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DNA Structure & Function. Biology 12. Functions of DNA. Controls cellular functions Central Dogma – DNA makes … DNA (replication) RNA (transcription) Protein (translation). DNA. DNA. Central Dogma of molecular biology!. RNA. RNA. Protein. Protein. Structure of DNA.

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Dna structure function

DNA Structure& Function

Biology 12


Functions of dna
Functions of DNA

  • Controls cellular functions

  • Central Dogma – DNA makes …

    • DNA (replication)

    • RNA (transcription)

    • Protein (translation)


DNA

DNA

Central

Dogma

of molecular

biology!

RNA

RNA

Protein

Protein


Structure of dna
Structure of DNA

  • Made of nucleotides

  • Double helix

    • Two parallel strands wound around each other

    • Like a twisted ladder


What is a nucleotide
What is a Nucleotide?

  • Each is made up of:

    • 1 deoxyribose sugar (a 5 carbon sugar)

    • 1 phosphate group

    • 1 of 4 nitrogenous

      bases


Like a twisted ladder
Like a Twisted Ladder …

  • Sides:

    • Made of alternating sugars & phosphates

    • “Sugar phosphate backbone”

  • Rungs:

    • Made of base pairs


Dna runs antiparallel
DNA Runs Antiparallel

Parallel but in opposite directions

5’ end of one strand of DNA aligns with 3’ end of the other strand


What is a 5 3 end
What is a 5` & 3` end?

  • Carbons of a deoxyribose sugar are numbered 1 to 5

    #1 - attaches to nitrogenous base

    #3 - attaches to phosphate

    group ENTERING

    deoxyribose sugar

    #5 - attaches to phosphate

    group EXITING

    deoxyribose sugar


Complimentary base pairing
Complimentary Base Pairing

  • Pairing of nitrogenous base on one strand with the corresponding nitrogenous base

    • adenine (A) always pairs with thymine (T)

    • guanine (G) always pairs with cytosine (C)


Hydrogen bonds
Hydrogen Bonds

  • Base pairs held together by weak hydrogen bonds

    • 2 between A&T

    • 3 between G&C

  • Why do they need to be weak?


Pyrimidine vs purine 5 pg216

Pyrimidine

Single ring

Thymine (T) & Cytosine (C)

Purine

Double ring

Adenine (A) & Guanine (G)

Pyrimidine vs. Purine (#5 pg216)


Goldilocks rule
Goldilocks Rule!

Why do you think the bases match up this way?

Purine + Purine = toobig

Pyrimidine + Pyrimidine = toosmall

Purine + Pyrimidine = just right!


2 page 216
#2 – Page 216

  • Purine & Pyrimidine always bond

  • Why can’t A-C and G-T form pairs?

    • Incorrect number of hydrogen bonds required


Rule of chargaff
Rule of Chargaff

  • Amount of A = T

  • Amount of G = C

  • Why was this important to the discovery of DNA?


6 page 216
#6 – Page 216

  • 20% = Thymine

  • Determine % of other bases

    • 20% = A

    • 60% remains, so:

      • 30% = G

      • 30% = C


How to read a dna strand
How to Read a DNA Strand

  • Start at the 5` end

    • CGAT

  • Start at 3’ end for complimentary strand (opposite strand)

    • GCTA


3 page 216
#3 – Page 216

  • DNA template:

    • 5’ ATGCCTTA 3’

  • Determine complementary strand:

    • 3’ TACGGAAT 5’


Short video
Short Video

DNA Structure


5’

thymine

guanine

3’

5’ end

adenine

3’

cytosine

3’

5’


Reading the DNA

3’

5’ end

DNA Template:

5’ C A G T 3’

Complimentary Strand:

3’ G T C A 5’

3’

5’



Draw a dna molecule
Draw a DNA Molecule

  • Create the sequence:

    • TAC CAG GGC ATC

  • Show:

    • Directionality (3’ and 5’ ends)

    • Hydrogen bonds

  • Create a legend


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