DNA mutation and repair Flashcards
what are nucleic acid?
they are polymers of nucleotide with very specific functions in cells
what are the 2 types of nucliec acid?
DNA and RNA
What is DNA?
genetic material that stores information regrading its own replication and order in which amino acids are to be joined to make a protein
what is RNA?
there are different types they are involved protein synthesis and control of gene expression
what are the similaries between DNA and RNA?
both have a 5 carbon sugar, phosphate backbone and 4 bases
what are some difference between DNA and RNA?
- DNA is found in chromosomes RNA location depends on its function
- bases are A,T,G,C in DNA, in RNA its A,U,G,C
- sugar is deoxyribose in DNA in RNA its ribose
how many hydrogen bond are there between A and T?
2
how many hydrogen bond are there between G and C?
3
where does protein interaction occur along the back bone?
in the major groove as proteins can fit in there as its larger than the minor groove
what is the function of DNA?
- it encodes proteins
- replication for reproduction growth and repair
- used genetic information for heredity mechanism
- for mutations
what is on the 5 prime?
phosphate
how much of our genome codes for proteins?
2%
what are the different types of RNA?
rRNA
mRNA
tRNA
what is rRNA function and where is it located?
participate in protein synthesis and is located in ribosomes
what is mRNA function and where is it located?
codes for proteins and is found in the nucleus and cytoplasm
what is tRNA function and where is it located?
used in protein synthesis as adaptors between mRNA and amino acids and are found in the nucleus and cytoplasm
what is the genome?
the complete set of genetic information in an organism
when might RNA encode for the organism genetic information?
in small viruses
how big is the nucleus in a typical human cell?
5 micrometers in diameters
what is our DNA packed into?
chromosomes
what are the different arms on a chromsome?
p shorter arm
q longer arm
how is DNA packed up?
highly coiled and folded around protein called histones to from a nucleosome
what is chromatin?
when the nucleosomes are packed together which is then packed up again to make chromosomes
what are nucleosomes made up of?
when DNA wraps around a central core of 8 histone proteins to form a single nucleosome
what are the different types of histones proteins?
H2A H2B H3 H4
what does H1 do?
packs the nucleosome all together
what does a gene do?
a region of DNA that controls a discrete hereditary characteristic, usually corresponding to a single protein or RNA
what is the function of the non-coding regions?
- regulation of gene expression
- redundancy
- miRNA
- epigenetic
- stability
what are the main steps to get from DNA to a protein?
DNA is transcribed into RNA
then its translated from RNA to a protein
what is an exon?
the coding regions
what is a promotor?
they control transcription and whether or not it will occur
what is a TATA box?
allows the formation of RNA polymerase to bind to start transcription
what is alternative splicing?
it generate different protein products from the same gene by combining different combinations of exons
what cell cycle phase does DNA replication occur in?
the S phase
what is semi-conservative replication?
when DNA acts as a template for its own duplication where there is a daughter and parent strand
how does DNA replication occur? enzymes used to explain steps
- topoisomerase decoils the DNA and DNA helicase breaks H-binding between pairs
- DNA primase attaches the RNA primer so synthesis can occur
- DNA polymerase will allow free nucleotides to join the template strands
- DNA ligase forms phosodiester bonds between shorter nucleotides
- DNA telomerase replicates DNA at the end of chromsomes
how many origins of replication is there?
around 20,000 and they are normally A-T rich
what direction can DNA polymerase work?
5’ to 3’
what is a leading strand?
when the template strand is able to bind to free nucleotides as DNA polymerase is working in the 5’ to 3’ direction
what is the lagging strand?
when okazaki fragments which is about 200bases are made due to DNA polymerase only working from 5’ to 3’ so having to work back on its self and the daughter strand taking longer to make
what steps are needed to be repeated for lagging strand to synthesis to the DNA?
- primer synthesis
- elongation
- primer removal
- ligation
what are the repetitive sequences at the end of chromosomes?
telomeres
what is used in order for repair of a damaged base?
the template strand
what are the 3 main steps for DNA repair?
- excision
- resynthesis
- ligation
during DNA repair what enzyme recognises the altered base?
DNA glycosylase
how does DNA glycosylase work?
by cutting the glycosidic bond between the base and the sugar and loses the base
what does AP endonuclease and phosphodiesterase do?
the remove the sugar and the phosphate
what are the different DNA repair mechanisms?
- base excision repair
- nucleotide excision repair
- non-homologous recombinational repair
- homologous recombinational repair
what happens during base excision repair?
when just one base is missing as a result of deamination and AP endonuclease and phosphdiesterase remove the sugar phosphate and DN polymerase adds new nucleotides DNA ligase selas them
what happens during nucelotide excision repair?
-enzymes recognise a bulky lesion like a dimer. exonuclease excises nucleotides around lision and DNA helicase peels it away from the double helix
what happens during non-homologous recombination repair?
occurs in G1
- overhanging single strand DNA ends are degraded
- results in loss of one or more nucleotides and cause juxtaposition
what happens during homoglous recombination repair?
occurs in S/G1 overhanging. The cell is provided with a copy and recombined into damaged DNA= fully repaired strand
