Mendelian & Post-Mendelian Heredity: A Comprehensive Overview

Mendelian Heredity

Gregor Mendel's experiments on pea plants revealed that inheritance is transmitted through heredity, following simple statistical norms.

Mendelian Inheritance

These are the rules governing the transmission of characteristics from one generation to the next.

1st Law (Uniformity)

In the first generation, all offspring are identical if one of the parents is homozygous dominant and the other is homozygous recessive.

2nd Law (Segregation)

Hereditary factors separate during gamete formation, leading to new combinations.

3rd Law (Independent Assortment)

Characters are transmitted independently, as long as the genes are located on different chromosomes.

Post-Mendelian Heredity

Mendel's laws were extended to animals, and it was later discovered that inherited factors are located on chromosomes within cells. In 1916, genes were shown to be on chromosomes. In 1927, treating cells with X-rays caused random mutations. In 1944, Avery demonstrated that DNA carries genetic information.

Molecular Biology

Born in 1953, this field studies life at the molecular level.

Replication

The process of creating two identical DNA copies, using one strand as a template.

Transcription

The creation of mRNA using a DNA strand as a template.

Translation and Genetic Code

mRNA carries instructions to ribosomes, where amino acids are placed to form proteins. There are 20 amino acids and 64 codon combinations. The code is universal. A genome is the total genetic material of an organism.

Genetic Engineering

Techniques that modify DNA.

Recombinant DNA

DNA containing fragments from different sources (using enzymes). There is a risk of cell death. A gene vector is used to carry donor DNA to a recipient.

DNA Amplification

Creating many copies of a DNA fragment. PCR (polymerase chain reaction), developed by Mullis in 1983, is used for DNA amplification.

The Human Genome

On June 26, 2000, the human genome was deciphered. However, much remains unknown about its function and environmental influences. The Human Genome Project began in 1990. 95% of the genome is considered "junk DNA". Humans share genetic similarities with other organisms: 98% with monkeys, 60% with fruit flies.

Biotechnology

The use of living organisms to obtain or modify products.

Medical Biotechnology

• Insulin production using bacteria
• Vaccine development
• Gene therapy

Agricultural Biotechnology

• Disease-resistant plants
• Increased yield
• Improved appearance
• Edible vaccines

Livestock Biotechnology

• Increased production
• Disease resistance
• Increased weight

Bioremediation

Using microorganisms to remove contaminants from soil and water.

Assisted Reproduction

Initially used for infertility, now used for preimplantation genetic diagnosis.

Artificial Insemination

Introduction of semen into the uterus.

In Vitro Fertilization

Sperm and egg are united in a laboratory.

Cloning

Obtaining genetically identical copies. Dolly the sheep was the first cloned mammal (1996).

Problems with Cloning

• Low success rate
• Potential diseases

Stem Cells

Cells that can multiply and develop into specialized cells.

• Embryonic stem cells
• Adult stem cells