4.1 The Nature of Heredity Flashcards
Cell Theory Review
- All living things are composed of one or more cells
- Cells are the smallest units of living organisms
- New cells come only from pre-existing cells through cell division
Multicellular organisms - cell division
Growth and repair
unicellular organisms - cell division
Asexual reproduction
Cell division
Parent cell will pass chromosomes to daughter cells
What are chromosomes
thread like structures in the nucleus that have genetic information for traits
- a typical human chromosome contains thousands of genes
Genetics
the study of heredity and variation
Locus
the physical location of a gene on a chromosome
Centromere
the middle of a chromosome
the site where sister chromatids are linked
what is a gene
segment of DNA molecule that codes for a particular trait
DNA stands for
Deoxyribonucleic acid
How do chromosomes occur
- Mostly in sets - haploid cells that have half of the normal number
- Diploid cells have a normal number
- Some cells contain 3 or more sets called polyploid
Asexual reproduction
The production of offspring from a single parent (no sex cells used)
Advantages of asexual reproduction
- Do not need to find a mate
- No specialized mating behaviours
- No specialized anatomy
- Nothing left to chance - hereditary is direct and invariable
Disadvantages of asexual reproduction
invariable offspring means if the environment changes, individuals may not longer be suited to survive
Sexual reproduction
offspring are produced from the fusion of two sex cells (gametes) usually coming from different parent organisms
Advantages of sexual reproduction
- Offspring are not genetically identical to parents or to each other
- Variability in offspring means that if the environment changes, some of the offspring are better adapted and survive.
- Offspring move away from the parents and don’t compete with parents for resources (in some cases)
Disadvantages of sexual reproduction
- Need to have specialized organs, mating calls or brightly coloured, etc…
- Sex is biologically “costly” – attracting a mate can also attract predators
- Requires two members of the species to interact
