DNA The Molecule of Heredity DNA Structure Deoxyribonucleic

DNA: The Molecule of Heredity

DNA Structure • Deoxyribonucleic acid. • A macromolecule composed of two strands of monomers called nucleotides. • These strands are joined in the middle by hydrogen bonds. • The strands twist around one another forming a double helix. Twists to the right. http: //cancergenome. nih. gov/media/DNAKit_illustration_image. jpg

Nucleotide Structure • 5 -C sugar – deoxyribose • Phosphate group • Nitrogen containing base -4 of two types – Adenine – Guanine – Cytosine – Thymine http: //www. msu. edu/course/isb/202/ebertmay/drivers/nucleotide. jpg

Types of Nitrogen Bases • Pyrimidines – have one ring in their structure – Thymine – Cytosine • Purines – have two rings in their structure – Adenine – Guanine http: //student. ccbcmd. edu/~gkaiser/biotutorials/dna/images/DNAbases. jpg

Nitrogen Base Pairing • Bases pair in a specific pattern. • A purine always bonds to a pyrimidine – Adenine bonds to thymine. – Guanine bonds to cytosine.

Nitrogen Base Pairing • The bases are held together by weak hydrogen bonds. • The sides of the DNA ladder are composed of alternating sugar and phosphate and are called “backbones”.

Functions of DNA • DNA must be able to copy itself exactly. This process is called REPLICATION - - Enzymes control the process. • DNA is the molecule of heredity. - It provides instructions for cell functioning and is a blueprint for the production of proteins that do the work of the cell.

Replication – Overview · DNA “unzips” down its H-bonds · One strand then acts as a template for the production of a new strand · Each new DNA molecule has one old strand of nucleotides and one new strand.

Control Of Cell Activities • DNA is copied into RNA. (Transcription) • RNA in turn controls the production of proteins. (Translation) • Proteins then do the work of the cell.

RNA • Like DNA, Ribonucleic acid is also made up a sugar, phosphate group and nitrogen bases. But there are some major differences- • The sugar in RNA, is Ribose. • RNA is single stranded • the nitrogen bases consist of Uracil (U), Adenine (A), Guanine (G) and Cytosine (C). • Uracil and Adenine = Base Pair • Guanine and Cytosine = Base Pair

TAKS PRACTICE: Question 1

Question 2 4 DNA passes information to RNA during the process of — F transcription G active transport H regeneration J osmosis

Question 3 5 Which of the following must occur before DNA replication can take place? A Translation of DNA into amino acids B Separation of the DNA molecule into codons C Transformation of DNA into RNA D Separation of the DNA double helix

Question 4 3 If a cat has 38 chromosomes in each of its body cells, how many chromosomes will be in each daughter cell after mitosis? F 11 G 19 H 38 J 76