S9Q1W4-5 | Non-Mendelian Inheritance

Summary

This video lesson for grade nine science focuses on non-Mendelian inheritance, exploring genetic variations beyond traditional Mendelian patterns. It defines key terms like genetics, inheritance, gene, genotype, and phenotype, and differentiates between them. The lesson delves into non-Mendelian inheritance types: incomplete dominance, co-dominance, and multiple alleles, using examples like flower colors and blood types. It also covers sex-linked inheritance, explaining how traits like baldness are passed down through X chromosomes. The use of Punnett squares to predict genetic outcomes is highlighted, with activities to engage students in applying these concepts.

Takeaways

• 🌟 Genetics is a 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, which is the combination of two alleles.
• 🌻 Phenotype is the physical appearance or trait of an organism, such as the color of a flower.
• 🎯 Homozygous means having two identical alleles, while heterozygous means having two different alleles.
• 📊 Punnett Square is a tool used to predict the genotypes of offspring from a particular cross or breeding event.
• 👨‍🔬 Gregor Mendel is known as the father of genetics for his foundational work on inheritance patterns.
• 🚫 Non-Mendelian inheritance occurs when genetic patterns do not follow Mendel's laws.
• 🌹 Incomplete dominance is a type of inheritance where one allele does not completely dominate another, resulting in a new phenotype.
• 🤝 Co-dominance is a type of inheritance where both alleles are expressed equally in the phenotype of the heterozygote.

Q & A

What is the focus of the lesson for grade nine science in week four to five?

The focus of the lesson is to describe the location of genes in chromosomes and explain different patterns of non-Mendelian inheritance.

What is genetics and how does it relate to the study of inheritance?

Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms. It relates to the study of inheritance as it deals with how genetic information is passed on from parents to offspring.

What is the difference between genotype and phenotype as explained in the lesson?

Genotype refers to the genetic makeup of an organism, which is the combination of two alleles. Phenotype, on the other hand, is the physical appearance or trait of an organism, which is the expression of the genotype.

Can you explain the concept of homozygous and heterozygous in the context of genetics?

Homozygous refers to having two identical alleles for a particular gene, while heterozygous means having two different alleles for that gene.

What is a Punnett square and how is it used in genetics?

A Punnett square is a graphical representation used to predict the possible genotypes of offspring from a particular cross or breeding event. It helps visualize the combination of alleles from each parent.

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

Gregor Mendel is considered the father of genetics. He began a decade-long research project to investigate patterns of inheritance, studying the inheritance of seven different traits in pea plants, and his principles form the basis for understanding heredity and variation.

What is non-Mendelian inheritance and how does it differ from Mendelian inheritance?

Non-Mendelian inheritance refers to patterns of inheritance where the traits do not follow Mendel's laws. This can occur in cases such as incomplete dominance, co-dominance, and multiple alleles, where the expression of traits is not simply dominant or recessive.

What is incomplete dominance and how is it demonstrated in the lesson?

Incomplete dominance is a form of inheritance where one allele does not completely dominate another, resulting in a new or third phenotype. In the lesson, this is demonstrated by crossing red and white snapdragon flowers, resulting in pink flowers.

What is co-dominance and how is it different from incomplete dominance?

Co-dominance is a type of inheritance where both alleles are expressed equally in the phenotype of the heterozygote. It is different from incomplete dominance in that both traits are visible in the offspring, rather than a blend of the two.

What are multiple alleles and provide an example from the lesson?

Multiple alleles occur when a gene is controlled by more than two alleles. An example from the lesson is blood types, where there are four possible blood types (A, B, AB, and O), each controlled by different combinations of alleles.

How is sex determination and inheritance explained in the lesson?

Sex determination and inheritance are explained through the understanding that humans have 23 pairs of chromosomes, with the 23rd pair being sex chromosomes. Males have XY and females have XX chromosomes. The sex of a child is determined by the chromosome contributed by the father's sperm (X for female, Y for male).

What are sex-linked traits and how do they differ from other types of inheritance?

Sex-linked traits are inherited through the X chromosomes and are more common in males because they have only one X chromosome. Females have two X chromosomes, so they can be carriers without expressing the trait. This differs from autosomal inheritance, where traits are inherited through any of the non-sex chromosomes.