Have you ever compared your own face to that of your parents or siblings when you looked in the mirror? Who do you think your face is more similar to? Then, is your skin color the same as your parents or siblings?
When you compare your face with the faces of your parents or siblings. Then it’s likely that you’ll see a lot in common. Why? Because some of the traits that you have are actually inherited from both parents. Therefore, you will have a resemblance to your parents or siblings.
The role of genetic material in the process of inheritance of genetic traits is undeniably one of the most important things. Where the shape of the face, skin color, or maybe the type of disease that a person has doesn’t necessarily just appear in the body. That means, the nature and also the characteristics of a person is an inheritance from their parents which is given through genetic material.
Genetic material that comes from parents will be combined in the fertilization process. From this merger, genetic material will appear characteristics that are almost the same as the father or mother. The molecules that have a role in genetic material are nucleic acids which consist of DNA and also RNA. In a sequence of DNA there is an order that will affect the nature or determine the characteristics of living things which we call genes.
In this article, we will discuss the inheritance of genetic traits which are very important to understand. Let’s see the full explanation below:
What Is Genetic Inheritance?
When learning about the role of genetic material in the inheritance of genetic traits, we will recognize the names of dominant traits and also recessive traits. Dominant traits are traits that stand out and usually overpower other traits. While recessive traits are traits that will be lost or characteristics that will be covered.
Usually, the dominant gene or dominant trait is written in capital letters. While recessive genes or recessive traits will be written in lower case. For example, someone who has a tall body shape will be written with a dominant T. Meanwhile, someone who has a short body shape will be written with a recessive t.
Alternative forms or variations of the gene are called alleles. Traits or characters that can be seen by the eye, such as hair shape, skin color, and also the type of earlobe. Not only that, in the inheritance of genetic traits, we will also be familiar with the terms phenotype and genotype.
Phenotype is the manifestation of gene “expression” or character expression that we can see. Meanwhile, the composition of the genetic information of an individual that codes for physical characteristics is called the genotype. Individual phenotypes can be estimated if we know the respective genotypes. This is because gene expression depends on whether the allele is dominant or recessive.
For example, A represents the genotype of an individual. Therefore, the genotype of these plants will show the yellow seed phenotype.
The constituent chromosomes derived from sex cells will be different from the chromosomes in body cells. In sex cells, chromosomes are haploid or unpaired. While the chromosomes in body cells, the arrangement of chromosomes is called diploid or in pairs. So it can be concluded that sex cells have half the number of chromosomes of the chromosome cells in the body.
The number of chromosomes in the body cells is 23 pairs. This is because the chromosomes in the body are diploid. For this reason, the total number of chromosomes in the body, which is 23 x 2, equals 46 chromosomes. Generally, the writing of chromosomes from the male sex can be written with the letter XY. The karyotype or male chromosome arrangement can be written using the formula 22 AA + XY. Meanwhile, the female chromosome can be denoted by the letter XX. Meanwhile, the karyotype or female chromosome arrangement will be written using the formula 22 AA + XX.
The chromosomal genes in the male genitalia are X and Y. Both of them have an important role in determining the sex of certain egg cells and sperm cells. When the Y gene chromosome in a male body meets the X gene chromosome in a female. Then it will produce offspring or children with male sex or XY.
If the chromosome from the X gene in a boy meets the X gene chromosome in a girl, it will produce a girl or XX. In terms of genetic inheritance, parents are known as parental or P. Meanwhile, the offspring produced in this process are called filial or F.
Gene is the smallest unit of genetic material that has a role in controlling the inheritance of traits. Within a chromosome, a gene or a family of genes resides in a specific location. The location serves as the focus. Because humans have two pairs of chromosomes, therefore, humans also have two pairs of loci for certain types of genes.
Where each gene that occupies a locus is called an allele. In Mendelian genetics, alleles are described as genotypes. This is because the genotype is a trait that is on the chromosome. Genotypes have traits that are hidden or not directly visible. Even though this genotype has properties that are invisible, the genotype will later determine the visible external characteristics of the organism’s body or what is called the phenotype.
The gene itself is the outer part of the DNA or Deoxyribonucleic Acid strand which symbolizes protein or RNA (Ribonucleic Acid). Protein or RNA that will then affect the nature of living things. This process is called gej expression. Then, how can genes affect the nature of living things?
Suppose there is a gene that symbolizes the nature of the eyes in blue. When the gene expression process takes place, DNA will be transcribed into RNA. Then the RNA will be translated into a protein. This protein will eventually be involved in the metabolism that makes the eye color blue.
Kinds of Crosses and Processes
The following are several types of crosses and their processes that must be understood:
1. Monohybrid Cross
Monohybrid cross is a cross made with one distinguishing trait. In this cross, Mendel’s First Law applies, because when the formation of gametes in the second generation, the allele natural genes will experience independent separation in the two gamete cells, the separation of the two genes is not influenced by one another or is independent.
Where monohybrid crosses made with one distinguishing trait can show dominance traits that appear fully or incompletely or intermediately. If one of the alleles has a stronger trait than the other alleles, then the result will also show complete dominance. While in the results of the second intermediate cross, the gene properties have the same strong position.
2. Dihybrid Cross
Dihybrid crosses are generally derived from crosses that have two distinguishing characteristics. Mendel’s second law applies to this crossing process. There will be separation or segregation and merging or assorting freely when forming the second generation. This dihybrid cross will present dominant, intermediate, and recessive traits.
Factors Affecting Phenotype on Inheritance of Traits
Below are several factors that will affect the phenotype in the inheritance of genetic traits, including:
a. Chromosome Characteristics
As previously explained that the chromosome is one of the main components in the process of inheritance. Of course, when crossing is done, the chromosomes will determine what genetic information will be passed on to the offspring. Where the chromosomes in the body or autosomes will inherit the phenotype of the parent. While the sex chromosomes will determine the sex of the offspring.
b. Gene Characteristics
As previously explained that genes are divided into two, some are dominant and some are recessive. The characteristics of the gene will determine the results of crosses and the inheritance of hereditary traits.
In the process of inheritance, nature can also be influenced by nutrients that enter the body of living things. If the elements of the body are met properly, especially with protein, then the inheritance will also work well. For example, in a plant that grows to get good nutrition, the plant will also produce good offspring like its parent. Vice versa.
c. Environmental conditions
Environmental conditions are quite influential on the physiological processes that occur in the body. One of them is the inheritance of traits using crosses. Therefore, good environmental conditions will also have a good effect on the crossing process. For example, in the process of crossing corn plants that grow on land conditions that have lots of pests, of course the success of the crossing will not be maximized.
From the explanation above, we can understand that an offspring will definitely have one or several of the traits possessed by its parent. Because there will be an influence of genetic inheritance. Surely we are no longer surprised, why do we sometimes feel similar to a family member.
Genetic Factors That Bring Heredity
As social beings, we must have heard someone say “it’s from nature” when commenting on someone’s character or behavior. That means, it’s destiny. However, can we review destiny from science? Basically, there are several hereditary factors that can be a destiny for someone to experience the same thing as their parents. Below are some genetic factors that can carry hereditary traits, including:
Perhaps, the children of alcoholics are not targeted to become alcoholics either. However, a recent study revealed that about 50 percent of children of alcoholics are at risk of suffering the same fate as their parents. Meanwhile, the other 50 percent will be determined by the environment. This is because there are a number of parental genes that are passed on to children. This is a kind of dependency gene.
2. Breast Cancer
The cause of this gene inheritance is still a mystery. However, scientists have found that this can happen because there are mutations in a number of genes such as BRCA1 and BRCA2 which trigger it. Women who inherit this gene are at risk of developing breast cancer. Meanwhile, men will experience prostate cancer.
3. Color Blind
As many as 10 million men in the United States cannot tell which color is red and which is green. Visual impairment is indeed more common in men. Why? Because the green and red color receptor genes are located near the chromosomes.
This of course would be very terrible if a father who likes to commit violence also has the potential to pass it on to his child. Boys’ aggressive behavior or traits are generally inherited from their father’s genes. Not only the habit of committing violence, but also antisocial behavior and also likes to steal. Gene likes to steal it works more in girls.
Obesity does not always occur due to the environment. There are lots of cases that have occurred regarding someone who has difficulty holding back his appetite. This is caused by a gene that makes the appetite suppression function not work properly. This gene will usually decrease. So, don’t be surprised if you see a family that has all fat bodies.
6. Heart disease
If you have a family member who suffers from stroke or diabetes, then you can be sure that your offspring will suffer from heart disease. Children who come from parents with heart and circulatory disorders will inherit the same disease. Especially for heart failure patients, they are also at risk of passing the same disease on to their offspring.
7. Twin Brothers
Does anyone have twins? Try to check it into the extended family. Usually twins are triggered by a gene that makes the mother release multiple eggs during evaluation. Twins don’t always pass directly to their children, but can also jump to grandchildren or cousins.
If you have severe acne, then both parents have the same problem. So the condition is rather difficult to cure. A study found that many school-age children who already had acne also had a family history of acne.
9. Don’t Like Milk
There are some people who are not fond of drinking animal milk which contains lactose. Indeed their bodies can not tolerate lactose at all. For babies, it can generally be replaced with soy milk, which has a lower lactose content. Such conditions are also hereditary in family members.
Although baldness is considered normal for men, it turns out that it can be triggered by heredity. There is a gene that is passed down by one parent or maybe both of them cause their offspring to suffer from baldness. There are also those who suffer from permanent baldness, which of course is caused by one type of gene.
11. Sickle Cell Anemia
This one gene abnormality is caused by a gene error which turns out to affect the development of red blood cells. Red blood cells that have the disease have an unnatural shape. So that it can cause blood cells that cannot live as long as other healthy blood cells. Sickle cell anemia can cause a lot of problems, because it allows the blood cells to get stuck in the blood vessels. Children who have this condition from birth may experience anemia, be susceptible to infection, and be sick in several parts of the body. Even so there are also sufferers who only suffer a few symptoms and can live a normal life.