Estimating Risk of Inherited Genetic Diseases Flashcards
Define fitness
The ability of organisms to survive (long enough) to pass on their genes
How do neural alleles affect fitness?
Don’t at all
How do deleterious alleles affect fitness?
Sometimes decrease
How do advantageous alleles affect fitness?
Rarely increase
Name recessive diseases
Sickle cell and Thalassaemia
What can mutations in dominant and X-linked genes arise?
Inherited or de novo (new)
When are De Node mutations common?
In dominant disorders especially were disease reduces reproductive fitness - 1/3 Lethal X-L diseases
alleles in people with genotypes: 400AA + 150Aa + 100aa
A - 950
a - 350
total = 1300
Frequency of A (p) + Frequency of a (f) = ?
1
How to determine frequency of allele frequency?
Sum of type of allele (A or a) divided by number of total alleles (A+a)
How to determine frequency of genotype?
Number of people for genotype (AA/Aa/aa) divided by number of people
What is the ratio in terms of p and q for a punnet square of genotypes Aa and Aa?
AA : Aa : aa = p2 : 2pq : q2
What is the constant relative frequency?
p : q
What is the allele frequency for A from punnet square?
2p2+2pq
What is the allele frequency for a from punnet square?
2q2+2pq
Do dominant conditions become more common at the expense of recessive ones?
No
What are two principle of HWE?
- Allele frequencies remain constant between generations
- Relative proportion of genotypic frequencies remain constant between generations
What will the allele frequency be no matter what in HWE?
1
Should mutation in ignored in an ideal population?
Yes
Should migration occur in ideal population?
No so that there is no gene flow
Should mating be random in an ideal population?
Yes
Should there be a selective pressure in an ideal population?
No
Should the population be big or small in an ideal population?
Large
In ideal population, are allele frequencies equal or unequal in the sexes?
Equal
What is the relationship between mutations and alleles?
Mutation increase the proportion of new alleles
How do new gene frequencies in hybrid populations?
Introduction of new alleles due to migration or intermarriage
How does non-random mating affect proportion of homozygotes?
Leads to increase in mutant alleles and thus number of homozygotes
Define assortative mating
Choosing partners due to shared characteristics - i.e. deafness & sign language
Define consanguinity
Marriage between close blood relatives
What is natural selection?
A gradual process where biological traits become either more or less common in a population
Affect of negative selection
- Reduces reproductive fitness
- Decreases prevalence of traits
- Leads to gradual eduction of mutant alleles
Affect of positive selection
- Increases reproductive fitness
- Increases the prevalence of adaptive traits
- Heterozygote advantage
What are the advantages of being heterozygous?
Can be carrier of recessive disorder and have resistance against other diseases
- Sicke cell - malaria
- Thalassaemia - malaria
- CF - cholera/typhoid
What occurs in small populations?
Exhibit genetic drift and cause founder effect
Define genetic drift
Random fluctuation of one allele transmitted to high proportion of offspring by chance
Mutations are widespread and neutral
Statistical drift of gene frequencies due to chance or random events rather than natural selection in the formation of successive generations
Define founder effect
The reduction in genetic variation that results when a small subset of a large population is used to establish a new colony - new population by few members of original population
