Unit 5: Heredity

Chapter 14

Sister chromatids

identical copies of the same chromosome (connected at the centromere).

Homologous chromatids

similar but not identical chromosomes; one comes from each parent.

Haploid

a cell with one set of chromosomes (n)

Diploid

a cell with two sets of chromosomes (2n)

Gametes

Sex cells (sperm and egg) produced through meiosis.

Somatic cells

cells that divide through mitosis, not meiosis

Zygote

A fertilized egg (diploid cell formed when gametes fuse)

Alleles

Different versions of a gene

Gene

A section of DNA that codes for a protein or RNA molecule

Genotype

The combination of alleles (e.g., BB, Bb, bb)

Phenotype

Physical expression of the genotype (eg brown eyes)

Dominant

Dominant alleles show up when present (B)

Recessive

Recessive alleles only show up when both alleles are recessive (bb)

Only one recessive is a carrier, typically unaffected (Bb)

Complete dominance