Non-Mendelian Inheritance | Grade 9 Science Quarter 1 Week 4-5 | Maestrang Techy

Summary

This educational video lesson for grade nine science students delves into the complexities of non-Mendelian inheritance. It revisits basic concepts like genetics, inheritance, and genes before introducing three types of non-Mendelian inheritance: incomplete dominance, co-dominance, and multiple alleles. The lesson uses examples and Punnett squares to illustrate these concepts, including blood types and sex-linked traits like pattern baldness. It aims to clarify the inheritance patterns that deviate from Mendel's laws, enhancing students' understanding of genetic variations.

Takeaways

• 🌟 Genetics is the branch of biology that studies genes, genetic variation, and heredity in organisms.
• 🔬 Inheritance is the process by which genetic information is passed from parents to offspring.
• 🧬 A gene is a unit of heredity, a section of DNA that codes for a specific trait.
• 🌱 Genotype refers to the genetic makeup of an organism, the combination of two alleles, while phenotype is the physical appearance or trait.
• 🌺 An example of genotype and phenotype differentiation is the four o'clock flower with genotypes fr fr and fw fwfw resulting in red and white flowers respectively.
• 🎲 Homozygous means having two identical alleles, whereas heterozygous means having two different alleles.
• 📊 Punnett square is a graphical representation used to predict the genotypes of offspring from a particular cross.
• 👨‍🔬 Gregor Mendel, known as the father of genetics, laid the foundation for understanding heredity and variation through his study of pea plants.
• 🚫 Non-Mendelian inheritance occurs when the patterns of inheritance do not align with Mendel's laws, such as incomplete dominance and codominance.
• 🌹 Incomplete dominance results in a new phenotype when one allele does not completely dominate another, exemplified by the pink snapdragon flower from a cross between red and white flowers.
• 🔴 Codominance is when both alleles are expressed equally in the phenotype of the heterozygote, like the red and white flower resulting from a cross between red and white flowers.
• 🔑 Multiple alleles refer to genes controlled by more than two alleles, such as the ABO blood type system with four possible blood types.

Q & A

What is the main topic of the video lesson?

The main topic of the video lesson is non-Mendelian inheritance in grade nine science, specifically focusing on the patterns of inheritance that do not follow Mendel's laws.

What is genetics according to the video?

Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.

What is the difference between genotype and phenotype?

Genotype refers to the genetic makeup of an organism, which is the combination of two alleles, while phenotype is the physical appearance or trait of an organism.

What is incomplete dominance in genetics?

Incomplete dominance is a form of inheritance where one allele does not completely dominate another, resulting in a new or third phenotype, such as a pink snapdragon flower from a cross between a red and a white flower.

How is a Punnett square used in the context of the video?

A Punnett square is used as a graphical representation to determine the possible genotypes of offspring from a particular cross or breeding event, as demonstrated with the red and white snapdragon flowers.

Who is Gregor Mendel and why is he significant in the study of genetics?

Gregor Mendel is known as the father of genetics; he conducted a decade-long research project investigating patterns of inheritance, studying seven different features in peas, and his principles form the basis for understanding heredity and variation.

What is co-dominance in non-Mendelian inheritance?

Co-dominance is a type of inheritance where both alleles are expressed equally in the phenotype of the heterozygote, such as a red and white flower resulting in a red and white flower offspring.

What are multiple alleles and how do they differ from typical Mendelian inheritance?

Multiple alleles are a gene that is controlled by more than two alleles. This differs from typical Mendelian inheritance, which usually involves only two alleles, and is exemplified by blood types with more than two variants.

How do sex chromosomes determine the sex of a human baby?

The sex of a human baby is determined by the father's sperm. If it carries a Y chromosome, the baby will be male (XY), and if it carries an X chromosome, the baby will be female (XX).

What are the three types of sex-related inheritance mentioned in the video?

The three types of sex-related inheritance are sex-linked traits (inherited through X-chromosomes), sex-influenced traits (phenotypes different between males and females with the same genotype), and sex-limited traits (expressed in one sex only).

How can a couple with blood type A have a baby with blood type B, according to the video?

If both parents have blood type A, they could potentially have a baby with blood type B if at least one of the parents is a carrier of the allele for blood type B (heterozygous), which is a part of the multiple alleles concept.