Midterm Flashcards
Dominance (allelic) serries
Complex relationship. Contains incomplete dominance and codominance
Wild type alleles
Most common, usually shown with a + superscript
Functional enzyme or protein is produced
Usually dominant over the loss of function allele (enzyme/ protein is either non- functional, not produced or produced less)
haploinsufficiency
When half of the protein is synthesized, but this is enough for the wild type phenotype
The gain of function mutations
This is an exception to the rule, dominant alleles. A detrimental function
haploinsufficiency
In a heterozygote, when half as much protein is synthesized and it is not enough
Lethal alleles
Affect on the tail is dominant, the lethal effect is recessive
environmental factors that affect penetrance and expressivity
Age, sex, chemicals, temperature (some pigments of cat hair is only in lower extremities where it is cooler)
Norm of reaction
How the genotype is affected by the reaction
genetic interaction
Combination of alleles from two or more genes can result in different phenotypes because of interactions between their products at the cellular or biochemical levels
Complementation
genes at different loci produce a single phenotype (this is the difference between dominance, where alleles are at the same loci)
The other gene supplies the wild type allele to complement the mutated allele
9:7
Heterogenous trait
A mutation in any one of a number of genes can give rise to the same phenotype`
Epistasis
Epistatic gene masks the hypostatic gene
Recessive epistasis
9:3:4
Dominant epistasis
12:3:1
Pleiotropy
A single gene can be responsible for a number of distinct and seemingly unrelated phenotypic effects
Inbreeding (consanguineous mating)
Double bars in a pedigree
Increases the probability they will be recessive for mutant alleles, can cause genetic problems
Heterosis
when two different inbred lines are crossed, the hybrids are heterozygous for many genes
hardy Weinberg principle
random mating, no mutation, migration or natural selection. Only needed when talking about genotype frequencies, use part of it when talking about allele frequencies
Phenocopy effect
Poisoning which produces a phenotype which mimics a genetically caused phenotype
Dosage compensation
Way of equalizing gene expression in the face of different gene dosage (numerous genes seem to escape for unknown reason)
X inactivation
Proposed that Barr bodies are inactive x chromosomes if a cell contains more than two x chromosomes all but one are inactive. therefore, females are functionally hemizygous for x- linked genes at the functional level
The x chromosome that is deactivated is completely random, happens early on in development
This is an example of dosage compensation in females
Aneuploidy
The number of sets of chromosomes does not change, individual chromosomes change. For some reason, humans can tolerate aneuploidies when it comes to sex chromosomes much better than autosomes.
Nullisomy
2n-2
Monosomy
2n-1
Trisomy
2n+1
Double trisomy
2n+1+1
Tetrasomy
2n+2
Turner syndrome
(XO) Short stature (can receive growth therapy, as well as estrogen at puberty for breast development) wide chested, normal IQ, webbing of the knee is common
Ovaries fail to develop, uterus and oviducts can be small and immature
Klinefelter syndrome
(XXY) sterile
Phenotypic features differ after puberty, breast development and female body fat distribution
testosterone therapy coupled with breast tissue removal will result in a more typical male phenotype
Triple X females
Phenotypically normal, can be taller than average, some fertility problems
Jacob’s syndrome
(XYY)
Phenotypically normal, usually taller than average
Trisomy and maternal age theories…
Bivalents with crossovers at the ends are fragile and increasingly unstable over time
Length of prophase arrest
Hormonal changes
Chemical changes
Inversions
No gain or loss of genetic information, phenotypes may pop up though
Gene may be broken up
Location of genes is an important “position effect”
May have played a role in the evolution of humans
Translocations
Reciprocal translocation: Pieces of two non-homologoius chromosomes are exchanged without any net loss of genetic material
Compound chromosomes: Formed by the fusion of homologous chromosomes, sister chromatids of homologous chromosome segments
Robertsonian translocations: Formed by the fusion of two non-homologous chromosomes at their centromeres
TH Morgan
Recombination
AH Sturtevant
Frequency of recombination reflects the distance between genes
Recombination
Happens between homologous chromosomes, does not always happen, is not as random as you think, happens during prophase one of meiosis (when gametes are forming)
Chiasma
The junction where crossing over happens
Miescher
Studies puss in white blood cells discovered nuclein (nucleic acid)
Griffith
Determined hereditary material was in the virus, determined to be hereditable as it stayed throughout generations
Avery- McCarthy, Mcleod
Concluded the hereditary material was DNA (not proteins) as it was killed by DNAse
Structure of DNA
Watson and Crick got the Credit, Franklin deserved it due to X ray crystallography
Pentose sugar: Deoxyribose, ribose
Nitrogen-containing sugars
Phosphate group: What makes the DNA negatively charged, phosphodiester bonds join the nucleotides (the backbone of DNA)
DNA strands are antiparallel
5’ end has the free phosphate, 3’ end has the OH
Chargaff
Purines= Pyrimidines (A=T, G=C0
Astbury
Showed that DNA is a polymer of stacked bases
Franklin/ Wilkins
DNA is a helix
How are bases held together?
Hydrogen bonding (3 between gc, 2 between at so they are easier to pull apart)
Grooves
Major grooves: where the backbones are far apart
Minor groups: Where the backbones are close together
DNA organization
Supercoiled to fit
Over rotated
Positive coil
Under rotated
Negative coil (most common, takes less time to separate)
Topoisomerases
Can add or remove turns in the DNA (noot all can do both)
DNA structure in prokaryotes
NO HISTONES
Still bound by proteins. Folded into loops (domains) and then supercoiled
Chromatin
DNA+ Histones+ protein
Euchromatin
Where the most transcription takes place
heterochromatin
Highley condensed (crossing over and transcription do not happen here)
Chromosome structure in eukaryotes
have anchored region to keep DNA from unwinding
Each chromosome contains one long linear piece of DNA, 5 histone proteins and a group of non- histone proteins
levels of DNA packaging
1) Nucleosome (wrapped around an October of histones)
2) Chromatin fibre (stacks of histones)
3) Interphase chromosomes (30nm fibres are anchored by proteins)
DNA is most condensed during metaphase, least condensed during interphase
Bacteria in research
Small, rapid, simple structure, variable
Prototroph
Can grow on minimal media
Auxotroph
Lacking certain enzymes to synthesize certain enzymes
Lytic phase (T4)
Kills host cell immediately
Lysogenic phase
More passive. Injects DNA into host cell genome and then goes to sleep
Lambda phase
Can be lytic or lysogenic
In its integrated state, the lambda chromosome is called prophage and its lytic genes are kept turned off
Plasmids and Episomes
Plasmids are much smaller and can replicate independently
Episomes are larger and can integrate into the bacterial chromosome
Both circular molecules of DNA
Phenotypes observed in bacteria
Colony colour, morphology and nutritional deficiencies
Parasexual process
No mitosis and meiosis
Transformation
Cells take up competent bacteria from the environment \
Can happen naturally or in a lab, can be used to determine the distance between genes
No cell contact required, yes sensitive to DNAse
Conjugation
Sexual process, mediated by F factor
Rolling circle replication
Yes cell contact requires, not sensitive to DNase
Transduction
Bacteriophages can hijack bacterial chromosome genes during infection of the phage, can donate hijacked genes to another cell
Generalized transduction
A random fragment of bacterial DNA is packaged in the phage head by mistake
Specialized transduction
Occurs when the prophage exists imprecisely from the chromosome and produces a phage chromosome containing only the adjacent bacterial genes
Competent bacteria
Can bind exogenous DNA and transport it into the cell
