DNADeoxyribose

Nucleic

Acid

DNA

• The chemical make-up of genes

• Stores and passes genetic info from one generation to the next. (heredity)

• Determines your traits

DNA is a long molecule made up of nucleotides.

Nucleotides have:

• A phosphate

• A 5 carbon sugarRibose

• One of four nitrogen bases:– Adenine- A– Thymine- T– Guanine- G– Cytosine- C

The DNA Molecule• Discovered by Watson, Crick, Wilkins, and Rosalind

Franklin. (1953)

• Molecular shape is a double helix.

Double Helix

• Like a twisted ladder.

• Sides made up of sugar and phosphate (backbone).

• Cross-rungs are made up of pairs of nitrogen bases.

Nitrogen Base PairingNitrogen Base Pairing

• Adenine and Thymine

• Guanine and Cytosine

ALWAYS!!!!

What would the nitrogen base pairs be to form a double helix?

A -G -G -C -C -T -A -

A and T always pair together.G and C always pair together.

A - TG - CG - CC - GC - GT - AA - T

What holds the two sides of What holds the two sides of the DNA molecule together the DNA molecule together (what connects the pair of (what connects the pair of

nitrogen bases)?nitrogen bases)?

Hydrogen Bonds

Histones• The double stranded DNA molecule is then coiled

(helix) and supercoiled (wrapped around proteins called histones).

• One human cell contains over 1 meter of DNA

Double Helix ActivityDouble Helix Activity

• 3 sections of backbone (other 3 will be complimentary strand)

• 5 nucleotides on each section• Complete one section of backbone first, and

then complete its complementary strand of DNA• Connect the two strands with tape. Use a blue

line to represent hydrogen bonds between the nitrogen bases.

• Continue with the other two complementary sections of backbone

Left = sugar up

Right = sugar down

Introduction to DNA

• http://learn.genetics.utah.edu/content/begin/tour/

Opener 4/23 – pg. 136

1. In your own words describe the structure of a DNA molecule.

2. Using a ladder as an analogy, what parts of a DNA molecule can be described as:

a.The sides of the ladder

b.Rungs of a ladder

Opener 4/28 – pg. 136

A single cell in your body has about 2 m of DNA.

•How does your cell package the DNA so it can efficiently be copied and transferred? (don’t answer this yet!)

DNA Replication

• The DNA molecule unwinds.

• The molecule “unzips” at the H bonds.

• New nucleotides attach following the rules of base pairing.

• Each strand of the DNA serves as a template for a new strand.

DNA replication is carried out by a series of enzymes.

• DNA Polymerase joins

individual nucleotides to the

strand and proofreads each

new strand reducing

the chance of mistakes.

DNA Replication Animations

• http://www.youtube.com/watch?v=yqESR7E4b_8

• http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter3/animation__dna_replication__quiz_1_.html

Warm-up 4/30 –pg. 139 1. People sweat to help maintain body temperature. What type of feedback happens when sweating regulates body temperature? Positive or Negative feedback and why?

2. Plants use nitrogen to make proteins. What is present in the soil that makes nitrogen directly available to plants?

DNA Replication Review

• Make 3 diagrams:• First: show a labeled 15-base (pair) section of

double-stranded DNA (so 30 nucleotides)• Second: show what the DNA would look like

during the replication process. • Third: show the results of replication

*Make sure to label the following: all base pairs, origin of replication, replication fork, DNA polymerase

Quick Write

• In a paragraph describe the process of DNA replication.– You can use diagrams in addition to help

make your point– Your task is to prove to me your

understanding of the entire process of replication with its “key players”