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