DNA Flashcards
(41 cards)
Role of DNA
Carries genetic information to determine our inherited characteristics
What is a gene?
Section of DNA that codes for a polypeptide and a functional RNA
What is a locus?
Location of a particular gene on a chromosome
What is a chromosome?
- DNA is stored in chromosomes
- 23 pairs = 46 in total
What is a homologous pair of chromosomes?
Pair of chromosomes with the same genes but different alleles
How is DNA stored?
- Stored as chromosomes in nucleus
- Chromosomes are linear so to fit tightly coiled DNA in nucleus = DNA wound around histone proteins = nucleosome
Difference between prokaryotic/eukaryotic DNA
EUKARYOTIC:
- Nucleus
- Linear
- Associated with proteins = chromosomes
- Mitochondria/chloroplast contain DNA
PROKARYOTIC:
- Free- floating
- Short + circular
- Not associated with proteins
What is the genetic code?
-The order of bases on DNA
- Consists of codons
Features of genetic code
- Degenerate
- Universal
- Non-overlapping
Describe degenerate and it’s advantage
- More than 1 triplet base codes for the same amino acid
- Advantageous: If mutation occurs and triplet base is different it may still code for the same amino acid = have no effect
Describe universal and it’s advantage
- Same triplet bases code for the same amino acids in all organisms
- Advantageous: Allows genetic engineering e.g. inserting human insulin gene in bacteria for mass produce
Describe non-overlapping and it’s advantage
- Each base is only part of 1 triplet code
- Codons are read as discreet units
- Advantageous: If mutation occurs it only affects 1 codon = 1 protein
What is an intron?
- Sections of DNA that do not code for amino acids
- Only in eukaryotic cells
- Spliced out of mRNA
What is an exon?
Sequences of bases that do code for amino acids
Describe genome
- Organisms full set of DNA contained by a cell
- Should never change
- Vary widely from organism to organism
Describe proteome
- Organisms full range of proteins that can be produced by a cell
- Constantly changing depending on which protein is needed
Describe structure of mRNA
- Long single strand
- Complementary to DNA
- 3 bases are called codons
- Carries the genetic code of 1 gene to the ribosome
Describe structure of tRNA
- Single strand folded into a cloverleaf shape by H-bonds
- Found in cytoplasm
- Amino acid binding site at top
- 3 complementary bases to mRNA codons called anticodon at the bottom
- Transfers amino acids to ribosome
Describe structure of rRNA
Combines with protein to make ribosomes
Compare RNA + DNA
MONOMERS:
- DNA has thymine RNA has uracil
- DNA pentose sugar = deoxyribose RNA pentose sugar = ribose
POLYMERS:
- DNA is larger as it has the whole genome RNA is shorter
- DNA double stranded RNA single stranded
2 stages of protein synthesis
1) Transcription: Gene of DNA copied into mRNA
2) Translation: mRNA joins with ribosome + corresponding tRNA brings specific amino acids
Explain transcription
- DNA helicase breaks H-bonds between bases = helix unwinds to expose bases
- 1 chain of DNA acts as a template
- Free mRNA nucleotides in nucleus align opposite complementary DNA bases
- RNA polymerase bonds together RNA nucleotides = new pre-mRNA
- introns spliced out = only exons = mRNA leaves nucleus via nuclear pores
Explain translation
- Modified mRNA attaches to ribosome at start codon
- tRNA with complementary anti-codons align and held in place by ribosome
- Ribosome moves along mRNA = another complementary tRNA to next mRNA codon
- Once 2 amino acids have been bought by tRNA = form peptide bond through enzyme +ATP
- Continues until stop codon reached = ribosome detaches = translation ends
- Polypeptide chain moves to Golgi apparatus = folding + modify
What is meiosis?
- Cell division = 4 genetically different haploid cells
- Gametes
