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

2. 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%)
Chargaff’s Rule
Since Adenine pairs with Thymine and Cytosine pairs with Guanine the percentages equal. All percentages equal to 100%

3. 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 cell

4. 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

5. 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.

6. 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

7. Quickcheck:
What are the two types of nucleic acids?
DNA and RNA

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

9. RNA= RiboNucleic Acid DNA RNA deoxyribose ribose 2 (double-stranded) 1
RNA is a nucleic acid and it is made of long strands of nucleotides like DNA, but there are important differences:
DNA
RNA
Type 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)

10. rRNA- ribosomal RNA is what ribosomes are made of
There are 3 types of RNA:
mRNA- messenger RNA carries a copy of the DNA code from the nucleus to the ribosome
rRNA- ribosomal RNA is what ribosomes are made of
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)

11. Protein Synthesis means 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

12. Step #1: Transcription (making mRNA)
First the cell must make a copy of the DNA because DNA never leaves the nucleus

13. DNA never leaves the nucleus.
Risk Box:
Hmmm…
DNA never leaves the nucleus.
Why do you think that is?

14. Safe inside the nucleus…
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
RNA Polymerase

15. mRNA is single stranded (only one strand)
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

16. INtrons are pieces that are taken OUT
Sometimes the mRNA needs to be edited a little before it’s ready to go to work.
INtrons are pieces that are taken OUT
and EXons are pieces that are left IN

17. INtrons are taken OUT mRNA editing: and Exons are left IN
mRNA editing:
INtrons are taken OUT
and Exons are left IN

18. What is one difference between DNA and RNA?
Record your response on a seperate sheet of paper.