The swine industry is re-emphasizing the importance of efficiently arising a top quality product. To accomplish this objective, industry hogs will should come from bigger litters and also convert feed into lean meat an ext efficiently. Because that this to happen in your herd, favorable genetic change needs to it is in made in those characteristics that impact efficiency of production. Therefore, pork producers must understand simple genetic ideas so that they can apply them come improve financially important traits.
You are watching: How many chromosomes do pigs have
Genetics is a scientific research that researches heredity and also variation. Heredity is characterized as the resemblance amongst individuals associated by descent, and variation is the occurrence of differences amongst individuals of the very same species. Therefore, genes is the science of the research of resemblances and also differences that exist amongst individuals.
Genes and Chromosomes
Genes, i m sorry are made up of DNA (deoxyribonucleic acid), are the simple unit of inheritance. Resemblances and also differences amongst related people are primarily because of genes. Genes reason the production of enzyme which in turn regulate chemical reaction in the body, for this reason affecting body development and function. For typical body development and function, genes must happen in pairs. Genes space a part of the chromosomes the reside in the nucleus of human body cells. Chromosomes in the cell core of a particular cell contain the same genetic information together the chromosomes in every cabinet of the body. As such the chromosomes in the cell of a pig’s tail room exact duplicates of the chromosomes in the pig’s heart; however, the gene on the chromosomes know their function in certain body tissues.
Figure 1. Karotype that male and also female pig chromosomes. Pigs have 19 bag of chromosomes within the cell core of each cell in the body. In 1a space chromosomes from a female and in 1b space chromosomes indigenous a male. The chromosome pair in the upper appropriate hand corner of each photo determine sex. In females this chromosome pair is designated XX, when in males it is designated XY.
In the normal cell that a pig, or any type of mammal, chromosomes take place in unique pairs. Pigs have 19 chromosome pairs for a total of 38 chromosomes (Figure 1). This contrasts through humans, who have 23 chromosome pairs for a complete of 46. Because chromosomes occur in pairs, genes likewise exist in pairs. If over there are an ext or much less than 2 chromosomes in a pair, an abnormality will certainly occur. A standard example the this is Down’s Syndrome in humans. Persons afflicted with Down’s Syndrome frequently have 3 members in a particular pair that chromosomes instead of the common two. Not all genetic abnormalities are caused by extra members in a chromosome group. Genetic abnormalities are also caused by deleterious or detrimental genes.
Gamete Formation and Fertilization
Chromosomes and also gene numbers change during gamete or sex cell formation. This gametes room the eggs produced by sexually mature gilts or sows and also the sperm cells developed by sexually tires boars. Throughout gamete formation, the chromosome pairs of a cell duplicate, and also then one of the four members the are linked with the duplicated chromosome pairs is randomly moved to among four creating sex cells or gametes (Figure 2). The newly created gamete now contains only one member of every chromosome pair. This splitting of chromosome pairs reasons a random deliver of each member into a creating gamete.
Figure 2. Gamete formation and also fertilization. A and A’ represent 2 chromosomes that have the right to be in a specific pair. B and also B’ represent 2 chromosomes that deserve to be in a various pair. No B nor B’ deserve to be in the very same pair v A or A’. The fertilization of an egg cell by a details sperm cell occurs in ~ random
When the egg and also the sperm unite at fertilization, every carries just one member of each initial chromosome pair. The authorized of a specific egg and also sperm cell occurs at random. After fertilization, the brand-new cell, which develops into the fetus, will have one member every chromosome pair from its sire and the other member indigenous its dam. Thus, the chromosome number is revitalized to its initial value (Figure 2). The resulting offspring will be genetically various from one of two people parent due to the fact that of the union the randomly suitable gametes. Because pigs have 19 chromosome pairs, there space 524,288 (2 to the 19th power) different chromosomal arrangements that can occur during gamete development. With many different genes on every chromosome, the possible number of distinct assortments of genes in creating gametes is infinite. Therefore, the possible number of genetically various pigs deserve to be much bigger than the total number of pigs being elevated on the nation’s farms.
Figure 3. Nonadditive gene activity for one gene pair. R to represent the black color gene and also r represents the red color gene. The boar carries 2 genes that cause black color and is mated come a Duroc female i m sorry carries two genes that cause red color. When the black gene is current with the red gene the black gene will certainly mask the red gene’s expression. Thus, all resulting progeny will be black.
Figure 3 continued. The boar dead one gene that causes black color (R) and also one red color-causing gene (r). The expression the the red gene is suppressed. Once this boar is mated, the is equally likely to pass either an R or an r gene. The Duroc female have the right to only happen an r, for this reason one-half that the resulting progeny will be black and one-half will be red.
Random Segregation and also Genetic Variation
The random move of chromosomes and also their gene to creating gametes is referred to as random segregation. Random segregation is a major cause of genetic differences among related individuals. Distinctions in hereditary makeup are often referred come as genetic variation. Traits reflecting a huge amount of genetic variation have actually a better chance the responding come selection. If a huge amount of hereditary variation is existing in a population, some pets will lug many favorable gene while others will certainly have more undesirable gene for a given trait. If people with favorable genes have the right to be identified, over there is an raised likelihood that those individuals will happen those favorable gene on to your offspring. The details genes that reside in the gene bag that regulate a properties is referred to as the animal’s genotype.
Figure 4. Additive gene action for one gene pair. T to represent a gene with a family member value that 1. T’ represents a gene through a relative value of -1. T and also T’ stand for 2 additive gene that have the right to belong come the very same gene pair.
Nonadditive vs. Additive Gene Action
For a given gene pair, the 2 genes deserve to be alike or different. A homozygous gene pair has actually two the same genes if a heterozygous gene pair has various genes. Gene action can be grouped into two categories, nonadditive and additive.
Nonadditive Gene Action
When nonadditive gene pairs control a trait, the members of the gene pairs will certainly not be same expressed. Because that example, the red-black color condition in pigs is regulated by one gene pair that has nonadditive gene action. If a black boar with two black genes is mated come a Duroc sow v two red genes, the offspring will all be black color (Figure 3a). This is because the black gene which is passed come the offspring native the boar will mask the expression of the red gene the is passed indigenous the sow. The black gene is claimed to be leading to the red gene since it will certainly not permit expression the the red gene. If the black boar had one black and also one red color causing gene (Figure 3b) then the case would be different. Top top the average, fifty percent of the boar’s offspring would obtain his black color gene, if the other fifty percent of the offspring would obtain his red gene. If this heterozygous black color boar is mated come Duroc females, fifty percent of the offspring would certainly be supposed to be black while the other half would it is in red. The red gene is stated to be recessive to the black color gene. Red pigs will occur only when two red genes space in the gene pair managing red-black shade in pigs. The visual characteristic that a properties that deserve to be seen (such as red or black color color) or measure up (e.g., expansion or backfat) is called an animal’s phenotype.
Additive genes are those in i beg your pardon members that a gene pair have actually equal ability to be expressed. Hence the expression that the gene pair is the sum of the individual effects of the gene in the pair. In figure 4, T represents a gene that has actually a loved one value of 1 when T’ to represent a gene which has actually a relative value that -1. An individual v a TT’ genotype would have a genotypic value of 0 (1+(-1)). As soon as a characteristics is regulated by additive genes, its expression is based upon the sum of the effects of the separation, personal, instance genes.
Quality vs. Quantitative Traits
All properties of swine are not managed by simply one gene pair. In fact, very couple of economically essential traits are managed by a solitary or couple of gene pairs. Traits together as period at 230 pounds, litter size, and also average backfat thickness are controlled by possibly hundreds of gene pairs.
Consequently, traits are generally grouped into two categories, qualitative and quantitative.
Qualitative traits have four separating characteristics. This are:Qualitative characteristics are managed by a solitary or a few gene pairs.Phenotypes (the visual characteristics we see), of qualitative traits, have the right to be broken into distinctive categories, in which every member in that group looks the same. For example, the red-black shade condition in pigs is a qualitative trait and also pigs space either red or black.The atmosphere has tiny effect ~ above the expression of the gene pair(s) managing a qualitative trait. In the red-black color example, red pigs would proceed to be red, regardless if castle were raised in environmentally controlled buildings or dust lots.The genotype of an individual for a qualitative trait have the right to be figured out (identifying the genes that occupy the gene pair(s)) through reasonable accuracy.
Quantitative traits space dissimilar in their attributes when compared to qualitative traits. Qualities of quantitative characteristics include:Quantitative properties are managed by probably hundreds or thousands of gene pairs situated on several different chromosome pairs. Part gene pairs will certainly contain additive gene while others can contain nonadditive genes. Most economically important traits are quantitative traits.The setting does affect expression that the gene pairs regulating quantitative traits. If two pigs are comparable genetically, v one increased in a confinement unit and also the other raised in a dust lot, their development performance will most likely be different.Phenotypes the quantitative traits cannot be share into unique categories since they will generally follow a consistent distribution. An example would be average everyday gain. If average day-to-day gain records from weaning to market weight the every pig in a group, to be plotted the point out would kind a continuous line. An exception of this are few of the reproductive traits. For example, litter dimension is a quantitative trait however can be grouped into distinctive groups the 7, 8, etc. The is impossible to accurately determine how many gene pairs are managing a quantitative trait; therefore, an accurate gene type can never be determined.
These components make it complicated to recognize individuals that have actually superior genotypes for quantitative traits.
Environment affects Genotypic Expression
With all traits, the individual’s phenotype is the amount of effects of the genotypic and the ecological effects (phenotype = genotype + environmental effects). Because qualitative traits space usually not influenced by the environment, the phenotype that a qualitative properties is a great indicator the the genotype. Environmental effects do influence the phenotypic expression the a quantitative trait. One individual v an inferior genotype deserve to rank higher phenotypically than people with remarkable genotypes due to the fact that of favorable eco-friendly effects. Therefore it is essential to law all pets the same to reduce eco-friendly effects. Typically an individual’s phenotype, contrasted to the herd average, is a an excellent indicator or estimate of his genotype, or genotypic value.
Since a boar overcome one-half that his chromosomes, and also thus one member of every gene pair, come his offspring, he additionally passes ~ above one-half the his genotypic value to his offspring. An individual’s genotypic worth is often called his breeding value (BV). The estimate of an individual’s genotypic value is his estimated reproduction value (EBV). Ranking individuals by their EBV’s for certain traits is a means of identifying people that room expected to have actually superior genotypes.
Genetic evaluation programs frequently estimate the transmitting capacity of one individual. The estimated transmitting ability is same to one-half of an individual’s estimated reproduction value. The estimate of transmitting ability is the donation that a sire or dam is supposed to make to the genotypic value of their offspring. The Swine Testing and Genetic Evaluation device refers come it as expected Progeny difference (EPD).
Swine producers who extensively understand hereditary principles and also utilize improved hereditary evaluation techniques will be able to improve production efficiency and also lower their manufacturing cost. This will allow them to stay competitive in today’s changing swine industry.
See more: Which Shows That Water Is Entering Cells ? What Shows That Water Is Entering Cells
referral to commodities in this publishing is no intended to be an proof to the exclusion of rather which might be similar. Persons making use of such commodities assume obligation for their use in accordance with existing directions of the manufacturer. The details represented herein is thought to it is in accurate however is in no means guaranteed. The authors, reviewers, and publishers assume no legal responsibility in connection with any use for the products discussed and also make no warranty, to express or implied, in that respect, nor have the right to it it is in assumed that all safety procedures are shown herein or that extr measures may be required. The user therefore, have to assume complete responsibility, both as to persons and as come property, for the use of these products including any kind of which might be spanned by patent. This product may be available in alternative formats.
Information occurred for the Pork info Gateway, a project of the U.S. Pork center of Excellence supported fully by USDA/Agricultural research Service, USDA/Cooperative State Research, Education, and Extension Service, Pork Checkoff, NPPC, state pork associations from Iowa, Kentucky, Missouri, Mississippi, Tennessee, Pennsylvania, and also Utah, and the expansion Services from numerous cooperating Land-Grant Institutions including Iowa State University, north Carolina State University, college of Minnesota, college of Illinois, university of Missouri, university of Nebraska, Purdue University, The Ohio State University, south Dakota State University, Kansas State University, Michigan State University, college of Wisconsin, Texas A & M University, Virginia technology University, college of Tennessee, north Dakota State University, university of Georgia, university of Arkansas, and Colorado State University