Genetics Test I
Terms
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- Genetics
- The branch of biology that deals with heredity and the expression of inherited traits
- Heredity
- Trasmission of traits from one generation to the next
- Traits
- Any detectable phenotypic variation of an inherited character
- Genotype
- Genetic makeup of an individual
- Phenotype
- The physical expression of the genotype
- Preformationism
- The idea that one of the sex cells contained within itself the entire organism in perfect miniature
- Pangenesis
- The idea that small, exact copies of body parts (pangenes) are transported by the bloodstream to the sex organs and are assembled into the gamets (consistent with the concept of acquired characteristics and Lamarckism)- DARWIN
- Epigenesis
- The idea that many new structures such as tissues and organs appear during the development of an organism which are not present at the time of original formation (de novo development)
- Genes in Pairs
- Genetic characters (traits) are produced by genes that exist in pairs within individual organisms (diploid alleles)
- Allele
- A gene copy
- Dominant/Recessive
- When two unlike alleles are responsible for a single trait are present in a single individual one allele is dominant over the other
- Principle of Segregation
- During the formation of gametes, the paired alleles separate (segregate) randomly so that each gamete receives one or the other (SEPARATION OF HOMOLOGS)
- Principle of Independent Assortment
- During the formation of gametes, segregating alleles assort (separate) independently of each other (separate loci, separate chromosomes)
- Alleles _________, Loci _________
- Segregate, Assort
- Incomplete Dominance
- Expression of a heterozygote phenotype which is distinct from, and often, intermediate to that of either parent (snapdragons)
- Signatures of Incomplete Dominance
-
- 1:2:1 Genotypic and Phenotypic F2 ratios
- F1 has a new phenotype - Examples of Incomplete Dominance
- Snapdragons, Frizzled Fowl, Siamese Fighting Fish, Radish, Rats
- Codominance
- Condition in which the phenotypic effects of each allele are fully and simultaneously expressed in the heterozygote
- Signatures of Codominance
- Genotype=Phenotype
- Examples of Codominance
- Roan Cattle, MN Blood Group
- Steps of Mitosis
-
1) Condenstation of Sister Chromatids
2) Prophase- Final condensation and loss of membrane
3) Metaphase- Homologs line up, spindle fibers grab centromere
4) Anaphase- pulling apart sister chromatids
5) Telophase- tearing of cell into 2 - Step of Meiosis where Sister Chromatids are Formed
- Prophase I
- Step of Meiosis where Principle of Segregation occurs
- Anaphase 1- Separation of homologs
- Step of Meoisis where Independent Assortment Occurs
- Metaphase I- Lining up in center
- Lethal Gene
- An allele whose expression results in death
- Recessive Lethal
- A lethal allele that is expressed only in the homozygote
- Dominant Lethal
- A lethal allele that is expressed by both a homozygote and heterozygote
- Recessive Allele
- Any allele that needs two copies to be expressed
- Dominant Allele
- Any allele that is expressed when one copy is present
- Pleiotrophy
- Multiple phenotypic effects from a single gene
- Signature of Recessive Lethal
- 2:1 Ratio
- Penetrance
- Proportion of genotpyes that are actually expressed as the appropriate phenotype
- Sex chromosome
- Chromosome involved in sex determination
- Autosome
- Chromose other than sex chromosomes
- Protenor Mode
- XX/XO System (Male is 2N-1)
- Lygaeus Mode
-
-XX/XY in Humans and mammals
-ZZ/ZW in fish, moths, butterflies, and birds - Heterogametic Sex
- XY or ZW- male in humans and mammals
- Homogametic Sex
- XX or ZZ- female in humans, MALE in fishes, moths, butterflies, and birds
- Holandric
- Carried on the rare sex chromosome
- Sex Linkage
- Mode of inheritance resulting from loci being on the same chromosome
- Signature of Sex Linked Mode of Inheritance
- Reciprocal crosses will differ
- Sex Limited
- A trait that is expressed in only one sex though both sexes can carry the allele (autosomal) (feathering in chickens)
- Sex Influenced
- A trait whose expression is conditioned or influenced by the sex of the individual (autosomal) (pattern baldness)
- Epistasis
- Interaction between two or more loci that results in the production of a single trait. Most often results when one locus interferes with or prevents the expression of the other
- Single Dominant Epistasis Ratio
- 12:3:1
- Double Dominant Epistasis Ratio
- 15:1
- Single Recessive Epistasis Ratio
- 9:3:4
- Double Recessive Epistasis Ratio
- 9:7