Review: DNA, Transcription & Translation

Structure DNA Code for proteins Double Stranded Helix Can NOT leave nucleus Made of Sugar (deoxyribose), Phosphate & nitrogen base Thymine Adenine Guanine Cytosine RNA Copy of the code for proteins Transports code to Ribosome Single Stranded Can leave nucleus Made of Sugar (ribose), Phosphate & nitrogen base Uracil Adenine Guanine Cytosine

Replication Two new strands of DNA Occurs in nucleus. DNA makes a copy of itself. Two new strands of DNA T A C G A T G C T A C G A T G C

Transcription mRNA molecule Occurs in nucleus. DNA makes a mRNA copy of the code. T A C G A U G C A T G C mRNA molecule

Every 3 letters represents one amino acid or codon. Translation Occurs at Ribosome. mRNA binds with tRNA to build an amino acid chain or protein. Every 3 letters represents one amino acid or codon. Example: GUU = Valine

Summary

11.3 Section Summary 6.3 – pages 296 - 301 Mutations Any change in DNA sequence is called a mutation. Mutations can be caused by errors in replication, transcription, cell division, or by external agents. 11.3 Section Summary 6.3 – pages 296 - 301

Mutations Mutations can be harmful. Mutations can be beneficial. Sickle cell anemia Cystic fibrosis Mutations can be beneficial. Phenotypic (physical) changes Flower color Fur color

Mutations Mutations can occur in both types of cells: Body cells (muscle, skin, brain, bone etc) Gametes (Sex Cells – sperm or egg) Sperm Cell & Egg Cell Skin Cells

11.3 Section Summary 6.3 – pages 296 - 301 Mutations in body cells If a body cell’s DNA is changed, this mutation would not be passed on to offspring. Damage to a gene may impair the function of the cell. When that cell divides, the new cells also will have the same mutation. This can result in the cells growing and dividing rapidly, producing cancer. 11.3 Section Summary 6.3 – pages 296 - 301

11.3 Section Summary 6.3 – pages 296 - 301 Mutations in Gametes Mutations that occur in the gametes or sex cells can be passed on to the offspring. 11.3 Section Summary 6.3 – pages 296 - 301

11.3 Section Summary 6.3 – pages 296 - 301 Types of Mutations A point mutation is a change in a single base pair in DNA. THE DOG BIT THE CAT. THE DOG BIT THE CAR. A change in a single nitrogenous base can change the entire structure of a protein because a change in a single amino acid can affect the shape of the protein. 11.3 Section Summary 6.3 – pages 296 - 301

11.3 Section Summary 6.3 – pages 296 - 301 An example of a point mutation, is sickle-cell disease. Sickle-cell diseases cause the red blood cells to be deformed. The result is that they get stuck in the blood vessels, depriving tissues of oxygen, causing strokes, and blood clots. 11.3 Section Summary 6.3 – pages 296 - 301

What would happen if a single nitrogenous base (letter) is deleted? Types of Mutations What would happen if a single nitrogenous base (letter) is deleted? THE DOG BIT THE CAT. THD OGB ITT HEC AT. A mutation in which a single base is added or deleted from DNA is called a frameshift mutation.

11.3 Section Summary 6.3 – pages 296 - 301 Chromosomal Alterations Sometimes during mitosis or meiosis chromosomes break and then rejoin incorrectly, or just a piece breaks off for good. Structural changes in chromosomes are called chromosomal mutations. Deletion- part is missing Insertion- part breaks off and attaches in the wrong place Inversion- part breaks off and attaches upside down Translocation- breaks off and attaches to different chromosome 11.3 Section Summary 6.3 – pages 296 - 301

11.3 Section Summary 6.3 – pages 296 - 301 Non-Disjunction Occurs during meiosis, when chromosomes fail to separate properly. Normal humans have: 46 chromosomes 22 pair of Autosomes 1 pair of Sex chromosomes Non-Disjunction: Too many chromosomes? Too few? 47 or 45 chromosomes 11.3 Section Summary 6.3 – pages 296 - 301

Normal karyotype Is this a male or female?

Down Syndrome Also called Trisomy 21 3 chromosomes instead of 2

11.3 Section Summary 6.3 – pages 296 - 301 Causes of Mutations Some mutations seem to just happen, perhaps as a mistake in base pairing during DNA replication. These mutations are said to be spontaneous. However, many mutations are caused by factors in the environment, such as radiation, chemicals, and even high temperatures. Ex: Chernobyl explosion Any agent that can cause a change in DNA is called a mutagen. 11.3 Section Summary 6.3 – pages 296 - 301