Populations and Genes Flashcards
D: Crude birth rate
number of births per unit of person-time. The world average crude birth rate is around 18.5 births per 1000 person-years.
D: Crude death rate
number of deaths per unit of person-time. The world average crude death rate is around 7.8 births per 1000 person-years.
D: Crude rate of natural increase (or decrease)
Crude rate of natural increase (or decrease) = crude birth rate – crude death rate.
The world average crude rate of natural increase is 10.7 per 1000 person years.
D: Total fertility rate
Total fertility rate represents the total number of babies per average reproductive lifetime.
The total fertility rate in England and Wales is approximately 1.76 births per women’s reproductive lifetime.
D: Gross reproductive rate
Gross reproductive rate represents the total number of daughters per average reproductive lifetime.
The England and Wales gross reproductive rate is approximately 0.86 daughters per women’s reproductive lifetime (= proportion of female births x total fertility rate).
D: Infant mortality `rate’
Infant mortality `rate’ represents the probability of dying before the first birthday.
The infant mortality rates in most western countries is less than 1 per 1000 live births, whereas in low income countries the infant mortality rates are greater than 100 per 1000 live births.
D: Child (or under 5) mortality `rate’
Child (or under 5) mortality `rate’ represents the probability of dying before age 5.
D: Adult mortality `rate’
Adult mortality `rate’ is usually defined as the probability of dying between the ages of 15 and 60 years.
Adult mortality varies substantially across countries and over time.
is age standardisation important in demography?
very
example coming
what are Person years
measurement take into account both the number of people in the study and the amount of time each person spends in the study.
For example, a study that followed 1000 people for 1 year would contain 1000 person years of data
rate vs risk?
Rate - frequency by which events occur (in person-time) - e.g. births
Risk - probability of a specified event within a specified period - e.g. stroke risk
3 measures of fertility?
- Total fertility rate – total births in the average reproductive lifetime
- Gross reproductive rate - are mother’s reproducing themselves?
- Net reproductive rate - are mother’s being maintained?
does crude mortality rate tell you if a person is healthy or unhealthy?
no
Sex ratio at birth commonly assumed to be …
Sex ratio at birth commonly assumed to be 105 males : 100 females
describe why age standardisation is important?
how many methods are there?
Ie. Retirement town vs university town
- This allows us to specify the relative weight of the contribution of each age stratum to the summary rate
- It requires sufficient deaths in each age-stratum to produce stable age-specific rates
2 methods
= age standardized rates, or life expectancy
describe the direct method of age standardisation
The ‘direct method’ projects the age-specific death rate of the population of interest onto a ‘standard population’ and calculating the overall death rate for that standard.
i.e. expected / observed
NB. The standard population must contain the population of interest (such as projecting the population of Cambridge onto that of the whole UK)
describe age standardisation - indirect method?
‘Indirect method’ - looking at population of interest through use of national average
i.e. observed / expected
gaps:
T or F
Life tables are usually constructed for men and women separately
T
why are life table projections are not truly representative?
since they are based on estimated age-specific mortality rates in the recent past, the projections are not truly representative, especially due to current advances in medicine, public health and safety standards which did not exist in the early years of the cohort.
are life expectancy values dependant on age structure
independant
when are life expectancy values calculated at?
birth
do many people outlive their life expectancies?
yes - due to medical advancement.
Is life Expectancy usually done for men and women differently?
yes
T or F
The increasing proportion of elderly population in western countries is decreasing the apparent birth rate
T
list the 7 big health transitions that caused life expectancy to rise, adn mortality to fall
when were the biggst gains made in the reductionof child mortality?
and adult mortality?
child mortality: early 20th century
adult mortality: late 20th century
did child (<5) mortality plumet around 1900?
why?
yess.
conquored in the home
lost of baby care, cleaness advice
campagines to cahnge parental behaviour
what leads to the main gains for adult drop in mortality in late C20?
Streptomycin for TB
and the drop in tobbaco related
Multiplegenomealignment for comparing genomes?
what is a Principal component analysis
a 2D representation of the distribution of polymorphisms
used for entire populations too
Principal component analysis big picture
Penetrance vs. expressivity
‘Penetrance’ - % of individuals with a given genotype who exhibit the phenotype - complete vs. incomplete
‘Expressivity’ - variation in phenotype when the genotype is present
What are the processes underlying genome evolution?
Beneficial alleles (increasing fitness) are favoured; deleterious alleles (decreasing fitness) disfavoured.
poor card
+
Natural selection
Germline mutation
fgenetic Drift
Founder effect
D: natural selection
Natural selection - choosing between existing alleles - positive, negative, balancing
D: Germline mutation
Germline mutation - introducing new alleles
D: Genetic drift?
Genetic drift - transition in allele frequency between generations - mapped by the Wright-Fisher model
D: Founder effect and population bottlenecksneity’
Founder effect and population bottlenecks - ‘causing non-representative heterogeneity’
genetic drift is larger in _____populations
smaller populations -
smaller or larger populations show higher loss of Genetic diversity
Smaller
D: chi squared test
The Chi-squared test is a statistical method used to determine the likelihood that differences in data sets are due to chance.
- Small p values mean the likelihood it is due to chance is very low
- We can use this test in GWAS studies when determining the likelihood that an allele has on the development of a particular polygenic condition
Most traits, including common diseases, are highly polygenic. They depend on many loci (1000s) genome-wide, each contributing only a very small effect.
what are GWAS
GWAS Studies
Calculate association tests at loci across the genome – for polygenic conditions
Low P-values correspond to loci associated with the disease in question
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