Genetics
Hey, have you ever thought about why you look like your parents? It's because of genes. Gene is the basic unit of heredity. Genes play an important role in the human body. Genetics was discovered by Gregor Mendel. It helps to know the physical information about the traits. Traits mean the features and characteristics that we are gifted by our parents.
Some children have the same eye colour as their parents. While the other children have the same hair colour as their parents. Not even these but the way of smiling, laughing and the way of walking, and the many things that are passed from one generation to another generation. Genes also inherit diseases from their parents. Genes provide the information that decides which features are passed on to you from your parents. In this article, we are going to learn facts about genetics.
Genes and Chromosome
Definition of Genetics
Genetics is a branch of life science that deals with the study of genes, genetic variation and the transmission of the characters from parent to offspring.
Genetics has opened up a new horizon in the field of life sciences research. For centuries, humans were eager to know how characters are transmitted from parents to the offsprings. Genetics has been able to give an answer to it and even in this age of advanced biosciences, where all the mysteries of life are being divulged one by one with the emergence of new branches of science such as bioinformatics, metagenomics, etc, only genetics has the ability to answer how organisms differ from each other and how characters are manifested in them.
Heredity and a Brief History of Genetics
The study of genetics begins with understanding heredity. It is the mechanism by which physical and behavioural traits are transmitted from one generation to another. These traits are nothing but genetic factors. “How these traits are manifested in an organism”, “How are they transmitted through generations”- are some of the questions that genetics attempts to answer quite successfully?
The origin of genetics can be traced back to the development of the theories of evolution by Darwin and Wallace which later on took a definitive turn when Gregor Johan Mendel, a scientist and Augustinian friar working in the 19th century started to study genetics scientifically. Mendel is called the ‘Father of Genetics.’ He selected pea plants, did experiments of monohybrid and dihybrid crosses with those plants, and successfully showed that the characters of pea plants get transmitted from one generation to another. His research was published in a German journal with the headline of "Experiments on Plant Hybrids."
Significance of Genetics:
The significance of genetics in biology and medical science is huge. Following are some of the important points:
1. Genetics helps us to know about genes and their (nucleotide) sequences. It helps us to study the diseases related to a particular gene.
2. It forms the molecular basis of life.
3. In medical science, Genetics is very much important to detect various syndromes and pave a way to the development of the diagnosis for those syndromes.
Some Important Terminologies in Genetics:
The subject of genetics has a lexicon of its own. There are numerous technical terms which one must know to be able to understand the functioning of life. Some of the key terms in genetics are as follows:
Phenotype: The structural, functional and biochemical observable characteristics of an organism is called the phenotype. It is regulated by the interaction between genes and environment.
Genotype: The structural organisation of genes of an organism is called the genotype. Phenotype is always regulated by Genotype.
Allele: The region of the opposite characteristics of the same gene is called Allele.
Gene: Gene is the unit of heredity. It controls all the mechanisms in our body. It transmits from parent to offspring.
Chromosome: In the cell's nucleus, thread-like structures which tightly hold the DNA in them and provide the structural support are called chromosomes.
Genome: The total number of genes in a haploid set of chromosomes of an organism is called Genome.
Homozygosity: This is the condition of having similar alleles in a particular gene.
Monohybrid Cross: It is the cross between two individuals having homozygous genotype.
Heterozygosity: This is the condition of having opposite alleles in a particular gene.
Dihybrid Cross: The cross between two individuals i.e. line of genes that represent heterozygosity in two observable traits.
Linked Genes: The genes which are located in the same chromosome and tend to get transmitted together are called ‘linked genes.’
Dominant: The allele which is expressed in the heterozygous condition is called Dominant.
Recessive: The allele which is not expressed in the heterozygous condition is called Recessive.
Euchromatin: The regions in the less tightly coiled chromosomes containing active DNA molecules are called Euchromatin.
Heterochromatin: The regions in that tightly coiled, inactive DNA is present is called Heterochromatin.
Sister Chromatids: Each of the two identical copies of a replicated chromosome which are linked in centromere are called sister chromatids.
Clone: In genetics, an exact replica or copy of a genetic molecule or organism is called a clone. The first cloned animal is Dolly, a sheep.
Genetic Recombination: It is the exchange of genetic material between different chromosomes of different organisms which results in the production of offsprings having combinations of traits that are different from those of their either parent.
Now that we are acquainted with the basic terminology of genetics let’s a have a look at the experiment that Mendel performed with the pea plants.
Mendel’s Experiment
Mendel took pea plants with seven pairs of opposite characters and crossed them in his garden. The experiments involved monohybrid and dihybrid crosses.
Establishment of Mendel's Laws of Heredity Through the Experiment:
Mendel enunciated the following laws of heredity after concluding the experiments:
1. Principle of Dominance: If there are two conditions of opposite characters present in a chromosome, the gene which is expressed is called dominant and the other is recessive.
2. Law of Segregation: During gametogenesis, the two copies of each hereditary factor segregate so that offspring can get one factor from each parent and the probability of the chance of getting is equal.
3. Law of Independent Assortment: The law of independent assortment describes that the alleles of the different genes are segregated independently within the organisms during sexual reproduction.
Nucleic Acids
Nucleic Acids are central to all known forms of life. They are biopolymers composed of nucleotide monomers. Each nucleotide has three components: a nitrogenous base, a 5-carbon sugar, and a phosphate group. The polymer is RNA or ribonucleic acid if the sugar is a ribose compound; if the sugar is deoxyribose, then the polymer is DNA or deoxyribonucleic acid.
The information encoded in the gene is basically contained in the nucleic acid sequence and conveyed via the same. It is interesting to note that the nucleic acid monomers are arranged in a ‘ladder-step’ pattern within each molecule of DNA or RNA forming a helical backbone. There is single helix in RNA and 2 helices in DNA. The chains of nucleotides have bases (nucleobases) paired with each other. There are five such nucleobases: adenine, guanine, cytosine, and thymine (in DNA) or Uracil (in RNA). The specific sequences of these bases constitute the genes the instructions from which are transferred in coded format to the RNA. From RNA, the genetic instructions are further decoded to form proteins. Before we discuss this two-step method of genetic code transmission, here’s a brief outline of the characteristics of DNA:
1. DNA stands for Deoxyribonucleic Acid. DNA was first discovered by Scientist Watson and Crick.
2. DNA is the genetic material of cells.
3. DNA is self-replicating and the replication occurs in the time of Cell cycle.
4. DNA is a double helix structure with Nucleotides, hydrogen bonds and sugar-phosphate backbones.
5. From DNA, RNA is formed during transcription.
6. The mutation is a phenomenon by which the sequence of DNA structure is changed by the influence of environmental and biochemical factors (mutagen).
Central Dogma
The Central Dogma is a mechanism by which from DNA to DNA, DNA to RNA and RNA to Protein are formed. The process in each step is known as replication, transcription and translation respectively. These three processes are together known as the Central Dogma of Molecular Biology.
DNA Replication:
This is a mechanism by which DNA is formed from a DNA during cell division. It occurs in the nucleus. The main enzyme of DNA replication is DNA polymerase. Besides this many enzymes and proteins are associated with this mechanism.
Transcription:
This is the mechanism by which RNA is formed from DNA, and it occurs in the cytoplasm of a cell.
Translation:
This is the mechanism by which protein is formed from RNA, and after this event, protein is modified and translocate in the different parts of the cell.
Characteristics of Genes
1. Genes are located in chromosomes.
2. Each gene has a fixed place on the chromosome. The position is called a locus.
3. They give instructions to the cells which are known as proteins.
4. They can make a copy of themselves. This process is called repetition.
5. There are about 400000 genes present located on 23 chromosomes.
6. Genes are responsible for the features that are passed on from one generation to the other.
Work of Genes
There are many genes in the human body. Each gene has a different work to do. Gene spells out instructions to the proteins and chromosomes that how they work in the human body. Genes come in pairs. Genes work in the body when they think about anything. They give a message to the brain. For example, if we think about dogs, genes are the ones that make us think about dogs instead of cats.
Interesting Facts About Genetics
There are some facts about genetics that you should know:
1. Genetic material in all human bodies is almost the same. Only 0.1% of genetic material makes them different.
2. Chromosomes are tiny structures inside the gene cells. We get 23 chromosomes from our mother and 23 from our father.
3. Humans share 90% of genetic material from mice and 98% from chimpanzees.
4. Octopuses can edit their genes.
5. Genes are tiny so we can see them.
6. Genes can’t tell how smart you are.
7. Twins share the same genetic code.
8. The work of genes is to store information.
Things you Should Know
There are some important things about genetics that we should know:
1. Any diseases in one generation can pass on to the next generation by genes in different ways.
2. By collecting the history of genes and family health history, you can know about the health problems that may occur in the future and reduce the risk to take precautions.
3. There are many different tests available for gene-disease.
4. The only small proportion of genes that is different helps a human to be unique.
Summary
In this chapter, we learn about the basics of genetics for kids and important things about genetics. Genetics is the branch of biology that deals with the study of heredity and variation. Genes are the unit of heredity. Genes are made up of DNA. DNA is Deoxyribonucleic acid. Without DNA characters can not be transferred from one generation to the other. Genes are present inside chromosomes. Chromosomes are long DNA molecules that are present inside the nucleus of a cell. Chromosomes are made up of proteins. There are 23 pairs of chromosomes in the human body. 1 pair is the sex chromosome that decides the sex of humans. XX is for girls and XY is for boys. Hope this article will give you lots of knowledge about genetics.
FAQs on Some Interesting Facts About Genetics
1. What is the difference between a gene, DNA, and a chromosome?
These three terms are closely related but distinct levels of genetic organisation. A gene is a specific segment of a DNA molecule that contains the instructions for building a particular protein or functional RNA molecule. DNA (Deoxyribonucleic acid) is the long, complex molecule that contains all the genetic instructions for an organism. Finally, a chromosome is a highly organised structure made of a single DNA molecule tightly coiled around proteins. You can think of it as a library (chromosome) containing many books (genes), with the text in the books written in the language of DNA.
2. What is the Central Dogma of Molecular Biology?
The Central Dogma describes the two-step process of how genetic information flows within a biological system. It states that information is transferred from DNA to RNA, and then from RNA to protein. The key processes involved are:
- Replication: DNA makes a copy of itself.
- Transcription: A segment of DNA is used as a template to create an RNA molecule.
- Translation: The RNA molecule's code is read to build a specific protein.
3. What are some surprising facts about human genetics?
Genetics is full of fascinating details that highlight our shared biology and unique individuality. Here are a few interesting facts:
- Human Similarity: The DNA of any two humans on Earth is about 99.9% identical. The tiny 0.1% difference accounts for all the variations we see in appearance, disease susceptibility, and other traits.
- Shared Ancestry: Humans share approximately 98% of their DNA with chimpanzees and about 90% with mice, demonstrating our common evolutionary roots.
- Parental Contribution: Every child inherits exactly 23 chromosomes from their mother and 23 from their father, resulting in a total of 46 chromosomes in most body cells.
4. What is DNA fingerprinting and what is its main application?
DNA fingerprinting, also known as DNA profiling, is a laboratory technique used to identify individuals based on their unique DNA sequences. As every person's DNA is unique (except for identical twins), this method can create a distinctive profile. Its most significant application is in forensic science, where it is used to link suspects to crime scenes by comparing DNA evidence (like hair or blood) with the DNA of individuals. It is also used in paternity testing and identifying hereditary diseases.
5. Is there a difference between genetics and heredity?
Yes, while the terms are often used interchangeably, they have distinct meanings. Heredity refers specifically to the process of passing traits from parents to their offspring. It is the phenomenon of inheritance. Genetics is the broader scientific study of heredity and the variation of inherited characteristics. It includes the study of genes, genetic variation, how traits are passed down, and how they are expressed, making heredity a core concept within the field of genetics.
6. Why is some of our DNA called 'junk DNA', and is it really junk?
The term 'junk DNA' was historically used to describe the large portions of the genome (up to 98%) that do not code for proteins. For a long time, their function was unknown. However, this term is now considered outdated and misleading. Modern research has revealed that much of this non-coding DNA plays crucial roles in regulating gene activity. It acts like a switchboard, controlling when and where genes are turned on or off, which is essential for normal development and cellular function. Therefore, it is not 'junk' but rather a vital part of our genetic instruction manual.
7. If identical twins share the exact same DNA, how can they have different traits?
This is an excellent question that highlights the difference between genotype (the genetic code) and phenotype (the observable traits). While identical twins start with the same genotype, their phenotype can differ due to environmental factors and a process called epigenetics. Epigenetic changes are modifications that don't alter the DNA sequence itself but affect how genes are expressed. Factors like diet, lifestyle, and exposure to different environments can cause these epigenetic markers to change over time, leading to subtle differences in health, personality, and appearance between the twins.
8. What is the difference between dominant and recessive alleles?
Alleles are different versions of the same gene. In diploid organisms like humans, you inherit one allele from each parent for a particular gene. The difference is in how they are expressed:
- A dominant allele will express its trait even if only one copy is present. For example, the allele for brown eyes is dominant.
- A recessive allele will only express its trait if two copies are present (one from each parent). The allele for blue eyes is recessive.
