DNA Replication -> Similarities between prokaryotic and eukaryotic DNA replication

What are the three similarities between prokaryotic and eukaryotic DNA replication?

1. DNA copies itself via a semi-conservative replication mechanism

2. Similar types of enzymes are used each step of the process

3. DNA is comprised of the same nucleotides

What is the difference in terms of the origin of replication between prokaryotic and eukaryotic DNA replication

- Prokaryotes have one origin of replication because they only have the one circular/single chromosome

- Eukaryotes have multiple origins of replication because they multiple linear chromosomes

Do prokaryotes or eukaryotes replicate DNA faster?

Prokaryotes - though they make more mistakes because they are going so fast

*prokaryotes = 500 nucleotides/second

*eukaryotes = 50 nucleotides/second

Name 4 types of DNA polymerase used by eukaryotes

- DNA Pol Alpha

- DNA Pol Beta

- DNA Pol Delta

- DNA Pol Epsilon

*note that these should be represented by their greek letters

What is the role of DNA Pol Alpha?

It starts polymerisation directly off of a primer

What is the role of DNA Pol Beta

- DNA repair and proofreading

- Important for maintaining error-free copying

What is the role of DNA Pol Delta

- Lagging Strand Synthesis

- Primer Substitution

What is the role of DNA Pol Epsilon

Leading Strand Synthesis

What are the 3 DNA Polymerases in prokaryotes

- DNA Pol I

- DNA Pol II

- DNA Pol III

Eukaryotes have much more complicated ____

replication forks (there are more enzymes/mechanisms involved)

What are telomeres

DNA at the tips of chromosomes

Why are telomeres required for eukaryotes

because they have linear chromosomes so primer removal results in incomplete and unprotected ends

When is DNA subbed for RNA in eukaryotes

during primer removal by RNAse and DNA Pol Delta

What is the end replication problem?

shortening of chromosomes after each round of replication because the primers at the ends of chromosomes cannot be replaced

What do telomeres solve

the end replication problem

What are telomeres associated with?

- cancer

- cell aging and death

Define a telomere

- they are "caps" of repetitive nucleotides at the ends of chromosomes

- they are also dispensable because they do not code for anything

What happens to telomeres/the ends of chromosomes with successive rounds of cell division

they get shorter and will age, eventually dying off

What do telomeres regulate

- they regulate a cell's response to DNA damage

- they are comprised of thousands of tandem repeats of a short DNA sequence

A telomere DNA sequence is typically rich in what base pair and why?

It is generally G-C rich because G/C is stronger due to having 3 H-bonds so it is more stable and that much more resistant to change

What is telomerase

- An enzyme that can lengthen telomere sequences, filling in the gap left by RNA primer removal

What does telomerase do

It copies RNA to synthesize DNA

Telomerase uses RNA as template to....

synthesize DNA

Where/in what is telomerase expressed?

In:

- Single-celled organisms

- Germline cells

- Stem cells

- very few somatic cells

Telomerase expression in somatic cells results in... (how/why)

cancer because telomerase keeps the cell from dying by preventing telomeres from shortening (keep growing back), so instead of making new cells and dying off, cell life is dragged on and DNA will eventually begin to make more and more mistakes when it undergoes replication/transcription which results in mutated gene expression

Define senescence

stage at which telomeres disappear and cells stop dividing

What is the Hayflick Limit

The number of cell divisions which may occur before senescence

What is often tied to the length of telomerases?

Cell turnover/rate

What is cloning (how do you clone something)

You have to take a nucleus from an adult living animal and substitute it for an embryonic nucleus

What does cloning result in

genetically identical offspring

Why do cloned species/babies die faster

Their cells will have the same DNA and thus the same telomere length as their older parents, so they have shorter telomeres and their DNA is older/more damaged than it should be for an organism of that age