Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key


Play button


Play button




Click to flip

27 Cards in this Set

  • Front
  • Back
All genetic Material
Why circular chromosomes for chloroplasts?
Bacterial origin
Structure of Eukaryal chromosomes
-They have centromeres at the center and telomeres at the end with sequences in between.

- Gene density of eukaryal cells is less than in prokaryal

-Have a higher number of repeats and repeated sequences in general than do prokaryal genomes.
Are needed for replication
Is used in partitioning the chromosomes during cell division.
What are the four major non-chromosomal DNA elements?
3.Mitochondria, Chloroplast genomes
4.Transposable elements
-DNA or RNA genome, which controls their replication and transfer to host cells

-Their chromosomes encode virus related functions and are autonomous from the cell's chromosome.
-Self-replicating extra-chromosomal elements

-Often carry useful genes and are generally beneficial

-Do not have extracellular forms as viruses do

-Usually small, some large, carry essential genes.
Mitachondria and chloroplast genomes
-Carry genetic elements or chromosomes

-Independant and separate from the nuclear chromosomes of the eukaryal cell

-Usually encode specialized functions especially those involved in energy metabolism or photosynthesis

-Have own protein synthesis machinery but are dependent on nuclear encoded proteins for many functions.
Transposable elements
-These are moblile genetic elements that can move from one place on the chromosome to another.

-In prokaryotic cells there are 3 elements

1.Insertion Sequences

1 and 2 encode transposase
DNA replication is semi-conservative, meaning that both strands are replicated. Both strands serve as templates, and the two DNA strands are copied.
What are the specific sites of initiation and termination for the replication of E.coli chromosome? How many replication forks are formed during a typical replication cycle?
-initiation occurs at the origin of replication

-The DNA double helix is opened and replication begins on both strands resulting in two replication forks

-Theta intermediate forms

-Termination of DNA replication occurs at specific sequence elements and the two double stranded circular DNA's are separated.
Bidirectional replication
Means there are two replication forks, one movingg in each direction
Theta Structure
In circular chromosome, the replication intermediate appears as a theta structure
Is the main processive enzyme and synthesizes the leading and lagging strands
Is reponsible for removing the RNA primer on the lagging strand and also participates in DNA repair processes

-synthesizes DNA using dNTPS, a template and a primer. This enzyme has 3' to 5' activity and also has 5' to 3' exonuclease activity that partcipates in the removal of RNA primers
DNAP III con't
Requires a templete and a primer with a 3'-OH. Synthesis proceeds 5' to 3' requires using dNTPs as substrates and WC pairing with the templates determining the correct nucleotide to be added.

Also has 3' to 5' exonuclease active that is used in proof reading.
DNA helicases
Bind at the replication fork and separate the DNA strands.
What strand is discontinous in the replication process?
The lagging strand, made by Okazaki fragments.
How is the acccuracy of the replication process monitored?
DNAP I has 5' to 3' exonuclease activity but can't close the phospodiester backbone, so DNA ligase closes the phosphodiester backbone.

DNAP III encounters a mismatch in the WC pairing of a newly synthesized base pair it recognizes the distortion and initiates 3' to 5' exonuclease activity

The mismatched base pair is removed and a new correct nucleotide is inserted.
Spontaneous mutations
Are a result of the action of natural radiation and errors in replication.
Point mutations
These can be base-pair substitutions, or insertions or deletions of a single base pair.
What are the major classes of point mutations? What are their likely effects on the coding potential of a mRNA?
1. Missense- change from one amino acid to another

2. Nonsense- Change from an AA to a stop codon

3. Silent- Base change withouth changing AA
Frame shift and Conditional mutants
-Frame shift- Deletion or insertion of 1 or 2 base pairs

-Conditional mutants- Base pair changes where the phenotype of the mutant is observed only under specific growth conditions
How do frame shift mutations differ from point mutations?
Frame shifts actually change the sequence by adding or deleting base pairs while point mutations
How are back (revertant) mutations classified? How can tRNA act as a suppressor?
1. Same site Revertant- the change is the base pair is converted back to its original sequence

2. Second site revertant- a mutation occurs at a site other than the original mutation that restores the phenotype
Point mutations are reversible
The wild type phenotype can be restored