Marco Rodríguez - BIOCHEMISTRY : CHECK YOUR KNOWLEDGE AT BIOCHEMISTRY WITH MCQ (FRESH MAN)

The shape of cells in mul cellular organisms is extremely varied. There are discoid cells, as in the case of red blood cells, those that resemble a star, like the neurons, and even some elongated, such as muscle.

In one same body, the differen a on of these cells occurs by

a) produce specific muta ons .

b) have different mitochondrial DNA .

c) present a set of dis nct genes .

d) express dis nct por ons of the genome.

e) have a dis nct number of chromosomes.

The plant biosynthesize certain substances (for example, alkaloids and flavonoids), whose structure chemistry and concentra on range in a single body in different seasons of the year and stage of development. Many of these substances are produced to adapt the body to environmental varia ons ( UV radia on , temperature, parasites, herbivores, s mula on of pollinators, etc.) or physiological varia ons (growth, aging, etc.).

The varia ons qualita ve and quan ta ve in the produc on of these substances for a year are possible because the material gene c of individual

a) undergoes constant recombina on to adapt.

b) changes to over the years and in different stages of life.

c) creates new genes for biosynthesis of specific substances .

d) alters the sequence of nitrogenous bases to create new substances.

e) has genes transcribed differently according to each need.

DNA (deoxyribonucleic acid), the gene c material of living beings, is a double - stranded molecule that can be extracted at home from fruits, such as mashed strawberries or bananas, using detergent, table salt, alcohol commercial and one sieve or of one colander of paper.

The role of detergent that extrac on of DNA is

a) agglomerate the DNA in solu on so that it becomes visible.

b) promo ng lysis mechanical 's ssue to obtain the DNA.

c) emulsifying the mixture to promote the precipita on of DNA.

d) promote ac vi es enzyme to accelerate the extrac on of DNA.

e) breaking the membrane cell to release the DNA in solu on.

In the days of today, we can say that almost all the beings human 've heard in some me talking about the DNA and its role in heredity of most organisms. But it was only in 1952, a year before the descrip on of the model of DNA in double helix by Watson and Crick, who was confirmed without a shadow of doubt that DNA is gene c material. In the ar cle in which Watson and Crick described the DNA molecule, they suggested a model of how this molecule should be replicated.

In 1958 Meselson and Stahl performed experiments using heavy isotopes of nitrogen bases that were incorporated to the nitrogen to evaluate as it would give the replica on of the molecule. The from the results confirmed the model suggested by Watson and Crick, who was premised basic the breaking of the bridges of hydrogen between the nitrogenous bases.

GRIFFITHS, AJ F. et al . Introduc on to Gene cs . river of

January: Guanabara Koogan, 2002.

Considering the structure of the molecule of DNA and posi on of hydrogen bonding in the same, the experiments conducted by Meselson and Stahl to about the replica on of this molecule have led to the comple on of that

a) DNA replica on is conserva ve, that is, the daughter double strand is newly synthesized and the parental strand is conserved.

b) DNA replica on is dispersive, that is, the daughter strands contain newly synthesized and parental DNA on each of the strands.

c) the replica on is semi - conserva ve, i.e., the tape daughters consist of one tape parental and a newly synthesized.

d) DNA replica on is conserva ve, that is, daughters tapes consist of molecules of DNA parent.

e) the replica on is semi - conserva ve, i.e., the tape daughters consist of one tape mold and one tape coding.

The following figure represents a model of transmission of gene c informa on in biological systems. At the end of the process, which includes replica on, transcrip on and transla on, there are three different protein forms called a, b and c.

It appears from the model that

a) a single molecule that par cipates in produc on of proteins is the DNA.

b) the flow of gene c informa on in biological systems is unidirec onal.

c) the ac ve sources of informa on during the process of transcrip on are proteins.

d) it is possible to obtain different varia ons protein from a same product of transcrip on.

e) the DNA molecule has circular shape and the other molecules have a shape of ribbon simple linearized.

Genome is defined as the set of all gene c material of a species, which, in most cases, are DNA molecules. For a long

me it has been speculated about the possible rela onship between the size of the genome

measured by the number of base pairs (bp) the number of proteins produced and the complexity of the organism. The first answers begin to appear and it is already clear that this rela onship does not exist, as shown in the table below.

In accordance with the informa on above,

a) the set of genes from one organism defines the its DNA.

b) the produc on of proteins not is bound to the molecule of DNA.

c) the size of the genome is not directly propor onal to the number of proteins produced by the organism.

d) how much more complex the organism, the greater the size of its genome.

e) genomes with more than one billion pairs of bases are found only in beings vertebrates.

During long me, the scien sts believed that varia ons anatomical between animals due to differences were significant between their genomes. However, the project of sequencing the genome revealed otherwise. Today, it is known that 99% of the genome of a mouse is the same as that of man, despite the notable differences between them. It is also known that genes occupy only about 1.5% of the DNA and that less than 10% of genes encode proteins that play a role in the construc on and defini on of body shapes . The rest possibly cons tute non-coding DNA. How to explain, then, the differences phenotypic between the various species animals? The answer may lie in the non-coding region of DNA.

The non-coding region of DNA may be responsible for the marked differences in phenotype because it contains

a) the sequences of DNA that encode proteins responsible for defining the shapes of the body.

b) an enzyme that synthesizes proteins from the sequence of amino acids that make up the gene.

c) hundreds of amino acids that make up most of our proteins.

d) informa on which, in spite of not being translated into sequences of proteins interfere with phenotype.

e) the genes associated with the forma on of structures similar to other species.

A manufacturer claims that a commercially available product has plant DNA , an element that would provide be er hair hydra on .

About the characteris cs chemical of this molecule essen al to life, it is correct to say that the DNA

a) of any kind would do, as they have the same composi on.

b) of vegetable origin is chemically different from the others because it has chlorophyll.

c) of bacteria could cause muta ons in the scalp.

d) the animal is always coiled and is of difficult absorp on.

e) of basic characteris cs , ensures its moisturizing efficiency .