What is genetic recombination?
Recombination occurs when two or more genes from different species combine with each other to form a new gene. When these genes are combined they give rise to entirely new organisms. For example, a bacterium might have genes from several different species mixed together to make a new organism. A plant might have genes from many different species mixed together to produce a completely new organism.
How does it work?
When two or more genes from different species combine with each other, they create a new gene. These genes are called “recombining” genes. These new genes are called “recombinants.”
What types of recombination are there?
In the simplest forms, there are two different types of recombination as described below. However, in more complex systems, there may be additional types of recombination.
Crossing over: In this form of genetic recombination, genes from four different chromosomes (one from each pair) swap places with one another. These genes are known as “alleles.” During this process, the genes on the same chromosome remain together.
This process leads to each allele having a chance to be represented twice in the offspring’s genes. This process is also known as “chromosomal crossover.”
Chimerism: This form of genetic recombination involves the occurrence of two organisms. In this case, the offspring is a mixture of both of its parents.
For example, the offspring may have some skin that is from the mother and some skin that is from the father.
What does “allele” mean?
An allele is one of the forms of a gene (or part of a gene). For example, human eyes come in different colors. Each different color is an allele for the color gene. For example, if a person has blue eyes, then the allele for blue is present. If a person has brown eyes, then the allele for brown is present. If a person has green eyes, then the alleles for green and blue are present in equal measure.
What is the difference between “allele” and “gene?”
The main difference is that an allele is one form of a gene, while a gene is a combination of alleles within one particular species or organism. Also, the term “gene” is more general, and it can refer to the hereditary unit in general, whether or not it is on a chromosome.
What is the difference between “allele” and “chromosome?”
The main difference is that an allele is one form of a gene, while a chromosome is the physical structure that genes are found on. Also, the term “chromosome” is more general, and it can refer to the physical structure that genes are found on in general, whether or not it is within a cell.
How many genes are there in the human genome?
As of January 2013, the number of genes in the human genome is approximately 20, 000. This number only includes the genes that have an identified purpose. It does not include what are known as “junk DNA” or “pseudogenes.”
What is junk DNA?
Junk DNA is a name given to non-coding DNA. This is DNA that does not give rise to a protein product. It once was thought that this section of the genome was “junk” that accumulated as evolution “got rid of” genes that were no longer necessary. However, more recent research has shown that this type of DNA still has an important purpose. For one, it may be involved in regulating gene expression. In addition, it may also play a role in diseases such as cancer.
What is a pseudogene?
A pseudogene is a gene that has the same sequence of DNA as a normal gene, but does not function normally. For example, it may code for a non-functional form of the protein. In some cases, it may produce a functional form of the protein, but at an abnormal rate or composition.
What is horizontal gene transfer?
Horizontal gene transfer refers to the passing of DNA from one organism to another organism that is not its offspring. This can occur in several different ways. Bacteria may become infected with viruses known as bacteriophages that alter the bacterial genome. In some cases, this can include insertion of a full sequence of DNA. This can lead to an acquisition of new traits. For example, genes coding for antibiotic resistance may be acquired in this manner. Some organims can also pass on DNA via a process known as transduction. In this process, the DNA is incorporated into a virus and then used to infect another organism. It is then incorporated into the genome of the second organism. It is worth noting that most forms of horizontal gene transfer involve the transfer of DNA between bacteria. Because of the large size of animals, it would be rare for a single virus to transfer DNA from one animal to another. The most likely path would be through a virus that infects a common ancestor and then is passed down through the family tree.
What is an intron?
An intron is a region of DNA that is transcribed into RNA, but then is subsequently removed from the RNA before it is translated into proteins. These regions were once thought to be useless by-products of reverse transcription, but now it is known that they have an important role in regulating the expression of genes. In fact, some genes may have multiple introns and the same intron may be used in the coding sequence of one gene, but not another.
What is a lysosome?
A lysosome is a vesicle that is involved in the breaking down of biomolecules within a cell. It contains a number of enzymes that break down the biomolecules into their component parts so they can be recycled within the cell.
What is an organelle?
An organelle is a specialized sub-unit within a cell that has a specific function. There are many different types of organelles within the cell. The nucleus is one example. Another example is the mitochondrion, which is the organelle that converts energy in the cell into a form that can be used.
What is an organism?
An organism is any living creature. In biology, the definition of an organism is rather vague and flexible. In general, it is a cell or group of cells that are physiologically and genetically cohesive and are separated from other groups of cells by a relatively distinct border.
What is a plasmid?
A plasmid is a small loop of DNA that is not part of the main chromosomal sequence. There are two types of plasmids. An example of a class 1 plasmid is the well-known fertility factor found in the common gut bacterium E. coli. This plasmid allows the bacteria to survive in the presence of a certain drug. An example of a class 2 plasmid is found in the insect pathogen known as “Wolbachia”. This plasmid confers antibiotic resistance upon the insect.
What is a prokaryote?
A prokaryote is a bacterium. They are cells that lack a true nucleus and typically have no membrane-bound organelles. Most bacteria are prokaryotes.
What is a ribosome?
A ribosome is a complex of RNA and protein that serves to translate mRNA into a sequence of amino acids, the building blocks of proteins. Without ribosomes, the information stored in DNA could not be used to produce proteins. Thus, the ribosome is essential to life.
What is a scientific theory?
Scientific theories are explanations of phenomena that are supported by vast amounts of experimental evidence. They are the closest thing to absolute certainty that exists in science. For example, evolution is a theory. Gravity is a theory. The existence of sub-atomic particles is a theory. However, in all of these cases, it would take a tremendous amount of evidence to overturn these theories.
What is a sequence?
A sequence is a series of nucleotide bases in DNA or RNA. The order of the bases in a sequence determines the order of the amino acids in a polypeptide chain. This, in turn, determines the shape and function of a protein.
What is a sequence alignment?
A sequence alignment is the process of lining up a set of sequences in the same area of the genome (or even in separate genomes).
What is a transcription factor?
Transcription factors are sets of proteins that bind to a specific DNA sequence and regulate the rate of transcription of mRNA from that DNA segment.
What is a unicellular organism?
Unicellular organisms are any one-celled organisms. They can be either eukaryotes or prokaryotes.
What is a virus?
A virus is a small infectious agent that can only reproduce inside the living cells of other organisms. Viruses contain either DNA or RNA, but not both. The virus consists of two parts, the core and the capsid. The core is made of nucleic acid and either attaches to a cell or is taken inside by the cell. The capsid is a protein shell that protects the core and attaches to the cell.
What is a yeast?
Yeast is a kind of fungus. It is used in baking and brewing.
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The information stored in an organism’s DNA is passed on from one generation to the next.
The double helix shape of A, the fact that C is a single molecule, and that D is a large complex of molecules make them all invalid choices.
A codon is made up of three nucleotide bases. GAG, GAA, and GGG all code for the same amino acid, glutamic acid.
The 24 possible combinations of three-base sequences are known as triplets, or codons. There are 4 possible codons, making TTT the correct answer.
Each frame in a movie is a snapshot of a still life. Each codon is a snapshot of an amino acid.
Each gene is a series of codons that make up a set of instructions for a protein.
If the cell reads ATCGAC, it will produce alanine. If the cell reads ATGCGA, it will produce arginine.
The remaining codons produce other amino acids.
The process of “reading” the triplets of DNA and using them to create proteins is known as translation.
The mRNA carries the instructions created by the genome.
The remaining choices all describe features of the genome, but only A describes a nucleotide base.
Each set of three bases on one strand of DNA codes for a particular amino acid in a protein. This is the relationship between nucleotides and proteins.
A, T, G, and C are all nucleotides found in RNA (as well as DNA).
Transcription is the process of creating mRNA from DNA. It requires an enzyme called RNA polymerase.
Each codon on mRNA is recognized by a particular transfer RNA (tRNA). Each tRNA has three bases on it; when the correct base pair is in front of it, the tRNA will hold onto that amino acid.
There are four bases in RNA (A, U, C, and G) as opposed to the four different kinds of DNA base pairs (A, T; C, G).
The cell uses ribosomes to “read” the mRNA and create a protein. Each ribosome is made up of two subunits, one large and one small.
The process of breaking mRNA down is known as “splicing.” In this process, introns (non-coding segments of mRNA) are cut out, and the remaining pieces are joined into a continuous strand of mRNA.
The cell uses transfer RNA to carry amino acids to the ribosomes, where they are added to the protein as it is created.
Prokaryotes have a single membrane, while eukaryotes have multiple.
Prokaryotes lack a nucleus, while eukaryotes have one.
Fungi do not have a cell wall like plants or bacteria.
Viruses are smaller than bacteria and aren’t considered either living or non-living.
All of the choices are correct.
The smallest unit of life is a cell, so D is the best answer.
The three states of matter are solid, liquid, and gas. Bacteria, archaea, and viruses can be in any of these states while still being alive.
The word “biota” refers to all the living things in a particular region, such as an ocean or a forest.
An example of an autotroph is a green plant that absorbs energy from sunlight.
A heterotroph must consume other organisms in order to get the energy and nutrients it needs.
The sun is a nuclear reactor, a large mass of energy that fuels the rest of the universe.
A food chain depicts who-eats-who in an ecosystem.
Decomposers such as bacteria and fungi break down waste and dead organisms in order to release nutrients back into the environment.
Sources & references used in this article:
- Initiation of genetic recombination and recombination-dependent replication (SC Kowalczykowski – Trends in biochemical sciences, 2000 – Elsevier)
- A general model for genetic recombination (MS Meselson, CM Radding – Proceedings of the National …, 1975 – National Acad Sciences)
- Mutants of Escherichia coli K-12 defective in DNA repair and in genetic recombination (P Howard-Flanders, L Theriot – Genetics, 1966 – ncbi.nlm.nih.gov)
- DNA repair and genetic recombination: studies on mutants of Escherichia coli defective in these processes (P Howard-Flanders, RP Boyce – Radiation Research Supplement, 1966 – JSTOR)