Basics of Genetics

Part 1

Introduction

• Cells come from existing cells – the cell theory• “Like produces like” – dogs produce pups not

kittensBut how???????

• Heredity- transmission of traits from one generation to the next

• Genetics- the science of heredity usually dealing with the molecular basis

DNA

• Genetics: Study of heredity and DNA• Discovered in the late 1800’s (not known as genetic

material yet.) (Proteins)• Limited by technology– Located inside nucleus of cell (also in mitochondria,

chloroplast, virus and bacteria).– Purpose of DNA is to code for proteins.– Made up of a phosphate, sugar and nucleotide bases.– Arranged in a double helix (twisted ladder).

• Watson and Crick (1953)

II. DNA

A. StructureNucleotide

Phosphate group + Sugar + Nitrogen base

DNA cont.

• Four nucleotide bases:– Adenine A always pairs w/ T– Thymine– Guanine G always pairs w/ C– Cytosine Complimentary base pairs– 2-3 billion base pairs in DNA

• Chargraff’s ratio: #A = #T and #G = #C

Diagram of DNA

RNA

• Acts as an intermediary between DNA and protein.– Common in cytoplasm of the cell.– Transfers code from DNA to ribosome (where

protein is made).– Made of phosphate, sugar and nucleotide bases.– Single stranded.

RNA cont.

• Four nucleotide bases:– Adenine A always pairs w/ U– Uracil (replaces thymine)– Guanine G always pairs w/ C– Cytosine

RNA cont.

• Three types of RNA– mRNA- (messenger) carries information from DNA

to ribosome– tRNA- (transfer) carries amino acids to ribosome– rRNA- (ribosomal) assembles amino acids to make

protein

3 Important Processes

• Replication: DNA making copies of itself• Transcription: DNA makes RNA• Translation: Protein synthesis (making

proteins)

Comparing DNA and RNA

• DNA– Deoxyribose (sugar)– Double stranded– Thymine– Located in nucleus

• RNA– Ribose (sugar)– Single stranded– Uracil– Found in cytoplasm

3. After amino acids have bonded, the tRNA leaves.- Continues until STOP codon- Protein synthesis is done- New protein is released

• DNA code TGA ______________ _______________

• mRNA codon _____________ UCU _______________

• tRNA anticodon`_____________ ________________ _______________

• Amino acid ____________ ______________ tryptophan

• DNA code CAT ______________ _______________

• mRNA codon _____________ GUU _______________

• tRNA anticodon`_____________ ________________ _______________

• Amino acid ____________ ______________ methionine

Sickle Cell Anemia