1 / 19

Ch 10: Nature, structure and organisation of genetic material

Ch 10: Nature, structure and organisation of genetic material. Nature of Genes-Analysing DNA. Genes made of deoxyribonucleic acid (DNA). DNA made of building blocks called nucleotides. Form a chain=4 diff types of nucleotides. Adenine-Thymine Cytosine-Guanine

trina
Download Presentation

Ch 10: Nature, structure and organisation of genetic material

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Ch 10: Nature, structure and organisation of genetic material

  2. Nature of Genes-Analysing DNA • Genes made of deoxyribonucleic acid (DNA). DNA made of building blocks called nucleotides. • Form a chain=4 diff types of nucleotides. • Adenine-Thymine • Cytosine-Guanine • Each nucleotide has a sugar (deoxyribose) part, phosphate part and a Nitrogen base. • Sugar & phosphate always same in all 4 nucleotides. • Bases differ A, T, C, G.

  3. DNA • When nucleotides join to form a chain, bonds form between the sugar of 1 nucleotide and phosphate group of the next nucleotide. • 1 chain of nucleotides run from head to tail • Phosphate is head end (5’ prime end) • Sugar is tail end (3’ prime end) • A-T and C-G are in equal proportion in the body. Known as Chargaff’s rule.

  4. DNA forms a double helix • Nucleotide chain organised into double helix shape. • Each chain runs in opposite direction and are anti-parallel. • Sugar phosphate backbone of the 2 chains are on the outside of helix-coil around. • Bases arranged to point inwards. • Bases in 1 chain pair with bases on the 2nd chain. A-T, C-G are held together by hydrogen bonds between the base pairs-complementary.

  5. DNA • DNA: • Can act as a template for its own replication. • Contain genetic instructions • Can undergo change or mutation • Base sequence could be GGTACGTA. Its complementary chain is CCATGCAT

  6. DNA partners • DNA strand can be separated into 2 single strands- Dissociation. • Done through heating at 90*- breaks strong sugar-phosphate bond that join nucleotides in 1 chain. • Forms 2 single chains of DNA • If cools, hydrogen bonds reform and DNA becomes double helix again: Re-association. • Pairing between complementary DNA chains or parts of chains from different sources-hybridisation.

  7. DNA to chromosomes and genes. • Longer chromosome, more DNA it has and more genes it carries. • Length of double-strand DNA determined by no. of base pairs (bp). Single strand is no. of bases (b). • DNA in a haploid cell 3000 million bp (1m). DNA divided among 23 chromosomes (4 cm) has about 120 million bp.

  8. Mitochondria DNA • Generate and store energy in ATP form (eukaryote cells). • Have DNA and mtDNA is double stranded circular molecule. • Have 16568 bp & 37 genes • 13 code for proteins involved in cellular respiration • 2 genes code for ribosomal DNA (rRNA) • 22 genes code for transfer RNA (tRNA) • Circular mtDNA has 37 genes. 1 part (D-loop) doesn’t contain genes. Why? Becomes displaced during replication.

  9. Gene sequencing • ATGGTGCA etc… is part of a nucleotide sequence of the HBB gene which controls production of haemoglobin. • Gene sequencing involves the process of identifying the nucleotides along a gene. • DNA bands are produced-tell you what nucleotide and the order of the bands tells you gene sequence. • Used on all org. except retrovirus because have RNA. • Different genetic instructions within & between species are due to different nucleotides sequences in the genes.

  10. Nature of the genetic code • Genetic code in DNA contains info from joining amino acids to form proteins. • Coded Info • Nucleotide seq. in DNA • Decoded Info • Order of amino acids in proteins

  11. Organisation of genetic code • DNA sequence can be separated into 3 bases-called triplet code or codon. • TAC,AAA,CAA,GCT,CCT • Produces amino acid: • met, phe, val, arg, gly amino acids produced. • Amino acid can be produced by more than 1 triplet code. • Amino Acid produced can be a STOP instruction or START instruction.

  12. What is a Genome • The genome is the total set of genes carried by an individual or cell. • About 20000-25000 total. • Mainly inside the nucleus or eukaryotic cells. • Genomes of individuals usually differ in a single base of the DNA sequence. Known as Single nucleotide polymorphisms (SNP’s) • Are similarities between 2 unrelated individuals. 99.9% same but over 3 million differences!

  13. Human Genome Project • Aims to completely analyse the genome sequence of humans. • 2 human genomes are sequenced & by comparing 2 sets of data, generalisations can be made. • Help provide info and diagnose genetic diseases • ID factors that cause diseases-help prevent • Understand how genes act and how they cause disease-treatment • Understand genetic control of human development. Proteomics: study of proteins made by the genome.

  14. Mutations • Genetic material can change-Mutations. • Genes can appear suddenly or change in the genome-Mutation • A mutation is a change in an allele due to a change in DNA. • Is an alteration/Change in the genome. • Spontaneous mutation: when causative agent cant be identified • Induced Mutation: When causative agent can be found. • Mutagenic agents: Agents that cause mutation (x-rays, ulltraviolet/nucelar radiation, chemical substances.

  15. Kinds of Mutations Original: AAT GTC GGA GTC 10 20 00 • Substitution: Replace 1 nucleotide with another AAT CTC GGA GTC 10 20 00 Replaced G with C at no.13 • Addition: Insert 1 or more nucleotides into DNA strand AAT GTC GGT AGT C 10 20 00 Adding a T between original nucleotides (17-18) • Deletion: removal of 1 or more nucleotides from DNA strand AAT GCG GAG TC 10 20 Deleted T between G and C from original (no 13-15)

  16. Effects? • Sometimes no effect: Change from GGA to GAG still codes for same amino acid leu-Silent mutation • Sometimes cause major change: Change from ACA to ACT makes diff. amino acid (cys) which is a STOP. • Single base mutations (deletions) have a big effect because affect certaiin triplet but all others that follow- Frameshift mutation.

  17. Trinucleotide repeat mutations • Some triplets codes are repeated in genome. • Trinucleotide repeat expansion (TRE) mutations involves additional repeats of these triplets and leads to disease. • Normal allele has smaller no. of nucleotide repeats whereas a mutant allele has a longer one because of all the repeats. • Mutation is unstable-repeats can change from 1 generation to the next. • E.g. HD mutated allele increases its repeats from father to kids.

  18. Does it matter? • Somatic mutation: mutation occurs in body cell (muscle, brain etc…). Only that cell and daughter cell made by mitosis will have mutation. • Not passed onto next generation. • Germline mutation: Mutation in cell that produces gametes. • Are heritable because gamete with mutation can give rise to offspring.

  19. DNA repair • DNA can repair itself but is limited. • Best way stop DNA damage from UV radiation-protection. • Sunblock, hats, sunscreen. • Can cause skin cancer • DNA damaging radiation in sunlight is UV-B. Increased exposure due to ozone hole.

More Related