNA, except that it contains ribose as its sugar and substitutes the nitrogenous base uracil for thymine.

An RNA molecule almost always consists of a single strand.

In DNA or RNA, nucleotides consist of a phosphate, sugar, and nitrogenous base the four nucleotide monomers. The specific sequence of hundreds or thousands of nucleotides in each gene carries the information for the primary structure of proteins, the linear order of the 20 possible amino acids.

The complimentary RNA molecule is synthesized according to base-pairing rules, except that uracil is the complimentary base to adenine.

Because codons are base triplets, the number of nucleotides making up a genetic message must be three times the number of amino acids making up the protein product. It takes at least 300 nucleotides to code for a polypeptide that is 100 amino acids long.

A particular triplet of bases in the template strand of DNA is AGT. The corresponding codon for the mRNA transcribed would be UCA.

Unlike DNA polymerases, RNA polymerases are able to start a chain from scratch; they dont need a primer.

RNA polymerase II is used for mRNA synthesis in prokaryotes, RNA polymerase can recognize and bind directly to the promoter region. In eukaryotes, proteins called transcription factors mediate the binding of RNA polymerase and the initiation of transcription.

RNA polymerase and DNA polymerase differ in that RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis. Specific sequences of nucleotides along the DNA mark where gene transcription begins and ends.

RNA polymerase attaches and initiates transcription at the promotoer. In prokaryotes, the sequence that signals the end of transcription called the terminator. Molecular biologists refer to the direction of transcription as "downstream" and the other direction as "upstream".

Noncoding segments of nucleotides called interveing regions, or introns, lie between coding regions. The final mRNA transcript includes coding regions, exons, which are translated into amino acid sequences, plus the leader and trailer sequences. RNA splicing removes introns and joins exons to create an mRNA molecule with a continuous coding sequence.

Each tRNA arriving at the ribosome carries a specific amino acid at one end and has a specific nucleotide triplet, an anticodon, at the other. The anticodon base-pairs with a complimentary codon on mRNA.

tRNA with an AAA anticodon and carrying phenylalanine will bind to it.

Suppose a particular eukaryotic protein is 300 amino acids long then it would take 900 nucleotides in the coding sequence to make that protein.

Polyribosomes reads single ribosomes.

Ligase not involved in translation

change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein. "stop codon in mRNA"

One basic cloning technique begins with the insertion of a foreign gene into a bacterial plasmid. E coli and it's plasmids are commonly used. First, a foreign gene is inserted into a bacterial plasmid to produce a recombinant DNA molecule.

Restriction enzymes cut DNA molecules at specific locations. In nature, bacteria use restriction enzymes to cut foreign DNA, to protect themselves against phages or other bacteria. They work by cutting up the foreign DNA, a process called

Bacterial cell protect its own DNA from restriction enzymes by adding methyl groups to adenines and cytosines.

Restriction enzymes cut covalent sugar-phosphate backbones of both strands, often in a staggered way that creates single-stranded sticky ends.

The original plasmid used to produce recombinant DNA is called. Defined as a DNA molecule that can carry foreign DNA into a cell and replicate there. Bacterial plasmids are widely used as cloning vectors for several reasons.

Bacteria containing recombinant plasmids are often identified by exposing the bacteria to an antibiotic that kills cells lacking the plasmid. The transformed bacteria are plated on a solid nutrient medium containing ampicillin and a molecular mimic of lactose called X-gal. Only bacteria that have the ampicillin-resistance (ampR) plasmid will grow. The lactose mimic in the medium is used to identify plasmids that carry foreign DNA. Cell clones with the right gene are identified

The enzyme reverse transcriptase is used to make single-stranded DNA transcripts of the mRNA molecules. It can also be used to make shorter gene from mRNA as the introns are already eliminated.

Double stranded DNA, modified by the addition of restriction sites at each end. Finally the cDNA is inserteed into vector DNA.

The principal problem with inserting an unmodified mammalian gene into a bacterial plasmid, and then getting that gene expressed in bacteria, is that bacteria cannot remove eukaryotic introns.

When the source of DNA is scanty or impure, the polymerase chain reaction (PCR) is quicker and more selective. This technique can quickly amplify any piece of DNA without using cells.

PCR (polymerase chain reaction) can make billions of copies of a targeted DNA segment in a few hours.

One indirect method of rapidly analyzing and comparing genomes is ...Restriction fragments of DNA are typically separated from one another by this process.

In gel electrophoresis, the restriction fragments from the two alleles will produce different band patterns, allowing us to distinguish the two alleles.

DNA fragments from a gel are transferred to a nitrocellulose paper during the procedure called...

The basic strategy in global expression is to isolate mRNAs from particular cells and use the mRNA as a template to build cDNA by reverse transcription.

All organisms use essentially the same genetic code that is a evidence for the origin of life on earth.

Carolus Linnaeus developed the binomial system of naming organisms according to genus and species. Linnaeus based his classification system on morphology and anatomy

Charles Lyell proposed a theory of uniformitarianism, which held that geological processes had not changed throughout earth's history.

The inheritance of acquired characteristics stated that modifications acquired during the life of an organism could be passed to offspring. A classic example is the long neck of the giraffe. Lamarck reasoned that the long muscular neck of the modern giraffe evolved over many generations as the ancestors of giraffes reached for leaves on higher branches and passed this characteristics to their offspring. However, modern genetics has provided no evidence that acquired characteristics can be inherited.

Darwin read Lyell's Principles of Geology, these observations reinforced Darwin's acceptance of Lyell's ideas and led him to doubt the traditional view of a yound and static Earth. The earth has an old age...earth is ancient.

Alfred Wallace, a young naturalist working in the east indies, sent Darwin a manuscript containing a theory of natural selection essentially identical to Darwin's. While both Darwin and Wallace developed similar ideas independently, the theory of evolution by natural selection is attributed to Darwin because he developed his ideas earlier and supported the theory much more extensively.

Thomas Malthus infuenced Darwin's views on "overreproduction". Malthus contended that much human suffering---disease, famine, homelessness, war---was the inescapable consequence of the potential for human populations to increase faster than food supplies and other resources. The capacity to overproduce seems to be a characteristic of all species.

Differential reproductive success--whereby organisms with traits favored by the environement produce more offspring than do organisms without those traits---results in the favored traits being disproportionately represented in the next generation. this increasing frequency of the favored traits in a population is the result of natural selection.

The Australian sugar glider and North american flying squirrel are adapted to the same mode of life and look somewhat similar. However, the sugar glider shares more characteristics with other Australian marsupials than with the flying squirrel. The resemblance between the two gliders in an example of convergent evolution.

Missing evidence of Darwin----->source of genetic variation. # of offsprings that survived to reproduce

Darwin proposed a mechanism for change in species over time. What was missing from Darwin's explanation was an understanding of inheritance that could explain how chance variations arise in a population while also accounting for the precise transmission of these variations from parents to offspring.

The total aggregate of genes in a population at any one time is calles the population's

The Hardy-weinburg theorem describes the gene pool of a nonevolving population. This theorem states that the frequencies of alleles and genotypes in a population's gene pool will remain constant over generations unless acted upon by agents other than Mendelian segregation and recombination of alleles. The shuffling of alleles by meiosis and random fertilization has no effect on the overall gene pool of a population.

In a Hardy-weinburg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.7. What is the percentage of the population that is homozygous for this allele? (49%)

In a hardy-weinburg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.7. What is the percentage of the population that is heterozygous for this allele? (42)

Most copies of harmful recessive alleles in a sexual species are carried by individuals that are heterozygous.

Gene flow is a concept best used to describe an exchange between population.

Genetic drift at small population sizes may occur as a result of two situations: The bottleneck effect or the founder effect.

the bottleneck effect occurs when the numbers of individuals in a large population are drastically reduced by a disaster. By chance, some alleles may be overrepresented and others underrepresented among the survivors. Some alleles may be eliminated altogether. Genetic drift will continue to change the gene pool until the population in large enough to eliminated the effect of fluctuations. The bottleneck effect is an important concept in conservation biology of endangered species. Populations that have suffered bottleneck incidents have lost genetic variation from the gene pool. This reduces individual variation and may reduce adaptation. Genetic drift would continue from generation to generation until the population grew large enough for sampling errors to be minimal.

Founder effects have been demonstrated in human populations that started from a small group of colonists. A population may lose or gain alleles by gene flow.

Geographic variation in the form of graded change in a trait along a geographic axis is called a...
A trend toward the decrease in the size of plants on the slopes of mountains as altitudes increase is an example
The average body size of many north american species of birds and mammals increases gradually with increasing latitude, allowing Northern populations to conserve heat in cold environments by decreasing the ratio of surface area to volume.

Mules are relatively long-lived and hardy organisms that cannot, generally speaking, perform successful meisosis. So they have a relative evolutionary fitness of zero.

Heterozygote advantage should be most closely linked to stabilizing selection.

It is important to distinguish between intrasexual and intersexual selection. Intrasexual selection is direct competition among individuals of one sex (usually males) for mates of the opposite sex. Competition may take the form of direct physical battles between individuals. The stronger individuals gain status.

Intersexual selection or mate choice occurs when members of one sex (usually females) are choosy in selecting their mates from individuals of the other sex. Male satin bowerbirds adorn structions that they build, called "bowers," with parrot feathers, flowers, and other bizzare ornaments in order to attract females. females inspect the bowers and if suitably impressed, allow males to mate with them, after which they go off to nest by themselves. The evolution of this behavior is best described as due to sexual selection

Adult male vervet monkeys have red penises and blue scrotums. males use their colorful genitalia in dominance displays wherein they compete with each other for access to females. The coloration of the male genitalia is best explained as the result of sexual selection and specifically of intrasexual selection.