dna & rna
DESCRIPTION
DNA & RNA. Section 1 DNA. Discovery of DNA. Griffith’s Experiment - 1928. Heat-killed, disease-causing bacteria. Harmless bacteria. Harmless bacteria. Disease-causing bacteria. Heat-killed, disease-causing bacteria. Control (no growth). Lives. Dies of pneumonia. Lives. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/1.jpg)
DNA & RNADNA & RNA
![Page 2: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/2.jpg)
Section 1 Section 1 DNADNA
![Page 3: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/3.jpg)
Discovery of DNA
![Page 4: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/4.jpg)
Disease-causing bacteria
Harmless bacteria
Heat-killed, disease-causing bacteria
Control(no growth)
Heat-killed, disease-causing bacteria
Harmless bacteria
Dies of pneumonia Lives Lives
Live, disease-causingbacteria
Dies of pneumonia
Griffith’s Experiment - 1928
The harmless bacteria had been permanently changed or “transformed” into the disease-
causing bacteria
![Page 5: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/5.jpg)
Griffith Experiment
![Page 6: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/6.jpg)
6
TransformationTransformation• Fred Griffith worked with 2
differnet strains of bacteria: virulent S (causes pneumonia) and nonvirulent R (does not cause pneumonia)
strain Pneumoccocus bacteria• He found that R-strain could
become virulent when it took in DNA from heat-killed S-strain
• Concluded that the transforming factor might be a gene.
![Page 7: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/7.jpg)
• Oswald Avery – repeated Griffith’s experiment (1944)
• He concluded: DNA stores and transmits the genetic information from one generation to the next
![Page 8: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/8.jpg)
Hershey-Chase Experiment - 1952
Alfred Hershey & Martha Chase experimented using Bacteriophages (a virus that infects and kills bacteria)
• Composed of a DNA or RNA core and a protein coat
• Attaches to a cell and injects its genetic information
Radioactive 32P was injected into bacteria!
Proved that DNA was the cell’s genetic material
![Page 9: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/9.jpg)
Percentage of Bases in Four Organisms
Source of DNA A T G CSource of DNA A T G C
Streptococcus 29.8 31.6 20.5 18.0
Yeast 31.3 32.9 18.7 17.1
Herring 27.8 27.5 22.2 22.6
Human 30.9 29.4 19.9 19.8
Streptococcus 29.8 31.6 20.5 18.0
Yeast 31.3 32.9 18.7 17.1
Herring 27.8 27.5 22.2 22.6
Human 30.9 29.4 19.9 19.8
What do you notice about the amount of A compared to T and the amount of G compared to C?
![Page 10: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/10.jpg)
Discovery of DNA Discovery of DNA StructureStructure
• Erwin Chargaff showed the amounts of the four bases on DNA ( A,T,C,G)
• % of A were roughly equal to the % of T and the % of G were roughly equal to the % of C
![Page 11: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/11.jpg)
Chargaff’s RuleChargaff’s Rule
• AdenineAdenine must pair with ThymineThymine
• GuanineGuanine must pair with CytosineCytosine
• The bases form weak hydrogen bonds
G CT A
![Page 12: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/12.jpg)
12
DNA StructureDNA Structure•Rosalind Franklin (1952)
took diffraction x-ray photographs of DNA crystals
• Showed an X-shaped pattern with twisted strands
![Page 13: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/13.jpg)
DNA StructureDNA StructureWatson and Crick – built cardboard models using Franklin’s x-rays; Given credit for determining the structure of DNA
![Page 14: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/14.jpg)
14
![Page 15: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/15.jpg)
DNA DNA StructurStructur
ee
![Page 16: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/16.jpg)
DNADNA•Stands for
Deoxyribonucleic acid•Made up of subunits
called nucleotidesnucleotides • NucleotideNucleotide made of: made of:
1. Phosphate groupPhosphate group2. 5-carbon sugar5-carbon sugar3. Nitrogenous baseNitrogenous base
![Page 17: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/17.jpg)
17
DNA NucleotideDNA Nucleotide
O=P-O O
PhosphatePhosphate GroupGroup
NNitrogenoNitrogenous baseus base (A, G, C, (A, G, C, or T)or T)
CH2
O
C1C4
C3 C2
5
SugarSugar(deoxyribose)(deoxyribose)
O
![Page 18: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/18.jpg)
DNADNA•Two strands coiled called
a double helix•Sides made of a 5-
carbon sugar Deoxyribose bonded to phosphate (PO4) groups (the backbone)
•Center made of nitrogen bases bonded together by weak hydrogen bonds
![Page 19: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/19.jpg)
DNA Double HelixDNA Double Helix
NitrogenousNitrogenousBase (A,T,G or C)Base (A,T,G or C)
““Rungs of ladder”Rungs of ladder”
““Legs of ladder”Legs of ladder”
Phosphate &Phosphate &Sugar BackboneSugar Backbone
![Page 20: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/20.jpg)
Nitrogenous Nitrogenous BasesBases
• Double ring Double ring PURINESPURINESAdenine (A)Adenine (A)Guanine (G)Guanine (G)
• Single ring Single ring PYRIMIDINESPYRIMIDINES
Thymine (T)Thymine (T)Cytosine (C)Cytosine (C) T or C
A or G
![Page 21: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/21.jpg)
Base-PairingsBase-Pairings•Purines only pair with
Pyrimidines•Three hydrogen bonds
required to bond G & C
CG
3 H-bonds
![Page 22: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/22.jpg)
T A
•Two hydrogen bonds required to bond A & T
![Page 23: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/23.jpg)
23
DNADNA
P
P
P
O
O
O
1
23
4
5
5
3
3
5
P
P
PO
O
O
1
2 3
4
5
5
3
5
3
G C
T A
![Page 24: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/24.jpg)
Hydrogen bonds
Nucleotide
Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
DNASection 12-1
A & G Purines (2 rings)C & T Pyrimidines (3 rings)
A to T with double bondG to C with triple bond
![Page 25: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/25.jpg)
DNA structure
![Page 26: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/26.jpg)
Microscopic Image of DNA
![Page 27: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/27.jpg)
27
Section 2: Section 2: ChromosomChromosomes and DNA es and DNA ReplicationReplication
![Page 28: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/28.jpg)
Where is DNA found in the cell?
• Prokaryotes – DNA is in the cytoplasm (because they do not have a nucleus!)
–One circular strand of DNA–One chromosome that contains all the genetic information
![Page 29: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/29.jpg)
• Eukaryotes – DNA is in the nucleus as a number of chromosomes
–The number of chromosomes varies by species•Humans have 46 chromosomes•Fruit flies have 8 chromosomes•Dogs have 78 chromosomes
![Page 30: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/30.jpg)
•DNA Length:
–DNA is long–It must be folded dramatically to fit in cells (it’s like trying to fit a thick rope that is 1000 feet long into a small backpack!)
![Page 31: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/31.jpg)
• Eukaryotic chromosomes contain both DNA and protein tightly packed together to form chromatin
• Chromatin consists of DNA that is tightly coiled around proteins called histones
• DNA and histone molecules form a beadlike structure called a nucleosome
Chromosome Structure
![Page 32: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/32.jpg)
Chromosome Structure of Eukaryotes
Chromosome
Supercoils
Coils
Nucleosome
Histones
DNA
double
helix
![Page 33: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/33.jpg)
• The copying of DNA• Each strand of DNA can re-build
the other half due to base pairing (A-T and G-C)
• Strands are complementary• Replication begins at many
places on the DNA segment and continues in BOTH directions
• Replication Forks – sites where separation and replication occur
DNA ReplicationDNA Replication
![Page 34: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/34.jpg)
DNA Replication
Growth
Growth
Replication fork
DNA polymerase
New strand Original strand
DNA polymerase
Nitrogenous bases
Replication fork
Original strandNew strand
![Page 35: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/35.jpg)
DNA ReplicationDNA Replication
• Begins atBegins at Origins of ReplicationOrigins of Replication• Two strands separateforming Two strands separateforming
Replication Forks (Y-shaped Replication Forks (Y-shaped region)region)
• 2 New strands grow at the forks2 New strands grow at the forks
ReplicationReplicationForkFork
Parental DNA MoleculeParental DNA Molecule
3’
5’
3’
5’
![Page 36: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/36.jpg)
How Replication Occurs• Replication is carried out by a
series of enzymes• Main replication enzyme is DNA
polymerase
1.Enzymes “unzip” DNA by breaking the hydrogen bonds between bases
2.DNA polymerase joins individual nucleotides to produce a new DNA molecule
3.DNA polymerase also “proofreads” each new DNA strand
![Page 37: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/37.jpg)
What would be the complementary strand of DNA for the following:
A T C T T G C G G A A T G G
T A G A A C G C C T T A C C
![Page 38: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/38.jpg)
Example of Replication: If the original DNA molecule contained the following base pairs:
A C G T A A T G CT G C A T T A C G
The two strands would separate into:
A C G T A A T G Cand
T G C A T T A C G
The complementary bases would then pair with each of these strands to form two new strands of DNA
![Page 39: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/39.jpg)
Replication of Replication of StrandsStrands
Replication Fork
Point of Origin
![Page 40: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/40.jpg)
Section 3:Section 3:RNA and RNA and Protein Protein
SynthesisSynthesis
![Page 41: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/41.jpg)
•Genes - coded DNA instructions that control the production of proteins
•To decode the instructions and make protein, DNA is copied into RNA
![Page 42: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/42.jpg)
The Structure of RNA
• Long chain of nucleotides like DNA
• 3 main differences between DNA and RNA• RNA’s sugar is ribose• RNA is single stranded• In RNA, Uracil (U), replaces Thymine
(T)
• Main job of RNA is protein synthesis (assembly of amino acids into proteins)
![Page 43: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/43.jpg)
Example of an RNA strand that is made from DNA
If this is your strand of DNA:A T G T A C G T A
What would be the complementary strand of RNA?
U A C A U G C A U
Remember Uracil (U) replaces Thymine (T) in RNA!!
![Page 44: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/44.jpg)
1. mRNA – messenger RNA•Carry copies of instructions for assembling amino acids into proteins•“messengers” from DNA to the rest of the cell
2. rRNA – ribosomal RNA•Combine with protein to form ribosomes
3. tRNA – transfer RNA•Transfers each amino acid to the ribosome as it is specified by coded messages in mRNA
(pictures)
There are 3 main types of RNA
![Page 45: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/45.jpg)
Transcription• Step 1 of protein synthesis
• Making mRNA from DNA
• Process in which part of the nucleotide sequence of DNA is copied into a complementary sequence of RNA
![Page 46: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/46.jpg)
• Transcription requires the enzyme RNA polymerase
– This enzyme:•Binds to DNA•Separates the DNA strands•Uses one strand of DNA as a template to assemble a strand of RNA
![Page 47: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/47.jpg)
How does RNA polymerase know where to start and stop making RNA from DNA?
• Enzyme will only bind to regions of DNA known as promoters, which have specific base sequences
• Tells the enzyme where to start and stop!
![Page 48: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/48.jpg)
RNA editing
• RNA requires editing before it goes into action
• Introns – DNA sequences that are NOT used to make proteins
• Exons – DNA sequences that DO code for proteins
• Both introns and exons are copied, but the introns are removed before mRNA leaves the nucleus
![Page 49: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/49.jpg)
The Genetic Code
• Proteins are made by joining amino acids into long chains called polypeptides
• There are 20 different amino acids
• The characteristics of proteins are determined by the order in which the amino acids are joined
![Page 50: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/50.jpg)
• The genetic code is the “language” of mRNA instructions
• Remember RNA has 4 bases: adenine, uracil, cytosine, guanine
• The genetic code is read three letters (bases) at a time
• Each three-letter word is known as a codon, which stands for an amino acid
![Page 51: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/51.jpg)
Codon Chart(read from the middle out)
![Page 52: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/52.jpg)
EXAMPLE:
An RNA sequence – U C G C A C G G U
Codons – U C G – C A C – G G U
Amino Acids – Serine – Histidine - Glycine
![Page 53: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/53.jpg)
• A codon cannot code for more than one amino acid
• The start codon is AUG, which signals to start
• The stop codons, UGA, UAA, and UAG signify the end of the polypeptide (like the period at the end of a sentence)
![Page 54: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/54.jpg)
![Page 55: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/55.jpg)
Translation
• STEP 2 of Protein Synthesis
• Translation – the decoding of an mRNA message into proteins– Takes place on ribosomes
Process of Translation1. mRNA is made from DNA and
released into the cytoplasm
![Page 56: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/56.jpg)
2. mRNA attaches to a ribosome3. Ribosomes read the codons or
instructions4. tRNA brings the right amino
acid to the ribosometRNA is a single strand of
unpaired basesThese bases, called
anticodons, complement mRNAStarts at the codon AUG,
which is the anticodon UAC
![Page 57: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/57.jpg)
• Example
mRNA (codon) :
U A U U G C G A C G C
tRNA(anticodon):
A U A A C G C U G C G
![Page 58: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/58.jpg)
![Page 59: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/59.jpg)
5. Ribosome forms peptide bonds between amino acids
6. The ribosome also breaks the bond that held the first tRNA molecule and then moves to the third codon
7. The polypeptide grows until a stop codon is reached
8. Ribosome releases the protein and the mRNA
Translation is complete!
![Page 60: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/60.jpg)
![Page 61: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/61.jpg)
Roles of DNA and RNA
Similar to information needed to construct a building:
• DNA – “master plan”• RNA – “blueprints”
![Page 62: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/62.jpg)
Section 4:Section 4:MutationsMutations
![Page 63: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/63.jpg)
• Mutations – changes in genetic material or “mistakes”– Sometimes cells make mistakes
when copying DNA
Types of Mutations:• Gene mutations – mistake is
made in a single gene• Chromosomal mutations –
mistake that affects the whole chromosome
![Page 64: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/64.jpg)
Gene Mutations
• Point mutations – gene mutation involving changes in one or a few nucleotides– Occurs at a single point
• Substitutions – one base is changed into another– Affects only one amino acid
![Page 65: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/65.jpg)
• Insertions – a base is inserted into DNA
• Deletion – a base is removed from DNA
- Can change every amino acid that follows because every codon will be changed!
•Frameshift mutations – shift the reading frame of the genetic message
-Can alter the protein so much that it can’t perform its function
![Page 66: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/66.jpg)
Substitution Insertion Deletion
Examples of Mutations
![Page 67: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/67.jpg)
Chromosomal Mutations
• Changes in the number or structure of chromosomes
-Many change the location of genes on chromosomes
-May change the number of copies of some genes
![Page 68: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/68.jpg)
Four types of chromosomal mutations
• Deletion – loss of all or part of a chromosome
• Duplication – extra copies of a chromosome
• Inversion – reverse directions• Translocation – part of a
chromosome breaks off and attaches to another
![Page 69: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/69.jpg)
Deletion
Duplication
Inversion
Translocation
Chromosomal Mutations
![Page 70: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/70.jpg)
Significance of Mutations– Many are neutral – they have little
or no effect on gene expression or function
- Some cause harm – dramatic changes in protein structure or gene activity
•Cause genetic disorders•Associated with cancer
![Page 71: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/71.jpg)
• Mutations are also the source of genetic variability in a species (Diversity)
– Helps species evolve (adapt) to changing environments
- If chromosomes fail to separate during meiosis – organism has extra set of chromosomes called polyploidy
- Polyploid plants are usually larger and stronger
- Used for bananas and citrus fruits
![Page 72: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/72.jpg)
Section 5: Section 5: Gene Gene
RegulationRegulation
![Page 73: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/73.jpg)
• Expressed gene – a gene that is transcribed into RNA– Some genes are expressed and
some are silent– Certain DNA sequences serve as
promoters – binding cites for RNA polymerase
– Others serve as start and stop signals for transcription
![Page 74: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/74.jpg)
Gene Regulation
• Operon – a group of genes that operate together
• Two regulatory regions on a chromosome
1.Promoter (P) – where RNA polymerase binds and then begins transcription
2.Operator (O) – where a repressor protein (DNA binding protein) binds to turn the gene off
![Page 75: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/75.jpg)
Eukaryotic Gene Regulation• Genes are controlled individually and
have regulatory sequences that are more complex than in prokaryotes
• Draw and label a typical eukaryotic gene
![Page 76: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/76.jpg)
• “TATA” box – – Contains a sequence of TATATA or
TATAAA before the start of transcription
– Helps RNA polymerase position itself to begin transcription correctly
![Page 77: DNA & RNA](https://reader030.vdocuments.net/reader030/viewer/2022013004/5681360c550346895d9d8257/html5/thumbnails/77.jpg)
Development and Differentiation
• During development of an organism, cells undergo differentiation– This means they become
specialized in structure and function
• Hox genes – control the differentiation of cells and tissues in the embryo