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Aim: What is a chromosome? Human Chromosomes Text p.291-294.

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Presentation on theme: "Aim: What is a chromosome? Human Chromosomes Text p.291-294."— Presentation transcript:

1 Aim: What is a chromosome? Human Chromosomes Text p

2 Electron Micrograph

3 Chromosome Structure Chromosome Supercoils Coils Nucleosome Histones DNA double helix Section 12-2 Go to Section:

4 Key Idea 2 Organisms inherit genetic information in a variety of ways that result in continuity of structure and function between parents and offspring. 2.1 f In all organisms, the coded instructions for specifying the characteristics of the organisms are carried in DNA, a large molecule formed from subunits arranged in a sequence with bases of four kinds (represented by A, G, C and T). The chemical and structural properties of DNA are the basis for how the genetic information that underlies heredity is both encoded in genes (as a string of molecular “bases”) and replicated by means of a template.

5 Bases (rungs of the ladder) in DNA Purine Bases Adenine (A) and guanine (G)are the larger of the two types of bases found in DNA.

6 Bases (rungs of the ladder) in DNA Pyrimidine Bases

7 The DNA backbone is a polymer with an alternating deoxyribose sugar-phosphate sequence DNA (deoxyribonucleic acid) is a double- stranded molecule that is twisted into a helix like a spiral staircase

8 Base Pairing in DNA A with T: the purine adenine (A) always pairs with the pyrimidine thymine (T)purine pyrimidine C with G: the pyrimidine cytosine (C) always pairs with the purine guanine (G)

9 Purines Pyrimidines AdenineGuanine Cytosine Thymine Phosphate group Deoxyribose DNA Nucleotides Section 12-1 Go to Section:

10 Hydrogen bonds Nucleotide Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Structure of DNA Go to Section:

11 RNADNA RNA polymerase Transcription – making RNA Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) Go to Section:


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