DNA and Genetic Replication (7) Flashcards
what are dna and rna
nucleic acids
what is the full name of Dna
deoxyribonucleic acid
what is the full name of RNA
ribonucleic acid
what does dna do simply
holds genetic information
what does RNA do simply
transfers genetic information from DNA to ribosomes
what are dna and rna polymers of
they are polymers of nucleotides
who discovered the structure of DNA
watson and crick
what is the structure of DNA
it consists of 2 polynucleotide strands joined together by hydrogen bonds to form a double helix
what is in each DNA nucleotide
1) the pentose sugar deoxyribose
2) the phosphate group
3) one of 4 nitrogen containing bases (adenine, thymine, cytosine, guanine)
what are the nucleotides in each polypeptide strand joined by and how
phosphodiester bonds formed by condensation reactions
what forms the backbone of the polynucleotide strands
and why are bases oriented towards the centre
the pentose sugar and phosphate group
to protect them from reacting with other chemicals
how is the structure of DNA relatively stable
the bases are joined by hydrogen bonds which individually are weak but due to their large number collectively maintain a stable structure
how can dna helix provide an even more compact store of genetic information
the dna helix is further coiled to produce a super helix providing a compact store of genetic information
what direction are the dna strands going in
anti parallel
what direction are the dna strands going in
anti parallel
how is the structure of DNA adapted for its function?
sugar phosphate backbone
provides stength
how is the structure of DNA adapted for its function?
helix
gives compact shape
protects sequence of bases
how is the structure of DNA adapted for its function?
double stranded
each strand serves as a template in replication
protects sequence of bases
makes molecule more stable
how is the structure of DNA adapted for its function?
large molecule
large amount of genetic material can be stored
how is the structure of DNA adapted for its function?
many hydrogen bonds
gives stability
individual hydrogen bonds are weak so allows strands to be separated for dna replication and protein synthesis’s
how is the structure of DNA adapted for its function?
sequence of bases
codes for specific amino acid sequence in a polypeptide
how is the structure of DNA adapted for its function?
complementary base pairing
enables information to be replicated accurately
when does dna replication occur and what important role does it have
dna replication occurs in cell division
important role in the growth and reproduction of organisms
outline the semi-conservative mechanism of DNA replication
1) when DNA replicates, the enzyme DNA helicase breaks the hydrogen bonds and separates the 2 polynucleotide strands
2) each of the strands acts as a template for the formation of 2 new complementary strands
3) individual DNA nucleotides align and attach by hydrogen bonding to the exposed bases on each template strand according to specific complementary base pairing
4) adenine pairs with thymine and cytosine pairs with guanine
5) the dna nucleotides in the new strand are joined together by phosphodiester bonds in condensation reactions catalysed by the enzyme DNA POLYMERASE
6) the 2 new dna molecules are identical to each other and the original DNA
why is dna replication called semi conservative
because the 2 new dna molecules contain one of the original polynucleotide strands and a new one
is RNA a relatively short or long polynucleotide molecule
short
how does RNA differ in structure from DNA
(3)
1) the pentose sugar is ribose not deoxyribose
2) the nitrogen base Thymine is replaced with Uracil
3) mRNA and tRNA are single stranded in comparison to double stranded dna
what structure is messenger RNA (mRNA)
a linear structure and contains codons (mRNA base triplets)
what is messenger rna (mRNA) involved in and where is it formed
mRNA is involved in protein synthesis
it is formed in the nucleus during transcription
how many different types of tRNA are there and where are they found
there are atleast 20 different types of tRNA molecules found in the cytoplasm
what shape is tRNA molecules and why is it?
tRNA molecules have a ‘clover leaf’ structure
due to the presence of hydrogen bonds between complementary base pairs
what are the 2 things on a tRNA molecule ?
on one end of the molecule there is an ANTICODON ( 3 unattached tRNA nucleotide bases )
on the other end : a binding site for the attachment of a specific amino acid
in prokaryotic cells what are dna molecules structure ?
they are short circular and are not associated with proteins called histones
prokaryotes do not form chromosomes
in eukaryotic cells what is the dna structure like
how are chromosomes formed
dna is long and linear and are associated with proteins called histones
together dna molecule and histones form a chromosome
what is the dna like in mitochondria and chloroplasts of eukaryotic cells
it is like the dna of prokaryotes :
short circular and not associated with proteins and does not contain introns
what is a gene
a gene is a specific sequence of dna bases that code for the specific amino acid sequence of a polypeptide
where are homologous chromosomes found
Homologous chromosomes are found in diploid organisms (organisms with two sets of chromosomes, such as humans). Each pair consists of one chromosome inherited from the mother and one from the father.
what is the structure of homologous chromosomes
Each homologous chromosome is similar in length, shape, and centromere position. They contain the same genes arranged in the same loci.
However, the alleles for each gene may differ. For example, one chromosome might have an allele for brown eyes, while its homolog might have an allele for blue eyes.
