| What is a chromosome | - Thread-like structures in nucleus
- Made up of protein + single DNA molecule |
| Chromosome structure | - Two treads joined at centromere
- Each tread called a chromatid
- DNA held by histones
- DNA highly coiled |
| The coiling of the DNA molecule | - Wound in histones to fix it in position
- DNA-histone complex is then coiled
- Coil looped further
- Packed into chromosome, condensed |
| Differences between DNA in prokaryotes + eukaryotes | - Eukaryotes: DNA longer, linear, associated with proteins, histones, forms chromosomes
- Prokaryotic: DNA shorter, circular, not associated with proteins, no chromosomes |
| Homologous chromosomes ~ HC (huh - mo - luh - gus) | - A pair of chromosomes, 1 maternal homolog1 paternal homolog
- Have same gene loci
- HC line up and synapse during meiosis |
| Diploid | - Two complete sets of chromosomes
- Human cells are diploid with 23 pairs (46) of chromosomes in nucleus
- Each pair of chromosomes in a diploid cell is a homologous chromosome set |
| Alleles meaning | - Different forms of genes
- Each gene exists in 2, or usually more, different forms
- Each individual inherits 1 allele from each parent
- These 2 allele may the same or different |
| When alleles from parent are different | - When different, each allele has different base sequence, so different seq. amino acid, dif. polypept.
- Changes in base sequence of gene produces new allele (mutation) = different seq. amino acids = dif poly.
- May not function properly or at all |
