DNA, genes and chromosomes

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Cards (22)

What are the features of prokaryotic DNA?
Short
Circular
Not associated with proteins
What are the features of eukaryotic DNA?
Long
Linear
Associated with proteins called histones
Why is the DNA wound around histones to form chromosomes?
To take up as little space as possible, so it can fit in the nucleus. Histones also support DNA.
The DNA in chloroplasts and mitochondria is similar to....
Prokaryotic DNA. It is short, circular and not associated with proteins. This was the spark for the endosymbiotic theory.
What are sister chromatids held together by?
A centromere
What is a gene?
A base sequence of DNA that codes for either the amino acid sequence of a polypeptide or a functional RNA (rRNA or tRNA)
What is the fixed location of a gene on a particular DNA molecule called?
The locus
What is the name and function of a sequence of three DNA bases?
This is called a triplet and codes for a specific amino acid.
What determines the order of amino acids in a polypeptide (the primary structure)?
The order of bases in a gene.
Genome
The full set of genes in a cell
Proteome
The full range of proteins a cell is able to produce
What are the three key features of the genetic code?
Universal
Non-overlapping
Degenerate
Universal
Same genetic code is used in all living organisms
Non-overlapping
Codons are read consecutively so each base is read only once.
Degenerate
More than one codon codes for each amino acid.
How many different amino acids exist?
20
Most DNA does not code for polypeptides.
Genes only make up a fraction of DNA.
Within coding sections of DNA...
There are two areas of non-coding DNA.
Within genes- introns
Between genes- non-coding multiple repeats of base sequences
Introns
Non-coding base sequences.
Only exist in eukaryotes
Exons
Coding base sequences
Expressed in the phenotype
Make proteins
Non-coding multiple repeats of base sequences
Same non-coding base sequence repeated many times
Between genes
Do not code for amino acids