How does DNA in eukaryotes differ to prokaryotes? In prokaryotic cells, DNA molecules are
short, circular and not associated with proteins whereas in eukaryotic cells they are longer,
linear and associated with proteins
What is the role of histones? support DNA
What forms a chromosome? DNA molecule and its associated proteins (histones)
Do mitochondria and chloroplasts contain DNA? Yes
Is the DNA in mitochondria and chloroplasts similar to DNA in prokaryotes or eukaryotes?
Prokaryotes
What is a gene? A sequence of DNA that codes for the amino acid sequence of a
polypeptide or a functional RNA
What determines the order of amino acids in a polypeptide? The order of bases in a gene
What is a triplet? a sequence of 3 bases which code for an amino acid in DNA
What is functional mRNA? RNA molecules other than mRNA which peform special tasks
during protein synthesis
What is a cell's genome? The complete set of genes in a cell
What is the cell's proteome? The full range of proteins that the cell is able to produce
Name three attributes of the genetic code and their meanings. Universal
Non-overlapping
Degenerate
What does universal mean, when referring to the genetic code? same specific base triplets
code for the same amino acids in all living things
What does non overlapping mean when referring to the genetic code? Each base
sequence is its own - no sharing
What does degenerate mean when referring to the genetic code? Some amino acids are
coded for by more than one triplet
What is an intron? sequence of DNA that does not code for a polypeptide
What is an exon? sequence of DNA that does code for polypeptide
Does prokaryotic DNA have introns? NO
What is a non-coding repeat? Regions of multiple repeats outside of genes that do not code
for amino acids
Where are non coding repeats found, in eukaryotic or prokaryotic DNA? Eukaryotic
What is a locus? A fixed position occupied by a gene on a particular DNA molecule
What is an allele? Different forms of a gene
What makes each allele different? Order of bases
How is DNA stored in a eukaryotic cell? Chromosomes
How many pairs of chromosomes do humans have? 23
What are homologous pairs? Pairs of matching chromosomes
What is the structure of mRNA? single polynucleotide strand
What is the role of mRNA? carries genetic code from DNA to ribosomes
In mRNA what is the sequence of 3 bases called? codon
When is mRNA made? transcription
What is tRNA involved in? translation
What is the job of tRNA? carries the amino acids that are used to make proteins to the
ribosomes
What is the point of transcription? The production of mRNA from DNA
How is the clover shape held in tRNA? held by hydrogen bonds between specific base
pairs
Describe the structure of tRNA? - single polynucleotide strand
- clover shape
- amino acid binding site
, - anticodon
What is an anticodon? specific sequence of 3 bases at one end of the tRNA molecule
What is the role of RNA polymerase? Joins mRNA nucelotides
Where does transcription take place in eukaryotes? Nucleus
Where does transcription take place in prokaryotes? cytoplasm
Describe what happens during transcription. - RNA polymerase attaches to DNA double
helix at the beginning of a gene ( promoter )
- Hydrogen bonds are broken by DNA helicase which is attached to RNA polymerase
- This separates strands and DNA uncoils exposing some of the bases
- One of the strands is used as a template to make mRNA
- Specific complementary base pairing occurs:
- free RNA nucleotides line up alongside exposed bases on template strand
- Joined together by RNA polymerase ( phosphodiester bonds )
- Forms mRNA molecule
- Hydrogen bonds reform and strands coil back into double-helix
-RNA polymerase moves along DNA and stops at stop signal
- Detaches from DNA
- mRNA move out of nucleus through nuclear pore and attaches to ribosomes
What is the difference in transcription between prokaryotes and eukaryotes
( excluding location )? - Forms pre-mRNA which contains introns in eukaryotes
- In prokaryotes mRNA is produced directly
What is splicing? Removal of introns from pre-mRNA to form mRNA
What is the point of translation? To produce polypeptides from the sequence of codons
carried by mRNA
Where does translation occur? Is it different for prokaryotes and eukaryotes? In the
ribosomes and its the same for both
Are anticodons and codons complementary? Yes
Describe what happens during translation? -mRNA attaches itself to a ribosome and tRNA
carries amino acids to it
- ATP provides energy for the bond between amino acid and tRNA molecule to form
- tRNA carries anticodon to first codon on mRNA
- anticodon attaches through specific base pairing
- second tRNA molecule attaches itself to the next codon
- First 2 amino acids are joined by a peptide bond
- first tRNA molecule moves way leaving its amino acid behind
- third tRNA molecule attaches to the next codon on mRNA
- this amino acid binds to the first two
- second tRNA molecule move away
- process continues until a stop signal
- polypeptide chain moves away
Are codons complementary to DNA triplets? Yes
Are triplets and anti codons the same? No anticodons contain uracil, triplets contain
thymine
Are gametes haploid or diploid? haploid
Is fertilisation random? Yes
What does this achieve? Random fertilisation increases genetic diversity within a
species
How? Produces zygotes with different combinations of chromosomes
Cells that divide by meiosis start of as... diploid
short, circular and not associated with proteins whereas in eukaryotic cells they are longer,
linear and associated with proteins
What is the role of histones? support DNA
What forms a chromosome? DNA molecule and its associated proteins (histones)
Do mitochondria and chloroplasts contain DNA? Yes
Is the DNA in mitochondria and chloroplasts similar to DNA in prokaryotes or eukaryotes?
Prokaryotes
What is a gene? A sequence of DNA that codes for the amino acid sequence of a
polypeptide or a functional RNA
What determines the order of amino acids in a polypeptide? The order of bases in a gene
What is a triplet? a sequence of 3 bases which code for an amino acid in DNA
What is functional mRNA? RNA molecules other than mRNA which peform special tasks
during protein synthesis
What is a cell's genome? The complete set of genes in a cell
What is the cell's proteome? The full range of proteins that the cell is able to produce
Name three attributes of the genetic code and their meanings. Universal
Non-overlapping
Degenerate
What does universal mean, when referring to the genetic code? same specific base triplets
code for the same amino acids in all living things
What does non overlapping mean when referring to the genetic code? Each base
sequence is its own - no sharing
What does degenerate mean when referring to the genetic code? Some amino acids are
coded for by more than one triplet
What is an intron? sequence of DNA that does not code for a polypeptide
What is an exon? sequence of DNA that does code for polypeptide
Does prokaryotic DNA have introns? NO
What is a non-coding repeat? Regions of multiple repeats outside of genes that do not code
for amino acids
Where are non coding repeats found, in eukaryotic or prokaryotic DNA? Eukaryotic
What is a locus? A fixed position occupied by a gene on a particular DNA molecule
What is an allele? Different forms of a gene
What makes each allele different? Order of bases
How is DNA stored in a eukaryotic cell? Chromosomes
How many pairs of chromosomes do humans have? 23
What are homologous pairs? Pairs of matching chromosomes
What is the structure of mRNA? single polynucleotide strand
What is the role of mRNA? carries genetic code from DNA to ribosomes
In mRNA what is the sequence of 3 bases called? codon
When is mRNA made? transcription
What is tRNA involved in? translation
What is the job of tRNA? carries the amino acids that are used to make proteins to the
ribosomes
What is the point of transcription? The production of mRNA from DNA
How is the clover shape held in tRNA? held by hydrogen bonds between specific base
pairs
Describe the structure of tRNA? - single polynucleotide strand
- clover shape
- amino acid binding site
, - anticodon
What is an anticodon? specific sequence of 3 bases at one end of the tRNA molecule
What is the role of RNA polymerase? Joins mRNA nucelotides
Where does transcription take place in eukaryotes? Nucleus
Where does transcription take place in prokaryotes? cytoplasm
Describe what happens during transcription. - RNA polymerase attaches to DNA double
helix at the beginning of a gene ( promoter )
- Hydrogen bonds are broken by DNA helicase which is attached to RNA polymerase
- This separates strands and DNA uncoils exposing some of the bases
- One of the strands is used as a template to make mRNA
- Specific complementary base pairing occurs:
- free RNA nucleotides line up alongside exposed bases on template strand
- Joined together by RNA polymerase ( phosphodiester bonds )
- Forms mRNA molecule
- Hydrogen bonds reform and strands coil back into double-helix
-RNA polymerase moves along DNA and stops at stop signal
- Detaches from DNA
- mRNA move out of nucleus through nuclear pore and attaches to ribosomes
What is the difference in transcription between prokaryotes and eukaryotes
( excluding location )? - Forms pre-mRNA which contains introns in eukaryotes
- In prokaryotes mRNA is produced directly
What is splicing? Removal of introns from pre-mRNA to form mRNA
What is the point of translation? To produce polypeptides from the sequence of codons
carried by mRNA
Where does translation occur? Is it different for prokaryotes and eukaryotes? In the
ribosomes and its the same for both
Are anticodons and codons complementary? Yes
Describe what happens during translation? -mRNA attaches itself to a ribosome and tRNA
carries amino acids to it
- ATP provides energy for the bond between amino acid and tRNA molecule to form
- tRNA carries anticodon to first codon on mRNA
- anticodon attaches through specific base pairing
- second tRNA molecule attaches itself to the next codon
- First 2 amino acids are joined by a peptide bond
- first tRNA molecule moves way leaving its amino acid behind
- third tRNA molecule attaches to the next codon on mRNA
- this amino acid binds to the first two
- second tRNA molecule move away
- process continues until a stop signal
- polypeptide chain moves away
Are codons complementary to DNA triplets? Yes
Are triplets and anti codons the same? No anticodons contain uracil, triplets contain
thymine
Are gametes haploid or diploid? haploid
Is fertilisation random? Yes
What does this achieve? Random fertilisation increases genetic diversity within a
species
How? Produces zygotes with different combinations of chromosomes
Cells that divide by meiosis start of as... diploid
