GENETICS
1. Introduction to Genetics :
Genetics forms a crucial part of biology. It studies genes, gene changes, and how
traits are inherited in living things. The word refers to the way characteristics transfer from
parents to offspring. It also explores differences among individuals.
2. Understanding Traits :
A trait is a clear physical feature or quality found in a living thing. Examples include
height, eye color, skin tone, or hair shade. For instance, a girl with dark hair, tan skin, and a
small build shows traits. Traits are the visible characteristics you can observe.
3. Structure of a Cell :
Cells make up the basic building blocks of life. They handle the smallest tasks and
shapes in organisms. At the center sits the nucleus. Chromosomes live inside it. These hold
the genes that guide life and pass on features.
4. Chromosomes and DNA :
DNA stands for deoxyribonucleic acid. It's a twisted, double strand that holds all
genetic details. This molecule stretches out so far it won't squeeze into the small nucleus
alone. It coils tight around proteins to pack in. That bundle turns into a chromosome.
Chromosomes pack DNA and proteins to fit snugly in the nucleus.
5. Genes and Their Function :
Genes are set pieces of DNA. They guide the making of proteins that shape certain
traits. DNA has spots that don't build proteins. Only gene sections do that work. One gene
might set height through a protein. Another could handle hair color.
6. Homologous Chromosomes and Alleles :
People carry 23 pairs of chromosomes. Half come from mom, half from dad. Each
pair matches in length, form, and gene spots. They are homologous chromosomes. The same
gene sits at the same spot on each. But the gene can have different versions, called alleles.
An allele is a version of a gene. Each gene pair can have two alleles. Each allele
gives instructions for a trait. For example, one allele might say to grow tall. The other allele
might say to grow short.
7. Locus (Location of a Gene) :
A locus marks the exact spot of a gene on a chromosome. Take the height gene. If it
sits at one place on both matching chromosomes, that spot is its locus.
8. Dominant and Recessive Alleles :
A dominant allele uses a big letter, like T. It shows its trait with just one copy. A
recessive allele uses a small letter, like t. It only shows when both copies match as recessive.
9. Types of Genetic Combinations :
a. Heterozygous :
Heterozygous means one dominant allele and one recessive, like Tt. The strong
one hides the weak. So the look, or phenotype, shows the dominant side.
A tall plant is an example.
b. Homozygous :
Dominant Both alleles dominant, like TT, means homozygous dominant. The look
stays dominant. Think tall plant again.
1. Introduction to Genetics :
Genetics forms a crucial part of biology. It studies genes, gene changes, and how
traits are inherited in living things. The word refers to the way characteristics transfer from
parents to offspring. It also explores differences among individuals.
2. Understanding Traits :
A trait is a clear physical feature or quality found in a living thing. Examples include
height, eye color, skin tone, or hair shade. For instance, a girl with dark hair, tan skin, and a
small build shows traits. Traits are the visible characteristics you can observe.
3. Structure of a Cell :
Cells make up the basic building blocks of life. They handle the smallest tasks and
shapes in organisms. At the center sits the nucleus. Chromosomes live inside it. These hold
the genes that guide life and pass on features.
4. Chromosomes and DNA :
DNA stands for deoxyribonucleic acid. It's a twisted, double strand that holds all
genetic details. This molecule stretches out so far it won't squeeze into the small nucleus
alone. It coils tight around proteins to pack in. That bundle turns into a chromosome.
Chromosomes pack DNA and proteins to fit snugly in the nucleus.
5. Genes and Their Function :
Genes are set pieces of DNA. They guide the making of proteins that shape certain
traits. DNA has spots that don't build proteins. Only gene sections do that work. One gene
might set height through a protein. Another could handle hair color.
6. Homologous Chromosomes and Alleles :
People carry 23 pairs of chromosomes. Half come from mom, half from dad. Each
pair matches in length, form, and gene spots. They are homologous chromosomes. The same
gene sits at the same spot on each. But the gene can have different versions, called alleles.
An allele is a version of a gene. Each gene pair can have two alleles. Each allele
gives instructions for a trait. For example, one allele might say to grow tall. The other allele
might say to grow short.
7. Locus (Location of a Gene) :
A locus marks the exact spot of a gene on a chromosome. Take the height gene. If it
sits at one place on both matching chromosomes, that spot is its locus.
8. Dominant and Recessive Alleles :
A dominant allele uses a big letter, like T. It shows its trait with just one copy. A
recessive allele uses a small letter, like t. It only shows when both copies match as recessive.
9. Types of Genetic Combinations :
a. Heterozygous :
Heterozygous means one dominant allele and one recessive, like Tt. The strong
one hides the weak. So the look, or phenotype, shows the dominant side.
A tall plant is an example.
b. Homozygous :
Dominant Both alleles dominant, like TT, means homozygous dominant. The look
stays dominant. Think tall plant again.
