3.1 Biological molecules - DNA & RNA, DNA replication Flashcards
what codes for the sequence of amino acids in the primary structure of a protein?
Deoxyribonucleic Acid (DNA)
is DNA a monomer or a polymer?
polymer
what shape does DNA have?
double helix shape
what is the monomer that makes up DNA called?
a nucleotide
what is a nucleotide made up of?
deoxyribose (a pentose sugar)
a nitrogenous base
one phosphate group
what are the different possible nitrogenous bases in a nucleotide?
guanine
cytosine
adenine
thymine
what is a polymer of nucleotides called?
a polynucleotide
what reaction makes a polynucleotide?
via condensation reactions
in the condensation reaction between nucleotides, what does it happen between?
between the deoxyribose sugar and the phosphate group
what bond is created during the condensation reaction of nucleotides?
phosphodiester bond
what is a phosphodiester bond like?
phosphodiester bonds are strong covalent bonds
therefore help ensure that the genetic code is not broken down
what type of ‘backbone’ does a polynucleotide have?
sugar-phosphate
what does the sugar phosphate backbone in a polynucleotide describe?
the strong covalent bonds between the sugar and phosphate groups that hold the polymer together
what bonds are the DNA polymers held together by?
hydrogen bonds between the bases
where can hydrogen bonds only form between?
complementary base pairs
what are the complimentary base pairs?
the base cytosine can only form hydrogen bonds with guanine and adenine can only bond with thymine
how many hydrogen bonds do adenine and thymine form?
adenine and thymine form 2 hydrogen bonds
how many hydrogen bonds do cytosine and guanine form?
cytosine and guanine can form 3 hydrogen bonds
why is complimentary base pairing important?
to help maintain the order of the genetic code when DNA replicates, therefore reducing the chance of mutations
why does DNA have a stable structure?
due to the sugar-phosphate backbone (covalent bonds) and the double helix to prevent damage
why is DNA double stranded?
so replication can occur using one strand as a template
why does DNA have weak hydrogen bonds?
for easy separation of the two strands in a double helix during
replication
why is DNA a large molecule?
to carry lots of genetic information
why does DNA have complimentary base pairing?
complementary base pairing allows identical copies to be made
is RNA a monomer or a polymer?
is a polymer of a nucleotide
what is RNA made up of?
ribose
a nitrogenous base
a phosphate group
what are the nitrogenous bases in RNA?
adenine, guanine, cytosine and uracil
what base does RNA have instead of thymine?
uracil
what is RNA like in comparison to DNA?
in comparison to the DNA polymer, the RNA polymer
is a relatively short polynucleotide chain and it is single-stranded
what is the function of RNA?
the function of RNA is to copy and transfer the genetic code from DNA in the nucleus to the ribosomes
what is some RNA also combined with to make proteins?
proteins
what are the three types of RNA?
mRNA
tRNA
rRNA
what does mRNA stand for?
messenger RNA
what does tRNA stand for?
transfer RNA
what does rRNA stand for?
ribosomal RNA
what is mRNA?
a copy of a gene from DNA
where is mRNA created?
created in the nucleus
where does the mRNA carry the copy of the genetic code
of one gene to?
a ribosome in the cytoplasm
why is mRNA much shorter than DNA?
it is only the length of one gene
therefore it can leave the nucleus as it is small enough to fit through the nuclear pores
why is mRNA short lived?
it is only needed temporarily to help create a protein, therefore by the time any enzymes could break it down, it would have already carried out its function
is mRNA single stranded?
yes
what are the 3 bases in mRNA called?
codons
where is tRNA found?
only in the cytoplasm
is tRNA double stranded?
no - single stranded
what shape is tRNA folded into?
a cloverleaf shape
what bonds hold the cloverleaf shape of tRNA in shape?
hydrogen bonds
what is the function of tRNA?
to attach to one of the 20 amino acids and transfer this amino acid to the ribosome to create the polypeptide chain
what amino acids attach to specific tRNA molecules?
specific
what are the 3 bases found on the tRNA which are complementary to the 3 bases on mRNA called?
anticodon because they are complementary to the codon on mRNA
what is rRNA?
the type of RNA that makes up the bulk of ribosomes
what is the rest of the ribosome made up of that is not the rRNA?
protein
what are the differences between the DNA and RNA monomer?
DNA contains the base thymine, whereas RNA contains uracil instead
DNA contains the pentose sugar deoxyribose, whereas RNA contains the pentose sugar ribose
what are the differences between the polymers of DNA and RNA?
DNA is much larger because it contains approximately 23,000 genes, whereas RNA is much shorter because it is only the length of one gene
DNA is double-stranded, whereas RNA is single-stranded
what must all cells do before division?
all the DNA must replicate to provide a copy for the new cell
what is the process for DNA replication called?
semi-conservative replication (in the daughter DNA, one strand is from the parental DNA and one strand is newly synthesised)
what enzymes does semi conservative replication require?
DNA helicase and DNA polymerase
what is step 1 of semi conservative replication?
DNA helicase breaks the hydrogen bonds between the complementary base pairs between the two stands within a
double helix
this causes the DNA double helix to unwind
what is step 2 of semi conservative replication?
each of the separated parental DNA strands acts as a
template
free-floating DNA nucleotides within the nucleus are attracted to their complementary base pairs on the template strands of the parental DNA
what is step 3 of semi conservative replication?
the adjacent nucleotides are joined together (to form the
phosphodiester bond) by a condensation reaction
DNA polymerase catalyses the joining together of adjacent
nucleotides
what is step 4 of semi conservative replication?
the two sets of daughter DNA contain one strand of the parental (original) DNA and one newly synthesised strand
What acts as a template during DNA replication?
Each of the separated parental DNA strands
Parental DNA strands guide the synthesis of new strands.
What are free-floating DNA nucleotides attracted to during DNA replication?
Their complementary base pairs on the template strands of the parental DNA
This attraction ensures accurate pairing of nucleotides.
What is the process called that joins adjacent nucleotides together in DNA replication?
Forming a phosphodiester bond by a condensation reaction
This reaction results in the formation of the DNA backbone.
Which enzyme catalyzes the joining of adjacent nucleotides during DNA replication?
DNA polymerase
DNA polymerase is essential for synthesizing new DNA strands.
What is the name given to the new DNA molecules formed after replication?
Daughter DNA
Each daughter DNA molecule consists of one original and one new strand.
Fill in the blank: The newly synthesised strands of DNA contain one strand of _______ DNA and one newly synthesised strand.
[parental]
Parental DNA serves as a template for the new strand.
True or False: During DNA replication, both daughter DNA strands are newly synthesized.
False
One strand is parental while the other is newly synthesized.
What is the process of DNA replication called?
Semi-conservative replication
In semi-conservative replication, each daughter DNA contains one original strand and one newly synthesized strand.
What are the complementary base pairs in DNA?
- Cytosine + Guanine
- Thymine + Adenine
Complementary base pairing is essential for accurate DNA replication.
What enzyme is responsible for unwinding the DNA double helix?
DNA helicase
DNA helicase breaks the hydrogen bonds between complementary base pairs.
What enzyme synthesizes new DNA strands during replication?
DNA polymerase
DNA polymerase adds free nucleotides to the growing DNA strand.
What is the function of free nucleotides in DNA replication?
To be added to the newly synthesized DNA strand
Free nucleotides are the building blocks for creating new DNA strands.
What are the four key stages to semi-conservative DNA replication?
- Unwinding of the DNA double helix
- Breaking hydrogen bonds by helicase
- Synthesizing new strands by DNA polymerase
- Formation of two identical DNA molecules
Each stage is crucial for accurate DNA replication.
Fill in the blank: DNA helicase breaks the hydrogen bonds between the _______ base pairs.
complementary
This step is vital for the unwinding of the DNA double helix.
True or False: In DNA replication, both strands of the DNA double helix are synthesized simultaneously.
False
DNA replication occurs in a leading strand and a lagging strand, synthesized at different rates.
What is the replication fork?
The area where the DNA double helix is unwound
The replication fork is a Y-shaped structure that forms during DNA replication.
What are the two types of strands involved in DNA replication?
- Leading strand
- Lagging strand
The leading strand is synthesized continuously, while the lagging strand is synthesized in fragments.
What is the role of the original (template) DNA strand in replication?
To provide a pattern for the synthesis of a new strand
The template strand ensures that the new DNA is complementary to the original.
What base does DNA contain that RNA does not?
Thymine
RNA contains uracil instead of thymine.
What is the pentose sugar found in DNA?
Deoxyribose
RNA contains ribose.
How many genes does DNA contain approximately?
23,000 genes
This represents the entire genome.
What is the structural difference between DNA and RNA?
DNA is double-stranded; RNA is single-stranded.
What type of acid is RNA?
Ribonucleic acid.
What type of acid is DNA?
Deoxyribonucleic acid.
Fill in the blank: RNA contains the base _______.
Uracil.
Fill in the blank: DNA contains the sugar _______.
Deoxyribose.
Fill in the blank: The nucleobases of DNA include adenine, cytosine, guanine, and _______.
Thymine.
Fill in the blank: The nucleobases of RNA include adenine, cytosine, guanine, and _______.
Uracil.
What is the primary function of transfer RNA (tRNA)?
To attach to one of the 20 amino acids and transfer this amino acid to the ribosome to create the polypeptide chain.
tRNA plays a crucial role in translating the genetic code into proteins.
What is the shape of tRNA?
Cloverleaf shape.
The cloverleaf shape is formed by folding of the single-stranded tRNA held in place by hydrogen bonds.
Where is tRNA found?
In the cytoplasm.
tRNA is specifically located in the cytoplasm where it interacts with ribosomes.
What determines the specific amino acid that attaches to a tRNA molecule?
3 bases found intramolecular on the tRNA which are complementary to the 3 bases on mRNA.
These complementary bases form the anticodon on tRNA.
What are the bases on tRNA that are complementary to the codon on mRNA called?
Anticodon.
The anticodon is essential for ensuring the correct amino acid is added during protein synthesis.
What type of RNA makes up the bulk of ribosomes?
Ribosomal RNA (rRNA).
rRNA combines with proteins to form ribosomes, which are essential for protein synthesis.
What are the two subunits of a ribosome and their sizes?
Large subunit: 50S, Small subunit: 30S.
The combined size of the ribosome is often referred to as 70S.
Fill in the blank: tRNA is ________ but folded to create a shape that looks like a cloverleaf.
single-stranded.
The folding of the single-stranded tRNA is crucial for its function.
What is mRNA?
A copy of a gene from DNA.
Where is mRNA created?
In the nucleus.
What does mRNA carry to the ribosome?
The copy of the genetic code of one gene.
What is the structure of mRNA?
Single-stranded.
Why is mRNA considered short-lived?
It is only needed temporarily to help create a protein.
What is the role of RNA polymerase?
To synthesize mRNA from DNA.
What are the two strands of DNA involved in transcription?
Coding strand and template strand.
Why can’t DNA leave the nucleus?
It is too large and would risk being damaged by enzymes.
How does the size of mRNA compare to DNA?
mRNA is much shorter, only the length of one gene.
What is the function of codons in mRNA?
Every 3 bases code for a specific amino acid.
Fill in the blank: mRNA is _______ and carries the genetic code from the nucleus to the cytoplasm.
single-stranded
True or False: mRNA can be permanently damaged by enzymes.
False
What happens to mRNA after it has performed its function?
It is broken down by enzymes.
What stabilizes the structure of DNA?
The sugar-phosphate backbone and the double helix prevent damage.
Covalent bonds in the sugar-phosphate backbone provide stability.
Why is DNA double-stranded?
So replication can occur using one strand as a template.
This allows for accurate copying of genetic information.
What type of bonds allow for easy separation of DNA strands during replication?
Weak hydrogen bonds.
These bonds facilitate the unwinding of the double helix.
What is a key feature of DNA that allows it to carry genetic information?
It is a large molecule.
A larger size enables the storage of extensive genetic data.
What enables the production of identical copies of DNA?
Complementary base pairing.
This mechanism ensures accuracy in replication.
What is RNA a polymer of?
A nucleotide formed of ribose, a nitrogenous base, and a phosphate group.
RNA’s structure is simpler compared to DNA.
Which nitrogenous base is found in RNA instead of thymine?
Uracil.
This is a key difference between RNA and DNA.
What is the general structure of RNA compared to DNA?
RNA is a relatively short polynucleotide chain and is single-stranded.
This contrasts with DNA’s longer, double-stranded structure.
What is the primary function of RNA?
To copy and transfer the genetic code from DNA in the nucleus to the ribosomes.
This process is essential for protein synthesis.
What role does some RNA play in ribosomes?
It is combined with proteins to create ribosomes.
Ribosomes are crucial for translating mRNA into proteins.
Name the three types of RNA.
- mRNA
- tRNA
- rRNA
Each type has a distinct function in the process of protein synthesis.
What is a polynucleotide?
The polymer of nucleotides created via condensation reactions.
How is a polynucleotide formed?
Through condensation reactions between deoxyribose sugar and phosphate group, creating a phosphodiester bond.
What type of bond do phosphodiester bonds represent?
Strong covalent bonds.
What is the role of phosphodiester bonds in DNA?
They help ensure that the genetic code is not broken down.
What does the term ‘sugar-phosphate backbone’ refer to?
The strong covalent bonds between the sugar and phosphate groups in a polynucleotide.
What structure does DNA polymer occur in?
Pairs, joined together by hydrogen bonds between the bases.
What are hydrogen bonds in DNA formed between?
Complementary base pairs.
Which bases form complementary base pairs in DNA?
- Cytosine with Guanine
- Adenine with Thymine
How many hydrogen bonds do adenine and thymine form?
2 hydrogen bonds.
How many hydrogen bonds can cytosine and guanine form?
3 hydrogen bonds.
Why is complementary base pairing important?
It helps maintain the order of the genetic code during DNA replication, reducing the chance of mutations.
What does DNA stand for?
Deoxyribonucleic Acid
What is the shape of the DNA polymer?
Double helix
What are the components of a DNA nucleotide?
- Deoxyribose (a pentose sugar) * Nitrogenous base * One phosphate group
Which nitrogenous bases are found in DNA?
- Guanine * Cytosine * Adenine * Thymine
What is the role of DNA in cells?
Codes for the sequence of amino acids in proteins
What is essential for cells regarding DNA?
Cells must contain a copy of the genetic code that can be passed to new cells without being damaged
Fill in the blank: The DNA backbone is made up of _______ and deoxyribose.
Phosphate group
What are the ends of the DNA strand called?
5’ end and 3’ end
True or False: The sequence of amino acids determines the final 3D structure and function of a protein.
True
What type of sugar is found in DNA?
Deoxyribose
