Cellular And Genetic Mechanisms 2 Flashcards
What is the f2 for incomplete dominance
1:2:1
Incomplete dominance what is it
When the dominant and recessive breed forming a mixture
Co dominance what is the main example
And what do they do
Blood type
A and B are dominant to I
A and B are co dominant
Both expressed fully effects are additive
Dihybrid gene interaction
What is it
When 2 gene loci (each with 2 alleles)
Interact to produce a single phenotype
What is epistasis
Is the interaction between genes
Takes place when one gene is modified by one or several other genes
recessive epistasis
What is it
Phenotypic ratio 9:3:4
Homozygous recessive allele makes the expression of the dominant allele for another gene
Dominant epistasis
What is it
Phenotypic ratio 12:3:1
The dominant allele for a gene may mask the effect of another allele for another gene
Duplicate recessive epistasis
What is it
9:7
Both dominant alleles from each gene required for pigment
Duplicate genes with cumulative effect
What is it
9:6:1
Effect of both dominant alleles additive
Individual dominant alleles have same effect
Duplicate dominant genes
What are they
15:1
Both dominant alleles have identical effect
No additive effect
Dominant and recessive interaction
What is it
13:3
Dominant from one gene and recessive allele from other gene have the same phenotype
Gene A able to suppress expression at B gene
Polygenic inheritance (multiple genes) What is it
Many more then 2 genes to control something like height
Additive effect on phenotype
Multiple alleles what are they
Single gene with more then 2 alleles
Different mutations cause this
Only 1 allele is expressed at any time
Penetrance
Portion of individuals showing expected phenotype
Ie extra finger
Expressivity
3 answers
Degree of expression of phenotype in an individual
Temp sensitive
Nutritional
Retinoblastoma
How is it developed
Dominant allele, but not all develop Tumour
Incomplete penetrance in the population
When expressed there are different severity
Different expressivity between individuals
Environmental effects
Temp sensitive alleles examples are
Himalayan rabbits
Siamese cats
Activating the gene at different temps
Environmental effects via Nutrition
What are the examples
Lactose intolerance (expressivity differs) PKU (expressivity differs)
Pleiotropy
What causes it and what does the allele do
Single allele multiple phenotypes
PKU cause mental retardation, blue eyes, light skin colour
Pleiotropy melanin in cats
What doe it cause
Lack of melanocytes (blance in ear) during embryo development
Results in white fur and deafness
Environmental determination
Temperature dependent sex determination in crocodiles
Temp sensitive aromatase
Converts androgen to
Testosterone or oestrogen
Sex determination
Haplo-diploidy
Bees
Sex chromosome system
XX-XO protenor system grasshopper
XX-XY MAMMALS
ZZ-ZW birds
What does the SRY gene code for mammals
Male sex
Drosophila
Humans
Mouse if they were all XO
Sterile
Female turners syndrome sterile
Male y promote male development
Functional female
Birds sex determination
What are ZZ AND ZW called
Homogametic
Heterogametic
Sex determination in plants
Plants can be either
Monoecious- hermaphrodite
Dioecious- male/ female flower on separate plants
Male sex linkage
2 possible genotypes
X+ Y
Xm Y
Inherited from mother
Hemizygous
Females 3 possible genotypes
X+X+
X+Xm
XmXm
Heterozygotes are carriers of recessive traits
X linked dominant traits
Affected males (XBy) will produces all affected daughters, not affect sons
50% heterozygous affected females will pass in trait to the son not daughter
Homozygous females pass on traits to all offspring
Sex limited inheritance
Autos ones not XY
Autosomal gene
Allele cannot be expressed and individual is the wrong sex
Sex influenced inheritance
Sex influences dominance relationship between autosomal alleles
Pattern baldness dom in males reces F
Pedigree analysis
3 primary patterns of inheritance
Autosomal recessive Autosomal dominant Sex linked (X chromosomal)
Autosomal recessive pedigree
What does it mean
If neither parent has it and child does it’s recessive
Not in the x or y means it’s autosomal
Can skip gens
Eg of recessive autosomal
Albinism
PKU
Sickle cell anaemia
Tay Sachs disease
Dominant autosomal pedigree
What is it
Not in x or y
Trait always appears in successive gens
Example of autosomal dominant
Huntingtons disease
Polydactly
Sex linked pedigree and egs
Female carrier
Male gets it
Colour blindness
Haemophilia
Determined
Committed to specialised development
Self perpetuation
Differentiated
Overt cell specialisation grossly apparent
Usually a cell becomes determined before differentiation
Cell replacement: permanent cells
Eye lens and auditory hair cells
3H leucine pulse follows the passage of radioactive protein
3-4 new discs of photoreceptive membrane are formed per hour
Simple duplication
What does this
Endothelial cells
Undifferentiated stem cells can do what
Divide without limit
Either stem or differentiate
Unipotent
Olfactory
Oligopotent
Epithelial cells
Pluripotent
Blood cells
Totipotent
Embryo cells
Pluripotent differentiation of blood cells what happens
2 progenitor steps to form everything apart from platelet and RBC
Which require 3
Things that affect pluripotent differentiation
Factors - colony stimulating RBC formed by low O2 In blood
Receptor- cytokines
Target cells- with receptors for CSF’s
