HMMM…..If there is 16% Thymine and 34% Cytosine in a DNA strand, what percent would be Adenine and Guanine?

DO NOW:

Chargaff’s Rule

Since Adenine pairs with Thymine and Cytosine pairs with Guanine the percentages equal.

All percentages equal to 100%

If there is 24% Cytosine, there would be an equal amount of Guanine (24%)

If there is 26% Thymine, there would be an equal amount of Adenine (26%)

DNA and Chromosomes• When cells get ready to divide, they pack up

all their DNA into chromosomes • Humans have 46 chromosomes located in the

nucleus of every cellhttp://www.youtube.com/watch?v=E8NHcQesYl8

DNA Wrapping• A lot of DNA must be tightly packed into the nucleus

• CHROMOSOMES are made of CHROMATIN, which is DNA wrapped around PROTEINS called HISTONES

DNA Replication• Make a copy of its DNA. • DNA unwinds and “unzips” splits down

the middle• DNA polymerase (an enzyme) joins new

nucleotides using base-pairing rules to

• make complementary strands of DNA: one strand makes two identical strands.

• DNA polymerase also “proofreads” the code to make sure it makes exact copies.

http://www.youtube.com/watch?v=hfZ8o9D1tus http://www.youtube.com/watch?v=7wh0m5WRLSU&feature=relmfu

http://www.youtube.com/watch?v=bee6PWUgPo8&feature=relmfu

http://www.phschool.com/atschool/phbio/active_art/dna_replication/index.html

Think Pair Share

What does “COMPLEMENTARY” mean?

Complementary means things that go well

together.In DNA, this refers to the

two strands and their bases:

A always goes with T C always goes with G

http://johnkyrk.com/DNAreplication.html

Quickcheck:

What are the two types of nucleic acids?

DNA and RNA

Risk Box:The second type of nucleic acid is RNA or ribonucleic acid. Using the diagram, compare and contrast DNA and RNAFill in the table on your guided notes sheet

DNA RNA

RNA= RiboNucleic AcidRNA is a nucleic acid and it is made of long strands of nucleotides like DNA, but there are important differences:

DNA RNAType of Sugar

deoxyribose ribose

# of Strands

2 (double-stranded)

1 (usually single-

stranded)

Bases A, T, C, G A, U, C, G (Uracil instead of

Thymine)

There are 3 types of RNA:

1.mRNA- messenger RNA carries a copy of the DNA code

from the nucleus to the ribosome2.rRNA- ribosomal RNA is what ribosomes are made of

3.tRNA- transfer RNA carries amino acids to the ribosomes according to the 3-letter code

RNA has a very important role in the cell: Protein Synthesis (building proteins)

• DNA is divided into segments called genes

• Genes can be 100 or more than 1000 base pairs long

• Each gene is a coded instruction for building a protein

• Proteins do all the jobs in the cell/body

Protein Synthesis means building proteins

Step #1: Transcription (making mRNA)

First the cell must make a copy of the DNA because DNA never leaves the nucleus

Risk Box:

Hmmm…DNA never leaves the nucleus.

Why do you think that is?

• DNA unwinds and unzips• Transcription starts at a site on DNA called a promoter• RNA polymerase (an enzyme) uses the template strand

of the DNA to make mRNA (messenger RNA) from

free-floating nucleotides

Safe inside the nucleus…

RNA Polymerase

• In RNA, A—U , C—G • mRNA is single stranded (only one strand)• the mRNA is a copy of the gene• when the gene is completely copied, the

mRNA leaves the nucleus

http://www.youtube.com/watch?v=5MfSYnItYvg&NR=1 http://www.youtube.com/watch?v=OtYz_3rkvPk&feature=related

Sometimes the mRNA needs to be edited a little before it’s ready to go to

work.

INtrons are pieces that are taken OUTand EXons are pieces that are left IN

http://johnkyrk.com/DNAtranscription.html

mRNA editing:

INtrons are taken OUTand Exons are left IN

http://johnkyrk.com/DNAtranscription.html

What is one difference between DNA and RNA?

Record your response on a seperate sheet of paper.