DNA and RNADNA and RNAChapter 12Chapter 12
12-1: DNA
DNA Structure
DNA is made up of monomers called nucleotides
each nucleotide is made up of three parts:
1. 5-carbon sugar (deoxyribose)
2. phosphate group
3. nitrogenous base FOUR types of nitrogenous bases
adenine (A) & guanine (G) – purines
cytosine (C) & thymine (T) – pyrimidines
Nitrogenous bases
purines (A & G):two rings
pyrimidines(C & T): one ring
Chargaff’s Rules
# of A = # of T # of G = # of C # of purines = # of pyrimidines
DNA “double helix”
discovered by Watson & Crick two strands are wound around each other
like a spiral staircase or twisted ladder
DNA “double helix”
base pairing explains Chargaff’s Rules A always bonds with T (“points”) – double bond C always bonds with G (“curves”) – triple bond
So if you have one side of DNA that has thesethese bases,
Cytosine (C)Cytosine (C) Adenine (A)Adenine (A) Thymine (T)Thymine (T) Guanine (G)Guanine (G) Guanine (G)Guanine (G) Thymine (T)Thymine (T)
--(G) Guanine--(G) Guanine--(T) Thymine--(T) Thymine--(A) Adenine--(A) Adenine--(C) Cytosine--(C) Cytosine--(C) Cytosine--(C) Cytosine--(A) Adenine--(A) Adenine
TheseThese bases will make the other side.
DNA Origami
Two types of FOLDS
Step 1
Cut the white border off the top, bottom, and sides of the template.
Step 2
Fold all solid lines going lengthwise down the page into “mountain folds”.
Step 3
Fold all dashed lines going lengthwise down the page into “valley folds”.
Check Yourself
Your paper should look like this:
Step 4
Bring the two sides of the model together, similar to an “I” beam.
Step 5
Look for the words ‘front’ and ‘back’ at the top of your model. Hold the model with the ‘front’ side facing you.
Step 6
Fold the two sides of the DNA model so the ‘front’ side is flat.
Step 7
Crease each solid, horizontal line into a mountain fold (away from you).
Step 8
Flip the model to the ‘back’ side. Crease each solid diagonal line into a mountain fold (away from you).
Check Yourself
Your model should look like this.
Step 9
Fold ALL of the creases together in the directions of the folds made in steps 7 and 8. Your model will fold up like an accordion. While you are folding, pinch the middle of the model to keep it together to make a cylindrical shape.
Step 9
Step 10
Release the model. You should be able to see the shape of a double helix.
Step 11
Straighten out the sides of the DNA model (the DNA “backbones”) to make them perpendicular to the creases in the middle.
You’re DONE!
Bell Work 2/22/10
A scientists is researching the effect long-term exposure to sunlight has on cell reproduction. Which scenario extends the current understanding of this relationship?– A) a culture of liver cells exposed to different pH levels
over a 10-day period– B) a culture of muscle cells exposed to different nutrients
over a 30-day period– C) a culture of skin cells exposed to different
temperatures over a 50-day period– D) a culture of brain cells exposed to different electrical
impulses over a 75-day period
12-2: Chromosomes and DNA Replication
DNA and Chromosomes
prokaryotes have a SINGLE, circular chromosome in the cytoplasm containing their DNA
DNA and Chromosomes
prokaryotes have a SINGLE, circular chromosome in the cytoplasm containing their DNA
eukaryotes have MANY chromosomes in the nucleus containing their DNA
Chromosome Structure
DNA is very tightly packed DNA is wound around histones (proteins) to form nucleosomes nucleosomes wind into coils and supercoils to ultimately form
chromosomes
tightly wound DNA is called tightly wound DNA is called chromatidschromatids
Flashback!
What happens during the S phase of the cell cycle?
DNA replicates (copies) itself!
DNA Replication
DNA Replication
to make a copy of itself, DNA “unzips”
C—GC—G
G-- --CG-- --C
T-- --AT-- --A
A-- --TA-- --T
G-- --CG-- --C
G-- --CG-- --C
DNA Replication
new bases come in to make a new complementary strandcomplementary strand
C—GC—G
G--G--CC GG --C --C
T--T--AA TT--A--A
A--A--TT AA--T--T
G--G--CC GG--C--C
G--G--CC GG--C--C
Notice these strands are the same.Notice these strands are the same.
Your turn
copy and complete the DNA strandC--C--
G--G--
G--G--
T--T--
A--A--
A--A--
C--C--
G--G--
Does it look like this?C--GC--G
G--CG--C
G--CG--C
T--AT--A
A--TA--T
A--TA--T
C--GC--G
G--CG--C
“Unzip” and copy it!
C—G
G-- --C
G-- --C
T-- --A
A-- --T
A-- --T
C-- --G
G-- --C
Does it look like this?C—G
G--C G--C
G--C G--C
T--A T--A
A--T A--T
A--T A--T
C--G C--G
G--C G--C
DNA Replication
the main enzyme involved in DNA replication is DNA polymerase
RESULTS in two identical DNA molecules!
Bellwork 2/23/10
When designing a scientific investigation, which of the following should be identified first?– A) lab equipment needed– B) appropriate sample size– C) useful analysis software– D) a testable hypothesis
12-3: RNA and Protein Synthesis
RNA vs DNA structure
RNA sugar: ribose
DNA sugar: deoxyribose
single-stranded double-stranded
uracil (U) base thymine base
3 Types of RNA
RNA is mainly involved in RNA is mainly involved in PROTEIN SYNTHESISPROTEIN SYNTHESIS messenger RNA (mRNA) ribosomal RNA (rRNA) transfer RNA (tRNA)
Protein Synthesis
1.Transcription
2.RNA Editing
3.Translation
Overview
Transcription
DNA is “transcribed” into a RNA strand with the help of RNA polymerase
Transcription
how does RNA polymerase “know” where to start and stop making the RNA copy of DNA?
the promoter region of the DNA is the light switch ON
then the middle part is the coding region, or the TV show you watch
the RNA polymerase stops at the termination sequence, the light switch OFF
RNA Editing
like a writer’s 1st draft introns
(intervening sequences) are removed
exons (expressed sequences) are left to make up the mRNA
Translation
mRNA “translated” into amino acids (which form proteins!)
occurs in the RIBOSOME
How does the ribosome “read” the mRNA?
using the GENETIC CODE! this “code” only uses 4 letters:
A, U, C, G these 4 letters represent 20 different amino
acids the code is read 3 letters at a time (in triplicate)
– these are called codons example:
RNA sequence UCGCACGGU
would be read UCG CAC GGU
The Genetic Code each codon
represents an amino acid
there are 64 codons that code for 20 amino acids
1 start: AUG
3 stops: UAAUAG UGA
Translation
before translation starts, mRNA is transcribed in the NUCLEUS
Translation
then, in the cytoplasm, an mRNA molecule attaches to a RIBOSOME
translation starts at AUG, and the transfer RNAs come in! (AUG = methionine)
Translation
it’s a polypeptide “assembly line” of amino acids …
Translation
… until a stop codon is reached
Protein Synthesis
Bell Work 2/26/10
In 1928 Alexander Fleming observed the mold Penicilium notatum growing in a Petri dish. Also in the dish was the bacteria Staphylococcus aureus. Fleming observed that no bacteria colonies were found growing in the area where the Penicillium notatum was. Which conclusion is BEST defended by Fleming’s discovery?– A) P. notatum destroys all colonies of S. aureus– B) P. notatum prevents the growth of all bacteria– C) P. notatum inhibits the growth of S. aureus– D) P. notatum promotes the growth of certain bacteria
colonies
Bell Work 3/1/10
A pesticide manufacturer claims that a new product will decrease the pest population 15% more than the current pesticide for a 10-week period. A population of 50 beetles of the same species is exposed to the new pesticide for a 10-week period. A separate population of the same species of beetle is exposed to the same amount of the current pesticide for a 10-week period. The data collected is sent to an independent research company to verify the results. Which statement BEST explains how an independent research company verifies data to ensure unbiased results.
A) The company compares the data given to similar investigations B) The company performs the same investigation and compares
results C) The company sends out the data to another researcher to
investigate D) The company tests many types of pesticides and draws its
own conclusion
12-4: Mutations
What is a mutation?
any change in the DNA sequence two types:
1. gene mutations (changes in a single gene)
2. chromosomal mutations (changes in whole chromosomes)
Gene Mutations
POINT mutations
- mutations that affect ONE nucleotide
- mainly substituting one nucleotide for another
FRAMESHIFT mutations
- mutations that affect MULTIPLE nucleotides and shift the “reading frame”
- adding/deleting a nucleotide
Gene Mutations
Gene Mutations
Chromosomal Mutations
4 types:
deletion
duplication
inversion
translocation
MUTATIONS