Molecular Biology: DNA, gene, chromosome and genome (Outline)

Transcription

1 Molecular Biology: D, gene, chromosome and genome (utline) ucleic acid structure and composition D and R Base-pairing rule in D Definition of D, gene, chromosome and genome. D structure and chemical bonds hromatin and D packaging in the nucleus of eukaryotic cells D replication Steps of D replication and major enzymes D template strand and newly synthesized leading and lagging strands

2 enetic Basis of Development From a diploid zygote to a multi-cellular organism uclei containing D Sperm cell Egg cell Fertilized egg with D from both parents Embyro s cells with copies of inherited D ffspring with traits inherited from both parents

3 E FLW F EEI IFRMI he D of the gene is transcribed into R which is translated into the polypeptide (protein) D ranscription R rotein ranslation Figure 10.6

4 ucleic cid hemical Structure D and R are polymers of nucleotides Sugar-phosphate backbone hosphate group itrogenous base Sugar D nucleotide hosphate group itrogenous base (,,, or ) 3 2 hymine () Sugar (deoxyribose) D nucleotide Figure 10.2 D polynucleotide

5 D has four kinds of nitrogenous bases:,,, and 3 hymine () ytosine () denine () uanine () urines yrimidines Figure 10.2B

6 R is also a nucleic acid with a slightly different sugar U instead of Figure 10.2, D hosphate group 2 itrogenous base (,,, or U) Sugar (ribose) Uracil (U) Key ydrogen atom arbon atom itrogen atom xygen atom hosphorus atom

7 ene: a linear stretch of nucleotides with information for one product (polypeptide or protein) hromosome: a very long stretch of D carrying many genes. D is always associated with protein as chromatin D oiling into chromatin and condensed chromosomes enome: totality of D in a cell

8 Erwin hargaff, 1947 Biochemical analysis of D nucleotides from different species = & = uman D = 30.9% = 29.4% = 19.9% = 19.8%

9 D Shape D is a double-stranded helix James Watson and Francis rick worked out the threedimensional structure of D, based on work by Rosalind Franklin Figure 10.3, B

10 he structure of D two polynucleotide strands wrapped around each other in a double helix Figure 10.3 wist

11 ovalent bonds hold the sugar phosphate backbone ydrogen bonds between bases hold the two strands Each base pairs with a complementary partner with, and with Figure 10.3D Base pair ydrogen bond Ribbon model artial chemical structure omputer model

12 D RELII D replication depends on specific base pairing Starts with the separation of D strands protein enzyme uses each strand as a template to assemble new nucleotides into complementary strands Figure 10.4 arental molecule of D ucleotides Both parental strands serve as templates wo identical daughter molecules of D Build a D Molecule

13 D replication is a complex process the helical D molecule must untwist or unwind several proteins are involved including D olymerase it start at specific D sequences, origin of replication Figure 10.4B

14 Replication of long stretches of D Begins at multiple specific sites on the double helix rigin of replication arental strand Daughter strand Bubble Figure 10.5 wo daughter D molecules

15 Each D strand of the double helix is oriented in the opposite direction 5 end 3 end Figure 10.5B end 5 end

16 he enzyme D polymerase uses a single strand and makes a new complementary strand in a 5 to 3 direction one daughter strand is made as a continuous piece the other strand is synthesized as a series of short piece which are then connected by the enzyme D ligase 5 3 D polymerase molecule arental D 3 5 Daughter strand synthesized continuously 3 5 Daughter strand synthesized in pieces 5 3 Figure 10.5 D ligase verall direction of replication