Lecture notes from Imperial College London, Medical Biosciences BSc, 2nd year, genetics and genomics (GEN) module.
What are Genetics and Genomics and why are they so important? As more and more was learned about genes, and the chromosomes that carry them, the importance of genomes emerged. Genom...
Genetics and genomics: understanding the difference
- Genetics = study of genes and their inheritance
- Genomics = study of genome
- Genome = complete set of genetic material in a cell (not genes only)
- Genes = stretches of DNA located on chr that code for proteins and RNA molecules that
determine the characteristics of the host cell or organism
- Chromosome (chr) = long DNA molecules that are inherited during sexual or asexual reproduction
- Nucleotides = structural components of DNA and RNA (A, T, C, G, U)
- in eukaryotes, chr are in nucleus but 1 small chr is in mitochondria
- genes have associated DNA sequences (promoters...) => ensure transcription into RNA
- Exons = protein-coding DNA // Introns = non-coding DNA
- after transcription into pre-RNA, introns are spliced out => mRNA => cytoplasm for translation
- many genes transcribed into ncRNA (non-protein-coding RNA) with functions on their own
- human genome: 23 pairs of nuclear chr (23 from each gamete)
=> gametes are haploid (23 chr)
=> fertilised cells are diploid (46 chr) => somatic cells (body cells)
- 23 pairs - 6 billion nucleotides - 21,000 protein-coding genes (2 alleles for each gene)
, lexons +
introns)
conly exons)
environment
influences epigenome
- transcriptome: all of the RNA in a cell (include ncRNA or not) => also proteome +
transcriptome
- not all genes are expressed in all cells => transcriptome is variable bw cells (even within 1 cell type)
- exome: all exons in the genome (2% of genome) => doesn’t vary
- proteome: complete set of proteins in a particular cell time at a particular time
Genetics and genomics: a brief history
- Gregor Mendel (19th) began work on inheritance using peas
Human Genome Project (HGP): project to
determine the sequence of nucleotides that make up
human DNA + identify all genes of human genome
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