Chapter 9: DNA Structure and Replication Flashcards
DNA Polymerase
Catalyzes the addition of nucleotides as the new DNA chain grows to the 3’ end of each new strand
How is DNA replicated?
DNA replication is semiconservative
What is semiconservative in DNA replication
It is where each parent strand acts as a template for synthesis of a new strand where two replicated DNA molecule each contain one parent strand and one newly synthesized strand
Leading Strand
is synthesized continuously
Lagging Strand
Is synthesized in pieces called Okazaki fragments held together by ligase
Ligase
The enzymatic glue that holds Okazaki fragments
Origin of Replication (ori)
Is the place where the pre-replication complex binds. Binding occurs when proteins in the complex recognize specific DNA sequences within the ori
Chargaff’s Rule
Is the amount of adenine = the amount of thymine and the amount of guanine = the amount of cytosine
Why are mutation rates so much lower than expected?
DNA polymerase has proofreading capabilities and mismatched-repair occur
How does DNA polymerase replicates DNA?
It replicates it by adding nucleotides only to the 3’ end of each growing strand
New synthesized DNA goes in what direction?
It goes in the 5’ to 3’ direction
DNA Proofreading
It occurs right after DNA polymerase inserts a nucleotide.
Mismatch Repair
Occurs after DNA has been replicated and is a second set of proteins surveys the newly replicated molecule
What does DNA proofreading do?
When a DNA polymerase recognizes a mispairing of bases, it removes the improperly introduced nucleotide and tries again
What does mismatch repair do?
It looks for mismatched base pairs that were missed in proofreading and removes the incorrect nucleotides and then has DNA polymerase insert the correct sequence
Mutations
Are changes in the nucleotide of sequence of DNA that are passed on from one cell or organism to another. It may or may not affect the phenotype
What are the two types of mutations?
Somatic mutations
Germline mutation
Somatic Mutation
It occur in the somatic (body) cells of a multicellular organism that are passed onto the daughter cells during mitosis and in turn to the offspring of those cells. These mutations are not passed on to gametes
Germline Mutation
It occurs in the cells of the germ line - the specialized cells that give rise to gametes and gametes with this mutation will pass it on to a new organism at fertilization
Silent Mutation
They do not affect gene function and are mutations in DNA that are not expressed or mutations within an expressed region that do not have any effect on the encoded protein. Most mutations in large genomes are silent
Loss of Function Mutation
It can result in either the loss of expression of a gene or in the production of a nonfunctional protein or RNA (usually seen in recessive inheritance)
Gain of Function Mutation
It leads to a protein with an altered function and usually shows dominant inheritance and is common in cancer
Conditional Mutation
This causes their phenotypes only under certain restrictive condition (usually under temperature)
Miessence Mutation (Single point Mutation)
Is the addition or subtraction of a single nucleotide base that results in an altered phenotype or creates different amino acid
Chromosomal Mutation
They are extensive and they change the position or cause a DNA segment to be duplicated or lost
Deletion mutation of chromosomes
It is the removal of part of the genetic material and the consequences can be severe or even fatal
Duplication mutation of the chromosome
It can be produced at the same time as deletions and would arise if homologous chromosomes broke at different positions and then reconnect with the wrong partners.
Inversion mutation of the Chromosome
Is the result of breaking and rejoining chromosomes by removing a segment of DNA and reinsert it into the same location of the chromosome that’s in the wrong direction
Translocation mutation of the chromosome
Results when segments of chromosomes break off and become joined to different chromosomes
What are the benefits of Mutations?
- May cause an advantageous change in offspring
2. May provide the raw material for evolution in the form of genetic diversity
