Module 2- Gentics, Linkage, Cell cycle Flashcards
Genotype
- information stored in the DNA
- indirect target of selection
Phenotype
- physical representation of the genotype
- Direct target of selection
Monogenic Phenotype
One gene affects one phenotype/ Trait
Polygenic Phenotype
Many genes affect one phenotype/trait
Pleiotropic Phenotype
One gene affects many phenotypes/traits
Continuous variation
All values in the phenotypic range can occur
Discrete Variation
Traits are differentiable (Color, Number)
Phenotypic Variation
results from the interaction between information from the genotype and from the environment
Phenotypic Plasticity
the ability for an individual with a specific genotype to express different phenotypes as a result of environmental differences
Evolution
Changes in heritable traits in a population over time
Natural selection
traits will arise and be passed on to offspring that will increase survival
Sexual Selection
The ability to obtain mates
Genetic Recombination
crossing over of alleles in meiosis
Mutation
Error in genetic replication that causes a large change in an organism
Primary sexual selection
Traits that are directly related to sexual reproduction (production of gametes, ability to mate, and nurturing young)
Secondary sexual selection
Traits to increase an individuals reproduction
-Intersexual selection: attracting mates
- Intrasexual selection: competing for mates
Crossing over
alleles from both parents exchange lengths of their chromosomes
Independent assortment
- random distribution of chromosomes/sister chromatids when cells divide in meiosis
- no linkage results in a true breeding test cross having an F2 generation of 1:1:1:1 ratio
Homologous chromosomes
nearly identical chromosomes
Diploid
Two sets (2n)
Haploid
One set (n)
Allele
variant of a gene
True Breeding
Always give rise to the same genotypes
Homozygous
the individual has two of the same alleles for a specific gene
Heterozygous
the individual has two different alleles for a specific gene
Hybrid cross
crossing of two true breeding lines
Law of segregation
during the formation of gametes, genes are randomly separated into the gamete cells
Complete Dominance
the dominant allele completely over powers the recessive allele
incomplete dominence
heterozygous individuals express a blend of the two phenotypes
Semi-dominance
Heterozygous individuals express an exact intermediate between the two phenotypes
Co-dominance
a heterozygous individual expresses both phenotypes at once
multi-locus crosses
two or more traits are studied in a cross
multi-locus cross with two true breeding individuals
F2 generation shows a 9:3:3:1 ratio
Additive traits
each allele of a given type adds a certain amount of phenotypic effect
Epistasis
one trait determines the expression of another
Complete linkage
- linkage results in a true breeding test cross having an F2 generation of 1:1 ratio
- There is no recombination of alleles
Incomplete Linkage
- some linkage results in a true breeding test cross having an F2 generation of 1:1 ratio of recombinants and a 1:1 ratio non-recombinants
high recombination frequency
- Crossovers are essentially certain at a high percent
- percent translates to distance apart
Aneuploidy
Abnormal number of chromosomes
non-disjunction
chromosomes fail to separate in anaphase
- Meiosis 1: all gametes are affected
- Meiosis 2: only half the gametes are affected
