Topic 7 - Genetics, Populations, Evolution And Ecosystems Flashcards
Gene pool
All alleles in population
Mark release recapture
- capture someplace and mark and release
- non harmful marks
- allow time for redistribution after release
- recapture
- est. pop. = total of 1st x total of 2nd / marked in 2nd
Succession
- pioneer species colonise
- change in abiotic factor in environment
- less hostile extreme conditions
- increase biodiversity
- gets too climax community
Est. Size of population
- grid
- random coordinates
- calculate frequency Per quadrant
- calculate % cover
- large sample
- calculate average
Features of climax community
- consistent abiotic factors
- stable populations and community
Inter/intraspecific competitions
- inter = between different species
- intra = between same species
Species
Group of similar organism in same place at same time that can successfully breed to produce fertile offspring
Allele frequency
Number of times allele appear in gene pool
H-W principle
- calculate frequency of different alleles of a gene in a population
- assume frequencies of alleles in a population remain constant between generations
Assumptions of H-W principle
- no selection - alleles all equal
- no mutation - no new alleles
- no migration - alleles not removed or changed
- large population - no genetic bottlenecking
- random mating
Allele frequency equation
Dominant - p
Recessive - q
2 alleles = p+q=1
Genotype equaiton
Dom homo
Rec homo
Hetro
- DH = P2
- rh = q2
- H = 2pq
P2+2pq +q2 = 1
Define:
Gene
Allele
Genotype
Phenotype
Monohybrid
Gene - inherited instruction which codes for a polypeptide
Allele - alternate form of a gene. Can arise from mutation
Genotype - genetic constitution of an organism that determines characteristics
Phenotype - observable traits of an organism
Monohybrid cross - cross in which the allele of only one gene are inherited
Monohybrid inheritance
The inheritance of a characteristic controlled by a single gene.
Show the likely hood of different alleles of that gene being inherited from parents.
HH + hh = 100% Hh offspring
Hh + hh = 50/50 Hh hh
Codominance
• When alleles of a gene share dominance of characteristics
- both are expressed in the phenotype
• example of diagram is capital letters with smaller letters as powers and as the characteristic
Dihybrid cross
RrYy RRYY rRyY rryy
Inheritance of two genes with 2 different alleles each on different chromosomes
Independent segregation = alleles on different chromosomes
so can pass into gametes in any combo
Autosomal linkage
• non sex chromosomes
• if genes are on same chromosome it is assumed they are inherited together (linked and no crossing over)
• stay together during independent segregation
• ## closer they are together, the closer they are linked
Sex-linked inheritance
• genes on sex chromosomes
• female is XX
• males is XY
• Y is smaller so carries less genes
• some genes like faulty only carried by X so more likely inherited by male offspring due to only one X
Epistasis
• polygenetic characteristics
• when alleles of one gene mask expression of another
• dominant = mask expression of alleles at second gene
locus
• recessive - 2 recessive at one gene mask allies expression of another
In genetic crosses, why are observed phenotypic ratios not the same as the expected ratios
-random fertilisation of gametes
-mutation/crossing over
-small sample size
-linked genes
-epistasis
-lethal genotypes
Test cross
Determines if an organism is homozygous dominant or heterozygous
Whether 2 genes are linked or not
Always cross homo rec
Autosomal
Not sex chromosome
ABO blood groups
I0 is allele for O (recessive)
IA is allele for A
IB is allele for B
IA and IB are codominant (AB)
9:3:3:1
DD:Dr:Dr:rr
XX and XY
XX = female
XY = male
Y = smaller so most genes go on X and no homologous pairs present of Y
Characteristics caused by recessive alleles have greater chance of appearing in males
Chi squared
- assess if observed if significantly different from expected
- categorical raw values
- null hypothesis = no significant difference between O and E
- if calculated value is less that critical value then accept null
Describe these phenotype frequencies:
1860,580,68,57
Larger number linked genes
- smaller numbers means a mutation has occurred which means they are random, not linked and not expected but observed
- smaller numbers caused by crossing over
Assumptions to why expected and observed are not the same
- small sample size
- random fertilisation of gametes
- lethal genotypes
Why is chai squared test used
- to show if differnce between observed and expected is significant or not
- its categorical data
Diploid
2 sets off chromosomes so 2 alleles for each gene
Gametes
Sex cells
Only one allele for each gene
FOIL
FIRST
OUTSIDE
INSIDE
LAST
Phenotypic ratio
- ratio of different phenotypes in ratios
Can predict ratios in F1 and F2
Causes of genetic variation
Crossing over
Random fertilisation
Independent segregation
Lethal alleles
Locus
Position of gene on chromosome
Recessive epistasis
2 copies of recessive epistasis allele masks or blocks expression of other gene
9:3:4
Dominant epistasis
When dominant allele completely masks allele at 2nd locus
12:3:1
Chi squared equation
X2 = sum of (O-E)2/E
STATS OUTCOME
Equal or more = AND
Less = RSN
Allopathic speciation
- geographical isolation
- different pressure once separated differentiate two groups into two different species
- genetic drift
- frequency of alleles in each population differs
- ## reproductively isolated
Sypactric speciation
- without geographical isolation
- random mutations occur that prevent members of population breeding with another member of the species
- mutations occur to produce polyploidy when the chromosomes are increased ion number
- individuals with different numbers of chromosomes can’t reproduce to produce fertile offspring
- leads or asexual production
- more common in plants
