18.3 Flashcards
What is a permanent change in the genetic material of an organism?
Mutation
What are somatic cell mutations?
Mutations that occur in body cells
What are germ cell mutations?
Mutations that occur in reproductive cells
What are point mutations?
Permanent changes that affects just one or a few nucleotides - small change
What is a silent mutation?
Mutation that has no affect on the cells metabolism or the protein that is produced
What is a mis sense mutation?
When a substitution leads to a slightly altered but still functional polypeptide
What is a result of a mis sense mutation?
Sickle cell anemia - change of a single amino acid in on of the polypeptides that make of hemoglobin
What are non sense mutations?
Mutations that render the gene unable to code for a functional polypeptide - start signal is deleted or there is a premature stop codon
How many stop codons are there, and what are they?
There are three stop codons
* UAA
*UGA
*UAG
How many start codons are there, and what are they?
One start codon
* AUG
What is a frame shift mutation?
Causes the entire reading frame of a gene to be altered
Do nucleotide substitutions affect neighboring code sequences?
NO
How many genes do point mutations affect?
Only one gene
What happens when there are mutations that rearrange the genetic material.
Several genes can be affected, including genes located on different chromosomes
What are two examples of chromosomal mutations?
- Crossing over - recombines genetic material on different chromosomes
- DNA replication - the loss or duplication of a portion of chromosome - change in the structure of DNA sequences
What is spontaneous mutations, and what is a source?
Mutations that are caused by molecular interactions that take place naturally in the cell
* Incorrect base pairing by DNA polymerase during the process of DNA replication
What are induced mutations?
Mutations that are caused by agents that are outside the cell
What is a mutagen?
A substance that increases the rate of a mutation in an organism
What are two types of mutagens?
A physical mutagen and a chemical mutagen
What do physical mutagens do, and what are examples of physical mutagens?
They cause physical changes in the structure of DNA(breaks nucleotide sequence)
X ray, UV radiation, gamma rays
What do X rays do?
They are high form of radiation that tear through DNA molecules
* causing random changes from point mutations to the loss of large proportions of chromomes
What does UV radiation do?
It causes a chemical reaction between adjacent pyrimindes Thymine and Cytosine
* Distortion of the DNA molecule that interferes with replication
What can be caused from UV radiation?
Cancer - melanoma
What are chemical mutagens?
Mutagens that enter the nucleus of a cell and induce mutations by reacting chemically with DNA
How can a chemical mutagen insert itself in a cell?
- May insert in a manner that causes point mutations or frameshift mutations
- May have a structure that is similar to to the ordinary nucleotides but with different base pairing properties
What are chemical mutagens that are associated with one or more forms of cancer?
Carcinogenic mutagens
What is the definition of cancer in molecular terms?
The result of somatic cell mutations that disrupt the expression of genes in the regulation of the cell cycle
Does a single mutation have an effect on a living cell?
No
What is responsible for some of the tremendous variation that we see?
The accumulation of mutations over time
What are the two factors for mutations?
They can be inherited
* or the result of exposure to mutagens in the environment
Which things do not share a similar genetic code?
- Mitochondria and chloroplasts
- They have their own DNA, and their genome is replicated, transcribed, and translated independently from the DNA in the nucleus of the cell
What is the endosymbiont theory?
Eukaryotic cells arose through a process in which one specifics of prokaryote engulfed another
What is mitochondrial DNA used for?
To gather information about the history of an individual species
* If two people have identical mtDNA sequences - they most likely share a relatively maternal ancestor
What is examining genetic variations among deferent species?
Study of biological diversity
What is a crucial tool in the study of biological diversity and evolution?
Non coding stretches of DNA
What do non coding stretches of DNA do?
They have a higher mutation rate than the DNA within genes
* The higher the mutation rate - the more genetic variation there is between the same species
What is genetic engineering?
Working in a laboratory, and manipulating genetic material to alter genes and blend plant, animal and bacterial DNA
What is a recombinant DNA?
A molecule of DNA that includes genetic material from different sources
What do prokaryotic organism use to defend themselves against infection by foreign bacteria?
They use restriction enzymes
What do restriction enzymes do?
catalyze the cleave of DNA at a specific nucleotide sequence
What are restriction endonucleases?
Restriction enzymes that cuts the interior of a DNA molecule rather than at the end
What is the target sequence?
The nucleotide sequence that restriction enzymes targets
What is the restriction site?
The point that the DNA strand is cut
What two characteristics of DNA make it useful to genetic engineers?
- Specificity - Cuts made by RE are specific and predictable
- The DNA is cut the same way each time into identical small DNA fragments
- Staggered cuts - RE leave unpaired nucleotides on a single strand at each end of the restriction fragment (sticky ends)
- Can form base pairs with one another with a restriction fragment by the action of the same restriction endonuclease on a different strand
What splices the sticky pairs together that forms base pairs?
DNA ligase
What is gel electrophoresis?
- The tool used to sort and analyze DNA fragment
How does gel electrophoresis separate DNA fragments ?
They separate them according to mass and charge
What is the process of gel electrophoresis?
- Solution that contains DNA fragments is applied at one end of a gel
- An electric current is passed through the gel - causes one end of the gel to develop a positive charge and the other negative charge
- Because DNA is negative it will move towards the positive side - smaller fragments move down
- After a period of time - fragments separate into a pattern of bands (DNA fragments)
