Chapter 13 Terms Flashcards
genes
Each chromosomes contains hundreds to thousands of genes
gametes
A gamete (sperm or egg) contains a single set of chromosomes and is haploid Humans - 23 chromosomes
locus
A gene’s specific position along a chromosome
homologous chromosomes
- The two chromosomes in each pair are called homologous chromosomes, or homologs
- Chromosomes in a homologous pair are the same length and shape and carry genes controlling the same inherited characters
- Humans have 46 chromosomes (23 homologous pairs)
karyotype
an ordered display of the pairs of chromosomes from a cell
autosomes
Human females have a homologous pair of X chromosomes (XX)
Human males have one X and one Y chromosome (XY)
The remaining 22 pairs of chromosomes (that are not sex cells) are called autosomes
sexual reproduction
, two parents give rise to offspring that have unique combinations of genes inherited from the two parents
life cycle
generation-to-generation sequence of stages in the reproductive history of an organism
sex chromosome
In an unfertilized egg (ovum), the sex chromosome is X
In a sperm cell, the sex chromosome may be either X or Y
fertilization
the union of gametes (the sperm and the egg)
zygote
The fertilized egg is called a zygote and has one set of chromosomes from each parent
The zygote produces somatic cells by mitosis and develops into an adult
synapsis
In early prophase I each chromosome pairs with its homolog (synapsis)
crossing over
the process by which non-sister chromatids exchange alleles (alternate versions of genes)
alleles
alternate versions of genes
-Alleles are located at the same locus on each homologous chromosome
chiasmata
X-shaped regions
- are sites of crossover
