A1.2 & D1.1 - Nucleic Acids & DNA Replication

nucleosomes consist of

-2 negatively charged strands of DNA wrapped twice around a core of 8 (positively charged) histones

-a 9th "linker histone" holds the nucleosome together

what do nucleosomes do

involved in the supercoiling of DNA and controlling gene expression

a condensation reaction is

when 2 monomers bond together through the loss of a water molecule

hydrolysis is

when a polymer is disassembled through the addition of a water molecule

what does gyrase do?

relieves the tension on the double stranded DNA d

what does helicase do?

unwinds and separates the double helix

what does DNA primase do?

(an RNA polymerase) which synthesizes a short RNA primer

what does RNA primer do?

tells DNA polymerase III where to start adding nucleotides

what do single stranded binding proteins do?

prevent single strands from rewinding

what does DNA polymerase I do?

digests RNA primer and replaces it with DNA

what does DNA polymerase II do?

double checks if there are any errors in the copies of DNA

what does DNA polymerase III do?

adds nucleotides in the 5' to 3' direction

what does DNA ligase do?

joins neighboring fragments together

what are okazaki fragments?

Short lengths of DNA made on the lagging strand

nucleotides are added in a continuous fashion on the...

...leading strand

replicated DNA is

semi - conservative: one daughter strand, one parent strand

each of the newly formed DNA molecules create a...

...chromatid

DNA replication occurs

before both mitosis and meiosis.

PCR (polymerase chain reaction) allows

scientists to amplify (produce many copies of) the DNA

materials needed for PCR

DNA to be amplified, buffer solution, primer to attach to the DNA to be copied, Taq DNA polymerase, DNA nucleotides

what does taq DNA polymerase do?

it attaches to the primer and creates a new strand of DNA nucleotides

why is taq polymerase used?

its obtained from a bacterium that lives in hot springs and doesn't denature from PCR temperatures

the three steps of PCR:

denaturation, annealing, extension. these are repeated many times to get many DNA copies

Denaturation:

(step 1) the DNA sample is heated to 95c to break hydrogen bonds and separate the two DNA strands

Annealing:

(step 2) temperature is reduced to 54c-60c which allows DNA primers to bond to both DNA strands next to the sequence to be copied

Extension:

(step 3) temperature is increased to 72c which allows Taq DNA polymerase to replicate both strands, starting at the primer

what does extension produce?

2 identical double stranded DNA molecules that are exact copies of the original DNA

the shortest human gene is...

(coding for tRNA) 76 nucleotides long

the longest human gene is...

dystrophin, 2,300,000 nucleotides long

the average human gene is...

between 10,000 and 15,000 nucleotides long

what is gel electrophoresis of DNA

a method of separating DNA in a gelatin-like substance using an electrical field

DNA is a ... substance

acidic

in water, DNA

dissociates to become negatively charged

we can cut DNA using

restriction enzymes

the electrophoresis gel is porus, which means that

smaller fragments move faster and farther through it

why is each persons DNA pattern difference?

introns and other non-coding regulatory sequences:

-don't code for proteins

-make up repeated patterns/STRs

-many sites on 23 chromosomes with different repeating patterns

what are STRs

short tandem repeats/sequences of DNA that are repeated

what is DNA fingerprinting used for?

forensics, medical diagnostics, paternity, evolutionary relationships

MRINGER/7 characteristics of life:

movement, respiration, irritability, nutrition, growth, excretion, reproduction

PMC model of determining life:

P-program (way to encode instructions for building life form)

M-metabolism (a way to capture and use energy)

C-container (barrier that holds in life form)

what are the purines and their distinguishing factors?

adenine and guanine, they have a double ring structure

what are the pyrimidines and their distinguishing factors?

thymine and cytosine, they have a single ring structure

which nucleotide bases bind to each other and with how many bonds?

- adenine and thymine bond with two hydrogen bonds

- guanine and cytosine bond with three hydrogen bonds

what is linker DNA?

the segment of DNA between two nucleosomes