patterns of inheritance Flashcards
1
Q
chlorosis
A
- leaves look pale/yellow
- cells aren’t producing the normal amount of chlorophyll
- reduces amount of food by photosynthesis
- change in phenotype caused by environment
lack of light : - plants turn off chlorophyll production to conserve resources
mineral deficiencies : - lack of Fe/Mg
- Fe = co-factor of some enzymes that make chlorophyll.
- lacking ions = plant can’t make chlorophyll so leaves turn yellow
virus infections: - when virus’ infect plants
- interfere with cell metabolism
- yellowing in the infected tissues because they can’t support the synthesis of chlorophyll
2
Q
animal body mass
A
- combination of genetic/env
- env : obesity/anorexia : amount/quality of food/quantity of exercise
- obesity can be because of genes : mutation
3
Q
continuous variation
A
- individuals within a population vary within a range
- genetic and env
- controlled by a number of genes
- animal mass
4
Q
discontinuous variation
A
- characteristic that only appears in discrete values
- mostly genetic / env has little effect
- one/two genes
- albinism
5
Q
co-dominance
A
- when 2 diff alleles occur for a gene
- both alleles of one gene are dominant
- both alleles of the gene are expressed in the phenotype of the organism
6
Q
sex linked
A
- some characteristics are determined by genes on the sex chromosomes
7
Q
multiple alleles
A
- more than two alleles of the same genes
8
Q
dihybrid inheritance
A
- inheritance of 2 characteristics which are controlled by different genes
9
Q
autosomal linkage
A
- linked genes that aren’t on the sex chromosome
- genes on the autosome
- when on the same autosome = autosomal linkage bc they stay together even during independent assortment in meiosis I
10
Q
recombinant offspring
A
- different combinations of alleles than either parent
11
Q
recombination frequency equation
A
R.F = number of R-offspring / total number of offspring
- measure of the amount of crossing over occurred in meiosis
- RF of 50% = no linkage + genes on separate chromosomes
- RF less than 50% = gene linkage + random process of I.A was hindered
- as crossing over reduces , RF gets smaller
- closer the genes are the less likely they are to cross over
12
Q
what is the chi-squared test
A
- statistical test
- measures size of difference between the results you observe and the expected
- whether difference is significant
13
Q
chi-squared test formula
A
X2 = Σ(O-E)2 / E X2 : test statistic Σ : sum of O : observed E : expected
14
Q
if X2 is smaller than critical value `
A
- null hypothesis is accepted
- diff between predicted and actual cross results is not significant at 5%
- any diff between expected and actual results is due to chance.
15
Q
epistasis
A
- interaction between 2 non-linked genes
- genes at diff loci
- causes one gene to mask the expression of the other in the phenotype
- the one supressing = epistatic gene , one being suppressed = hypostatic gene.
16
Q
dominant epistasis
A
- expression of the dominant alleles for the epistatic gene will suppress the expression of the hypostatic gene
17
Q
recessive epistasis
A
- two recessive alleles at first locus prevents expression of another allele at the second locus
18
Q
gene pool
A
- range of alleles in a population
19
Q
define evolution
A
- change in the frequency of an allele in a population
20
Q
factors affecting evolution
A
- mutation
- gene flow : movement of alleles between populations (imm/emigration)
- genetic drift : changes allele freq in the gene pool by chance a not selection pressures
- natural selection
21
Q
limiting factors for size of a population
A
density dependant :
- dependant on population size
- competition, predation, communicable disease
density independent :
- factors affect population of all sizes in the same way
- climate change, natural disasters, seasonal activities
22
Q
genetic bottle neck
A
- catastrophic event
- large reduction in population size + gene pool
- decrease in genetic diversity
- beneficial mutation will have a greater impact
- quicker development of new species
23
Q
the founder effect
A
- few organisms from a population start a new population
- by chance these individuals are mostly one particular genotype
- without any further gene flow (new alleles from outside)
- new population grows wide reduced genetic variation
- bc small population = more influenced by genetic drift
- occurs bc of migration/geographical separation
24
Q
genetic drift
A
- chance dictates which alleles are passed on
- individuals within a population show variation in their genotypes
- by chance, allele for one genotype is passed onto the offspring more often than others
- no. of individuals with the allele increases
- allele becomes more common in the population : leads to evolution
25
stabilising selection
- env isnt changing much
- individuals with alleles for characteristics towards the middle are more likely to survive and reproduce
- reduces range of possible phenotypes
26
directional selection
- change in env
- individuals with alleles for characteristics of extreme phenotype type are positively selected
- more likely to survive + reproduce
- increase of a favoured allele over time
27
disruptive selection
- extremes selected for and the norm is selected against
28
speciation
- forming a new species through process of evolution
29
how does speciation happen
- variation as a result of genetic mutation exists within a population
- members of a population become isolated
- can't interbreed
- no gene flow between the two groups
- allele undergo random mutations
- different selection pressures
- large changes in the phenotypes
- become so different can no longer interbreed to produce fertile offspring
- reproductively isolated
- diff species
30
allopatric speciation
- when members of a population are separated from the rest of the group by a physical barrier
- geographically isolated
- diff selection pressures = diff physical adaptations
- separation = founder effect = genetic drift = more difference
31
sympatric speciation
- forming 2 species from one original
- due to reproductive isolation
- whilst occupying the same geographical location
- when members of diff species interbreed and form fertile offspring (plants)
32
artificial selection
- selective breeding of organisms
- human selecting desired characteristics
- interbreeding those phenotypes
- selecting genotypes which contribute to the gene pool of the next gen
- reduced diversity of the gene pool
- inc chance of inheriting a recessive disorder
- reduces the ability of the species to adapt to env changes
33
problems of artificial selection
- inbreeding : breeding of closely related individuals
- limits the gene pool
- dec genetic diversity
- reduces chance of evolution and adapting to changes
- genetic disorders are caused by recessive alleles
- reduces ability to reproduce and survive
34
hardy weinberg principle
- allele frequency wont change from one gen to next under conditions :
- large population
- no immigration
- no emigration
- no mutations
- no natural selection
- random mating
- if allele freq does change then immigration, emigration or NS must have happened
35
HWP allele freq equation
p + q = 1
p = freq of dominant allele
q = freq of recessive allele
36
HWP genotype freq equation
p2 + 2pq + q2 = 1
p2 = freq of homo dom genotype
2pq = freq of hetero genotype
q2 = freq of homo recessive genotype
37
epistasis dom/recessive expected cross ration
dom : 12:3:1
| rec : 9:3:4
38
dihybrid unlinked / autosomally linked expected ratio
| dom/rec
unlinked : 9:3:3:1
| linked : 3:1
39
codominance monohybrid autosomal (dom/rec) ratio
1:2:1
40
monohybrid autosomal (dom/rec)
3:1
