objectives_unit_3_ch_17_molecular_genetics1.docx | |
File Size: | 13 kb |
File Type: | docx |
•Mutation - the appearance of a new allele on a chromosome. A sudden change in the structure or the
amount of genetic material. While most
mutations are harmful to an organism, some have no effect and others are
beneficial.
Two kinds of mutations:
•chromosomal mutation - abnormal change in the structure of all or part of a chromosome or in the number of chromosomes an organism has... results in new gene combinations. •Gene mutation - change that affects a gene on a chromosome (white eyed fruit fly that Morgan found- mutation for eye color)
Deletion - a piece of chromosome breaks off, resulting in the loss of some genes. Ex. Cri-du-chat
Duplication (addition) - a piece of a chromosome breaks off and attaches to a homologous chromosome. The homologous chromosome then has some gene repeated. Ex. Fragile X
Inversion - a piece of chromosome is rotated, which reverses the order of genes in the segment. Ex. Some types of autism
Translocation - transfer of a part of a chromosome to a non-homologous chromosome. Ex. Some types of Down syndrome and leukemia
Nondisjunction - addition or loss of a whole chromosome (remain together during meiosis). Ex. Down syndrome or Turner syndrome.
http://www.youtube.com/watch?v=C58yMPF18YY&safety_mode=true&persist_safety_mode=1&safe=active – chromosome mutations
Objective 2 - See handout (table) from Karyotype Lab.
Objectives 3 & 4
Contributors to the concept of a gene:
Two things being researched:
•What contained genetic information – DNA or proteins • the structure of DNA
Mendel (observed inheritance of traits)
Sutton and Boveri (movement of chromosomes)
Phoebus Levene (early 1900s)
-isolated and named DNA and RNA (noticed the different makeup of sugars)
-termed the individual units that make up DNA as nucleotides (sugar, phosphate group, and nitrogen base)
-five different nitrogen bases (adenine, thymine, uracil, guanine, and cytosine)
- only difference in nucleotides is their bases
- nucleotides connect between their phosphate group and another=s sugar
- Levene incorrectly concluded that DNA was made up of the same number and combination of nucleotides
- he thought the nucleotides occurred in the same patter over and over ACTGACTGACTG
- because of this assumption, scientists didn=t think DNA was complicated enough to be the unit of heredity
- it was figured then that proteins had heredity
- took several decades to clear up this misconception
Fred Griffith (1928) -
Erwin Chargaff (late 1940's)
James Watson and Francis Crick – (1953-64)
RNA - 3 differences
•Sugar: ribose instead of deoxyribose •Nitrogen base: no thymine in RNA – uracil •RNA is single stranded; DNA is double-stranded
Watson and Crick double helix model of DNA - Objective 5
Biology 3201 - DNA replication - the fine details :)
Genome - the sum of all the DNA carried in an organism=s cells.
DNA Replication - Two molecules of DNA are made from one. Each new molecule contains one parent strand and one new strand.
Stages:
Two kinds of mutations:
•chromosomal mutation - abnormal change in the structure of all or part of a chromosome or in the number of chromosomes an organism has... results in new gene combinations. •Gene mutation - change that affects a gene on a chromosome (white eyed fruit fly that Morgan found- mutation for eye color)
Deletion - a piece of chromosome breaks off, resulting in the loss of some genes. Ex. Cri-du-chat
Duplication (addition) - a piece of a chromosome breaks off and attaches to a homologous chromosome. The homologous chromosome then has some gene repeated. Ex. Fragile X
Inversion - a piece of chromosome is rotated, which reverses the order of genes in the segment. Ex. Some types of autism
Translocation - transfer of a part of a chromosome to a non-homologous chromosome. Ex. Some types of Down syndrome and leukemia
Nondisjunction - addition or loss of a whole chromosome (remain together during meiosis). Ex. Down syndrome or Turner syndrome.
http://www.youtube.com/watch?v=C58yMPF18YY&safety_mode=true&persist_safety_mode=1&safe=active – chromosome mutations
Objective 2 - See handout (table) from Karyotype Lab.
Objectives 3 & 4
Contributors to the concept of a gene:
Two things being researched:
•What contained genetic information – DNA or proteins • the structure of DNA
Mendel (observed inheritance of traits)
Sutton and Boveri (movement of chromosomes)
Phoebus Levene (early 1900s)
-isolated and named DNA and RNA (noticed the different makeup of sugars)
-termed the individual units that make up DNA as nucleotides (sugar, phosphate group, and nitrogen base)
-five different nitrogen bases (adenine, thymine, uracil, guanine, and cytosine)
- only difference in nucleotides is their bases
- nucleotides connect between their phosphate group and another=s sugar
- Levene incorrectly concluded that DNA was made up of the same number and combination of nucleotides
- he thought the nucleotides occurred in the same patter over and over ACTGACTGACTG
- because of this assumption, scientists didn=t think DNA was complicated enough to be the unit of heredity
- it was figured then that proteins had heredity
- took several decades to clear up this misconception
Fred Griffith (1928) -
- English medical officer
- studying bacteria responsible for a pneumonia epidemic
- discovered that dead pathogenic bacteria passed their deadly properties to non-pathogenic bacteria
- came up with transforming principle
- not
sure what caused the transformation
- took up Griffith=s research after he was killed
- conducted several experiments
- when they destroyed the protein of the bacteria, transformation still occurred
- when they destroyed the DNA of the bacteria, transformation didn=t occur
- when they destroyed the RNA of the bacteria, transformation occurred
- found out that it was the DNA responsible for the transformation
- had resistance from science community
Erwin Chargaff (late 1940's)
- examined Levine=s research
- discovered that nucleotides were not present in equal quantities
- did find that guanine was proportionate to cytosine
- adenine was proportionate to thymine
- Chargaff=s Rule
Alfred Hershey and Martha Chase (1952)
- Carried out an experiment that provided the final proof that DNA, not protein carried genetic information.
- Using radioactive tracers of sulphur and phosphorus, they discovered that DNA (not protein) was transferred within tagged bacteriophages infected normal cells (confirming Avery’s belief)
- Virus – DNA core surrounded by protein coat
- Wanted to determine whether the whole phage entered the bacteria or one of DNA or protein coat
- Tagged DNA with radioactive phosphorus (contains no sulphur)
- Tagged protein coat with radioactive sulphur (contains no phosphorus)
- Bacteria was exposed to the radioactive DNA
- Other was exposed to radioactive protein
- Cytoplasm was tested for radioactivity
- Cells infected by phages with radioactive DNA – radioactive
- Cells infected by phages with radioactive protein – not reactive
- DNA of bacteriophages (virus) enters cell
- Phage protein stays outside
- Therefore it must be the DNA
that carries the genetic instructions.
- Bombarded DNA with X-rays and discovered that a pattern of repeating structures appeared (nucleotides)
- Arranged in the form of a helix, nitrogen bases inside and sugar-phosphates on the outside
- (Helix – a shape like a coiled sprig, used to describe the structure of DNA molecules)
- Her observations proved to be important keys to understand the structure of DNA
James Watson and Francis Crick – (1953-64)
- Discovered the structure of DNA and the DNA code
- First to make a structural
model of DNA (double-helix)
- Discovered transposons (jumping genes) that can rearrange genetic material.
- Transposons are short strands
of DNA capable of moving from one location to another within a cell’s genetic
material
RNA - 3 differences
•Sugar: ribose instead of deoxyribose •Nitrogen base: no thymine in RNA – uracil •RNA is single stranded; DNA is double-stranded
Watson and Crick double helix model of DNA - Objective 5
- Ladder-shaped
- Handrails (sugar and phosphate)
- Rungs (nitrogen bases)
- Adenine and guanine – purines (double ring)
- Thymine and cytosine – pyramidines (single ring)
- Together three ring structure width (keeps ladder same distance) so A pairs with T and G with C
- Base pairs held together with hydrogen bonds
- Strands are complementary and antiparallel (run in opposite directions)
- 5’ end is matched with
3’ end of other strand
(See Fig 17.12, pg 574 and Fig 17.13, pg 575,)
DNA replication – the overview to objective 7
- Double Helix
- Weak hydrogen bonds hold the nitrogen bases together
- Helix unwinds and bonds break
- Two strands of DNA come apart
- Free nucleotides in the nucleus of the cell fasten to their complentary bases on each exposed strand
- Join together to make a complementary strand, just like the old one
- Two double stranded molecules of DNA are exactly like the original molecule
- Each molecule contains one old and one new strand
- Don’t begin at one end and continue to the other, like a zipper
- Rather, begins simultaneously at many points.
Biology 3201 - DNA replication - the fine details :)
Genome - the sum of all the DNA carried in an organism=s cells.
DNA Replication - Two molecules of DNA are made from one. Each new molecule contains one parent strand and one new strand.
Stages:
- initiation
- elongation
- termination
- proofreading and correction
Initiation (pic page 583)
- Enzymes cause the DNA strands to separate, forming a replication bubble.
- In this bubble (space) DNA polymerase is the enzyme that goes in there and adds nucleotides (withnin the nucleus) to the open strands.
- The bubble moves throughout the length of the strand, as a replication fork unwinds the DNA ahead of the bubble.
- It is able to do this with the help of the enzyme helicase.
Elongation (pic page 584)
- Replication takes place in a 5' to 3' directon
- Primer (chain of RNA nucleotides) is the starting point.
- There are two strands, a leading strand and a lagging strand
- The leading strand only needs one primer and nucleotides are added steadily in the same direction that the replication fork moves.
- With the lagging (slower) strand, even though the fragments are built in the 5' to 3' direction, DNA polymerase works in the opposition direction of the replication fork, requiring a primer for each fragment. These Okazaki fragments are then joined by enzyme DNA ligase
- The primer is then removed by another DNA
polymerase,
Termination
Once the new strand is created, it isn=t as long as the original because there=s one primer at the very beginning that=s removed that cannot be filled in. Fortunately the DNA molecule has extra nucleotides called telomeres that adds extra useless information to a strand, which is lost as the strand shortens, but doesn=t damage the genetic material. The parent DNA rewind to their original state at this point.
Proofreading and Correction
This is the Aspell check@ of DNA replication. DNA polymerase detects whether the complementary nucleotides are bonding together (hydrogen bonds). If this isn=t happening, the polymerase determines there is a problem and removes all the problem areas and adds the correct bases.
All of the components that work together for DNA replication is called the replication machine
http://www.youtube.com/watch?v=DGGIhfe7YZg – overview 1:35
Protein Synthesis (refer to handout) - Objective 9
•DNA controls all the actions of the cell, and ultimately the things that make up the body (making of 20 different amino
acids, which combine to formpolypeptides
and proteins (ex. hormones, enzymes, etc.)).
•The way in which an amino acid is made is determined by the DNA sequence.
• Genes are expressed through proteins which get their info from DNA.
• Each amino acid has 3 nucleotides (codons) and there are even stop and start codons which tell the replicating strand where to begin and end the process.
•The area in a nucleotide sequence that is replicated is the reading frame
http://www.youtube.com/watch?v=h3b9ArupXZg – Bozeman 12:00 - Protein synthesis tutorial
http://www.youtube.com/watch?v=NJxobgkPEAo – 2:50 - Protein Synthesis overview
•transcription - the first stage of gene expression, in which a strand of mRNA is produced that is complementary to a segment of DNA.
• RNA polymerase opens a portion of the double helix of DNA. RNA polymerase is used to build this strand the same way DNA polymerase does in DNA replication.
•Only one strand is copied, so Okazaki fragments aren’t needed.
•Then some sections of the strand are removed, as the strand contains both exons (expressed sequences) and introns,which get copied in the process but aren’t needed. It carries this code from the nucleus where it’s copied to the ribosomes in the cytoplasm
•translation - the second stage of gene expression, in which tRNA and ribosomes help to make proteins.
•The ribosomes bring together the mRNA strand, tRNA molecules carrying the amino acids, and the enzymes involved in building proteins at the site of translation: called ribosomal RNA.
•Transfer RNA is a cloverleaf shaped object that serves to connect a mRNA to an amino acid.
•At this point, the mRNA binds to a ribosome and the codons on the mRNA are made available for bonding, with the first exposed codon
in the chain attracting the complementary anticodon on the tRNA (which is carrying an amino acid).
•Then the second tRNA molecule arrives at the second exposed codon. The two amino acids connect, and the chain is given to the second tRNA.
•Ribosome moves to the next codon on the strand, with the tRNA molecules leaving after they give away their amino acids.
•The third tRNA molecule arrives next to the second, bringing an amino acid which becomes a part
of the chain, and takes on the chain from the second tRNA.
•This continues until the ribosome reaches a stop codon. Then the completed polypeptide is released to be used by the body
http://www.youtube.com/watch?v=5oyQXR9gJrs – 3:31 overivew of protein synthesis
http://www.youtube.com/watch?v=Ikq9AcBcohA&safety_mode=true&safe=active&persist_safety_mode=1
– shows translation (I usually turn the volume down and describe the video - you do what you wish :)
•DNA controls all the actions of the cell, and ultimately the things that make up the body (making of 20 different amino
acids, which combine to formpolypeptides
and proteins (ex. hormones, enzymes, etc.)).
•The way in which an amino acid is made is determined by the DNA sequence.
• Genes are expressed through proteins which get their info from DNA.
• Each amino acid has 3 nucleotides (codons) and there are even stop and start codons which tell the replicating strand where to begin and end the process.
•The area in a nucleotide sequence that is replicated is the reading frame
http://www.youtube.com/watch?v=h3b9ArupXZg – Bozeman 12:00 - Protein synthesis tutorial
http://www.youtube.com/watch?v=NJxobgkPEAo – 2:50 - Protein Synthesis overview
•transcription - the first stage of gene expression, in which a strand of mRNA is produced that is complementary to a segment of DNA.
• RNA polymerase opens a portion of the double helix of DNA. RNA polymerase is used to build this strand the same way DNA polymerase does in DNA replication.
•Only one strand is copied, so Okazaki fragments aren’t needed.
•Then some sections of the strand are removed, as the strand contains both exons (expressed sequences) and introns,which get copied in the process but aren’t needed. It carries this code from the nucleus where it’s copied to the ribosomes in the cytoplasm
•translation - the second stage of gene expression, in which tRNA and ribosomes help to make proteins.
•The ribosomes bring together the mRNA strand, tRNA molecules carrying the amino acids, and the enzymes involved in building proteins at the site of translation: called ribosomal RNA.
•Transfer RNA is a cloverleaf shaped object that serves to connect a mRNA to an amino acid.
•At this point, the mRNA binds to a ribosome and the codons on the mRNA are made available for bonding, with the first exposed codon
in the chain attracting the complementary anticodon on the tRNA (which is carrying an amino acid).
•Then the second tRNA molecule arrives at the second exposed codon. The two amino acids connect, and the chain is given to the second tRNA.
•Ribosome moves to the next codon on the strand, with the tRNA molecules leaving after they give away their amino acids.
•The third tRNA molecule arrives next to the second, bringing an amino acid which becomes a part
of the chain, and takes on the chain from the second tRNA.
•This continues until the ribosome reaches a stop codon. Then the completed polypeptide is released to be used by the body
http://www.youtube.com/watch?v=5oyQXR9gJrs – 3:31 overivew of protein synthesis
http://www.youtube.com/watch?v=Ikq9AcBcohA&safety_mode=true&safe=active&persist_safety_mode=1
– shows translation (I usually turn the volume down and describe the video - you do what you wish :)
Objective 10. influence of hormonal and environmental factors on gene expression (594-95).
Environment can change expression of some genetic info
•changes in temperature or light
–change color, thicker coats, plants germinate, us and alertness,
–Ex. Fur color of arctic foxes or hares
•presence or absence of nutrients in the environment
–When lactose is in the environment, E. coli will increase the production of enzymesthat synthesize lactose
–When the amino acid tryptophan is in the environment, E. coli will decrease the production of enzymes that synthesize tryptophan
•Presence of hormones in the body
–hormones can trigger protein synthesis in other cells
–Ex. Siamese cats: two colors... one hair colour gene produces a temperature sensitive enzyme, dark pigment occurs on cooler areas of body: feet, snout, tip of tail, ears.
–Ex. Sex and baldness - baldness gene is only dominant in males
–Ex. Differences in identical twins
–Ex. Male slipper limpet turning female if no females around
•Since conception each of your cells contains the same info. Homeobox (hox) genes control which parts of the genome are activated in different cells. Process ensures that each body cell develops the properties of only one particular tissue or organ.
Objective 11 (also part of objective 1) (p. 599)
What is a mutation?
•Mutation - the appearance of a new allele on a chromosome. A sudden change in the structure or the amount of genetic material. While most mutations are harmful to an organism, some have no effect and others are beneficial.
Two kinds of mutations:
•chromosomal mutation - abnormal change in the structure of all or part of a chromosome or in the number of chromosomes an organism has... results in new gene combinations.
•Gene mutation - change that affects a gene on a chromosome (white eyed fruit fly that Morgan
found- mutation for eye color)
Can also be defined as:
mutation - a permanent change in the genetic material of an organism
Caused by:
•spontaneous mutations - permanent change in DNA as a result of naturally occurring molecular
interactions (incorrect pairing of bases during replication)
•induced - permanent change in DNA caused by mutagen outside cell (X-ray & UV
radiation, chemicals).
mutagen- substance or event increasing the rate of mutation in an organism: chemical or physical
Objective 12. Explain what is meant by a gene mutation and predict the general effects it has on protein synthesis.
Change in genetic information. Can be expressed as:
•cancer
•sickle cell anemia
general effects: error in the protein, resulting in different amino acid, or none at all... (substitution or frameshift mutations)
Objective 13. Distinguish between somatic and germ mutation and compare the inheritability of each (page 596).
•Somatic mutations - occur in somatic cells (body cells) and thus cannot be passed on to offspring.
•Germ mutations - permanent change in DNA of reproductive cell of an organism (gametes). Occur during meiosis (gamete production) and thus such mutations can be passed on to offspring. Inherited gene mutations are usually recessive.
•For a mutation to be inherited, must be present in the DNA of a gamete. Mutations in body cells cannot be inherited in sexual organisms (not
transmitted to offspring).
Objective 14. Distinguish among the different types of point mutations (gene mutations). P. 597 - good pics here to illustrate material
All result in permanent changes in genetic material.
Substitutions:
•silent -no effect on metabolism of the cell – the nucleotide change still results in the same amino acid formed. ACU --> ACC (both code for threonine)
•mis-sense mutation - slightly altered but still functional proteins – the nucleotide change results in a different amino acid. GAA --> GUA (glutamate to valine – sickle cell anemia)
•nonsense mutation - gene is unable to code for any functional polypeptide product. Nucleotide changes from functioning amino acid to a stop, so the
polypeptide doesn’t function. UUG --> UAG (leucine to STOP codon)
Frameshift mutations
- change caused by insertion of deletion of one or two nucleotides within a sequence of codons.
–can cause a change in the entire reading frame of a gene. In most cases, a frame shift will result in a nonsense mutation.
Environment can change expression of some genetic info
•changes in temperature or light
–change color, thicker coats, plants germinate, us and alertness,
–Ex. Fur color of arctic foxes or hares
•presence or absence of nutrients in the environment
–When lactose is in the environment, E. coli will increase the production of enzymesthat synthesize lactose
–When the amino acid tryptophan is in the environment, E. coli will decrease the production of enzymes that synthesize tryptophan
•Presence of hormones in the body
–hormones can trigger protein synthesis in other cells
–Ex. Siamese cats: two colors... one hair colour gene produces a temperature sensitive enzyme, dark pigment occurs on cooler areas of body: feet, snout, tip of tail, ears.
–Ex. Sex and baldness - baldness gene is only dominant in males
–Ex. Differences in identical twins
–Ex. Male slipper limpet turning female if no females around
•Since conception each of your cells contains the same info. Homeobox (hox) genes control which parts of the genome are activated in different cells. Process ensures that each body cell develops the properties of only one particular tissue or organ.
Objective 11 (also part of objective 1) (p. 599)
What is a mutation?
•Mutation - the appearance of a new allele on a chromosome. A sudden change in the structure or the amount of genetic material. While most mutations are harmful to an organism, some have no effect and others are beneficial.
Two kinds of mutations:
•chromosomal mutation - abnormal change in the structure of all or part of a chromosome or in the number of chromosomes an organism has... results in new gene combinations.
•Gene mutation - change that affects a gene on a chromosome (white eyed fruit fly that Morgan
found- mutation for eye color)
Can also be defined as:
mutation - a permanent change in the genetic material of an organism
Caused by:
•spontaneous mutations - permanent change in DNA as a result of naturally occurring molecular
interactions (incorrect pairing of bases during replication)
•induced - permanent change in DNA caused by mutagen outside cell (X-ray & UV
radiation, chemicals).
mutagen- substance or event increasing the rate of mutation in an organism: chemical or physical
Objective 12. Explain what is meant by a gene mutation and predict the general effects it has on protein synthesis.
Change in genetic information. Can be expressed as:
•cancer
•sickle cell anemia
general effects: error in the protein, resulting in different amino acid, or none at all... (substitution or frameshift mutations)
Objective 13. Distinguish between somatic and germ mutation and compare the inheritability of each (page 596).
•Somatic mutations - occur in somatic cells (body cells) and thus cannot be passed on to offspring.
•Germ mutations - permanent change in DNA of reproductive cell of an organism (gametes). Occur during meiosis (gamete production) and thus such mutations can be passed on to offspring. Inherited gene mutations are usually recessive.
•For a mutation to be inherited, must be present in the DNA of a gamete. Mutations in body cells cannot be inherited in sexual organisms (not
transmitted to offspring).
Objective 14. Distinguish among the different types of point mutations (gene mutations). P. 597 - good pics here to illustrate material
All result in permanent changes in genetic material.
Substitutions:
•silent -no effect on metabolism of the cell – the nucleotide change still results in the same amino acid formed. ACU --> ACC (both code for threonine)
•mis-sense mutation - slightly altered but still functional proteins – the nucleotide change results in a different amino acid. GAA --> GUA (glutamate to valine – sickle cell anemia)
•nonsense mutation - gene is unable to code for any functional polypeptide product. Nucleotide changes from functioning amino acid to a stop, so the
polypeptide doesn’t function. UUG --> UAG (leucine to STOP codon)
Frameshift mutations
- change caused by insertion of deletion of one or two nucleotides within a sequence of codons.
–can cause a change in the entire reading frame of a gene. In most cases, a frame shift will result in a nonsense mutation.
Objective 15 - McClintock's jumping genes - see Objective 4.