dna test

what is the structure of DNA?

2 coiled strands called a double helix

what makes up the sides of a DNA molecule?

phosphate group and deoxyribose (sugar), which are put together by dehydration synthesis

where are nitrogen bases found on DNA & how are they bonded?

center - rungs of ladder - Hydrogen bonds

what type of twist is in DNA?

a right-hand twist

how many base pairs are in DNA’s complete turn?

10

what does DNA stand for?

deoxyribose nucleic acid

what is a south paw/zDNA?

DNA that takes a left-handed twist (hot spot where you can get a mutation)

what are the subunits of DNA?

nucleotides

name the 3 parts of a nucleotide

phosphate group, 5-carbon pentose, nitrogen base

why is deoxyribose called a pentose sugar?

it has 5 carbons

sketch a pentose sugar & label the numbered carbons

\:)

what are purines?

double ring nitrogen bases

what are pyrimidines?

single ring nitrogen bases

what do purines pair with?

pyrimidines & vice versa

what did scientists think made up the genetic material of the cell & why?

protein because it was more complex than DNA

what makes up proteins?

* 20 different amino acids
* long chains of amino acids

which bacteria did Griffith use?

streptococcus pneumococcus

what did Griffith find out about S and R strains of bacteria?

S bacteria (smooth - virulent) can transform R bacteria from nonvirulent to virulent

what is transformation?

the process of picking up DNA from the environment

did Griffith’s experiment prove that DNA was the genetic material?

no, just that something was transferred

what are the 2 things that make up chromosomes?

proteins and DNA

what did Avery want to prove?

what the genetic material was (DNA or protein)

how did Avery prove that DNA was the transforming substance?

by removing protein from S bacteria & mixing in R.

R became virulent

what did Hershey & Chase use in their experiment to prove DNA was the cell’s genetic material?

bacteriophages

what did Hershey & Chase radioactively tag the viral DNA with? what did the protein capsid with?

they tagged it with 32P

the protein capsid with 35S

what radioactive substance was injected into & took over the host cell’s dna (Hershey & Chase)?

32P - E. Coli

what did Chargaff do?

he showed the amount of the 4 nitrogen bases present in DNA

what bases are complementary?

Adenine - thymine

Guanine - Cytosine

what joins base pairs on DNA?

hydrogen bonds

what did Rosalind Franklin do?

supplied diffraction x-ray photographs which helped determine DNA’s structure

what did Watson and Crick do?

* built the first model of DNA showing it as a double helix with base pairs in the middle.
* hypothesized that DNA replicated using the semiconservative model

how many hydrogen bonds join guanine to cytosine?

3

how many hydrogen bonds join adenine to thymine?

2

if there is 20% adenine, how much cytosine is present?

30%

cells must copy their DNA before they do what? explain why.

mitosis & meiosis, cell division so that the right amount of DNA is passed on

at what stage of the cell cycle is DNA copied?

S (synthesis)

where is DNA copied in eukaryotes?

the nucleus

what is DNA replication?

the process of copying DNA

where does DNA replication begin?

at the Origins of Replication

what are Replication Forks?

Y-shaped areas that are formed when the 2 DNA strands open/seperate at the origins of replication

where do new DNA strands grow?

at the replication forks

how do replication bubbles form?

when the 2 DNA strands open at the origins of replication

how many replication bubbles do prokaryotes and eukaryotes have?

prokaryotes - 1

eukaryotes - many

what is Helicase & what are its 2 functions?

* the enzyme that uncoils DNA so it can be replicated or copied.
* separates DNA molecule by breaking the hydrogen bonds between the base pairs.

what is the job of single-strand binding proteins?

attach & keep the 2 DNA strands separated & untwisted

what does Topoisomerase do?

enzyme that relieves stress on the DNA strands at the replication forks, so they don’t break

when must an RNA primer be present?

to start the addition of new nucleotides (indicates the starting point inside the bubbles)

what does the enzyme primase do?

makes the RNA primer

what does DNA polymerase do?

the enzyme that adds new complementary base pairs

DNA polymerase adds nucleotides to which end of the DNA molecule?

3’ end, so 5’ to 3’ new strand is made

which direction is the leading DNA strand?

* 5’ to 3’ direction
* goes from origin towards replication fork

which direction is the lagging DNA strand?

* 3’ to 5’ (against direction of replication)
* many short segments from replication fork towards origin

what are Okazaki fragments?

the short segments of the lagging strand

what does the enzyme DNA ligase do?

joins Okazaki fragments together into one strand

what do chemicals (pollutants, UV radition) do to our DNA?

they can damage the DNA in our body cells so it must be continuously repaired.

what is excision repair?

When over 50 enzymes remove the damaged DNA pieces & they can be replaced by the correct pieces.

what 2 enzymes replace damaged sections of DNA and rebind the molecule?

DNA polymerase & DNA ligase

what is the complementary strand for: **5’ - CGTATG - 3’**

3’ - GCATAC - 5’

explain the semiconservative model of DNA replication

each new molecule of DNA has an old strand & a new strand

what did meselson & stahl do?

they experimented and proved watson and crick’s hypothesis about the semiconservative model.