Download Honors_Genetics_B_Student_Notes

Unit 3
Genetics Part B
G11: Genomics
Genome: the complete sequence of an
organism’s genetic material (the order
of nitrogen bases are analyzed and
sequenced).
Genomics can be used to study
human health
• Identifying DNA sequences associated with
genetic disorders can help create treatments
for the disorder
• Studying these sequences can help create
testing to determine if someone is at risk of
developing a certain disease
Manipulating genomes can be used for commercial
value:
- used to improve quality of livestock
and crops
- used to improve disease resistance
to increase crop production
(ex: Bt corn)
Genome sequencing can also help us study
evolutionary relationships
Human Genome
Project
G12: DNA
Replication
G12 Notes:
DNA Replication:
when DNA makes an
exact copy of itself.
(also known as DNA
synthesis)
Takes place during the
“S” phase of the cell
cycle.
Replication is “semi-conservative”, each DNA
molecule contains 1 old strand and 1 new
strand (hypothesis 2).
1. Original DNA molecule consists of 2
complementary strands (A=T, C=G)
2. DNA helicase “unzips” the DNA double helix
to form 2, single stranded molecules
3. Individual nucleotides are added to reform complementary strands
4. Final product = 2 identical DNA
molecules. Each contains one old DNA
strand and one new DNA strand.
DNA Replication
Animation
G13: Meiosis and
Sexual Reproduction
Human Body Cells vs. Sex Cells
- Somatic Cells (body cells) are diploid
(2n). Human somatic cells contain 46
chromosomes.
- Gametes (sex cells) are haploid (n).
Human sex cells contain 23
chromosomes.
Mitosis
• Creates somatic (body)
cells
• Produces 2 genetically
identical cells
• Involves 1 round of
division
• No crossing over
• (diploid → diploid)
46
→
46
Meiosis
• Creates gametes
• Forms 4 genetically
different cells
• Involves 2 rounds of
division (PMAT I and
PMAT II)
• Crossing over occurs
• (diploid → haploid)
46
→
23
• Homologous chromosomes – code for the
same traits
• One homologous chromosome is from your
mother and the other is from your father.
At the start of meiosis (prophase I) homologous
chromosomes will pair together and crossing
over occurs.
Crossing over makes each sperm and egg cell
unique.
Meiosis Video
(9 min)
Animation: How Meiosis Works
Meiosis Simulation
Meiosis I
Homologous chromosomes
pair up and crossing over
occurs. The homologous
chromosomes separate,
producing two haploid cells.
Meiosis II
Similar to mitosis BUT
instead of starting with a
diploid cell, you are starting
with a haploid cell.
Sister chromatids separate
producing 4 haploid cells.
Animation:
Stages of
Meiosis
Random
Orientation of
Chromosomes
During Meiosis
Nondisjunction: occurs when
chromosomes do not separate properly
during meiosis.
• Sperm or egg contain an abnormal
number of chromosomes (↑ or ↓ than
23)
• Ex: Down Syndrome (person has 47
chromosomes instead of 46)
G16/BSCS Chapter 9:
Transcription and
Translation
DNA
transcription
replication
DNA
RNA
translation
PROTEIN
Protein synthesis: the process of making a
protein
- 2 major phases: transcription and translation
Chapter 9.3 - RNA Synthesis
Transcription: DNA is used to create mRNA
DNA
C
G
T
A
RNA
G
C
A
U
DNA: A C A G G A T A T C A A A C A T A T G
mRNA: U G U C C U A U A G U U U G U A U A C
• RNA = ribonucleic acid
• single stranded
• contains the sugar ribose
• U’s (uracil) instead of T’s
(thymine)
- mRNA is transcribed in the nucleus then
moves to the cytoplasm
- RNA polymerase = enzyme that creates mRNA
Transcription
Simulation
Chapter 9.4 - RNA Processing
To prevent mRNA from being damaged in the
cytoplasm:
- a methyl-guanine (mG) cap is
added to 5’ end
METHOLATED
CAP
- a poly A tail (~100-200 A’s) is
added to 3’ end
mRNA is spliced before it leaves the nucleus:
introns removed
exons parts of the gene that
will be expressed (translated)
Chapter 9.5 - Translation
Translation: Turns mRNA into a protein
- Takes place in the cell’s cytoplasm, in
a ribosome
codon (triplet): 3 mRNA bases which code for 1
amino acid
AUG= start codon
UAA, UAG, UGA = stop codons
Transcribe, then translate the DNA
strand below:
ATCTACAAGGGCTCAATCCAG
Translation Involves 3 types of RNA:
mRNA- carries genetic code from the nucleus to
the ribosome
tRNA- transports the amino acids
rRNA- holds the tRNA and mRNA together
Translation Animation
Protein Synthesis
Simulation
rRNA has 3 sites:
A site- acceptor site, holds the tRNA carrying
a.a. to be added to chain
P site- hold tRNA with growing polypeptide
chain
E site – exit site
P
Site
A
Site
mRNA
Steps of Translation: (review diagrams on p. 250-251)
Initiation: ribosome attaches to mRNA,
tRNA carrying methionine binds to P site
Elongation: ribosome moves down 1
codon, amino acids are added to
polypeptide chain
Termination: stop codon reaches A site, release
factor binds to stop codon, polypeptide and
ribosome are released
Translation Simulation (mcgraw-hill)
Once translation is complete the string of
amino acids (polypeptide) is folded up to
create a protein. The order of amino acids in
the polypeptide determines the final shape of
the protein.
Mutation- any change in a cell’s DNA sequence
- Some mutations are harmful, some are
beneficial and some have no effect on the
organism
G17: Cell
Differentiation and
Gene Expression
Gene expression: the process by which a gene
(DNA sequence) is used to produce a protein
DNA → mRNA → protein
• All of your body (somatic) cells are
genetically identical.
– Ex: The liver and skin cells in your body all have
the same DNA sequence
• All of the cells in your body express their
DNA differently
– Ex: a liver cell does not produce the same proteins
as a skin cell
transcription factor: a molecule that controls the
transcription of DNA into mRNA
transcription activator: turns a gene “on”, specific
protein is produced
(DNA → mRNA → protein)
transcription repressor: blocks the process of
transcription, turns a gene “off”, protein is not being
produced
(DNA → mRNA)
G18: Which Corn is Genetically
Modified?
Restriction Fragment Length Polymorphisms
(RFLP): differences in DNA fragments sizes cut by
restriction enzymes
RFLP analysis:
- restriction enzyme cuts everyone's DNA at
different places
- creates fragments with different lengths
- diff. DNA lengths made visible by gel
electrophoresis
Gel Electrophoresis: a process which separates
DNA fragments based on their size
Process:
1. place DNA fragment pieces in gel wells
2. run current through gel DNA –
other end of gel+, smaller DNA
fragments will travel farther
3. DNA is stained to make banding
pattern visible
- DNA fragments are compared to DNA
fragments of other suspects
- more frag. that match= closer relation
- probe can then be added
probe: complementary DNA
sequence labeled with a radioactive
atom
G19: Biopharming
Edible Vaccines
Making an edible vaccine (p. 395-399)
1. DNA is isolated from the pathogen
2. Scientists extract the gene of
interest and make copies of that gene
using the PCR process.
3. Scientists create a DNA construct
4. Scientists insert the DNA construct
into the desired organism.
5. The modified target organism is
grown to mature size. Scientists test
the organism to see if it contains the
inserted gene.