Download Genetics 1 Notes

Warm Up
1. Write the equation for photosynthesis
2. Write the equation for aerobic cellular
respiration.
3. In what organelle does photosynthesis
occur? In what organelle does respiration
occur?
4. How are prokaryotic cells different from
eukaryotic cells?
5. Give an example of a prokaryotic cell. Give
an example of an eukaryotic cell.
Genetics Part I
History of DNA:
Discovered by: James Watson, Francis Crick,
Maurice Wilkins, and Rosiland Franklin
Franklin and Wilkins discovered there was
DNA.
Watson and Crick discovered the molecular
shape.
Structure of DNA
Structure of DNA
• “Twisted ladder”
• Sides of ladder are alternating sugarphosphate groups
• “Rungs” are complementary nitrogenous
bases that are joined together by
hydrogen bonds
Structure of DNA
•Nucleotide (SUBUNIT) is:
-1 sugar (deoxyribose), 1 phosphate and
1 nitrogen base.
•Why are they so important?
-In DNA they code for proteins, which is the
central key to cell function and life
“Rungs” or Nitrogen Bases
•
•
•
•
Adenine=A
Thymine=T
Cytosine=C
Guanine=G
• A bonds with T
• G bonds with C
•
•
Structure of DNA
Two nucleotides bond at the nitrogenous
base and form a double helix. This double
helix twists on itself to give it the
characteristic shape.
DNA looks like a ladder in that the sugarphosphate is termed the ‘backbone’ (on
outside) and the nitrogenous bases are
termed ‘rungs’ (on inside).
•
•
•
Structure of DNA
The bases are connected to a complimentary
strand by hydrogen bonding between paired
bases, adenine (A) with thymine (T) and
guanine (G) with cytosine (C)
A and T are connected by two hydrogen
bonds while G and C are connected by three
The hydrogen bonds are very, very, very
weak. They need to be weak so that the
DNA can separate in order for replication.
Warm Up
1. What is DNA? What can the name tell you?
2. What are the 3 parts of a nucleotide?
3. What are the names of the four nitrogenous
bases?
4. What base pairs with G? What base pairs
with A?
5. What is the “backbone” of a DNA molecule?
What are the “rungs” of a DNA molecule?
ASEXUAL CELL CYCLE
Asexual Reproduction
-one ‘parent cell’ is needed
-offspring are genetically similar
to the parent
-Cells do this anytime a
“replacement” is needed
-Mitosis occurs (will review!)
Cell cycle
4 phases
1.G1: Gap 1
2.S: Synthesis
3.G2: Gap 2
4.M: Mitosis
Cell Cycle Cont’d
• G1, S, and G2 make up the largest portion
of the cycle and are collectively called
INTERPHASE
• Sometimes cells temporarily or
permanently stop dividing. If this occurs
they are said to be in the G0 phase (Gap
0) or RESTING phase
G0- GAP 0
1. Cell exits the cell cycle
2. Cell no longer divides
3. Examples: neuron, red blood cell, sperm,
unfertilized egg
G1- GAP 1
1. Cell increases in size
2. Cell produces RNA and proteins to prepare
the DNA to replicate.
S=Synthesis
DNA Replication
1. An exact copy is made
2. Enzymes (proteins) work to link nucleotides
together.
Steps to DNA Replication:
-Helicase splits at the hydrogen bonds (remember they
are very weak).
-Another enzyme brings individual nucleotides to leading
strand. (top down)
-Another enzyme brings nucleotides to the lagging strand.
(bottom up)
-End result: a chromosome.
Parts of a chromosome
Centromere
Sister chromatids
What is a chromosome?
• Tightly coiled DNA and the proteins
associated with DNA
• Why? Allows large amounts of DNA to fit
into the nucleus.
Function of the different parts
of a chromosome
Centromere- holds sister
chromatids together until they
need to separate for
replication.
Sister chromatids- contain the
same genetic information.
Separate so exact copies can
be made when producing an
identical cell.
G2- GAP 2
1. Continue to produce proteins and grow
2. Determines if the cell is prepared for M… if
not, it will fix problems.
Mitosis
• After G2, cell may be ready to undergo
mitosis-the actual dividing of a cell.
• You MUST memorize the characteristics
during each stage of mitosis!
• Mitosis PPT
Warm Up
1. During what phase of mitosis does the
nuclear envelope disappear?
2. During what phase do the sister chromatids
pull apart and go to opposite ends of the
cell?
3. During what phase is DNA replicated?
4. During what phase would the DNA first
appear as chromosomes?
5. During what phase do the spindle fibers
begin to form?
PROTEIN SYNTHESIS
DNA -vs- RNA
DNA
-Deoxyribose
-Thymine
-Double Helix
RNA
-ribose
-Uracil
-single twisted strand
Both
-Nucleic acid
-Nucleotides: C, G, A
Protein Synthesis
• The process of taking DNA and bringing
the “chemical code” to life. We do this by
making proteins that we need to carry out
life-sustaining processes.
• Two key steps:
– Transcription
– Translation
Protein Synthesis
1. Transcription
-mRNA (messenger
RNA) is
TRANSCRIBED
-Take the DNA single
strand and add
complimentary base
pairs except RNA
format-uracil (U)
instead of thymine (T)
-Occurs inside the
nucleus
Terminology for Translation
• Codon:A sequence of three nucleotides
located on the mRNA
• Anticodon:A sequence of three adjacent
nucleotides located on one end of the
tRNA molecule
2. Translation
-Occurs inside a ribosome.
-Codon on mRNA that will match the anticodon
on the tRNA
-tRNA links the anticodon to the codon
-tRNA has an amino acid attached-determined
by codon. As codon/anticodon is matched amino
acids are bound together by means of a peptide
bond
-Linking amino acids together forms a
polypeptide chain, which is folded into proteins.
Matching codons to amino acids
• Use chart.
• Find codon-look
up amino acid.
• Practice
problems in
packet are for
homework.
Why do we need Protein Synthesis?
• Make proteins- chain of amino acids.
• We need proteins for growth and
development of cells
• More specifically, we need
polypeptide chains (proteins) with a
specific code so it can do a specific
job within our body
Few more things about protein
synthesis:
1. DNA can never leave the nucleus
2. Transcription occurs in the nucleus
3. Translation occurs at the ribosome (in
cytoplasm)
4. There is always a ‘start’ message (AUG)
and a ‘stop’ message (UGA).
-start gets the ribosome working
-stop lets the ribosome release the
polypeptide chain.
Protein Synthesis Video
http://www.youtube.com/watch?v=NJxobgkP
EAo
Warm Up
1. Write the equation for photosynthesis.
2. Write the equation for aerobic respiration.
3. What type of mutation?
CCTGAG into CCTAAG
4. What type of mutation?
CCTGAG into CTGAG
5. What type of mutation?
CCTGAG into CCTGATG
Protein Synthesis Activity
Roles (mRNA, ribosome, tRNA):
1. mRNA- go to the nucleus and write the
compliment to the DNA code
2. Ribosome- receive the mRNA message,
write down the tRNA anticodons, determine
amino acids based on chart, tell tRNA what
anticodons to locate on cabinets.
3. tRNA- receive the anticodon from the
ribosome and locate it; flip the card over
and read the word; bring the word to the
ribosome so that they can write the word
down.
Protein Synthesis Activity
Summary: EACH PERSON MUST
COMPLETE THIS!!!
1. What does each word represent?
2. What does the sentence represent?
3. What happened if you wrote down the
wrong mRNA code based on the DNA?
4. What happened if you wrote down the
wrong tRNA code based on the mRNA?
5. Summarize how making a sentence is
similar to protein synthesis.
Some animations on the web
http://www.cns.pdx.edu/~newmanl/ChapterOutlines/Chapter01.html
http://www.ai.mit.edu/lab/olympics/98/events/MITosis/
Warm Up
1. What are the monomers of DNA?
2. Transcribe:
ATC-GCC-TAA-ACT
3. Translate:
UGC-ACU-GGU-UAC
4. Where does transcription occur?
5. Where does translation occur?
MUTATIONS
What is it?
• Accidental changes in a sequence of DNA
• Can prevent a gene from functioning
properly or completely
Mutation
Types:
1. Substitution- a mutation that exchanges
one base for another
a mutation that exchanges one base for another
- Can cause a small change in the protein
produced or nothing at all will happen.
Mutation
2. Insertion- mutations in which extra base
pairs are inserted into a new place in the
DNA
-Can lead to added amino acids in
polypeptide chain
Mutation
3. Deletion- mutations in which a section of
DNA is lost, or deleted
-Can lead to missing amino acids in
polypeptide chain
What causes mutations?
• Spontaneous/random
• Radiation or chemical exposure
Radiation
• Overexposure to radiation creates an
excess of energy which causes the bases
to pair incorrectly—creating mutations
Why does radiation cause
cancer?
• Cancer: The disease caused by an uncontrolled
division of abnormal cells in a part of the body.
• Why does radiation cause cancer?
– Mutations ultimately create an error in the
DNA blueprint. If the DNA is wrong, it causes
the cell to lose control of cell division. When
cells begin to divide rapidly, it creates a
tumor.
Advantages and Disadvantages
of errors in protein synthesis
• Advantages: an overproduction in proteins
can be helpful if you have an injury and
need rapid repair
• Disadvantages: an overproduction in
proteins can cause cancer. An
underproduction in proteins can cause
genetic disorders