Genetic Variability

Homologous Chromosomes

  • The 23 chromosomes from mom correspond to the 23 chromosomes from dad. These chromosomes are called ______
  • Each homologous chromosome contains a set of alleles for the same gene.

Homologous Chromosomes & Meiosis

  • Each chromosome is ______before cell division.
  • Each chromosome now has ______
  • In meiosis, homologous chromosomes pair up to form a ______

In meiosis, homologous chromosomes pair up to form a tetrad.

•Each homologous chromosome has been replicated into two sister chromatids.

•Altogether, there are ______in a tetrad.

During metaphase 1, tetrads line up across the middle of the cell.

______determines what each gamete will look like.

Genetic Variability

•After the chromosomes separate, they are packaged into individual ______.

•Each chromosome moves independently of all the others.

–This is called ______.

Gamete Variability

The order of the tetrads in ______determines what the gametes will look like.

Genetic Variability

•Humans have 23 homologous chromosomes (______) that sort independently during gamete production.

•The total number of possible chromosome combinations is over 8 million!

•You have over 8 million ______

•With those kinds of odds, it is extremely unlikely that ______with the same assortment of chromosomes will meet ______with the same assortment of chromosomes.

•Thus, each individual (with the exception of identical twins) ______

CROSSING OVER

•During prophase 1, the homologous chromosomes pair up inside the cell and form tetrads.

•While the homologous chromosomes are paired together, ______of their chromatids.

•Each chromosome may ______for the matching portion on its homologue.

Reproduction:

Asexual Reproduction

  1. involves only ______parent
  2. offspring______to parent
  3. involves______body cells

Sexual Reproduction

  1. involves______parents
  2. offspring ______of both parents
  3. involves ______sex cells

Types of Asexual Reproduction:

Binary Fission:

  1. happens in ______, ______, some algae
  2. one ______cell splits into ______identical daughter cells

Spore Formation:

  1. happens in ______, ______, ______and non flowering plants (e.g. ferns)
  2. ______are produced and each spore develops into offspring which are ______to parent

Budding:

  1. happens in ______, ______, corals
  2. parent produces a ______.
  3. bud gets ______. and develops into offspring which is ______.

Vegetative Reproduction:

  1. does ______involve ______
  2. some offspring can grow from cuttings (e.g. coleus), runners (e.g. strawberries), tubers (e.g. potatoes) or bulbs (e.g. tulips)…which are part of the parent plant

Sexual Reproduction in Animals:

  1. involves specialized sex cells called______
  2. the union of a male and female gametes results in the formation of a ______ that develops into a new individual.

Some do Both:

•most ______that produce seeds (sexual reproduction) can also reproduce ______by things like ______or ______

•this gives them an advantage for survival

Asexual Reproduction

Advantages

  1. does not require special cells or a lot of energy
  2. can produce offspring quickly

in a stable environment creates large, thriving population

Disadvantages

  1. limited ability to adapt
  2. face massive die-off if environment changes

Sexual Reproduction

Advantages

  1. lots of variation within a species
  2. able to live in a variety of environmental settings
  3. able to adapt to changes in the environment

Disadvantages

  1. needs time & energy
  2. produce small population