Extra resources Flashcards
What is DNA?
The molecule of inheritance in living organisms.
Who created the modern discipline of geentics?
Gregor Mendel.
What was Mendel’s experiment?
Breeding plants and animals.
How did Mendel do his experiments?
With pea plants in his monastery garden.
What was Mendel doing with peas in his experiment?
Observing several plants’ characteristics.
What were some of the characteristics Mendel was observing in his experiments?
Seed colour, shape, flower location, colour, pod colour, shape, height.
How was Mendel breeding the peas in his experiment?
Breeding standard generation twice –> 3 generations of peas.
What did the standard deviation of Mendel’s experiment have?
One homozygous plant dominant.
One homozygous recessive.
What did the first generation of Mendel’s experiment with peas have?
All peas heterozygous.
What did the second generation of peas in Mendel’s experiment have?
- homozygous dominant.
- homozygous recessive.
3 & 4. heterozygous.
What were the generalizations of Mendel’s experiment?
- Mendel’s Law of Segregation: every organism has 2 alleles of a gene.
- Mendel’s Law of Independent Assortment: alleles are passed on independently of each other.
What did Mendel proposed?
Dominant traits mask recessive traits.
Where else is Mendel’s experiment applied?
On individual genes.
What experiments did August Weismann do?
With mice.
What did mice experiments of Weismann show?
Traits inherited by organisms during lifetime did not pass on to offspring.
What theory did Weismann proposed?
The germ plasm theory.
What did the germ plasm theory state?
Hereditary information stored in egg and sperm cells of eukaryotic organisms.
What were proteins responsible for?
Genetic inheritance.
What did Johann Miescher do in 1869?
Isolated DNA from white blood cells.
What did Albrecht Kossel do in 1878?
Isolated nucleic acids of DNA and RNA.
What were the 3 choices presented for genetic inheritance?
- DNA.
- RNA.
- Proteins.
What was Frederick Griffith investigating?
How organisms pass on genetic information to their offspring.
With what was Griffith working?
Streptococcus pneumoniae bacteria.
With which types of Streptococcus pneumoniae did Griffith work?
Rough.
Smooth.
What was the differences between rough and smooth Streptococcus pneumoniae bacteria that Griffith worked with?
Smooth: covered with saccharide layer, harder to detect for white blood cells.
Rough: easily killed.
Where did Griffith test bacteria?
On mice.
What did Griffith find about testing bacteria on mice?
Mice exposed to smooth bacteria –> died.
Mice exposed to rough bacteria –> survived.
What else did Griffith do with the bacteria?
Exposed them to heat.
What did Griffith with bacteria exposed to heat?
Exposed them to mice.
What did Griffith find when exposed heat bacteria to mice?
Heat stressed rough bacteria –> no negative effects on mice.
Heat stressed smooth bacteria –> died.
What did Oswald Aver, Colin MacLeod and Maclyn McCarty do experiments for?
To show if DNA, proteins, or RNA acted as the molecule of genetic transmission.
What did Avery’s team do?
Isolated DNA, RNA, Proteins from cells of strep pneumoniae as Griffith –> treated with enzyme to break down one type of molecules –> solutions exposed to rough strains –> injected to mice –> not died.
What was the conclusion of Avery’s team?
DNA is the molecule of genetic inheritance.
What experiments did Hershey and Chase do?
Experiments on bacteriophages, viruses that infected bacteria –> proliferate themselves –> exposing bacteriophages to radioactive isotopes of phosphorus and sulphur –> incorporated in virus’ DNA or proteins –> sulphur found in one of each not in both –> phosphorus into DNA & sulphur into proteins –> check which bacteria inherited radioactive indicators –> bacteria with phosphorus became radioactive –> bacteria with sulphur did not.
What was the conclusion of Hershey and Chase experiment?
Virus molecule of inheritance is DNA.
What did Edward Tatum and George Beadle show in 1940?
DNA genes are directly responsible for creation of cellular proteins.
What did Tatum and Beadle use for experimental subject?
Neurospora crassa = bread mould.
How did Beadle and Tatum use Neurospora crassa?
Spores of Neurospora lighted –> mutate genes –> crossed mutated spores with normal ones –> mutant offspring.
What happened in Beadle and Tatum’s experiment with Neurospora?
Normal spores grew on regular growth medium.
Mutant offspring required addition of arginine to grow on medium.
Why did the mutant offspring require addition of arginine to grow on medium?
Mutated genes are coded for protein that produces arginine amino acid.
What did Levene identify in 1919?
Deoxyribose saccharide phosphate group.
Nucleic acids DNA is made up of.
What did Levene propose?
DNA consists of nucleotides linked by phosphorus groups.
DNA is very short.
What did Elsif propose?
DNA structure = 2 strands = template for reproduction.
What did Jean Brock show in 1933?
DNA is organised in chromosomes.
What did William Astbury provide in 1937?
X-ray diffraction images –> DNA regular structure.
What else did Chargaff use?
X-ray chromatography.
What did Chargaff find with X-ray chromatography?
Relative amount of each nucleic acid in DNA.
Cytosine = Guanine. Adenine = Thymine.
What did James Watson and Francis Crick create in 1953?
Double helix model of Deoxyribonucleic acid.
What is important about Francis and Watson model?
Accepted DNA model today.
On what was Watson and Crick’s model based?
On X-ray diffraction by Rosalind Franklin.
What did Watson and Crick find with Rosalind’s model?
2 strands of DNA backbone = identical.
On what is molecular biology based?
Double helix model of DNA with nucleic acids in centre and phosphate + deoxyribose groups chains.
What did Matthew Mason and Franklin Stoll show in 1958?
DNA replicates semi-conservatively = DNA replicates –> half of new strand from parent strand + half newly made up.
What did Mason and Stoll do?
Bacterial DNA –> took light and heavy isotopes of Nitrogen –> centrifuged DNA after replication –> separating it by consistency.
How is DNA used?
Template –> transcription –> creates RNA –> template –> translation –> creates proteins.
What happens during transcription?
mRNA lives cell nucleus –> enters cytoplasm –> binds ribosome –> 3 nucleic acid of RNA interpreted as a codon –> correspond to an amino acid –> amino acids go to ribosome by tRNAs –> synthesized into primary protein structures –> fold in functioning proteins.
What can we find inside DNA?
Double-stranded DNA = 2 strands braid –> form double helix.
What is the most common form of a DNA double helix?
B-form DNA.
What is each strand of DNA?
A polynucleotide made up of many individual units, nucleotides.
What does a nucleotide have?
3 components:
- 5-C sugar.
- Phosphate.
- One possible base (A, G, T, C).
Where is the nitrogenous base always attached?
At 1-C of sugar.
Where is the phosphate attached?
At 5-C of sugar on 1 nucleotide and 3-C sugar on previous nucleotide.
How is the sugar of DNA called?
Deoxyribose.
Why is the sugar called deoxyribose?
Missing a OH group at 2-C present in ribose.
How are nucleotides in DNA, called?
Deoxynucleotides.
How are nucleotides bind to each other in a DNA strand?
By phosphodiester bonds.
What do phosphate group + sugar make?
DNA backbone.
What is the direction of the DNA strands?
Top: 5’- 3’.
Bottom: 3’- 5’.
How can we see clearly the structure of DNA?
Unwinding.
Flattening double helix.
How do the 2 DNA strands interact with each other?
Through non-covalent hydrogen bonds between bases..
What does each base of DNA structure form?
Hydrogen bonds with the complementary base on the opposite strand.
What is a base pair?
A unit of 2 bases connected with each other through hydrogen bonds.
How are bases connected?
A = T (2 H bonds) G = C (3 H bonds)
How are thymine and cytosine called?
Pyrimidines = single ring structure.
How are adenine and guanine called?
Purines = double rings.
Is the geometry of bases in DNA the same no matter what base is?
Yes.
Why can not other bases form base pairs?
No geometry.
Not strong H bonds are formed.
Disturb helix.
How many base pairs occur in each turn of the DNA helix?
10.
What does the structure of bases and connection through H bonds forms?
Stable structure of DNA.
When are the pi-pi interactions formed?
When aromatic rings of bases stack next to each other –> share electron probabilities.
What else is it formed from the double helix structure of DNA?
2 spaces:
- Major grooves.
- Minor grooves.
How do grooves in DNA act?
Base pair recognition.
Binding sites for proteins.
What does the major groove of DNA contain?
Base pair specific information.
What is the minor groove of DNA?
Base pair nonspecific.
Why are major and minor grooves of DNA different?
Due to different acceptors and donor which proteins can interact with.
In which ways can DNA be acted?
- Sequence specific.
2. Non-sequence specific manner.
What is the cell?
The basic unit of all living tissue.
Where can nucleus be found and what does it contain?
In human cells.
The genome.
Into what is the genome split in humans?
To 23 chromosome pairs.
What does each chromosome contain?
Long strand of DNA –> tightly packaged around proteins = histones.
What does occur within DNA?
Sectors = genes.
What do genes contain?
Instructions to make proteins.
What happens when a gene is switched on?
Enzyme RNA polymerase –> attaches gene’s start.
What does RNA polymerase do?
Moves along DNA –> makes mRNA strand, in nucleus.
What does DNA do while RNA polymerase creates mRNA?
Codes bases of mRNA ON new strand.
Can the mRNA used as a template once it is transcribed from DNA?
No.
It needs to be processed.
How is mRNA processed to used as a template?
Removing and adding RNA sections.
Where does mRNA go once it is processed?
Out of nucleus –> into cytoplasm.
What happens to mRNA once it enters cytoplasm?
Ribosomes bind to it –> read code on it –> produce amino acids chain.
How many different types of amino acid occur?
20.
What do tRNAs do?
Transfer amino acids to ribosome as each triplet on mRNA is read.
How is mRNA read?
3 bases at a time.
Where are amino acids from tRNA added?
To a growing chain of amino acids.
What happens once the last amino acid is added?
Chain falls to a 3D shape –> form protein.
What is transcription and translation?
Collective process where genetic code read by enzymes –> produces proteins in organism.
What is a chromosome?
A very long molecule.
Of what does a chromosome consist?
Millions of base pairs.
Are all of the parts of chromosome special?
No.
What parts of chromosomes are special?
Genes.
What do genes do?
Code for different things.
How long is a gene in humans?
10-50 thousand base pairs.
How long can the longest chromosome be?
2.5 million base pairs.
What happens when a gene is expressed?
A specific protein is produced?
What is transcription?
Process of enzymes use one of strands of DNA in gene as template –> produce mRNA.
How does transcription occur?
Enzyme RNA Polymerase + proteins transcription factors bind to specific sequence promoter –> 2 strands apart –> 1 strand = template/antisense strand –> used to generate mRNA –> other strand = nontemplate strand/sense strand.
Does RNA polymerase need a primer?
No.
What does RNA Polymerase do?
Moves along DNA –> elongation –> synthesizes mRNA as it goes.
Reading antisense strand from 3’- 5’ –> generating mRNA 5’ - 3’.
What is the difference between the newly synthesized mRNA and the template DNA strands?
DNA: deoxyribose sugar, A-C-G-T
RNA: ribose sugar, A-C-G-U
How many bases of DNA are exposed at a time?
10-20.
What happens to DNA strands after mRNA is synthesized?
Wraps back up.
What happens once RNA polymerase reaches the end of the gene?
Termination occurs =
Enzyme detaches from gene –> DNA returns to original state –> mRNA produces.
Where does translation occur?
In ribosome.
What happens during translation?
mRNA acts as a code for a specific protein –> 3 codons on mRNA –> code for a specific anti-codon –> carried by tRNA –> covalently linked to amino acid.
What is the reading frame?
Nucleotides into codons on mRNA strand.
How many possible codons occur?
64 (3 on 4).
What is the strange thing in the universal genetic code?
Multiple codons code same amino acid.
To what does each codon correspond?
To a particular amino acid.
Which is the start codon?
AUG.
What does AUG codon do?
Initiates translation –> codes for Methionine.
Which are the stop codons?
UAA
UAG
UGA
What do stop codons do?
Terminate (finish) translation.
Where does the small ribosomal subunit bind?
To mRNA.
To tRNA.
What does the large ribosomal subunit do?
Joins after first tRNA binds small ribosomal subunit –> completes translation initiation.
What happens after the large ribosomal subunit binds mRNA?
Second tRNA brings second anti-codon to mRNA (codon) –> second amino acid binds first amino acid –> first tRNA leaves –> process continues along mRNA sequence.
What happens in the end of translation process?
Polypeptide chain grows.
When does translation stop?
When a stop codon occur –> completed polypeptide flies away –> enters cell/organelle for modification.
How does DNA –> transcribed –> mRNA –> translated –> protein?
Obeying to base pairing in nucleic acids.
What do proteins do?
Make the most of us = tissues, organs, receptors, enzymes.
What does DNA do?
Carries genetic code for living organisms.
What is protein synthesis?
Process of making proteins.
Which steps include protein synthesis?
- Transcription.
2. Translation.
What is transcritpion?
Copying a single DNA to mRNA.
What is Translation?
Taking mRNA strand –> use it –> produce a protein.
What does occur inside almost every cell?
Nucleus.
What occurs in nucleus?
All genetic material of each cell in DNA form.
Why do we save DNA?
- Essential for life.
- Controls what cells do.
- Contains thousand genes.
What are genes?
Smaller DNA sections with specific sequences –> code for specific amino acids sequences –> combined –> form a protein.
How can we make a protein?
Specific sequence of gene –> read by ribosomes.
Where do ribosomes occur?
Outside nucleus.
Is DNA big?
Yes.
Why do we need to make a copy of a gene to use it?
Because DNA is so big –> cannot leave nucleus.
What do we actually copy?
A single gene.
Not the whole DNA strand.
Can the copy of gene leave the nucleus?
Yes.
Small enough.
Where does the copy of the gene go?
To the ribosome.
What is the copy of the gene?
mRNA = messenger RNA.
How is the structure of mRNA?
Mostly similar to DNA.
Differences:
Much shorter.
Only a single strand.
Uracil base not Thymine.
How do we see DNA normally in nucleus?
2 strands fold into a helix.
What is a simplified version of DNA?
Unwind.
How does Transcription process start?
With RNA Polymerase enzyme.
Where does RNA Polymerase bind?
To DNA right before the gene to be coded, starts.
Where do the 2 strands of DNA separate apat?
Just ahead of RNA Polymerase.
What happens when the 2 strands of DNA separate apart?
Bases are exposed.
What does RNA Polymerase do once the 2 strands separate?
Moves along DNA strand –> read bases one by one –> use them –> make mRNA.
What will always mRNA bases be?
Complementary to DNA bases.
With what will the DNA bases bind with an mRNA base?
C, G, T, A?
C = G G = C T = A A = U
With what are all of the thymine on DNA replaced on mRNA?
With Uracil.
What does the DNA strand do while RNA Polymerase is moving along the strand and synthesizing mRNA?
Opens up to the right and closes up from the left.
How much of the DNA is exposed at a time?
Only a small section of it at a time.
What do RNA Polymerase and DNA do once mRNA is fully synthesized?
RNA Pol: Detaches from DNA.
DNA: closes back up.
Where does mRNA go at the end of transcription?
Leaves nucleus –> heads to ribosome.
How is the DNA strand where RNA Polymerase moved along, called?
Template Strand.
What is the template strand of DNA sued for?
To make mRNA.
Once mRNA moves to the ribosome what happens?
Undergoes translation –> produces protein.
How is each group of 3 bases for both DNA and RNA, called?
Codon/Triplet.
For what does triplet from DNA/RNA code?
A specific amino acid.
For which amino acid does the triplet ‘AGU’ code?
Serine.
‘CCA’?
Proline.
How does the translation process start?
mRNA and ribosome bind together.
Where are amino acids bind?
At tRNA = transfer RNA.
What do tRNA molecules have?
Anti-codon on bottom.
Amino acid on top.
What is an anti-codon?
3 bases complimentary to the 3 bases on mRNA.
What do the 3 bases on mRNA do?
Code for amino acid that tRNA carries.
To what is each type of tRNA specific?
To a particular triplet on mRNA.
Which anti-codon and amino acid does the codon ‘AGU’ code?
‘UCA’: anti-codon
‘serine’: amino acid.
What do linked amino acids build?
A chain of amino acids.
What does the ribosome do once the amino acids are linked together?
Moves along mRNA slightly, to the next codon.
What happens once ribosome moves to the next codon?
First tRNA is detached –> amino acid is left behind linked to the next amino acid.
What happens to the amino acid chain once is detached from the ribosome and mRNA?
Folds up itself –> forms a protein.
What does synthesis mean?
Make something.
Where are enzymes involved?
In transport.
Structure.
Enzymes to make materials.
Protecting the body.
Why is protein synthesis essential?
To live.
When does protein synthesis occur?
All the time.
Where is our DNA?
In nucleus.
What is RNA?
A nucleic acid like DNA, with few differences.
Which of the protein synthesis process comes first?
Transcription.
In what to transcribe DNA in transcription?
To a message.
Where does transcription occur?
In nucleus.
Of what does messenger RNA consist?
A message made from RNA based on the DNA.
What is the good thing about the mRNA in eukaryote organisms?
Gets out of nucleus.
In cytoplasm.
Attach ribosomes.
What do ribosomes make and where?
Proteins in translation.
Of what are ribosomes made?
rRNA = ribosomal RNA.
Where do we have tRNAs available?
In cytoplasm.
What are tRNAs?
Transfer RNAs.
What do tRNAs carry?
An amino acid.
What is an amino acid?
A monomer of a protein.
A building block for a protein.
Why is mRNA important in translation process?
Directs which tRNAs come in –> which amino acids are transferred.
What are tRNAs looking for?
Complementary bases.
What do tRNAs do once they find their complementary base on mRNA?
Transfer their amino acid.
What do tRNAs read?
Bases on mRNAs as 3, in triplets = codon.
What do we use the codon chart for?
To find which amino acid each mRNA codon will code for.
Which is most of the times/normally the first amino acid in proteins?
Methionine = AUG.
How do tRNAs work in translation process?
Bring one amino acid –> link it –> leave –> bring another amino acid.
How are amino acids linked to build a protein (polypeptide)?
With a peptide bond.
What do stop codons do?
Indicate that protein building is finished.
Do stop codons code for an amino acid?
No.
