5-Structure of DNA and RNA 6-DNA Transcription (Gene Expression) 7- DNA Translation 8-Mutation LABs

In the last lab

The DNA  Deoxyribonucleic Acid (DNA); the genetic material of all cellular organisms and most viruses.  DNA responsible for preserving, copying and transmitting information within cells and from generation to generation.

General Structure of Nucleic Acid DNA and RNA are long chain polymers of small chemical compound called nucleotides.

Nucleotides Nucleotides; ring shaped structures composed of:  Nitrogenous base; these bases are classified based on their chemical structures into two groups:  Purine; double ringed structure (Adenine and Guanine).  Pyrimidine; single ring structures (cytosine and thymine).  Sugar  Phosphate group

DNA: Four different types of nucleotides differ in nitrogenous base:  A is for adenine;  G is for guanine;  C is for cytosine and  T is for thymine.  RNA: thymine base replaced by uracil base. Nucleotides

 Three major classes of RNA: o messenger (mRNA), o transfer (tRNA) and o ribosomal (rRNA).  RNA is a single stranded; the pyrimidine base uracil (U) replaces thymine and ribose sugar replaces deoxyribose. The RNA

Transcription RNA polymerase makes a copy of information in the gene (complementary RNA) complementary to one strands of DNA (Gene Expression)

Translation a messenger RNA (mRNA) molecule, leaves the cell nucleus and enters the cytoplasm, where it directs translating to a sequence of amino acids during protein synthesis. (Gene Expression)

F ROM DNA TO P ROTEIN

Most of the genes consist of; short coding sequences or exons are interrupted by a longer intervening noncoding sequence or introns. G ENE S TRUCTURE

To get an mRNA molecule that yields a working protein, the cell needs to trim out the intron sections and then stitch only the exon pieces together (see drawing). This process is called RNA splicing.RNA splicing

The codon AGC codes for the amino acid serine, and the codon ACC codes for the amino acid threonine.

Methionine A C U Anticodon How Codons Work?

A E Large subunit P Small subunit T RANSLATION - I NITIATION fMet UAC GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 5’ mRNA 3’

A E Ribosome P UCU Arg Aminoacyl tRNA Phe Leu Met Ser Gly Polypeptide CCA T RANSLATION - E LONGATION GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 5’ mRNA 3’

A E Ribosome P Phe Leu Met Ser Gly Polypeptide Arg Aminoacyl tRNA UCUCCA T RANSLATION - E LONGATION GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 5’ mRNA 3’

A E Ribosome P CCA Arg UCU Phe Leu Met Ser Gly Polypeptide T RANSLATION - E LONGATION GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 5’ mRNA 3’

A E Ribosome P T RANSLATION - E LONGATION Aminoacyl tRNA CGA Ala CCA Arg UCU Phe Leu Met Ser Gly Polypeptide GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 5’ mRNA 3’

A E Ribosome P T RANSLATION - E LONGATION CCA Arg UCU Phe Leu Met Ser Gly Polypeptide CGA Ala GAG...CU-AUG--UUC--CUU--AGU--GGU--AGA--GCU--GUA--UGA-AT GCA...TAAAAAA 5’ mRNA 3’

What is a mutation?  change in the nucleotide sequence or arrangement in DNA.  Mutations may be beneficial, neutral(Eye color) or harmful(Sickle Cell Anemia).  Mutations are changes in the genotype which may or may not affect the phenotype.

Types of mutation  -change in chromosome number.  -error in separation in mitosis or meiosis. e.g. Turner’s syndrome - 45, X. Kleinfelter’s syndrome – 47, XXY. 1-Genomic Mutation

 - change in chromosome structure.  -part of chromosome is: * duplicated (may be beneficial ). * deleted. * inverted. translocated (moved to another spot on the same chromosome or another chromosome) may cause transformation of cell to a cancer cell. 2-Chromosome Mutations

 - change in an individual gene due to an error in replication or failure of repair mechanism. mutation may occur in a somatic cell or in a ‘germ cell’ 3-Gene Mutations

2-Induced mutations Chemical agents - alkylating agents. Physical agents - Ionizing radiation. - UV radiation

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