inquiry question 3 mod 5 Flashcards
what does DNA stand for
deoxyribose nucleic acid
DNA
Hereditary material that carries all the genetic code for proteins that enable cells to undergo growth, repair and other specialised functions
location of DNA
prokaryotes: stored as single looped chromosomes + smaller loops of DNA (plasmids)
eukaryotes:
- nucleus, chloroplast, mitochondria
structure of DNA
- double stranded helix with 4 nitrogenous bases
- long double stranded helix
- chain made up of nucleotides
- leading strand 5’ - 3’
- lagging strand 3’ to 5’
- anti-parallel
nucleotides
made up of
- deoxyribose sugar
- phosphate group
- nitrogenous base
- base pairs bonded by hydrogen bonds
- covalent bonds between sugar and phosphate group
deoxyribose sugar
- five carbon atoms
- four carbons and one oxygen forms a ring + one carbon branching off
nitrogenous bases in DNA
- adenine, thymine, guanine, cytosine
- purine (two rings) adenine and guanine
- pyrimidine (one ring) cytosine and thymine
enzymes needed for DNA replication
helicase, polymerase, topoisomerase, primase, rna primers
DNA replication
- DNA must replicate before a cell divides (mitosis)
- takes place in interphase
DNA replication steps
- Helicase unwinds and separates/unzips the 2 DNA strands into a replication fork (Y shape) –> breaks hydrogen bonds between bases
- bind proteins attach to the 2 DNA strands → keeps them separate and untwisted
- Enzyme topoisomerase relieves stress (caused by the unzipping) –> attaches ahead of the fork on the DNA molecule → prevents coiling so it can continue to separate
- primase makes RNA primers
- RNA primers are required to add new nucleotides from the surrounding cytoplasm
- DNA polymerase add new nucleotides to the replication fork stands
- leading strand –> Bind to DNA → moves along → reads bases → assemble complementary strand of nucleotides
- lagging strand –> discontinuous segments (okazaki fragments) glued together by DNA ligase
- bases are paired - new strand is created –> complementary of one of the template strands
what model is DNA
semi conservative –> watson and crick
leading strand: direction and enzymes needed
5’ to 3’
- DNA helicase
DNA polymerase
- Primase
- topoisomerase
lagging strand: direction and enzymes needed
3’ to 5’
- primase
- polymerase
- ligase
- helicase
role of DNA helicase
unwinds and separates/unzips the 2 DNA strands into a replication fork (Y shape)
which is done through breaking hydrogen bonds
Role of topoisomerase
relieves stress (caused by the unzipping) → attaches ahead of the fork on the DNA molecule → prevents coiling so it can continue to separate
role of primase
required to add new nucleotides from the surrounding cytoplasm
role of DNA polymerase
add new nucleotides to the replication fork stands
leading: binds to DNA –> moves along and reads bases -> assemble complementary strand of nucleotides
lagging: synthesises okazaki fragments
role of DNA ligase
glues the Okazaki fragments together in the lagging strand
okazaki fragments
short sections of DNA formed at the time of discontinuous synthesis of the lagging strand during replication of DNA
similarities in prokaryotes and eukaryotes
- DNA replicates before cell division
- DNA is combined with proteins
- they have the same role to make polypeptides
differences in DNA –> eukaryotes and prokaryotes
prokaryotes:
- little non-coding DNA
- circular chromosome in nucleoid region
- one copy of each gene
eukaryotes:
- large section of non-coding DNA
- densely packed in nucleus as linear chromosomes
- multiple copies of each gene
what is a gene in terms of DNA
length of a DNA
polypeptides
amino acid chains –> 20 amino acids joined by peptide bonds
- they fold to create a functional protein
amino acid structure
oxygen, carbon , hydrogen , nitrogen
non-coding DNA
introns –> spliced out (which helps regulate gene expression)
promoters –> TATA box
examples of proteins
keratin, haemoglobin
coding DNA
exons
2 steps of protein synthesis
- transcription
- base sequence is transcribed into mRNA - translation
- polypeptides are made from mRNA
what does RNA stand for
ribonucleic acid
- ribose sugar in the back bone
- uracill instead of thymine
- single stranded
three types:
- mRNA (messenger)
- rRNA (ribosomal)
- tRNA (transfer)
role of mRNA
- copied DNA code
- carries genetic information to the ribosome
role of rRNA
- site of protein synthesis
- single strand
- globular shape
- reads the mRNA sequence –> translates genetic code into amino acids
role of tRNA
transfers amino acids to ribosomes where proteins are synthesised
- clover leaf shape
- single stranded molecule with attachment site at one end with amino acid
- opposite end has an anti codon –> three nucleotide bases
UAG (mRNA) AUC (tRNA)
RNA
converts genetic information contained within DNA to build proteins
mRNA
- long single straight chain of nucleotides that carries information for a specific protein
- bases: ( A,U,G,C)
- made up of codons
codon
sequences of three bases
AUG start
anti-codon
complimentary of the codon (A - U ) (C - G)
protein synthesis
production or synthesis of polypeptide chains
role of transcription
Process by which the DNA base sequence is read by the enzyme RNA polymerase and copied onto a single strand of mRNA
characteristics of transcription
- requires RNA polymerase to build in the 5’ to 3’
- base sequence from template strand is transcribed onto mRNA
- mRNA needs to be processed before leaving the nucleus
- takes place in the nucleus
-tata start stops at stop codons
direction of transcription
5’ to 3’
what enzyme does transcription need to build in the 5’ to 3’ direction
RNA polymerase
how do you know where transcription starts
TATA box
where does transcription end
stop codons
direction of coding strand
5’ to 3’
direction of template strand
3’ to 5’
coding strand
contains the gene
template strand
U instead of T in mRNA
transcription stages
initiation
elongation
termination
transcription process
- Specific section of DNA continuing the gene of interest is unwinded, exposing the DNA base sequence through RNA polymerase which binds to DNA and separates the DNA strands
- RNA polymerase then uses one strand of DNA as a template to assemble the nucleotides into RNA in the 5’ to 3’ direction
Initiation stage:
promoters (TATA box) show where the polymerase must bind to begin transcription of RNA
Elongation stage:
RNA polymerase builds a new strand in the 5’ to 3’ direction → through adding RNA free floating mRNA nucleotides (A,U,C,G) to undergo complementary base pairing in 5’ to 3’ direction
Termination stage:
Specific base sequences → codons signal the process to stop → termination signal
mRNA processing
RNA editing needs to be done to the nucleotide chain to makes the RNA FUNCTIONAL
- Introns - spliced out
mRNA editing
Exons rejoined by ligase
- Guanine triphosphate cap is added to the 5’ end of new mRNA
- Poly A tail is added to 3’ end of RNA
mRNA transcript
Mature mRNA leaves nucleus through pores → goes to ROUGH ER ribosomes
exons
segments of DNA that code for proteins
why and where and what is guanine triphosphate cap and poly A tale
To protect the mRNA from being broken up while leaving the nucleus in mRNA editing stage
- guanine triphosphate cap –> 5’ side
- poly A tail –> 3’ side
what is used to protect the mRNA from being broken up while leaving the nucleus
guanine triphosphate cap 5’
poly A tale 3’
stages in translation
initiation
elongation
termination
role of translation
Process of decoding mRNA into polypeptide chain that will ultimately become a protein
translation characteristics
- occurs in the cytoplasm
- requires ribosomes and tRNA
- starts at AUG
- ends at stop codon
- polypeptide chain processed folded
- initiation
- AUG: start codon on mRNA - elongation
- termination
- stop codon on mRNA
initiation translation
- Small subunit attaches to large ribosomal subunit
mRNA transcript attaches onto a ribosome in the cytoplasm - mRNA transcript begins at AUG
- Ribosome reads one codon at a time
elongation translation
- ribosomes continue to read codons
- recruits tRNA molecules
- codons on mRNA are matched to anti-codons on tRNA
- tRNA molecule drops off respective amino acid to the sit
- amino acid is covalently bonded (peptide bonded) to previous acid in line
- process continues to form a long chain of amino acids
termination translation
Growth of amino acid chain ceases when the stop codon is reached
what does a polypeptide need to do in order to become a functional protein
fold into the correct 3D shape
gene expression
Process by which information encoded in a gene is used to direct the assembly of a polypeptide or protein
gene expression
Process by which information encoded in a gene is used to direct the assembly of a polypeptide or protein
difference in protein synthesis and DNA replication
DNA REPLICATION IS USED TO MAKE ADDITIONAL COPIES OF GENETIC MATERIAL IN PREPARATION FOR MITOSIS OR MEIOSIS WHEREAS PROTEIN SYNTHESIS INVOLVES THE EXPRESSION OF GENES INTO POLYPEPTIDE CHAINS
how are genes regulated
turning genes on or off which determines the structure and function of cells
- Important as not all proteins are needed all the time due to changing environmental conditions in the body
