ES🧬Genetics is the science that studies how living things inherit characteristics from one generation to the next. While this topic may seem complicated at first, it is actually fascinating and essential to understanding how we function as living things! 😊 Today we are going to talk about genes, alleles, dominance and recessivity . These concepts are the basis for understanding Mendel’s laws, which we will explore later. 👩🔬
🌿 What are genes? 🔍
Genes are small units of information contained in our DNA. They act as instructions that determine how we are, from the color of our eyes to our height and predisposition to certain diseases. Each gene is made up of a sequence of nitrogenous bases (A, T, C and G) and are found in chromosomes, inside the nucleus of our cells.
- Each chromosome contains thousands of genes. 🤯
- The thousands of genes that every living thing has determine everything from eye color to the ability to metabolize food.
💡 Fun fact:
The human body has 23 pairs of chromosomes in its cells, one of each pair we inherit from our mother and the other from our father! That’s why we share characteristics with our relatives. 👨👩👧👦
🤯 Did you know…?
- Your height, hair color and many other traits depend on how your parents’ genes combine. 🧑🤝🧑
- Humans have approximately 20,000 genes.
- There are dominant and recessive genes, which explains why some traits are more common than others.
❓What do you think?
- If you could modify one gene in your DNA, what would it be and why?
- Do you think gene editing should be regulated?
History of the discovery of genes ⏳
Although Gregor Mendel did not know about DNA, his experiments with peas laid the foundation for modern genetics. Later, in 1902, scientist Walter Sutton proposed the Chromosomal Theory of Inheritance, confirming that genes are in chromosomes. We will learn more about this in a future lesson.
In 1953, James Watson and Francis Crick described the famous double helix structure of DNA, which revolutionized science. Since then, genetics has not stopped advancing!
How do genes work? 🎮
Genes contain instructions for making proteins, which are the “building blocks” of our body. Each cell uses the instructions from genes to make the proteins it needs.
Types of genes:
- Structural genes: determine physical characteristics such as eye color or nose shape.
- Regulatory genes: Control when and where other genes are activated.
- Resistance genes: Help us fight disease.
🌟 What are alleles? 🧬
Alleles are different versions of the same gene. That is, within the same gene, there can be variants that cause different characteristics. Each gene has two alleles: one from the mother and one from the father. 🍼
- Dominant alleles: These are the alleles that are expressed (manifest themselves) when present, even if there is only one.
- Recessive alleles: are the alleles that are only expressed when both alleles (the one from the mother and the one from the father) are recessive.
Example:
Imagine that the gene that controls eye color has two alleles:
- Brown allele (B) – Dominant.
- Blue allele (b) – Recessive.
If a child inherits a B (brown) allele from his mother and a b (blue) allele from his father, he will have brown eyes, because the B (brown) allele is dominant.
⚡ Dominance and recessivity: how do they work? 🏆
Dominance and recessivity are key principles in genetics. They determine how alleles interact to influence the observable characteristics of an organism.
🧐 Dominance:
A dominant allele is an allele that is expressed in the organism’s characteristic, even when it is only present on one of the chromosomes. The dominant allele masks the recessive allele.
Example:
The allele for brown eyes (B) is dominant over the allele for blue eyes (b). If a person has one B allele and one b allele (Bb), his eye color will be brown because B is dominant. 🌰👀
🔄 Recessivity:
A recessive allele is only expressed when both alleles on an organism’s chromosomes are recessive. If the allele is recessive, it needs to be present on both chromosomes for the trait associated with it to be expressed.
Example:
If a person has two alleles for blue eyes (bb), then they will have blue eyes, because both alleles are recessive. 💧👀
💡 Questions for you 🤔
- What would happen if a dominant allele did not mask a recessive allele?
- How do you think dominance and recessivity affect offspring of parents with different traits?
- Think of a trait in your family – do you think that trait is due to a dominant or recessive allele?
🧬 Combination of alleles: genotypes and phenotypes 🔬
When we talk about genetics, it is important to understand two concepts: genotype and phenotype. Both are essential to understand how traits are inherited.
🧑🔬 Genotype:
It is the genetic combination that an organism has. It is formed by the alleles that it has in its chromosomes. It can be represented by letters:
- BB (two dominant alleles).
- Bb (one dominant and one recessive allele).
- bb (two recessive alleles).
🌻 Phenotype:
The observable characteristic of an organism. It is what you can see or measure. For example, eye color or height. The phenotype depends on both genotype and environmental factors.
💡 Example of genotype and phenotype 🧑🤝🧑
Trait: Eye color
Possible genotype:
- BB = Brown eyes (phenotype).
- Bb = Brown eyes (phenotype, because B is dominant).
- bb = Blue eyes (phenotype).
Remember: Dominant alleles are always exhibited over recessive alleles.
Explore more
🖌️ Creative Projects
- Create a diagram 🖍️
- Design a visual diagram that shows how alleles combine in offspring. You can use different colors or pictures to represent dominant and recessive alleles.
- Interactive presentation 🎥
- Record a video where you explain how dominance and recessivity work with real examples from your family or animals (such as eye color, flowers, or a pet’s fur).
- Mind Map 🧠
- Design a mind map to illustrate the concepts of genes, alleles, dominance, and recessivity. Be sure to connect all the terms in a clear way.
🔄 Your turn: Final reflection
How would you apply genetics concepts in real life?
Imagine you are a doctor who has to advise a family about the risks of inheriting a genetic disease. How would you use the concepts of dominance and recessivity to explain the risks of transmission?
🌱 Conclusion
Genes and alleles are essential to understanding how we inherit our characteristics. Through dominance and recessivity, we can predict how certain traits will be expressed in our offspring. Now that you know these basic concepts, you’re ready to delve deeper into Mendel’s laws and understand how these principles apply in biology! 🔬🧬
