Genetics Exam 1 Flashcards
Mendel’s first law/Law of segregation
Identifies segregation of alleles during gamete formation and proposes the random union of gametes to produce progeny in predictable proportions determined by chance. 2 alleles for each trait will separate.
Mendel’s second law/ Law of Independent Assortment
During gamete formation, the segregation of alleles at one locus is independent of segregation of alleles at another locus
Chromosome theory of heredity
Chromosomes are the cell structures that carry genes
Reciprocal cross
Where same genotypes are crossed but sexes of donating parents are switched
Test cross
Cross between F1 heterozygous and a pure breeding recessive phenotype
Haplosufficient
One copy is sufficient to produce wild type phenotype
Haploinsufficient
A single copy is not sufficient to produce wild type phenotype
Loss of function mutation
Results in a significant decrease or complete loss of functional activity of a gene product
Gain of function mutation
Identify alleles that have acquired a new function or express substantially more activity than the wild type allele
- almost always dominant
- some are lethal in a homozygous state
Incomplete dominance
Dominance of one allele over another is not complete. Phenotype of heterozygous is distinctive and is typically more similar to one homozygous phenotype than the other.
Codominance
Leads to a heterozygous phenotype different from the phenotype of either homozygous parent. Is characterized by the detectable expression of both alleles in heterozygotes.
sex-influenced traits
the phenotype corresponding to a particular genotype differs depending on sex of organism
nonpenetrant
when a particular genotype fails to produce corresponding phenotype
incomplete penetrance
when traits for which nonpenetrant individuals occasionally/routinely occur
variable expressivity
the same genotype produces phenotypes that vary in the degree/magnitude of expression of allele
pleiotropy
the alteration of multiple, distinct traits of an organism by a mutation in a single gene
epistasis
- causes altered ratios of wild type and mutant phenotypes
- minimum of 2 genes required
- results from mutation in pathways that require a specific activity from every gene in the pathway for wild type phenotype to be produced
duplicative recessive epistasis/9:7
results from complementary gene interaction that requires genes to work in tandem to produce a single product
genetic complementation
ability of 2 mutants with same mutant phenotype to produce progeny with wild type phenotype
-shows more than 1 gene is involved in determining the phenotype
duplicate dominant epistasis/15:1
a redudant genetic system in which any genotype possessing at least one copy of a dominant allele at either locus will produce dominant phenotype
dominant gene interaction/9:6:1
recessive at either gene causes same phenotype but recessive for both gene causes 1/16 different phenotype
recessive epistasis/9:3:4
homozygosity for a recessive allele at one locus can mask the phenotypic expression of a 2nd gene
dominant epistasis/12:3:1
a dominant allele at 1 locus masks the expression of alleles at a 2nd locus
non genetic complementation
offspring of a cross between 2 mutants will have a mutant phenotype and mutations are on the SAME gene
gene
fundamental unit of heredity
- controls some aspect of an organism’s form,
function, or behavior (phenotype)
- a segment of DNA that contains the genetic
information to express a (usually) protein
central dogma
DNA -> RNA -> Protein
Mitosis
ensures that all somatic cells of the body have the same set of chromosomes and 2 copies of each
Sister chromatids are the same, True or False?
True
Homologous chromosomes are the same, True or False?
False
Meiosis
specialized cell division that produces haploid gametes
5 important things about Mendel’s methods
- only used discontinuous traits
- counted everything and used real numbers
- did reciprocal crosses
- studied only monogenic traits
- studied traits without genetic linkage in crosses
When does crossing over occur?
Meiosis I during late prophase I
G1 phase
active gene expression and cell activity: preparation for DNA synthesis
S phase
DNA replication and chromosome duplication
G2 phase
preparation for cell division
M phase
Mitosis for somatic cells and Meiosis for germ-line cells
Interphase
Chromosomes are not visible but are duplicated
Prophase
Chromosomes condense and become visible as a pair of sister chromatids joined at centromere
Telomere
Stable ends of chromosome
Centromere
a constricted region of the chromosome where the kinetechores form and spindle microtubules attach
Chromosome
2 sister chromatids attached at centromere
Prometaphase
-nuclear envelope breaks down and
mitotic spindleforms
-microtubules connect to sister chromatids at
centromere
Metaphase
chromosome pairs line up along metaphase plate
Anaphase
Centromeres divide and the sister chromatids move to opposite poles of the cell
Telophase
- nuclear envelope forms around chromosomes
- cell divides into two -cytokinesis
- chromosomes return to interphase state
