3.4.1 DNA, genes and chromosomes, 3.4.2 DNA and protein synthesis Flashcards
Compare DNA in prokaryotic and eukaryotic cells?
Prokaryotic DNA:
- short
- circular
- not associated with proteins
Eukaryotic DNA:
- long
- linear
- associated with proteins (histones)
In eukaryotic cells mitochondria and chloroplasts contain prokaryotic like DNA
What is a gene?
- DNA base sequence
- that codes for the amino acid sequence of a polypeptide or a functional RNA
What is a locus?
The fixed position a gene occupies on a particular DNA molecule
What is the difference between a triplet and a codon?
- A triplet is a sequence of 3 DNA bases
- That codes for a specific amino acid
- A condon is a sequence of 3 mRNA bases
- that code for an amino acid
Give 3 features of genetic code and that they mean
- universal: same triplets ALWAYS code for the same amino acids in all organisms
- non-overlapping: each DNA nucleotide base only part of one triplet, triplets don’t overlap
- degenerate: most amino acids are coded for by more than one triplet
What is the genome and protogenone?
- genome - complete set of genes in a cell of an organism
- protogenome - the complete set of proteins a cell can produce
What are introns and exons?
- introns: non-coding DNA base sequences (spliced out from mRNA after transcription)
- exons: coding regions of DNA base sequence (left after introns are removed)
Compare DNA, mRNA and tRNA
- DNA double stranded, mRNA and tRNA single stranded
- DNA most stable, mRNA unstable, tRNA most unstable
- DNA largest, mRNA smaller than DNA, tRNA smallest
- DNA double helix, mRNA single helix/ linear, tRNA clover shaped
- DNA has base pairing between molecules, mRNA doesn’t, tRNA has some
- DNA deoxyribose sugar, RNA ribose sugar
- DNA thymine, RNA uracil
- DNA found in nucleus, mRNA in nucleus and cytoplasm, tRNA in cytoplasm (made in nucleus)
- DNA same quantities between most cells, RNA quantity varies due to cell metabolic activity
Describe how the structure of mRNA and tRNA are different
- mRNA no hydrogen bonding, tRNA has hydrogen bonding
- mRNA no base pairing, tRNA some base pairing
- mRNA linear/not folded, tRNA clover shaped/folded
- mRNA has no amino acid binding site, tRNA has amino acid binding site
- mRNA longer (more nucleotides), tRNA fixed length (less nucleotides)
- mRNA has many different kinds, tRNA only has 20
Describe the process of transcription
- an enzyme (RNA polymerase) breaks hydrogen bonds to separate DNA strands
- only one DNA strand acts as a template
- RNA nucleotides are attracted to and align to complement exposed bases on template strand
- according to pairing rule (adenine -> uracil, thymine -> adenine, guamine <-> cytosine)
- RNA polymerase joins adjacent RNA nucleotides together with phosphodiester bond to form pre-mRNA
- pre-mRNA spliced to remove introns
What happens in transcription (briefly), where does it occur?
- DNA converted to mRNA
- nucleus
What happens in translation (breifly), where does it occur?
- mRNA converted into protein
- cytoplasm
Describe the process of translation
- mRNA associates with a ribosome/attaches to mRNA
- ribosome moves to the start codon (AUG)
- tRNA carries specific amino acid
- anticodon on tRNA complementary to codon (on mRNA)
- Ribosome moves along to next codon
- / ribosome fits around 2 codon
- process repeated and amino acids join (using energy from ATP) by peptide bonds to form polypeptide
- tRNA released after amino acid is joined to polypeptide
- ribosome moves along to next mRNA to form polypeptide
What are homologous chromosomes?
Two chromosomes that carry the same geneS
