Biology - Chapter 6 DNA: Hereditary Molecules of Life
Learn
Practice Test
Spaced Repetition
Match
Flashcards1/102
There's no tags or description
Looks like no tags are added yet.
Name | Mastery | Learn | Test | Matching | Spaced |
|---|
No study sessions yet.
103 Terms
what is the primary carrier of genetic information in all living organisms?
DNA
DNA contains the instructions to manufacture all of the ______ necessary to build and maintain a living organism
proteins
DNA is passed from generation to generation in the form of _________
chromosomes
in eukaryotic organisms these chromosomes are visible during mitosis only
the _____ and ________ of chromosomes in a cell are specific to a particular species
size, number
nucleoid
a single looped chromosome in prokaryotes
plasmid
a ring of genetic material in bacteria
which organism has the most discovered chromosomes
the adder’s tongue fern has 1200 chromosomes
describe the series of events that occurs when a specific protein is required by a cell
the gene (the portion of DNA that codes for this protein) is activated
the sequence is copied into a molecule of RNA
this RNA molecule moves into the cytosol (makes sense that the DNA makes copies of the sequence in RNA so that the DNA itself doesn’t get damaged)
the sequence carried by the RNA is translated by ribosomes into chains of amino acids
polypeptides are then further modified to form functional proteins
Gregor Mendel
statistically analyzed the inherited characteristics of over 28,000 pea plants over a 7-year period
what conclusions did Gregor Mendel come to after his experiment?
‘factors’ for a given trait were passed from parent to offspring
these ‘factors’ that determine traits such as size, markings, etc are derived from genes
genes
coding regions of DNA that contain the instructions to build proteins that are responsible for that particular inherited trait
within a species, the gene for a particular trait is always found in ___ ____ ________ on a particular chromosome
the same location
how do eukaryotic cells fit an enormous amount of information into every chromosome?
by wrapping the DNA stored in chromosomes in the nucleus around special proteins called histones. this arrangement both protects the DNA and reduces volume, allowing it to fit into the nuclei
in what state is genetic material found in eubacteria?
it is usually found in loops (meaning that bacterial DNA is joined end to end to form one large ring)
(however, smaller accessory loops of DNA may also occur)
where is bacterial DNA found?
nucleoid
_______ often only carry a few genes
plasmids
Can plasmids be copied from one bacterium to another?
yes
____________ have circular chromosomes
archaebacteria
archaebacteria DNA is associated with ___________ ________
histone-like proteins
what contains small amounts of DNA in eukaryotes (similar to prokaryotes)
mitochondria and chloroplast
what is a genome
the complete set of an organism’s hereditary information
how is the genome of eukaryotes arranged?
it is spread out over many chromosomes, which often occur as homologous pairs
humans have __ homologous pairs in each cell
23
how many base pairs do humans have?
approx 3 billion base pairs
most eukaryotes are _______, but there are exceptions
diploids
diploid meaning
2 sets of chromosomes
what did the human genome project hope to achieve?
to map the human genome blueprint
when did the human genome project begin?
1990
when did the human genome project end?
2003
what is a DNA nucleotide composed of?
phosphate group, deoxyribose sugar, and a nitrogenous base
what bond holds together the phosphate group and the deoxyribose sugar in DNA?
ester bond
what bond holds together the nitrogenous base and the deoxyribose sugar in DNA?
glycosidic bond
how to tell pyrimidines and purines apart?
pyrimidines - 1 ring in the nitrogenous base
purines - 2 rings in the nitrogenous base
which nitrogenous bases are pyrimidines?
cytosine and thymine
which nitrogenous bases are purines?
adenine and guanine
which bond holds the nitrogenous bases together?
hydrogen bond
what is the distance between each base pair in DNA?
3.4 nm
how many base pairs in 1 turn of DNA?
10 base pairs
what bonds are in the sugar phosphate backbone?
phosphodiester bonds
which direction does the sugar-phosphate backbone go?
the 5’ to 3’ direction
at one end of the sugar-phosphate backbone, the free phosphate will not be attached to ________ _________ (5’ end)
another nucleotide
at one end of the sugar-phosphate backbone, the free OH will not be attached to _ _________ (3’ end)
a phosphate
why is the sugar-phosphate backbone arranged anti-parallel?
so the bases can meet up with each other
where is the nitrogenous base attached to on the deoxyribose sugar?
1’ carbon
where is the phosphate group attached to on the deoxyribose sugar?
5’ carbon on one sugar, and the 3’ carbon of another sugar
when did Watson and Crick establish the structure of DNA
1953
what was Watson and Crick’s suspicion?
that the specific base pairings in the double helix existed to allow a controlled system of DNA replication
when was the relationship between DNA structure and replication fully understood?
1958 by a classic experiment by Meselson and Stahl
what are the 3 theories on how DNA replicates?
DNA replicated semi-conservatively
DNA replicated conservatively
DNA replicated dispersively
What is conservative replication?
a DNA molecule would get copied and make a second DNA molecule
what is dispersive replication?
a DNA molecule would get cut at certain parts, each of which would get copied and reattached to form 2 DNA molecules
what is semi-conservative replication?
2 DNA strands would separate and each one would serve as a template to copy a second strand, thus producing 2 DNA molecules.
how did Meselson and Stahl prove that DNA replicates using semi-conservative replication?
used E. coli bacteria (since it could be easily grown in a lab)
grew the cells in the presence of a specific type of nitrogen, which is naturally found in DNA that would make all of the DNA very heavy
they used centrifugation, which can separate things according to their weight
initially all of the DNA in the cells was heavy, and was at the bottom of the tube since it was grown in heavy nitrogen
then they started growing these cells in the presence of light nitrogen, so all of the DNA made in subsequent cell divisions would be lighter
after one cell division, the DNA was half as heavy, so half of the molecule contained heavy nitrogen, and the other half didn’t
not in line with the conservative DNA replication model, which would predict that one molecule would be all light and the other all heavy
after two cell divisions, the DNA molecule was now either half heavy and half light, or fully light
not in line with the dispersive DNA replication model, which would predict that the DNA after two cell divisions would contain a mixture of heavy and light DNA
agrees with the semi conservative model: every cell gets one new DNA strand and one old one
heating DNA causes
the DNA strands to separate
histones
positively charged proteins, and the negatively charged DNA strands are wrapped around them
nucleosomes
a unit of DNA storage, consisting of 8 histones with DNA strands wrapped around them; the DNA around each nucleosome is about 147 nucleotides long
solenoids
a group of 6 nucleosomes
prokaryotes do not have chromosomes contained in a nucleus; what do they have instead?
prokaryotic DNA is one chromosome long that may be circular
step 1 of bacterial conjugation
a donor bacterial cell joins with a recipient cell
step 2 of bacterial conjugation
one strand of the plasmid breaks and begins to move through the bridge from donor to recipient
step 3 of bacterial conjugation
DNA replication of the plasmid is continuous in the donor and discontinuous in the recipient
step 4 of bacterial conjugation
when complete, replication has produced a copy of the plasmid in both the donor and recipient cells
what is supercoiling?
the continuous twisting of prokaryotic DNA that reduces the volume of the DNA
what causes DNA to continually shorten during every cycle of repetition
the DNA at the very end of the chromosome cannot be fully copied in each round of replication, resulting in a slow gradual shortening of the chromosome
telomeres
a repeating sequence of DNA at the end of a chromosome that protects coding regions from being lost during replication
4 functions of telomeres
help to prevent chromosome ends from fusing to other chromosomes
prevent DNA degradation from enzymes called nucleases
assist DNA repair mechanisms in distinguishing DNA breaks from chromosomal ends
play a role in determining the number of times that a cell can divide, and therefore may play a critical role in determining the lifespan of an organism
cell senescence
the period in a cell’s lifespan when it loses the ability to divide and grow
what is cell senescence also known as
cell aging
hayflick limit
the total number of times a cell can divide
explain why germ cells are unique
Germ cells are unique because they must be able to continue replicating. They must maintain their genetic integrity from parent to offspring, generation after generation. These cells could not tolerate the loss of genetic material, even telomeres that would eventually run out and leave coding DNA at risk. In these germ line cells, an enzyme called telomerase adds more DNA to the shortening telomeres, continually restoring their length.
Why are cancer cells dangerous?
because they never stop dividing
what do healthy cells do with their telomeres that cancer cells don’t do
they use up the telomeres in their DNA over time and begin cell senescence, but cancer cells never do
why do cancer cells not use up the telomeres in their DNA and not begin cell senescence?
because they produce the enzyme telomerase in great quantities
what does telomerase do?
it replaces the telomeres that are lost during cell division
which scientist cross pollinated pea plants?
Mendel
why did Mendel cross pollinate pea plants?
he cross pollinated pea plants based on their characteristics to prove how certain traits are inherited
what conclusion did Mendel draw from his experiment?
a dominant trait was always displayed in the offspring. a recessive trait was only displayed in the absence of a dominant trait
what is the law of segregation?
offspring inherit one hereditary factor from each parent
what is the law of independent assortment?
different traits have an equal opportunity of occuring together
what is the law of dominance
offspring will inherit the dominant trait, can only inherit the recessive trait if they have both recessive factors
what conclusion did Griffith draw from his experiment?
bacteria can take in genetic material from nearby bacteria and use this DNA as its own
what did Levene discover from his experiments?
he discovered 2-deoxyribose, how the nucleic acid components combine to form nucleotides and how the nucleotides combine to form in chains, discovered that DNA was made up of nucleotides, and that nucleotides were made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base.
he also managed to isolate nucleotides, as well as the five-carbon sugar D-Ribose from the RNA molecule
who identified purines and pyrimidines via their ultraviolet absorption spectra?
Chargaff
how did Miescher conduct his experiments?
he collected bandages of puss from patients, extracted it on phosphorus, named the substance that came out nucein (because he found it in the nucleus of white blood cells)
what was Miescher’s conclusion from his experiment?
he hypothesized that nucein was linked to the function of the organelle, and may have a role in the transmission of hereditary traits, but he ended up rejecting that idea
how did Griffith conduct his experiment?
S-strain bacteria were very pathogenic (virulent)
When Griffith injected the mice with the R-strain bacteria, the mice survived and showed no signs of pneumonia
Griffith concluded that the S-strain was responsible for pneumonia.
Griffith then heated the S-strain to destroy the bacteria, and the mice were no longer infected.
He then mixed the heat-killed S-strain with the R-strain, but the mouse still got pneumonia and died.
Griffith isolated living S-strain bacteria from the dead mouse
The R-strain bacteria had some acquired factor from the heat-killed S-strain that made newR-strain bacteria into virulent colonies
what was Chargaff’s hypothesis?
if DNA from different species exhibited different biological activities, there should also be chemically demonstrable differences between the DNA
describe Chargaff’s procedure:
separation of the DNA mixture into individual components by paper chromatography
the separated compounds were converted into mercury salts
the purines and pyrimidines were identified via their ultraviolet absorption spectra
describe Hammerling’s first experiment
he removed the cap, the foot, or the stalk of each of the structures to see if it would regenerate or not
he found that when the stalk or cap was cut off it would regenerate, when he cut off the foot it wouldn’t
from this discovery he concluded that hereditary information was located in the nucleus of the cell
describe Hammerling’s second experiment
he used 2 different acetabularia cells that had different cap morphologies called A. crenulata and A. mediterranea
he cut off the caps of the 2 cells and grafted the stalks onto the different algae cells
over time the cell with the A. crenulata cap and the A. mediterranea stalk and foot devoled a cap with the A. mediterranea morphology and vice versa with the other cell
from this experiment Hammerling determined that the nucleus was the location of genetic material that determines the cell’s properties
what are Avery, Macleod, and McCarty best known for?
they discovered that DNA is a material of which genes and chromosomes are made.
they grew different types of streptococcus bacteria in culture tubes that contained a growth medium. they kept the different strains isolated from each other. Streptococcus has S-strains and R-strains which differ in their disease causing ability, and the goal of this experiment was to determine which part of the S-strain bacteria cell was responsible for making the R-strain bacteria virulent. The possible transforming substances were DNA, RNA, and proteins
what did Wilkins and Franklin discover?
the double helix structure of DNA
what did Wilkins do that helped reveal the structure of DNA?
he was involved in X-Ray diffraction studies of DNA, which ultimately revealed the helical structure of the molecule
what is photo 51 and why is it significant?
photo 51 shows the clear X-Ray diffraction pattern of DNA, which was crucial in revealing its double helix structure
what did Watson and Crick discover?
they discovered the model and structure of DNA, and combined the ideas of several scientists and consolidated their findings to fully showcase the model of DNA. Using the information provided by Chargaff, Franklin, and Wilkins, they found that the double helix could incorporate all of their finds (4 nitrogenous bases, ratios between each other, phosphate sugar backbone)
What did Watson and Crick’s model show?
the DNA molecule can only be stable if the strands run anti-parallel.
The DNA strands must have the OH of the 3’ carbon attached to the deoxyribose sugar at one end and the phosphate attached to the 5’ carbon at the last sugar at the other end
their model also showed that that the bases are joined by hydrogen bonds, keeping the 2 strands together
A—T are joined by 2 hydrogen bonds, and C—G are joined by 3 hydrogen bonds
how did Hershey and Chase do the first part of the experiment?
took 2 samples of E. coli
infected sample 1 with sulphur labeled bacteriophages
infected sample 2 with phosphorus labeled bacteriophages
stirred each sample in a Waring Blender
the spinning force removes the bacteriophage particles that are on the membrane of the bacteria, but would preserve the bacteriophage material that entered the cell
what are the results from experiment 1?
in sample 1, the blender removed 80% of the marked material
in sample 2, the blender removed 40% of the marked material
what are is the conclusion from experiment 1?
the protein remained on the outside of the bacteria
since it does not enter the cell, it cannot be the genetic material
why did Hershey and Chase do a second experiment?
because the first experiment only remove 80% of the protein. they wanted to prove that the other 20% does not enter the bacteria, so they did another experiment