Structure of RNA Single stranded Ribose Sugar 5 carbon sugar Phosphate group Adenine, Uracil, Cytosine, Guanine
Types of RNA Three main types Messenger RNA (mRNA) – transfers DNA code to ribosomes for translation. Transfer RNA (tRNA) – brings amino acids to ribosomes for protein synthesis. Ribosomal RNA (rRNA) – Ribosomes are made of rRNA and protein.
Transcription RNA molecules are produced by copying part of the nucleotide sequence of DNA into complementary sequence in RNA, a process called transcription. During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of mRNA.
How Does it Work? RNA Polymerase looks for a region on the DNA known as a promoter, where it binds and begins transcription. RNA strands are then edited. Some parts are removed (introns) - which are not expressed – and other that are left are called exons or expressed genes.
The Genetic Code This is the language of mRNA. Based on the 4 bases of mRNA. “Words” are 3 RNA sequences called codons. The strand aaacguucgccc would be separated as aaa-cgu-ucg-ccc the amino acids would then be Lysine – Arginine – Serine - Proline
Translation During translation, the cell uses information from messenger RNA to produce proteins. A – Transcription occurs in nucleus. B – mRNA moves to the cytoplasm then to the ribosomes. tRNA “read” the mRNA and obtain the amino acid coded for. C – Ribosomes attach amino acids together forming a polypeptide chain. D – Polypeptide chain keeps growing until a stop codon is reached.
MUTATIONS Changes in DNA that affect genetic information
Mutations Gene mutations result from changes in a single gene. Chromosomal mutations involve changes whole chromosomes.
Gene Mutations Point Mutations – changes in one or a few nucleotides Substitution THE FAT CAT ATE THE RAT THE FAT HAT ATE THE RAT Insertion THE FAT CAT ATE THE RAT THE FAT CAT XLW ATE THE RAT Deletion THE FAT CAT ATE THE RAT THE FAT ATE THE RAT
Gene Mutations Frameshift Mutations – shifts the reading frame of the genetic message so that the protein may not be able to perform its function. Insertion THE FAT CAT ATE THE RAT THE FAT HCA TAT ETH ERA T H Deletion THE FAT CAT ATE THE RAT TEF ATC ATA TET GER AT H
Chromosome Mutations Changes in number and structure of entire chromosomes Original Chromosome ABC * DEF Deletion AC * DEF Duplication ABBC * DEF Inversion AED * CBF Translocation ABC * JKL GHI * DEF
Significance ofMutations•Most are neutral • Eye color • Birth marks• Some are harmful • Sickle Cell Anemia • Down Syndrome• Some are beneficial • Sickle Cell Anemia to Malaria • Immunity to HIV
What CausesMutations? There are two ways in which DNA can become mutated: Mutations can be inherited. Parent to child Mutations can be acquired. Environmental damage Mistakes when DNA is copied
Chromosome Mutations Down Syndrome Chromosome 21 does not separate correctly. They have 47 chromosomes in stead of 46. Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of inteligence.
Chromosome Mutations Cri-du-chat Deletion of material on 5th chromosome Characterized by the cat-like cry made by cri-du-chat babies Varied levels of metal handicaps
Sex ChromosomeAbnormalities Klinefelter’s Syndrome XXY, XXYY, XXXY Male Sterility Small testicles Breast enlargement
Sex ChromosomeAbnormalities XYY Syndrome Normal male traits Often tall and thin Associated with antisocial and behavioral problems
Sex ChromosomeMutations Turner’s Syndrome X Female sex organs dont mature at adolescence sterility short stature
Sex ChromosomeMutations XXX Trisomy X Female Little or no visible differences tall stature learning disabilities limited fertility