Task 2 PEAS, GENES, AND A POST-MORTEM WEDDING Flashcards
Homozygous
The case in which the plant has two copies of the same Allele (e.g. AA or aa)
Heterozygous
One copy of each of the two different alleles (e.g. Aa)
Probability of passing on alleles
it is always 50/50 which allele is passed on
Dominant
as long there is a least one copy of A the corresponding characteristic gets developed
Recessive
Both copies of the Gene has to be a to be expressed
Co-dominant
heterozygotes fully express the phenotype of both of their homozygotes parents
Incomplete dominance
means that the phenotype of the heterozygotes is intermediate in form between those of the two homozygotes (white + red flower= pink flowers which still can have white or red offspring) (only the phenotype changes not the genetic material)
Independent segregation
means that phenotypic traits controlled by different genes can become separated from each other through generations
Inbreeding
makes it more likely to become two diseases because of the recessive alleles
Genetic drift
in smaller populations it could happen that the recessive allele will not be expressed so allele frequency fluctuates
o The more people there are in a population the less likely it is that the gene reaches Fixation
o Fixation: The point where everybody in the population carries the gene
Law of segregation
the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes (if same allele thus true-breeding: allele present in all gametes)
Mendelian disease
A disease that is transferred by one single gene (e.g. Huntington)
Neutral theory of molecular evolution
The amount of divergence between the DNA sequences of any two populations or species basically reflects the time since their common ancestor.
Hardy Weinberg equilibrium
displays the distribution of alleles in a population without environmental influence
o Without natural selection alleles won’t become more rare and the distribution of hetero and homozygotes will stay the same
p^2 (AA) + 2pq(Aa) + p^2 (aa) = 1
Heritability
the proportion of the observed phenotypic variation that can be accounted for genetic variation in a particular population and time (difference
o Maximum heritability is 1 that means all phenotypic variation is related to genotypic variation and heritability of 0 would mean none of it is
o a heritability of 0 means that environmental effects account for all of the variation in the characteristic.
´Coefficient of relatedness
between a man and his father is one-half
o (r) – probability that any particular allele in individual A (dark blue) is identical by descent (derived from same immediate source) as the allele in individual B (any of the light blue ones)
Twin studies
o Shared environment: parental social class, parental behaviour, diet available, school, town etc. they will influence both kinds of twins in the same way
o Non-shared environment: childhood diseases or accidents that affect one twin but not the other. No kind of twins shares these factors by definition
Falconers estimate of heritability
if the height of MZ twins correlates at 0.9, and the heights of DZ twins correlate at 0.5, then the estimated heritability is (0.9 — 0.5) x 2 = 0.8.
ACE models
A (the heritability) C (the effect of the shared environment) E (the effect of the non-shared environment)
o Allows us to identify its relative strength
o Called narrow sense heritabilities because they don’t consider the dominance and epistatic effect
Problems with twin studies
o For MZ the rivalry in the placenta which they have to share
o MZ twins are treated more alike than DZ twins
Coefficient of additive genetic variance
is an estimate of the amount of genetic variation in a population relevant to a particular trait, independent of the amount of environmental variation.
Dominance effect
Effects on heritability that are due to the interaction between the pair of alleles at a locus
Epistatic effect
Effects on heritability that are due to the interactions between alleles at different loci
Polygeneic inheritance
additive effect of multiple genes on a single phenotypic character
• E.g. AABBCC darkest AaBbCc middle aabbcc lightest (majority in the middle)
Quantitative genetics
When one characteristic is influenced by multiple genes
Identical descent
derived from the same immediate source
Monozygotic
Twins from the same egg
Dizygotic
Twins from different eggs
All psychological traits show significant and substantial genetic influence
Traits such as political beliefs, religiosity, altruism, and food preferences also have shown significant genetic influence
They differ in how much influence genetic has
No traits are 100% heritable
Typically between 30% and 50%
Physical traits are more reliably measured than psychological
Heritability is caused by many genes of small effect
Many genes influence complex traits
There is no single effect that is higher than 1%
Phenotypic correlations between psychological traits show significant substantial genetic mediation
Phenotypic covariance between traits is significantly and substantially caused by genetic covariance, not just environmentally driven covariance.
Some genes effect several traits
The heritability of intelligence increases throughout lifetime
The inheritance of the states of intelligence through a lifetime
Age-to-Age stability is mainly due to genetics
trait across age), whereas age-to-age change is primarily the provenance of environmental factors
Most measures of the environment shows significant genetic influence
humans select, modify, and create environments correlated with their genetic behavioural propensities such as personality and psychopathology
Most associations between environmental measures and psychological traits are significantly mediated genetically
if these correlations are mediated genetically, interpretations that assume environmental causation are wrong
genetically sensitive designs can be used to identify causal effects of the environment free of genetic confound
genetic mediation of the association between environmental measures and behavioural traits is not just a nuisance that needs to be controlled
Most environmental factors are not shared by children growing up in the same family
for most behavioural dimensions and disorders, it is genetics that accounts for similarity among siblings
The message is not that family experiences are unimportant but rather that the relevant experiences are specific to each child in the family
Abnormal is normal
People with mental diseases are the extremes of the distribution of genes
Everybody carries some kind of abnormalities which don’t have to be expressed
Linkage
when two genes lie on the same chromosome
Closer together = greater linkage (lower probability of crossover)
Parental type frequency greater than 50%
Pleiotropy
one gene can have multiple phenotypic effects
