Grade 11 Biology Notes: Genetics Unit
What is Genetics?
• Genetics is the study of how traits are passed from parents to offspring through genes.
• Genes are sections of DNA that contain instructions for making proteins, which
determine traits like eye color, height, or blood type.
• DNA is stored in the nucleus of cells, packaged into structures called chromosomes.
Humans have 23 pairs (46 total) of chromosomes.
Key Terms:
1. DNA (Deoxyribonucleic Acid): The molecule that carries genetic information.
2. Gene: A segment of DNA that codes for a specific protein or trait.
3. Chromosome: A thread-like structure made of DNA and protein; humans inherit 23 from
each parent.
4. Allele: Different versions of a gene. For example, the gene for eye color might have
alleles for blue or brown eyes.
5. Genotype: The genetic makeup of an organism (e.g., BB, Bb, or bb).
6. Phenotype: The physical expression of a trait (e.g., brown eyes).
7. Homozygous: Having two identical alleles for a gene (e.g., BB or bb).
8. Heterozygous: Having two different alleles for a gene (e.g., Bb).
9. Dominant Allele: The allele that masks the effect of a recessive allele (e.g., B for brown
eyes).
10. Recessive Allele: An allele that is masked by a dominant allele (e.g., b for blue eyes).
Mendelian Genetics
• Gregor Mendel is known as the "Father of Genetics." He discovered the basic principles
of inheritance by studying pea plants.
• Mendel’s Laws:
o Law of Segregation: Each parent passes only one allele for each gene to their
offspring.
o Law of Independent Assortment: Genes for different traits are inherited
independently of each other.
Punnett Squares
• A tool to predict the probability of offspring inheriting certain traits.
• Example: If one parent is heterozygous for brown eyes (Bb) and the other is homozygous
recessive for blue eyes (bb):
What is Genetics?
• Genetics is the study of how traits are passed from parents to offspring through genes.
• Genes are sections of DNA that contain instructions for making proteins, which
determine traits like eye color, height, or blood type.
• DNA is stored in the nucleus of cells, packaged into structures called chromosomes.
Humans have 23 pairs (46 total) of chromosomes.
Key Terms:
1. DNA (Deoxyribonucleic Acid): The molecule that carries genetic information.
2. Gene: A segment of DNA that codes for a specific protein or trait.
3. Chromosome: A thread-like structure made of DNA and protein; humans inherit 23 from
each parent.
4. Allele: Different versions of a gene. For example, the gene for eye color might have
alleles for blue or brown eyes.
5. Genotype: The genetic makeup of an organism (e.g., BB, Bb, or bb).
6. Phenotype: The physical expression of a trait (e.g., brown eyes).
7. Homozygous: Having two identical alleles for a gene (e.g., BB or bb).
8. Heterozygous: Having two different alleles for a gene (e.g., Bb).
9. Dominant Allele: The allele that masks the effect of a recessive allele (e.g., B for brown
eyes).
10. Recessive Allele: An allele that is masked by a dominant allele (e.g., b for blue eyes).
Mendelian Genetics
• Gregor Mendel is known as the "Father of Genetics." He discovered the basic principles
of inheritance by studying pea plants.
• Mendel’s Laws:
o Law of Segregation: Each parent passes only one allele for each gene to their
offspring.
o Law of Independent Assortment: Genes for different traits are inherited
independently of each other.
Punnett Squares
• A tool to predict the probability of offspring inheriting certain traits.
• Example: If one parent is heterozygous for brown eyes (Bb) and the other is homozygous
recessive for blue eyes (bb):
