y4.2 molecular genetics 🧬 Flashcards
what is the relationship between DNA, genes and chromosomes?
Each chromosome contains one long DNA molecule, usually carrying several hundred or more genes.
characteristics of genes
a sequence of nucleotides
specific for its function
used in protein synthesis, contributes to the development of the body
structure of dna
double helix of two, anti-parallel, polynucleotide chains
what makes a nucleotide
phosphate group
deoxyribose sugar
nitrogenous base
now remember how the dna looks
ok the picture is on pg 5
rule of complementary base pairing (aka chargaff’s rule)
(Adenine) A-T (Thymine)
(Cytosine) C-G (Guanine)
hydrogen bonds form between nucleotide bases
process of DNA replication
semi-conservative replication
each strand of original DNA acts as as a template for the synthesis of new complementary DNA strand
double helix separated by enzymes, nucleotides within the cell are bound to separated parent DNA strand (rule of complementary base pairing)
formation of double stranded DNA molecule - half of original parent strand, half newly synthesized daughter strand
what is a gene
A sequence of nucleotides as part of a DNA molecule that contains the information to make a polypeptide (folded into protein in rough er)
can be expressed or not expressed
function of DNA
used to carry genetic code used to synthesize specific proteins
central dogma of molecular biology
DNA => RNA => protein
(DNA directs NRA synthesis, through RNA, DNA controls protein synthesis
RNA is an intermediate in protein synthesis)
structure of DNA and RNA (similarities)
both have a sugar-phosphate backbone joined by phosphodiester bonds
both contain 3 common nitrogenous bases (adenine, cytosine, guanine)
Structure of DNA and RNA (differences)
DNA vs RNA
Number of polynucleotide chains: two vs one
Monomers: deoxyribonucleotides vs ribonucleotides
pentose suger (see pic on pg 8 prolly not that impt though idk)
Nitrogenous bases: adenine, guanine, cytosine, thymine vs adenine, guanine, cytosine, uracil
Ratio of bases: A:T = G:C = 1:1 (chargaff’s rule) vs no fixed ratio
bonds between bases: hydrogen bonding present between bases vsno hydrogen bonds if NRA is a straight chain
how is the information in DNA used to synthesize polypeptides in eukaryotes (transcription)
Transcription: DNA→mRNA
transfer of genetic information from DNA to mRNA
formation of specific mRNA sequence complementary to a specific DNA sequence on the template strand by complementary bae pairing
how is the information in DNA used to synthesize polypeptides in eukaryotes (translation)
Translation: mRNA→DNA
mRNA contains a series of codons that interact via complementary base pairing with tRNA, which is attached to specific amino acids in ribosome
ribosome behaves like a small factory that travels along the mRNA, forming peptide bond between the corresponding amino acids to assemble to polypeptide
“fate of polypeptide chains” basically what happens aft translation
polypeptide chains are folded at the rough endoplasmic reticulum (ER) to form proteins
transport vesicles containing substances made by the endoplasmic reticulum (ER) are pinched off the ER
transport vesicles fuse with and release their substances into the Golgi apparatus
substances are chemically modified and packaged inside the Golgi apparatus
secretory vesicles containing these substances and pinched off the Golgi apparatus, move towards and fuse with the cell membrane, releasing the substances outside the cell by exocytosis
what is a mutation
a sudden or spontaneous change in the structure of a gene, chromosomes (sickle cell anaemia) or in the chromosome number (down syndrome)
they will probably give a case study for mutation but read the sickle cell anaemia and down syndrome notes on
pg 12-13
factors that may increase the rate of mutation
environmental forces (atomic radiation)
mutagens:
- ionizing radiation (gamma rays and x-rays)
- chemical mutagens
why do we use bacteria to produce insulin?
- relatively easy to transfer the genes into the bacterium, as bacteria contain plasmids which have a small number of genes, and an insulin gene can be inserted easily into a plasmid
- bacteria take a short time to replicate, and its plasmid is replicated along with it. a single cell reproduced through cell division to create repeated cell divisions to form clones of itself, transcribing and translating the insulin gene into the plasmid to produce large quantities of insulin
steps for inserting human insulin gene into bacterial DNA
obtain the DNA segment in human chromosome containing insulin gene
cut the gene using a restriction enzyme, producing ‘sticky ends’
obtain a plasmid from a bacterium
cut the plasmid with the same restriction enzyme to produced ‘sticky ends’ complementary to the ends of the insulin gene
mix the plasmid with the DNA fragment containing the insulin gene, allowing the insulin gene to bind with the plasmid through complementary base pairing between their ‘sticky ends’
add DNA ligase to seal the DNA fragment to the plasmid to form a recombinant plasmid
mix the plasmid with (x) bacterium, applying temporary heat or electric shock to open the cell wall and membrane to enter
transgenic bacterium with insulin gene will be isolated and grown in large scale under optimum conditions
transgenic bacterium will synthesize insulin together with other proteins from the plasmid
insulin must be extracted and purified before use
