Lecture #2 Flashcards
DNA (deoxyribonucleic acid)
thin (2nm diameter)
linear polymer fiber
double-stranded helix
4 nucleobases: adenine (A), thymine (T), guanine (G), cytosine (C) - foundation for everything
anti-parallel: A=T (2 hydrogen bonds), G=C (3 hydrogen bonds)
Genome
23 pairs of chromosomes
a genome is an organism’s complete set of DNA, including all of its genes. each genome contains all of the info needed to build and maintain that organism
in humans, a copy of the entire genome - more than 3 bllion DNA base pairs - is contained in all cells that have a nucleus (the exact # sometimes changes due to new research finding)
kilobase = 1,000 bp
megabase = 1 million bp
21,000 genes in human
Genes: an evolving concept
a gene is a sequence of DNA or RNA which codes for a molecule that has a function
a gene is the basic physical and functional unit of heredity
genes, which are made up of DNA, act as instructions to make molecules
in humans, genes vary in size from a few hundred DNA bases to more than 2 million bases
Gene classification
protein coding genes: genes that are expressed to be proteins - only 1-3% of the human genome are protein-coding sequences; ~20,000 genes found in the human genome
noncoding genes: final product is an RNA, not a protein; tRNA, rRNA, miRNA, others: long noncoding RNA (LncRNA), antisense RNA, pseudogenes
transfer RNA
transfer amino acids to the RNA template to make proteins
ribosomal RNA
the RNA component of ribosomes
microRNA
play very important role in regulating protein-coding gene expression
Structure of a gene
proteing coding gene:
promoter region - determines which tissue will be expressed; 5’untranslated region (doesn’t exist in protein), exon, intron, 3’untranslated region
on average: 8.8 exons/gene, 7.8 introns/gene
Chromatin
unwounded DNA with protein
observed through interphase
DNA is accessible for transcription
Chromosome
tightly packed DNA
observed only during cell division (metaphase)
DNA is not used
Why pairs of chromosomes?
increase genetic diversity for the population
one chromosome from dad and one from mom
Expression of genetic information
central dogma: current thinking is we know it’s not a one way process
DNA replication, transcription and reverse transcription, RNA replication, translation to protein, protein to prion
Transcription
mRNA maturation process
mature mRNA has NO introns
DNA –> mRNA precursor (has not promoter region) –> matured mRNA with no introns and a poly-A tail
DNA: adenine, thymine, guanine, cytosine; RNA: adenine, uracil, guanine, cytosine
Translation
matured mRNA with a poly-A tail –> protein
RNA to protein; starts with AUG (making amino acid methionine); stops at one of the three stop codons (UAG, UAA, UGA); open reading frame - coding DNA sequence, AUG to the codon before stop codon, protien starts with methionine
Elements of a real gene: identify exons, introns, and others
start at color change, first ATG is the start codon
exons: part of DNA that’s expressed; introns: not expressed
coding part of the exon region, noncoding is part of intron region
all gene stops with a stop codon (UAA, UGA, UAG)
