Download Unit 5 Molecular Genetics CLASS NOTES

UNIT 5: Molecular Genetics
Mrs. Howland
Biology 10
rev. November 2015
What is a GENOME?
A GENOME is an organism’s complete set of
genetic instructions
Each genome contains all of the information
needed to BUILD that organism, and to allow it
to GROW and DEVELOP
What is the HUMAN GENOME PROJECT?
JIGSAW ( Tier 2)
1) Count off by 1-2-3-4
2) Read your assigned text and do a QUICK WRITE summary (15 min)
3) Divide into your ‘expert groups’ to compare notes and decide on
main points
4) Return to your original group and report back on your topic!
Group 1 ~ All about GENOMES!
http://www.genome.gov/Pages/Education/AllAbouttheHumanGenomeProject/GuidetoYourGenome07_vs2.pdf
Group 2 ~ Comparative genomics
http://www.genome.gov/11006946
Group 3 ~ How do you sequence a genome? Whose DNA was
used?
http://www.genome.gov/11006943
Group 4 ~ How has HGP affected research and what’s next?
http://www.genome.gov/11006943
What is the HUMAN GENOME PROJECT?
JIGSAW (Tier 1)
1) Count off by 1-2-3-4
2) Read your assigned text and do a QUICK WRITE summary (15 min)
3) Divide into your ‘expert groups’ to compare notes and decide on
main points (5-7 minutes)
4) Return to your original group and report back on your topic!
Group 1 ~ What are GENOMES? (Guide to Genomes)
http://www.genome.gov/Pages/Education/AllAbouttheHumanGenomeProject/GuidetoYourGenome07_vs2.pdf
Group 2 ~ ‘YESTERDAY’ (Human Genome Project Fact Sheet)
http://report.nih.gov/NIHfactsheets/ViewFactSheet.aspx?csid=45&key=H#H
Group 3 ~ ‘TODAY’ (Human Genome Project Fact Sheet)
http://report.nih.gov/NIHfactsheets/ViewFactSheet.aspx?csid=45&key=H#H
Group 4 ~ ‘TOMORROW’ (Human Genome Project Fact Sheet)
http://report.nih.gov/NIHfactsheets/ViewFactSheet.aspx?csid=45&key=H#H
VOCAB: Chrom-WHAT???
Chromosome ~ organized package of DNA, located in
cell’s nucleus
Chromatin ~ fiber within a chromosome, consists of
protein and DNA, major proteins are histones
VOCAB: Chrom-WHAT???
Chromatid ~ one of TWO (2) identical halves of
a replicated chromosome (during cell division)
DNA Structure
 DNA consists of two molecules that are arranged
into a ladder-like structure called a Double Helix.
 A molecule of DNA is made up of millions of tiny
subunits called Nucleotides.
 Each nucleotide consists of:
1. Phosphate group
2. Pentose sugar
3. Nitrogenous base
Watson and Crick
Scientists who determined the helical structure of
DNA
Nucleotides
BASIC STRUCTURE
Phosphate
Nitrogenous
Base
Pentose
Sugar
Nucleotides
The phosphate and sugar
form the backbone of the DNA
molecule, whereas the bases
form the “rungs” called base
pairs
There are four types of
nitrogenous bases
Nucleotides
FOUR (4) TYPES
A
Adenine
C
Cytosine
T
Thymine
G
Guanine
Nucleotides
 Each base will only bond with one other specific
base.
 Adenine (A)
 Thymine (T)
 Cytosine (C)
 Guanine (G)
Form a base pair.
Form a base pair.
Chargaff’s Rule
 Adenine (A) must bind with Thymine (T)
 Cytosine (C) must bind with Guanine (G)
The base pairs form weak HYDROGEN BONDS
About the same amount of each base in DNA
Why DNA??
 Unique Structure!
 Because of the
complementary
base pairing, the
order of the bases
in one strand
determines the
order of the bases
in the other strand
A
T
C
G
T
A
C
G
A
T
G
T
C
A
http://www.nature.com/scitable/topicpage/dna-is-a-structure-that-encodes-biological-6493050
http://sciencenetlinks.com/media/filer/2011/10/13/dna.swf
DNA REPLICATION
When cells divide, DNA is replicated to give
each new cell a copy of the same DNA code
(This is why DNA replication is considered to be
semiconservative!)
Complimentary base pairing makes replication
possible
One strand of DNA acts as a TEMPLATE for a
new, complimentary strand!
Steps in DNA Replication
1) Enzyme TOPOISOMERASE unwinds the DNA
and enzyme HELICASE BREAKS the weak
hydrogen bonds between the bases
2) Enzyme DNA POLYMERASE brings in
complementary nitrogen bases (free
nucleotides)
3) Bases are inserted; paired according to
Chargaff’s Rule
4) RESULT: Semiconservative replication  Each
new DNA contains one OLD strand and one
NEW strand
HELICASE
Separates the TWO (2) strands of DNA by
breaking weak hydrogen bonds between the
bases
DNA POLYMRASE
REPLICATION FORK
Area of replicating DNA where the ORIGINAL
DNA separates into 2 NEW DNA copies
DNA Replication
Topoisomerase - unwinds DNA
Helicase – enzyme that breaks H-bonds
DNA Polymerase – enzyme that catalyzes connection of nucleotides to form complementary
DNA strand in 5’ to 3’ direction (reads template in 3’ to 5’ direction)
Leading Strand – transcribed continuously in 5’ to 3’ direction
Lagging Strand – transcribed in segments in 5’ to 3’ direction (Okazaki fragments)
DNA Primase – enzyme that catalyzes formation of RNA starting segment (RNA primer)
DNA Ligase – enzyme that catalyzes connection of two Okazaki fragments
How is DNA used?
 BLUEPRINT to make proteins for the
cell/organism
 To crack the genetic code found in DNA
we need to look at the sequence of bases.
 The bases are arranged in triplets called codons.
AGG-CTC-AAG-TCC-TAG
TCC-GAG-TTC-AGG-ATC
Using DNA
 A gene is a section of DNA that codes for a
protein
 Each unique gene has a unique sequence of
bases
 This unique sequence of bases will code for the
production of a unique protein.
 It is these proteins and combination of proteins
that give us a unique phenotype
DNA vs. RNA
DNA
RNA
• Nuclear DNA
• Mitochondrial DNA
• Chloroplast DNA
Nuclear DNA NEVER leaves
the nucleus
• Messenger RNA (mRNA)
• Transfer RNA (tRNA)
• Ribosomal RNA (rRNA)
DOES leave the nucleus:
RNA is assembled in
nucleus and moves to
cytoplasm
C, G, A, U (uracil)
Ribose
Single strand
C, G, A, T
Deoxyribose
Double stranded
DNA vs. RNA
DNA vs. RNA
Types of RNA
Messenger RNA = mRNA ~ Carry copies of
genes (instructions for assembling amino acids
into proteins) from DNA to other parts of the
cell
Ribosomal RNA = rRNA ~ The molecules that
make up the two subunits of ribosomes, where
proteins are assembled
Transfer RNA = tRNA ~ Transfers each specific
amino acid to the ribosome as proteins are
assembled – follows genetic code
Types of RNA
How do cells make RNA?
TRANSCRIPTION ~ Segments of DNA (used as
templates) make complementary RNA
molecules
WHERE: In eukaryotes, RNA made in nucleus
then moves to cytoplasm. In prokaryotes, made
in cytoplasm.
HOW: RNA polymerase separates the DNA
strands, then assembles nucleotides using DNA
as a template
IMPORTANT: A gene (sequence of DNA
nucleotides as a template) can be used to make
100s-1000s of RNA molecules
Transcription
https://www.youtube.com/watch?v=ztPkv7wc3yU
Details of RNA Synthesis
RNA Polymerase ONLY binds to DNA
where there are promoters (specific
base sequences)
Show where to BEGIN transcription
Similar-type sequences show where
to STOP
EDITING ~ Parts of RNA are
removed before it is used
INTRONS ~ parts that are removed
and discarded
EXONS ~ Remaining pieces that are
attached and used to make final RNA
PROTEINS SYNTHESIS & GENETIC CODE
How is the RNA ‘message’ READ?
REMEMBER: amino acids are the monomers
that join together to make PROTEINS
PROTEINS are determined by which amino acids
are used, and in what order
GENETIC CODE for RNA (A, C, G, U) is read
THREE (3) letters at a time ~ each 3-letter word
makes up a CODON
CODONS
CODONS are a group of THREE (3) nucleotide
bases that specify a particular amino acid
Figure 13.5
4 different bases (C, G, A, U), so there are 64
possible combinations (codons)
Some codons are specified by more than one
sequence
Use a table or circle to ‘decode’
START and STOP codons are the punctuation
marks for translation
Cracking the CODE ~ Gene template
Translation
1) Begins at START CODON (AUG)
2) Each tRNA has an anticodon (bases
complementary to bases of codon on mRNA
strand)
3) Codon and anticodon are ATTRACTED
4) Ribosome JOINS the two amino acids
https://www.youtube.com/watch?v=-zb6r1MMTkc
TRANSLATION
QUICK WRITE
Describe the role of each type of RNA molecule
in transcription and translation
mRNA
rRNA
mRNA
Genetic MUTATIONS
If DNA is a CODE, then what would happen if
the message gets changed?
Would the meaning still be the same?
MUTATIONS are heritable changes in genetic
information—the DNA copies have variation
Gene mutations change a single gene
Chromosomal mutations change a whole
chromosome
What do mutations look like?
Point mutations are gene mutations that happen at a single point in the DNA
sequence—involves one or a few nucleotides
Occurs during replication
Alterations can be passed on to future cells
Example of POINT MUTATION
Sickle Cell Anemia
TYPES of Point Mutations
Substitutions ~ one base changed to a different
base
Affect single amino acid or no effect at all
Insertions and deletions ~ one base inserted or
removed from DNA sequence
Can have dramatic effects
Because genes read in groups of THREE (3), and
adding/removing SHIFTS the reading frame
Proteins could be non-functional
Chromosomal Mutations
Changes number or structure of chromosomes
Location of genes on chromosomes
Number of copies of genes
Figure 13.12
Effects of MUTATIONS ???
Many mutations caused by errors in processes
(some caused by environmental factors)
Typical error is ONE incorrect base in every
10,000,000 bases, or 1/10,000,000
BUT small changes can ADD UP OVER TIME!
https://www.youtube.com/watch?v=exZYEIqwW8w (5 Real Strange Genetic Mutations)
POLYPLOIDY
POLYPLOIDY = organism has extra set of
chromosomes
COMPARING MUTATIONS
HARMFUL MUTATIONS
DRAMATICALLY change protein
structure or gene activity
May disrupt biological
processes
May cause genetic disorders
(cancer, sickle cell)
HELPFUL MUTATIONS
Proteins with new or altered
functions that are useful to
organisms in different or
changing environments
EXAMPLE: Insects’ resistance to
pesticides (good for the
insects!)
EXAMPLE: Humans’ resistance
to HIV and increased bone
strength/density
THINK-pair-SHARE
Describe what is happening in this picture