Introduction to Genetics

Overview

Lecture by Miss Angler for grade 8 to 12 biology.
Video is an introduction to genetics.
More detailed content available in Grade 12 playlist covering monohybrid and dihybrid crosses, sex-linked disorders.

Found inside the nucleus of cells.
Condenses into chromosomes during cell division (mitosis and meiosis).
Chromosomes:
- Collection of DNA.
- Humans have 46 chromosomes.
- DNA is condensed to form chromosomes.

DNA: Code of life, codes for all proteins in the body.
Genes: Sections of DNA coding for specific characteristics (e.g., height, hair color, blood group).
Characteristics expressed physically by genes.

Gene: Characteristic (e.g., eye color, height, blood group).
Allele: Variation of a gene (e.g., blue or brown eye color).
Homologous chromosomes carry alleles for the same gene.
- Example: Blue eye allele on one chromosome, green on another.

Humans have homologous pairs of chromosomes.
- One from mother (maternal), one from father (paternal).
Each gene has two alleles (one maternal, one paternal).
Alleles passed individually during reproduction (meiosis).

Dominant alleles: Use capital letters (e.g., B).
Recessive alleles: Use lowercase letters (e.g., b).
Allele combinations affect phenotype (physical appearance):
- BB (homozygous dominant): Purple flower.
- Bb (heterozygous): Purple flower (dominant masks recessive).
- bb (homozygous recessive): White flower.

Chromatin Network: Structure containing DNA.
Chromosomes: Carry DNA, visible during cell division.
Genes: Code for specific traits.
Alleles: Variations of genes.
Paternal and Maternal Chromosomes: Inherited from parents, separate during meiosis.
Dominant Alleles: Expressed even if only one copy is present.
Recessive Alleles: Require two copies to be expressed.
Homozygous: Two identical alleles (dominant or recessive).
Heterozygous: One dominant and one recessive allele.