Topic 3 Flashcards
Definition of Gene/Gene Locus/ Genome
Gene- A gene is a heritable factor that consists of a sequence of
DNA and influences a specific trait.
Gene Locus- The position of a gene on a chromosome.
Genome- Genetic information within an organism in its totality.
Haploid vs. Diploid
Diploid- Sexually reproducing organisms receive genetic material from both parents. Diploid = 2 sets of chromosomes (ex. body cells)
Haploid- To reproduce, these organisms only pass on half their genetic material. Haploid = 1 set of chromosomes (ex. sex cells / gametes)
Crossing Over during Meiosis
Crossing over occurs via synapsis in Prophase I. Homologous chromosomes form bivalents (or tetrads). Chiasmata represent the points where genetic information
has been exchanged between the homologous pair. The non-sister chromatids that have exchanged DNA are called recombinants.
Random Assortment during Meiosis
The homologous pairs form randomly in Metaphase I. This means there is an equal chance of a resulting gamete containing either the maternal or paternal chromosome. As humans have a haploid number of 23, so there are 223 potential gamete combinations (>8 million).
Complete Dominance
One allele is expressed over another. Dominant allele is expressed in heterozygous displayed as a capital letter. Recessive allele is not expressed in heterozygous displayed as a lower case letter. A recessive phenotype can only be expressed in homozygotes. Heterozygotes will display the dominant phenotype.
Codominance
Both alleles are equally expressed in the phenotype. Heterozygotes have a distinct phenotype shown through a superscript letter. An example of codominance is the ABO blood system.
Modes of Inheritance
Autosomal Dominance: If both parents are affected by a trait and any offspring is not, the trait must be dominant, so parents must be heterozygous.
Autosomal Recessive:If neither parents are affected by a trait but any offspring is, the trait must be recessive, so parents must be heterozygous.
Sex-Linked Traits: No way to conclusively prove sex-linkage with a pedigree chart, but certain patterns may suggest the possibility.
DNA Profiling
DNA profiling is a technique by which individuals can be
identified and compared by their genetic sequences. Individuals have different lengths of particular DNA segments called short tandem repeats (STR). These segments are emphasized by PCR and then separated by gel electrophoresis for comparison. Unique profiles appear when multiple loci are compared.
Forms of Animal Cloning
Binary Fission-
* The parental organism divides equally into two clones
* Occurs in flatworms (also used by bacteria and protists)
Budding-
* Cells split off from parent, generating smaller clones
* Occurs in Hydra, but is also common to yeast
Fragmentation-
* New organisms grow from separated fragment of parent
* Common to starfish and some species of annelid worm
Parthenogenesis-
* Embryos formed from an unfertilised (diploid) ova
* Occurs in some species of fish, insect, reptile, amphibian
Meiosis I vs. Meiosis II
Meiosis I: This is a reduction division going from diploid to haploid. This process separates the homologous chromosomes. Crossing over may occur during Prophase I to create genetically divergent sister chromatids.
Meiosis II: This is similar to a mitotic division, but of haploid cells. This process separates the sister chromatids. This occurs because DNA is replicated in interphase to create chromosomes with sister chromatids.
Sexual Reproduction vs. Asexual Reproduction
Sexual Reproduction- Involves two parents and produces offspring that are genetically unique.
Asexual Reproduction- Involves one parent and produces offspring that are genetically identical to each other and to the parent.
Definition of clone and cloning
Clone- A genetically identical organism that is derived from a single original parent.
Cloning- A cell replicating itself through asexual means without any genetic alterations or recombinations.
Methods that Natural Clones can arise
Garlic bulbs store food from photosynthesis from leaves and they grow bulbs all of which are genetically identical.
