What are homozygous and heterozygous organisms in biology: definition, properties, differences

The study of genetic heredity, patterns and variability of organisms, refers to science called - genetics. The discoverer in the field of genetic research was Gregor Johann Mendel, Austrian botanist and biologist.

He noticed a hereditary pattern, between offspring and parental individuals - signs of monogenic inheritance. In the future, this discovery acquired the name "The Law of Mendel", and laid the foundations for the development of genetics.

What is a homozygous organism in biology: definition, properties

• Homozygous -such organisms are called that contain alleles consisting exclusively of regressive or dominant genes. Chromosomes in homozygous organisms have the same alleles, symbolically designated: aa, aa.
• This type of genes encodes the same type in a homozygous body. For example, the color of the petals from a certain variety of flower - will receive all its further offspring, while preserving phenotypic phenomena and the genotype of this plant.

Homozygous organisms have the following properties:

1. At the time of the connection of such organisms, the separation of offspring is not traced by a certain basis.
2. Form according to the selected gene, the same type of gametes.

What is a heterozygous organism in biology: definition, properties

• Heterozygous -the body is considered in which alleles encoding various signs contain two types of genes: a regressive and dominant gene. It has a symbolic image: AA or BB.
• In heterozygous life forms, the phenotype is the same due to the dominant genome. For example: A - dark hair, a - blond hair, offspring with the genotype Aa - will be dark -haired. In this example, Allele And it is - dominant, and - a recessive allele.

The properties of heterozygous organisms include:

1. Separation and redistribution of signs of alleles, according to the indicated numerical ratio in hereditary heterozygous individuals, according to the basis of the genotype, is a ratio of 1: 2: 1, and on the grounds of a phenotype - 3: 1.
2. The development of two types of gametes.

What are dominant and recessive genes?

Any cellular organism consists of a certain set of chromosomes, including a paired number of chromatids divided into genes.

• Allel genes - These are the same type of genes with different forms, placed in the same chromosome. These genes are formed from a couple, paternal and maternal allele. In turn, the alleles are divided into a recessive and dominant form. The main sign that will manifest itself in the phenotype determines the dominant allele.
• Recessive allele - Performs secondary hereditary signs and is not fundamental. The dominant gene always limits the manifestation of a recessive gene. However, if there is a pair of recessive species in one locus of homologous chromosomes, this can affect and introduce a sign or defect belonging to this gene into the body.
• Schematically, alleles are depicted in the form of Latin letters. Each type of allele has its own graphic spelling: dominant alleles are indicated in capital letters: AA, VV, Recessive are noted in small letters: aA, BB.

The dominant signs of a person include:

1. Cunted hair, dark hair color, male baldness, sections of hair with a lack of pigmentation.
2. Eyes: square-green, brown or green.
3. Leather With normal pigmentation.
4. Defects: excess fingers on the upper or lower extremities, fusion or absence of several phalanges of the fingers, dwarfism with shortened limbs.
5. Lack of reaction to Sumakh poison.
6. Good blood coagulation, positive Rhesus, 2 and 3 blood type.

Recessive signs are considered:

1. Hair: light and red, straight, female baldness.
2. Gray or blue eyes.
3. Albinism or weak skin pigmentation.
4. Good the structure of the fingers.
5. A positive reaction to Sumaha's poison, dumbness and absence of hearing, chicken blindness, color anomaly, 1 blood type and hemophilia, a negative Rh factor of blood.

How to find out a heterozygous or homozygous body?

• Determine the genetic type of body, you can compatibility of alleles in pairs. If in a pair of alleles, both have the same look Aa and oo, then this organism of the homozygous genotype.
• With a different selection of AO alleles, the body is a heterozygous genotype. It has also been established that homozygous species Aa and oo Provide the 2nd and 1st blood group. And for the heterozygous genotype of AO, 2 blood groups on a dominant feature will be characteristic.
• Gene about - Performs the properties of a recessive sign. From this it follows that the dominant gene is able to prove itself in both cases: heterozygous and recessive condition.

• Recessive genes They stand out only in homozygous form, with a heterozygous state are absent. In practice, to determine the heterozygous and homozygous organism, the method of analyzing crossing individuals is used. It consists in the dominant genotype, cross with a homozygous genotype on a recessive feature.
• Lack of splitting in offspring - tells about the dominant form of an individual. Otherwise, splitting in proportions of 1: 1 indicates a heterozygous sign of the body.

What is incomplete homozygot: codomineanism and incomplete dominance?

• There are such alleleswhere dominant signs are not fully manifested. Such changes are commonly called cominant features. They combine both parental signs. When crossing inflorescences of different color, you can get a mixed type - this will be a manifestation of the effect copermine signs.
• The scientist Mendel in his experiments found that sometimes offspring has intermediate characteristicsinherent in hybrids. Such individuals do not have pronounced dominant and recessive features. This phenomenon is also known as incomplete dominance.

• This type of heredity is determined by the fact that in it dominant gene It does not have such an aggressive effect on the recessive gene, its secondary properties, not completely depressed.

Homozigot formula - heterozygous and homozygous genotype: Examples

• The formula of diploid cells of the body with a homozygous feature according to alleles A and A is schematically prescribed as follows: Aa and aa. In a trilogoid organism, this formula looks like this: AAA and AAA.
• For example, AA, SS, AAVV - values \u200b\u200bbelonging to homozygous individuals. Organisms with a genetic formula AAVB and AAVV - heterozygous individuals.

What does the predominance of homozygous individuals lead to?

• Crossing a pair of homozygous organisms that have a difference in several alternative signs leads to inheritance of genes And all kinds of options are formed, regardless of the combination - like mono -hybrid crossing.
• The predominance of phenotype and all signs is given to the offspring in the first generation. The next generation will have a split in the ratio 9:3:3:1.

What is the difference between heterozygous organisms and homozygous organisms?

The table provided shows the comparative characteristics of two body genotypes. The specified information allows you to give a brief analysis for each individual genotype and compare their differences among themselves.

• Methodology crossing homozygous and heterozygous organisms Promotes the removal and development of new signs of individuals. Selection and hybridization help to increase the resistance of organisms to a number of possible diseases.
• They enhance resistance when exposed to negative factors of the surrounding sphere on the body, increase life expectancy and the ability to adapt in the new habitat.
• Organisms with new genetic characteristics give high -quality offspring.
• Thanks to genetic crossing, many varieties of living cultures in the plant and livestock sphere have appeared.

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