8.1 & 8.2 DNA, Genes and Chromosomes Flashcards
Describe the structure of DNA in a eukaryotic cell
- linear DNA that exists as a protein
- the DNA is really long so it has to be wound up around histone proteins so it can fit in the nucleus
- DNA and the histone protein is then coiled up tightly to make a compact chromosome
Describe the DNA found in mitochondria and chloroplasts
- short and circular
- is not associated with proteins
- similar to prokaryotic DNA
Describe the structure of DNA in a prokaryotic cell
- DNA is short and circular and are carried as chromosomes
- isn’t associated with proteins
- fits into the nucleus by supercoiling
What is a gene?
Base sequence of DNA that codes for:
- amino acid sequence of a polypeptide
- functional RNA such as rRNA and tRNA
What is a locus?
The fixed position on a particular DNA molecule that a gene occupies
What is a triplet?
A sequence of 3 DNA bases that codes for a specific amino acid
What is the genetic code?
The sequence of base triplets (codons) in mRNA which code for specific amino acids
List 3 important things about the genetic code
- Universal
- Degenerate
- Overlapping
If a gene doesn’t code for a polypeptide, what does it code for?
A functional RNA
What is a codon?
The sequence of three bases on mRNA that codes for a single amino acid
What is an intron?
- section of a gene that doesn’t code for amino acids
- there can be several in one gene
What is an exon?
- a section of a gene that do code for amino acids
- what is needed for protein synthesis
Do prokaryotic cells have introns?
No
What is an allele?
- one of a number of alternative forms of a gene
- order of bases in each allele is slightly different so they code for different versions of the same polypeptide
