3.4.1 DNA, Genes + Chromosomes Flashcards
How many chromosomes do humans have
46 chromosomes (23 pairs)
What are DNA molecules like in prokaryotic cells
Short,circular and not associated with proteins
What are DNA molecules like in the nucleus of eukaryotic cells
Very long,linear and associated with histone proteins
What proteins are dna molecule sin a eukaryote associated with
Histones
What does a dna molecule and its associated proteins form
A chromosome
In eukaryotic cells, what other 2 organelles contain dna
What’s it like
Mitochondria + chloroplasts
Short,circular and not associated with proteins (like prokaryotic dna)
What are homologous chromosomes
Chromosome pairs where each chromosome is alike and have genes for the same characteristic at corresponding loci (positions)
What are alleles
Genes which occur at the same position (loci) on a pair of homologous chromosomes
What’s a gene
What does it code for
A short length of dna that codes for :
- amino acid sequence of a polypeptide
- a functional RNA (including ribosomal RNA + tRNAs)
What does a gene occupy on a particular dna molecule
A fixed position called a locus
What does each triplet on a gene code for
Amino acid
What does the degenerate code mean
Some amino acids have more than 1 codon
What does it mean when the code is non-overlapping
Each base is part of 1 codon sequence of triplets/bases that code for a protein
What does it mean if the code is universal
3 base triplets code for amino acid in every species +cell from simple to complex
How many codons code for 20 amino acids
64