Chap 5

- Shapes of bases only allow H-bonds between A & T and G & C
- antiparallel
- complementary

formed from an organic acid and an alcohol, usually with elimination of water

- major vs. minor groove
- Hydrophobic and van der Waal forces

Chromosomes physically-carry the genes
- Human chromosomes have been “painted” with fluorescent DNA probes to allow identification (karyotyping)

- Genes contain information to make RNA, some of which encode proteins

1. Genes are the unit of inheritance
- Genes are arranged along the chromosomes
- Note spaces between genes
At any one point on the chromosome why is only one strand yellow?

- allele: somatic cells contain two copies of a gene--one from each parent. Copies can be the same or different. These alternate (or same form) are called alleles
- homologous chromosomes: contain info for same biological functions
- dominant vs. recessive
- gametes

- Abnormal chromosomes are associated with some inherited genetic defects and many cancers

- Replication and segregation of chromosomes occurs in the cell cycle of proliferating cells
--Chromosomes exist in different forms throughout the life of the cell
-- during interphase the cell expresses many of its genes; during one part of this phase it also duplicates the chromosomes

1. Origins for initiation of DNA replication
2. The centromere
3. The two ends (telomeres)

- Interphase chromosomes are organized in the nucleus
--Different “territories” within nucleus

- chromatin = DNA + proteins
- histones - basic AA
- nucleosomes - repeating subunits of DNA and histones
- Local modification of histones determines whether chromatin in that region is transcribed

- Heterochromatin consists of chromosome regions that do not uncoil after mitosis
- euchromatin is uncoiled and active in interphase
- heterochromatin found in centromeres and telomeres

- Chromatin structure varies along a single interphase chromosome