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GENETIC-CONCEPTS

Discover the fundamentals of genetics, from genome structure to phenotypic expression, and key terms like alleles, traits, and DNA replication. Learn about prokaryotic and eukaryotic organisms and the central dogma of biology.

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GENETIC-CONCEPTS

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  1. GENETIC-CONCEPTS

  2. Genome • Chromosome • Gene • DNA/RNA • Nucleic Acid • Protein • Amino Acid

  3. Genome • Entirely of an organism’s heredity information • Complete set of instructions for making an organism • All of the hereditary information encoded in an organism’s DNA. • Master blueprints for all enzymes, cellular structures & activities • An organism‘s complete set of DNA • All the DNA contained in the cell of an organism • The collection of DNA that comprises an organism

  4. Prokaryotic Organism • Eubacteria and Archaea. Usually unicellular. • No internal membrane-bound compartments: DNA floats free in the cytoplasm. • 1 circular chromosome (plus optional plasmids, which are also circular) • reproduction usually asexual • sexual processes (mixing DNA from 2 individuals) occur, but with unequal contributions from the 2 partners • transcription and translation simultaneous

  5. Prokaryotic genomes • Most have a single, double-stranded circular DNA molecule • Usually without introns • Since there is no nucleus, the DNA floats freely within the cell • Proteins cause the DNA to coil tightly forming a nucleoid region • Relatively high gene density • Often indigenous plasmids are present

  6. Eukaryotic Organism • Plants, animals, fungi, protistas. Often multicellular. • DNA contained within a membrane-bound nucleus. • linear chromosomes (usually more than 1) • careful division of chromosomes in cell division: mitosis and meiosis • transcription separated from translation • sexual reproduction: 2 partners contribute equally to offspring • life cycle: alternation of haploid and diploid phases (i.e. 1 vs. 2 copies of each gene and chromosome)

  7. Eukaryotic genomes • Genetic information is divided in the chromosome. • The size of genomes is species dependent • The difference in the size of genome is mainly due to a different number of identical sequence of various size arranged in sequence • The gene for ribosomal RNAs occur as repetitive sequence and together with the genes for some transfer RNAs in several thousand of copies • Structural genes are present in only a few copies, sometimes just single copy. Structural genes encoding for structurally and functionally related proteins often form a gene family • The DNA in the genome is replicated during the interphase of mitosis

  8. Eukaryotic Genome

  9. Chromosome • A DNA – histone protein thread, usually associated with RNA, occurring in the nucleus of a cell • Chromosomes contain hundreds of genes encoded within their DNA

  10. Locus1 Possible Alleles: A1,A2 Locus2 Possible Alleles: B1,B2,B3 Chromosome Logical Structure • Locus Location of a gene/marker on the chromosome. • Allele One variant form of a gene/marker at a particular locus.

  11. Gene • The material that controls which traits are expressed in an organism • Genes come in pairs and offspring inherit one copy of each gene from each parent • A section of DNA that codes for a trait • Material of heredity

  12. Heredity The passing of traits from parent to offspring

  13. Allele The different forms of a trait that a gene may have. One form of a gene

  14. Traits • Ways of looking, thinking, or being. • Traits that are genetic are passed down through the genes from parents to offspring

  15. Recessive • A trait that is covered over, or dominated, by another form of that trait and seems to disappear • Hidden when the other copy of the gene contains the dominant allele. • A recessive allele shows up only when there is no dominant allele present • Shown with a lower-case letter (a)

  16. Dominant • A trait that covers over, or dominates, another form of that trait • Trait that always shows up, even when only one of the two alleles is in the dominant form • Shown by a capital letter (A)

  17. Homozygous • Both alleles [forms of the gene] are the same • When offspring inherit two dominant genes, (one dominant gene from each parent) they are said to be homozygous dominant (AA) • When offspring inherit two recessive genes, (one recessive gene from each parent) they are said to be homozygous recessive (aa)

  18. Heterozygous • When alleles occur in different forms • When offspring inherit one dominant gene and one recessive gene, they are said to be heterozygous (Aa) • Since the dominant gene will be expressed, they are said to be heterozygous dominant (Aa)

  19. Genotype An organism's genetic makeup

  20. Genotype

  21. PHENOTYPE Outward physical appearance and behavior of an organism

  22. PHENOTYPE

  23. Genes Segment of DNA which can be transcribed and translated to amino acid

  24. Central Dogma of Biology

  25. DNA, RNA, and the Flow of Information Replication Translation Transcription

  26. Central Dogma (Modifications) (2)Ribozymes Transcription Translation Protein DNA RNA • Reverse • transcription Replication (2)Self Replication (3)Self Replication

  27. DNA as Genetic Material • DNA encodes all the information in the cell • The composition of the DNA is the same in all cells within an organism • Variation among different cells is achieved by reading the DNA differently • DNA contains four bases that encode all the information to make an organism’s life

  28. RIBO NUCLEIC ACID • A polymer composed of nucleotides that contain the sugar ribose and one of the four bases cytosine, adenine, guanine and uracile • Polynucleotide containing ribose sugar and uracile instead of thymine • Primary agent for transferring information from the genome to the protein synthetic machinery

  29. Types of RNA Three types ofRNA: • messenger RNA (mRNA) • transfer RNA (tRNA) • ribosome RNA (rRNA) • Remember: All produced in the nucleus

  30. Codon • There are 20 different possible amino acids to make from different codons • Amino acids: the building of protein • 3 possible stop codon • 1 start codon TAC on DNA AUG on RNA

  31. Gene Expression Production of proteins requires two steps: • Transcription involves an enzyme (RNA polymerase) making an RNA copy of part of one DNA strand. There are four main classes of RNA: i. Messenger RNAs (mRNA), which specify the amino acid sequence of a protein by using codons of the genetic code. ii. Transfer RNAs (tRNA). iii. Ribosomal RNAs (rRNA). • Translation converts the information in mRNA into the amino acid sequence of a protein using ribosomes, large complexes of rRNAs and proteins.

  32. Steps of gene expression • Transcription – DNA is read to make a mRNA in the nucleus of cells • Translation – Reading the mRNA to make a protein in the cytoplasm

  33. aa5 aa4 aa3 aa2 aa199 aa1 aa200 Poly-peptide • A primary structure of a protein • A sequence of amino acid bonded together by peptide bonds.

  34. Protein A polymer of amino acids which may consists of one or more polypeptide chains Protein may be water insoluble and serve a structural role or be water soluble with catalytic activity

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