4.1 The Nature of Heredity
Cell division and reproduction are biological processes that are fundamental to life. All organisms use
these processes to grow____________ and reproduce ___________________. Multicellular organisms
use cell division for growth __________________ and repair_______________ , whereas unicellular
organisms use it as a means of reproduction. A key feature to cell division and reproduction is the
passing of chromosomes ___________________ from one parent
_______________ cell to the daughter__________________ cells.
Heredity _________________ : traits are passed from parents to offspring
Genetics : the scientific study of Heredity __________________ and
variation__________________
In Chromosomes , the genetic information is contained in the molecule
deoxyribonucleic acid _______________________ ( DNA )
A segment of a DNA molecule that codes __________ for a particular trait
_____________ is called a gene _____________. Each gene is found at a specific location
on a chromosome.
Locus ______________ : location of a gene on a chromosome.
Chromosomes
Chromosomes are found in the nucleus ______________ of all eukaryotic cells but vary widely between
organisms of different species in their number _______________ , size
________________ and shape_______________. Most multicellular organisms have
less________ than 100____________ chromosomes in the nucleus of each body cell.
In most multicellular organisms , chromosomes occur in sets________.
Diploid______________ cells have two________ sets of chromosomes.
Haploid_______________ cells have half ___________ the normal number of
chromosomes.
Polyploid__________________ cells containing three _____________ or more sets of chromosomes
( eg some plants )
Asexual ________________ reproduction : new individual is produced from a single parent by cell
division. The genetic makeup of the offspring is identical _________________ to that of the parent.
Advantages :
-the parent does not________ have to seek out a mate and preform
specialized mating behaviour .
-Generation after generation , offspring genetically identical____________to
parents
Sexual _____________ Reproduction : the production of offspring from the
fusion ____________ of two sex_______ cells ( usually from either
_____________ parents ) : the genetic makeup of the offspring is different
_________________ from that of either______________ parent.
Advantages :
-must have specialized organs to produce sex cells eg Male testicles _____________ make sperm cells
Female ovaries_____________ make egg cells
-animals produce mating ____________ calls or being brightly coloured_________________ can help
attract____________ a mate
-in plants , flowers attract pollinators __________________ like bees , but requires the production of
nectar___________
Why do so many of the Earth’s organisms participate in some form of sexual
reproduction. What is it about producing genetically variable offspring that creates a
benefit worth the cost of time _________ , energy _____________ and
resources___________________?
Environments change________________ : a fire , volcanic eruption, introduction of a
new disease______________ or competitor______________________. If a new
disease infects one individual , it could quickly infect virtually all individuals if they are
genetically identical_________________. Variation ( change ) in some offspring may
allow them to be better suited for the new environment and allow these to survive and
pass on their genes to the next generation. In this way the species ( as a whole , can
survive )
Questions :