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48 Cards in this Set

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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