WH meiosis and Genetics Flashcards
Haploid
N, one half set of chromosomes
Diploid
2N, where cells have 2 full sets of chromosomes
Autosomes
Non-sex chromosomes
Sex chromosomes
X and Y chromosomes that decide sex
Mono hybrid cross
Cross for ONE trait
Dihybrid cross
Cross examining two traits
Homologous chromosomes
Chromosome pairs that are similiar but not identical. Each carries the same genes in the same order, but the alleles for each trait may not be the same. One chromosome of each homologous pair comes from the mother and one comes from the father.
Meiosis
Produces cells with half the number of original chromosomes so that two cells can combine to create offspring with a complete number of chromosomes
Prophase I
Chromatin condenses, homologous chromosomes come together and intertwine in synapsis. Each pair contains four chromatids- called a tetrad. Crossing over occurs
Tetrad
Pairs of attached homologous chromosomes
Crossing over
Chromatids of homologous chromosomes break off and exchange equivalent pieces of DNA
Chiasmata
Where chromosomes remain joined after crossing over
Metaphase I
Homologous pairs align at equatorial plane and attaches to spindle fibre
Anaphase I
Homologous pairs deprecate and are pulled to opposite poles, called disjunction.
Disjunction
Separation of homologous chromosomes
Telophase I
Mem brain forms around each nucleus. Each chromosome has sister chromosomes joined at centromere. Cell devises into two daughter cells with haploid chromosome number
Prophase II
Centrioles move to opposite poles and spindle forms
Metaphase II
Chromosomes migrate to opposite poles and the spindle fibre forms, chromosomes are separated into sister chromatids
Anaphase II
Sister chromatids are pulled to opposite poles by spindle fibers
Telophase II
A nuclear membrane forms around each haploid nucleus. Cytokinesis occurs and two daughter cells are formed, completing four haploid cells
Increasing variation
Ways of increasing genetic variation:
- horizontal transfer: can move genetic material between bacteria.
- crossing over
- random assortment
- random fertilization
Law of segregation
Two alleles for a heritable character segregate independently during gamete formation and end up in different gametes
Law of independent assortment
Two or more genes assort independently during gamete formation. Only applies to genes located on different chromosomes
Complete dominance
Ex: Classic crosses. One trait is completley dominant over another
Incomplete dominance
Ex: red and white snapdragons make pink - the phenotype is in between parental varieties
Co dominance
both alleles affect phenotype in desperate distinguishable ways
Pleiotrophy
Genes with multiple phenotypic effects.
Epistasis
Expression of a gene at one locus alters that at a second locus
Polygenic inheritance
Inherited charecters that vary in gradients along a continum - there is not one specific determined expression . Caused by two or more genes
Multiple alleles
When there’s more than 2 different alleles for a possible phenotype
Pedigree analysis
A tree diagram that shows traits across generations. Mendelian genetics can be applied to the pedigree to understand trait inheritance
Chromosome mutations
Nondisjunction resulting in aneuploidy- too many or too few chromosomes
Non disjunction
Mishaps in meiotic spindle chromosome distribution. One gamete received two of the same chromosome the other receives none
Aneuploidy
When a gamete has abnormal chromosome number
Monosomic
When a gamete has no copy of a particular chromosome it leads to a missing chromosome in the zygote. 2N-1
Triatomic
When there is two of one chromosome in a zygote - 2n + 1
Polyploidy
When an organism has more than 2 complete sets of chromosomes
Gene mapping
Mapping where on each chromosome different genes lie
Chromosome breakage
Chromosome structure changes
Deletion
When a fragment of a chromosome is lost
Duplication
When a deleted fragment becomes attached as an extra segment to a sister chromatid. It can also attach to a non sister chromatid which results in non identical segments
Inversion
When a chromosomal fragment reattaches to the original chromosome in reverse orientation
Translocation
When a fragment joins a homologous chromosome. Least harmful
