Inherited Change Word Stimulants Flashcards
Genetics
Way individual inherit characteristics from parents
Monohybrid inheritance
One characteristic passed from parents
Dihybrid inheritance
Two different characteristics pass independently to offspring
Pure breeding
Characteristics unchanged generation to generation
Parental generation (P)
Pure breeding individuals producing offspring
Filial generations
First filial generation (F1)
Pure breed parents
Second filial generation (F2)
Cross breeding parents of F1
Punnett Square
Cross between parents
Mother Aa x Father Aa
Gene
Length of DNA encoding the whole or part of a protein
Expressed - protein produced from translation/transcription
Allele
One form of gene
Locus
Position of a gene on a chromosome
Homologous chromosome
Pair of alleles of a gene occupying the same locus
Might encode for part or whole protein
Homozygote
Individual pair of alleles coding for same protein
Heterozygote
Pair of different alleles coding for different proteins
Dominant
Expressed by heteozygote
Recessive
Allele partner dominant
Not expressed
Codominance
Contrasting parental alleles expressed equally in phenotype
Linkage
Alleles occupying different loci on same chromosome
Pass to offspring together
Closer the loci = more likely to occur
Sex Linkage
Alleles carried on sex chromosomes
Test cross
Known homozygeous recessive breeds with unknown genotype
Genotype
Genetic make up / genes of an individual
Phenotype
Outward appearance
Characteristics of cells
Genotype extresses characteristics
Monohybrid inheritance F2 ratio
3:1
Larger sample = closer to 3:1
Monohybrid inheritance cross
Two pure breeding individuals showing a pair of contrasting characteristics crossed
Eg TT x tt
Characteristics separate om definite proportions in F2
Parental Gamete
One of alleles
Genetic ratios
Show relative size of separate groups
Smallest/largest
Random fusion between gametes of parents
More gametes that fuse = less likely that randomness will effect 50:50 outcome of heterozygote/homozygote (25dominant:25recessive) combinations of alles
Dihybrid Inheritance F2 ratio
9:3:3:1
Law of independent segregation
Characteristics pass independently of one another
Either one of characteristics combine with either of other characteristic alleles
Each inherited like monohybrid (3:1)^2
Dihybrid inheritance eg
Height
Seed colour
Dihybrid cross F2
TYTytYty x TYTytYty
Codominance example
Cattle red/white coat
Roan (light red) coat
Codominance genotypes/gametes
C^R C^R
C^W C^W
Multiple Alleles
More than two alleles encode characteristic
Inherits two alleles from available
Multiple Allele example
Blood groups
O (recessive)
A, B Codominance
Polymorphism
multiple alleles combine
AB blood group
Autosomes
22 out of 23 chromosomes
Similar size/shape
Genes/alleles determine phenotype
Sex chromosome
23rd chromosome pair
X / Y
X chromosome
Larger
Carries other genes (not sex determining but sex linked)
Y chromosome
Smaller
Little space for non sex determining genes
Female
XX
Same sex chromsome
Homogeneous/heterogeneous for sex linked characteristics (not expressed or carriers)
Male
XY
Different chromosomes
Sperm contains X or Y - equal no of each at meiosis; determines gender
X linked gene expressed in phenotype
Homogametic
Same sex chromosome
XX
Heterogametic
Different chromosomes
XY
Sex linkage cross/square
X^H X^H
X^h Y
Sex linkage example
Haemoglobin
Women - uneffected/carriers
Male - uneffected/haemoglobin
Drosophilia
Autosomal linkage
Genetic experiments
Small fruit fly
Autosomal linkage
Genes inherited together
Autosomes not sex chromosomes
Form a linkage group
Autosomal linkage ratio
9:3:3:1
Not linked alleles
Different chromosomes
Failed law of segregation
Autosomal linkage
Failed to segregate independently during meiosis (inherited together, located on same chromosome)
More linkage
Nearer jeans on chromosomes
Crossing over in meiosis - autosomal linkage
Broken linkage
More likely of distance on chromosome is greater
Not always inherited together
Human autosomal linkage
Hair, eye, skin colour
Linkage group
3:1
Little/no segregation
Alleles on same chromosome
Epistasis
Interaction where expression of alleles of one gene masks the expression of alleles in others in a network
Network
Genes working together
Interact
Epistasis ratio
Different ratio to 9:3:3:1
Epistasis recessive
Two copies of epistasis allele required to mask expression
Epistasis recessive ratio
9:3:4
Epistasis dominant
1 copy of epistasis allele required to mask expression
Epistasis dominant ratio
12:3:1
Epistasis Complementary
Effect of 1 gene combines with another gene - at least one dominant
Epistasis complementary ratio
9:7
Epistasis example
Gene A = agouti A, black a
Gene B = colour present B, albino b
Gene B effects expression of gene A
bb blocks any A expression (albino)
Chi Squared (X)^2 equation
(X)^2 = sum of : (O-E)^2 / E
Chi Squared purpose
Judge between observed and expected
If significant
Expected
Row total x corresponding column/total no of observation
Based off cross ration (3:1)
Null hypothesis
No significant difference between observed and expected
Accepted (no significant difference)
Rejected (significant difference)
Confidence
95% confidence
0.05
Real not due to chance
Critical value - probability table
Significant difference
More than critical value
Degrees of freedom
Number of categories - 1
eg 2-1 = 1
Chi Squared Table
O // E // (O-E) // (O-E)^2 // (O-E)^2/E