Unit 2.1: BASIC PRINCIPLES OF HUMAN GENETICS

OVERVIEW OF THE CELLULAR BASIS OF LIFE Is the building blocks of life 50 to 100 Trillion About 2.5 billion at hand 200 types Each type has different functions

CELL THEORY A cell is the basic structural and functional unit of living organisms. The activity of an organism depends on the collective activities of its cells. Continuity of life has a cellular basis

What is DNA? BACKGROUND INFO SLIDE – What is DNA? DNA is a long molecule that encodes our genetic instructions. (Our bodies are made up of around 50 trillion (50 x 1012) cells. Most of these cells contain a person’s genetic information within a long molecule called DNA (deoxyribonucleic acid). This DNA contains the genetic information that we inherit from our parents). DNA has a distinctive helical shape, like a twisted ladder. Two strands of DNA are twisted together into the double helix shape. (Our DNA is made up of specific sequences of letters or bases that encode instructions on how to make proteins. These bases [Adenine (A), Guanine (G), Cytosine (C) and, Thymine (T)] are lined up along two strands of DNA). The rungs of the ladder are called base pairs. The order of these bases make up the genetic instructions for making molecules in the body. These base pairs can break, allowing the sides of the helix to unravel. This special property is what allows DNA to copy itself, and to act as the instructions.

What is DNA? DNA stands for Deoxyribonucleic acid DNA is the genetic material of all living things on the planet It is found in the nucleus of your cells DNA holds the instructions to make all things in your body work properly. In sexual reproduction, organisms inherit half of their nuclear DNA from the male parent and half from the female parent DNA is made of chemical building blocks called nucleotides

DNA

Functions of DNA Replication Metabolism From one generation to another -> inheritance From cell to cell division Metabolism - Gene expression and protein synthesis (transcription, translation)

DNA REPLICATION Definition: is the process of making a copy of itself. [existing strands of DNA serve as templates (pattern) for building a new strand of DNA] Function: to produce more cells for growth and repair processes. This process has three steps (see next slide).

3 Steps in Replication STEP 1- Unwinding and Strand Separation DNA helicase break the hydrogen bonds between base pairs and unwind the helix. As the strand separate, replication forks form STEP 2- Adding Complementary Bases - DNA polymerase forms the new DNA molecule by traveling along each single strand and adding complementary nucleotides. STEP 3- Formation of Two Identical DNA Molecules - The DNA winds back up producing 2 identical DNA molecules each consisting one new strands.

Enzymes involves during replication

Helicase An enzyme needed for DNA replication A protein that works to “unzip” the DNA and separate the antiparallel strands

Polymerase Reads the DNA strands Brings in complimentary nucleotides (bases) Replaces primer with DNA nucleotides

Primase is an enzyme involved in the replication of DNA. This enzyme is the first to act once the replication bubble begins.

Ligase “ligate” – means to tie together an enzyme that attaches 2 pieces of DNA together.

How does DNA control the cell? A cell’s DNA needs to change forms. DNA cannot leave the nucleus to give commands, so it needs to make a smaller copy of itself called RNA. RNA leaves the nucleus and is read by the ribosome. The ribosome then makes a protein. The protein is DNA’s command.

RNA has the instruction and can leave the nucleus

RNA (Ribonucleic acid) Carries out the instructions encoded in DNA Most biological activities are carried out by proteins.

THE THREE TYPES OF RNA mRNA or Messenger RNA - mRNA transcribes the genetic code from DNA into a form that can be read and used to make proteins. - mRNA carries genetic information from the nucleus to the cytoplasm of a cell.

THE THREE TYPES OF RNA rRNA or Ribosomal RNA - rRNA is located in the cytoplasm of a cell, where ribosomes are found. - rRNA directs the translation of mRNA into proteins.

THE THREE TYPES OF RNA tRNA or Transfer RNA - Like rRNA, tRNA is located in the cellular cytoplasm and is involved in protein synthesis. - Transfer RNA (tRNA) is the key to deciphering the code words in mRNA.