DNA Flashcards
Organisation of DNA
Double helix Sugar-phosphate backbone Complementary nitrogenous bases: Adenine - tyrosine Guanine - cytosine
Protein Synthesis
Cells constantly synthesise proteins; used for cell functioning or exported from cell
Proteome
All proteins made by the cell
Proteomics
study of proteins in a cell
Transcription
DNA to RNA
Translation
RNA to protein
The central dogma
flow of information from DNA to RNA
DNA vs RNA
Sugar; ribose vs deoxyribose
Single stranded
Contains uracil vs thyamine
RNA
the stage between DNA and protein; initiated by transcription factors
Exons
coding sections of RNA
Introns
non-coding sections of RNA
Types of RNA
Messenger RNA
Ribosomal RNA
Transfer RNA
Messenger RNA
translated in cytoplasm to make proteins
Ribosomal RNA
makes up ribosomes
Transfer RNA
translates mRNA into amino acid peptide
Transcription Process
- DNA strands are separated
- RNA polymerase binds at promoter region
- RNA polymerase catalyses formation of mRNA chain using DNA as a template, follows the rules of complimentary base pairing
- Transcription ends at terminator sequence
- mRNA exits nucleus through nuclear pores
Translation
Occurs in cytoplasm by ribosomes
mRNA carries genetic info from nucleus to ribosomes
Begins at start codon
Post-translational modification
chemical modification of protein following translation - may attach to other functional groups, may be shortened
Phosphorylation
controls the behaviour of the protein; activating/inactivating enzyme
Side chains (protein structure)
non-polar and hydrophobic, hydrophillic, positively/negatively charged
interactions between side groups and peptide bonds affects shape of protein
Classification of aa chains
2+ aa’s - peptide
10+ aa’s - polypeptide
50+ aa’s - protein
Primary protein structure
sequence of aa’s linked by peptide bonds
Seconday protein structure
proteins fold forming secondary structures due to side chains
Alpha helices and beta pleated sheets = regular folding patterns
Tertiary protein structure
3D shape determined by folding of secondary structure
a-helices and b-sheets foldto form structures held by bonds between aa’s spaced far apart in peptide chain
Quanternary protein structure
combined 3D structure of 2+ polypeptide chains
eg haemoglobin
Globular proteins
chains fold into compact shape Usually water soluable Mobile Chemically active Crucial in biological processes
Fibrous proteins
Simple, elongated
Insoluable, stable
Provides mechanical support, tensile strength
Abundant outside of cell, make up matrix between cells
eg. collegen, keratin, elastin
Somatic cell
biological cell forming body of multicellular organism
- most cells
- 46 chrs
- mitosis
Germ cell
give rise to gametes
- located in ovaries and testes
- meiosis
Gamete
cells fused during sexual reproduction
Interphase
between cell divisions
replication of DNA
Replication of DNA
Normal cell activities
Mitosis
results in production of two cells by division of mother cell to two genetically identical daughter cells
Mitosis - stages
Interphase Prophase Metaphase Anaphase Telophase
Cytokinesis
division of cell cytoplasm
Chromatin
DNA complexed with proteins (histones)
Locus
location of a gene on a chrs
Prophase
chromatin condenses into chrs, centrioles migrate to ends of cell, spindle fibres attach to centromeres, nuclear envelope disintegrates
Metaphase
chrs are aligned at nuclear equator
Anaphase
spindle fibres separate chromatids, 2 sets of chrs move to separate ends of cell, cytokinesis begins
Telophase
nuclear envelope reforms around each set of chrs, chromosomes decondense into chromatin, cytokinesis continues
Cells with high mitosis rate
skin, gastrointestinal tract, oral cavity, anus, cervix and vagina
Cells with normal mitosis rate
in-utero, puberty, wound healing, RBC
Cells with slow mitosis rate
brain, heart, skeletal muscle
Meiosis
Germ cells divide and produce gametes
Specialised for sexual reproduction
DNA replication followed by 2 cell divisions
Produces 4 genetically different daughter cells;
* gametes, haploid * one homolog from each homologous pair
Meiosis - prophase
Homologous chrs line up
DNA is exchanged between adjacent chromatids
Sister chromatids are no longer identical
Results in exchange of genetic material between maternal and paternal chrs
= new gene combination
= new human variation
