Lecture 7 Flashcards
How many chromosomes do most Eukaryotes have in their body cells?
10-50.
How many chromosomes do humans have?
46 chromosomes in 23 almost identical pairs.
What is a karyotype?
A particular array of chromosomes in an individual organism.
What is diploid?
2 complete sets of chromosomes.
What is Haploid?
One set of chromosomes.
What are chromosomes made of?
Chromatin.
What makes up chromatin?
DNA and protein.
What else is associated with chromosomes?
RNA during RNA synthesis.
What are 2 types of chromosomes?
- Heterochromatin
- Euchromatin
What are heterochromatin chromosomes?
Ones that are compressed and not expressed (turned off, not accessible)
What are euchromatin chromosomes?
Chromosomes that are loose and expressed (turned on, accessible).
What is a nucleosome?
A complex of DNA and histone proteins.
What do histone proteins do?
Promote and guide coiling of DNA
What are histone core proteins?
Proteins that act as a bobbin for the DNA to wrap around.
What are histone link proteins?
It holds the DNA on the core protein (kind of like a crimp bead).
What is the most compact form of DNA?
Chromosomes.
How are chromosomes organized for replication?
Each sister chromatid is held together by proteins in an x shape to keep them organized before they are moved to the new cell.
What do chromosomes look like before and after replication?
Before each chromosome is composed of a single DNA molecule and after each is composed of 2 identical DNA molecules.
What 3 things are required for DNA replication?
- Something to copy
- Something to do the copying
- Building blocks to make copy
What are the three things that are used for DNA replication?
- Parental DNA molecule
- Enzymes
- Nucleotide triphosphates
What are 3 stages of DNA replication?
- Initiation - replication begins
- Elongation - new strands of DNA are synthesized by DNA polymerase
- Termination - replication is terminated
What nucleotide bases are linked in DNA double helix?
CG and AT
What is a DNA polymerase?
A protein that matches existing DNA bases with complementary nucleotides and links them.
What are common features of polymerase?
- Adds new bases to 3 prime end of existing strands
- Synthesizes in 5’-3’ direction
- Requires a primer of RNA
How do DNA polymerase and RNA polymerase work together?
The RNA polymerase makes the primer and the DNA polymerase extends the primer.
What model does Prokaryotic replication use?
E. coli model.
What is the E. coli model of replication?
Starts with a single circular molecule of DNA. Replication begins at the origin of replication and proceeds in both directions around the chromosome.
What are the 3 DNA polymerases in E. coli?
- DNA polymerase 1
- DNA polymerase 2
- DNA polymerase 3
What is DNA polymerase 1?
Acts on lagging strand to remove primers and replace them with DNA.
What is DNA polymerase 2?
Involved in DNA repair processes.
What is DNA polymerase 3?
Main replication enzyme.
What do all three polymerase have?
3’-5’ exonuclease activity.
What is 3’-5’ exonuclease activity?
Proofreading oved the DNA.
What does DNA polymerase 1 also have?
5’-3’ exonuclease activity.
What is 5’-3’ exonuclease activity?
It goes back and removes the RNA primers.
What are helicases?
Enzymes that use energy from ATP to unwind DNA.
What are Single-stand-binding (SSBs) proteins?
Enzymes that coat DNA strands to keep them apart. (keeps the DNA from going back to the double helix form.)
What are topoisomerases?
Enzymes that prevent supercoiling (gets rid of knots and twists in the DNA).
What is DNA gyrase?
The topoisomerase involved in DNA replication.
What is a replication fork?
The partial opening of the DNA helix.
What is DNA primase?
The RNA polymerase that makes RNA primer.
How many directions can DNA polymerase synthesize in?
1.
What is the leading strand in DNA replication?
The strand that synthesizes continuously from an initial primer.
What is the lagging strand in DNA replication?
The strand that synthesizes discontinuously with multiple priming events.
What are Okazaki fragments?
DNA fragments on the lagging strand.
