The nature of heredity Flashcards
Heredity
All organisms use cell division to grow and reproduce.
Multicellular organisms use cell division for growth and repair.
Unicellular organisms use it solely for reproduction.
Heredity is passing traits from parents to offspring.
Genetics and DNA
Genetics is the scientific study of heredity and variation of inherited characteristics.
Genetic information is contained in molecules of DNA (deoxyribonucleic acid).
Each DNA molecule is made up of hundreds of thousands of chemical subunits that act as instructions for the cell.
Genes
Gene- a segment of DNA that carries information that helps to produce a particular trait of an organism.
Each gene occupies a specific location, or locus, on a chromosome.
One chromosome can carry information for hundreds or thousands of different genes.
Chromosomes
Chromosomes are found in the nucleus of eukaryotic cells.
Chromosome number, size and shape vary between organisms.
Most multicellular organisms have less than 100 chromosomes in the nucleus of each body cell.
How do the amount of chromosomes affect the cell
In most multicellular organisms, chromosomes occur in sets.
Remember……Diploid has two sets and haploid has one set.
Polyploid three or more sets of chromosomes.
Asexual Reproduction
A new individual is produced from a single parent by cell division (no sex cells involved).
The chromosomes of the parent are duplicated and then divide so that each daughter cell receives one copy of each chromosome.
The daughter cell is genetically identical.
Advantages: no need to seek out a mate, perform specialized mating behaviors or possess specialized anatomy.
Asexual reproduction is direct and invariable.
Sexual Reproduction
Individuals are produced from the fusion of two sex cells.
The sex cells usually come from two different parents.
Offspring obtain genetic information from each parent and offspring are genetically variable.
Disadvantages: must have specialized organs to produce sex cells, mating calls/bright colours can attract predators. It is costly and risky.
Sexual reproduction can also cause offspring to inherit a combination of genetic information that makes them weak and even unable to survive.
Is sex worth the time, energy and resources?
Genetically identical individuals are suited for environments that are not changing.
Genetically identical individuals are more susceptible to being wiped out by disease or competitors.
Sexual reproduction provides insurance and flexibility for the future.
