A1.2 Nucleic Acids Flashcards
what is inside nucleic acids
a genetic code seen in the order of bases in DNA that determine protein synthesis
what are the two types of nucleic acids
DNA and RNA
what does a nucleotide consist of and how are they combined
nitrogenous base
pentose sugar
phosphate group
combined by condensation reactions resulting in covalent bonds
what are the different nitrogenous bases
Cytosine,
Guanine
adenine
thymine
what are the two groups bases can be divided into
purines ( A and G) and pyrimidines ( C and T)
what is the polymer of nucleotides
polynucleotides or nucleic acids
what forms the backbone of nucleic acids
alternating sugar and phosphate molecules
they create a chain of covalently bonded atoms
where does info in the DNA lie
in the sequence of nitrogenous bases which form the genetic code
what does the sequence of bases dictate
which amino acids are assembled and combined to synthesize proteins
what is a codon
a sequence of three bases
what bases are found in RNA
Cytosine
Guanine
Adenine
Uracil ( instead of thymine)
difference between DNA and RNA
DNA has a deoxyribose sugar while RNA has a ribose sugar
what are the different forms RNA can be in
Messenger RNA
Transfer RNA
Ribosomal RNA
where is mRNA found
in the nucleus and is transported through nuclear pores to ribosomes
Where is tRNA and rRNA found
made in the nucleus but found in the cytoplasm
what is the bond formed between adjacent nucleotides
a 3’ to 5’ phosphodiester bond
what is the shape of the DNA molecule
two antiparallel polynucleotide strands, paired together and held by hydrogen bonds, that takes the shape of a double helix
why are the two strands of DNA called antiparallel
one strand runs 5’ to 3’ while the other is 3’ to 5’
what codes for proteins within the DNA molecule
sections known as genes
where are genes located
on chromosomes.
genes for a particular characteristic are always found in the same place, or ‘locus’
what is an allele
each gene has two or more forms known as alleles
what are homologous chromosomes
chromosomes of eukaryotic cells occur in pairs that resemble each other in structure and sequence of genes
what are the complementary base pairings
only A and T
only C and G
what are the number of hydrogen bonds in the base pairings
A with T, held by two hydrogen bonds
C with G, held by three hydrogen bonds
what is the purpose of complementary base pairings
allows genetic information to be replicated and expressed
what is genome size
the amount of DNA contained in the genome
what are conserved sequences
Sequences that stay unchanged with minor modifications
the most highly conserved genes are those found in all organisms, suggest common ancestry
what is the coding strand and what way is it read
the template for transcription and it always reads in the 3’ to 5’ direction
what is the result of a coding strand
a single strand of RNA that is formed by complementary base pairing
synthesized in 5’ to 3’ direction
what direction is mRNA translated in
in the 5’ to 3’ direction by a ribosome to produce a polypeptide chain
What did Watson and Crick discover in base pairings
they are all of equal length so DNA always has the same structure
how is DNA packaged
by coiling the DNA double helix and looping around protein beads known as nucleosomes
what is a nucleosome
a sequence of DNA wound around 8 histone protein cores that form a bead
what is the features of histones
a basic protein containing a high concentration of amino acid residues with additional basic groups
what happens to the nucleosomes when the nucleus divides in cell division
the beaded thread is coiled up, forming the chromatin fibre.
this is then coiled up again and looped around a scaffold protein fibre made of a non histone chromosomal protein
the whole structure is supercoiled into the much condensed chromosomes
What is the Hersey and Chase DNA experiment
through the use of phages, DNA and proteins were labelled with radioactive atoms that could be traced.
They saw that the DNA part of the virus was entering the host cell and carrying the genetic information, instead of proteins
What did Chargaff discover that
number of purine bases always equals number of pyrimidine bases
