Genetics 3.1 Genes

Genetic Material All organisms need to undergo cell division in order to grow and to reproduce. During cell division, genetic material is duplicated and passed on from a parent cell to new daughter cells GENETICS: is the study of heredity and variation. It explains how living things inherit traits from their parent.

Most organisms store their genetic information in the form of the molecule DNA (deoxyribonucleic acid). DNA contains a lot of information, and can be very long. In order to keep it organized, the cell condenses DNA into chromosomes.

Chromosomes are found in the nucleus of eukaryotic cells. The size, shape, and number of chromosomes vary based on the species. Ex: Humans have 46 chromosomes in each of their body cells but dogs have 78, and fruit flies have 8.

Gene a segment of a DNA molecule that codes for a particular trait; found at a specific location on a chromosome.

Locus The location of gene on a chromosome.

Alleles various specific forms of a gene. Brown eyes and blue eyes are different alleles for the eye colour gene. If Jason has blue eyes and Ellen has brown eyes, the locus for these genes are at the same place on the same chromosome of each individual.

Alleles Alleles differ from each other by one or a few bases only. Usually only one or a very small number of bases are different. Ex: adenine might present in a particular position in one sequence and cytosine that position in another allele.

Genome all the genetic information of an organism

The Human Genome Project This was a collaborative project amongst many scientists. Its purpose was to find the base sequences of the entire human genome. Began in 1990. Completed in 2003. While an entire genome was sequenced, Scientists are still interpreting the genes. Work continues to find variations in the sequence between different individuals (and different alleles)

Human Genome Project Analysis has snows that the vast majority of base sequences are shared by all humans, but there are also many single nucleotide polymorphisms which contribute to human diversity. Genomes for many other species have also been determined Comparisons between genomes of different species is key in understanding the evolutionary relationship and history of living organisms.

Reproduction Organisms inherit genetic information from their parents via reproduction. There are 2 basic types of reproduction: asexual and sexual.

Asexual Reproduction Production of offspring (a cell or an organism) from a single parent The offspring are genetically identical to the parent

Cell division (which includes mitosis) is a form of asexual reproduction. It is what causes growth of the overall organism. Cloning is a form of asexual reproduction

Advantage of Asexual Reproduction: The parent cell/organism does not have to seek out a mate (conserves energy), perform mating rituals or posses specialized anatomy. Disadvantage: there is little genetic variation It is the most common form of reproduction amount unicellular organisms. Many multicellular organisms use it too (plants, fungi)

Binary Fission Occurs in bacteria; Similar to mitosis

Budding Occurs in yeast and some multicellular organisms such as hydra. The organism grows and extensions, a “bud”, that eventually breaks off the parent.

Spore Formation Occurs in bacteria and mold The parent organism produces smaller cells called “spores” that can detach from the parent, land in another area and grow

Vegetative Propogation Occurs in many plants such as strawberries The plant produces a long stem-like feature called a “runner” that can detach from the plant and grow roots easily.

Fragmentation Occurs in algae, and some plants and animals A new organism is formed when part of the parent is broken off. Ex: when a starfish or earthworm is broken in half, 2 new organisms will grow.

Aphids In the spring female aphids can produce more female aphids that are essentially clones of themselves. In the fall, changes in their hormone levels causes them to produce males. Then male and female aphids can reproduce sexually.

Videos http://www.youtube.com/watch?v=jk2RJm5R BEk

Sexual Reproduction A form of reproduction in which individuals are produced from the fusion of two sex cells (gametes) The sex cells usually come from 2 different parent organisms

Sexual Reproduction Ie: Females produce egg cells, males produce sperm cells. When they combine, they form a fertilized egg called a zygote. We were all zygotes at one point.

The offspring of sexual reproduction are not genetically identical to either of its parents Offspring obtain half of their DNA from each of their 2 parents. Remember, even if an organism uses sexual reproduction to reproduce, the individuals will still undergo asexual reproduction to grow.

DISADVANTAGES Must have specialized organs to produce sex cells Must expend energy to find a suitable mate, and may also put oneself in danger from predators to make oneself visible to potential mates

ADVANTAGE Genetic variation!

GENETIC VARIATION Genetic Variation allows for evolution. If all the individuals of a species were genetically identical, when the environment changes, it can potentially wipe out all those individuals. But if a few individuals happen to possess different genes, genes that would allow them to potentially survive the environmental change, then life would perpetuate.