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