Lectures - Human Genetics Flashcards
What are the characteristics of a pedigree with autosomal dominant inheritance?
What are the characteristics of a pedigree with autosomal recessive inheritance?
What’s the Law of Segregation?
for any particular trait, the pair of alleles of each parent separate and only one allele passes from each parent on to an offspring.
Which allele in a parent’s pair of alleles is inherited is a matter of chance.
This segregation of alleles occurs during the process of meiosis.
What’s the Law of Dominance?
Each trait is determined by two factors (alleles), inherited one from each parent.
These factors each exhibit a characteristic dominant, co-dominant, or recessive expression, and those that are dominant will mask the expression of those that are recessive.
How many base pairs does the human genome consist of, what percentage of them are identical across humanity, and what percentage vary?
The genome of humans consists of about 3 × 109 base pairs.
99.4% are exactly the same for all of us.
.6% of base-pair variation among individuals is enough to cause a sizable genetic variation.
What’s the general model for statistical genetics?
Y (phenotype) = G (genes) + E (environment)
What’s Linkage Analysis?
Follows meiotic events through families for co-segregation of disease and particular genetic variants
- Large families
- Sibling pairs (or other family pairs)
- Works VERY well for “Mendelian” diseases
What are Association Studies?
Detects association between genetic variants and disease across families: exploits linkage disequilibrium
- Case-control designs
- Cohort designs
- Parents with affected child trios (TDT)
- May be appropriate for complex diseases
What’s Mendelian Genetics?
studies the transmission of alleles in pedigrees to understand genetic mechanism of a
qualitative trait.
What’s Population Genetics?
the rules of how genes behave in a population.
What’s Quantitative Genetics?
the rules of transmission of complex quantitative traits, those with both a genetic
and environmental basis.
What’s the relationship between variant effect size and allelic frequency?
Why do we care about statistical genetics?
What is the mean heterozygosity (HET) for an m-allelic marker with alleles A_i and allele frequencies p_i, i=1, …, m?
What’s Hardy-Weinberg Equilibrium?
The general statement of the Hardy–Weinberg equilibrium (HWE) is that under certain assumptions, the genotype and allele frequencies in a large, randomly mating population remain stable over generations and that there is a fixed relationship between allele and genotype frequencies.
How might we calculate the probabilities for all possible genotypes in the offspring?
Combine the parental mating type frequencies with their corresponding offspring genotypes e.g.
What’s the HWE law?
The allele frequencies in the offspring can be deduced and lead to the same values as in the parental generation.
What’s the Chi-Square Test for Hardy Weinberg Equilibrium?
Consider a single genetic locus with 2 alleles A and B. Suppose the population allele frequency of A is q. For a random sample of 2n genes from the population: What’s the MLE for q and the variance of the MLE?
Consider a single genetic locus with 2 alleles A and B. Suppose the population allele frequency of A is q. For a random sample of 2n genes from the population: What’s the Fisher information and the large sample variance of the MLE?
The Fisher information is 2n/q (1− q) and the large-sample variance of the MLE is q(1 − q)/2n.
In this example, it is the variance for any sample size. For large
2n, MLEs are approximately unbiased, and have approx the
smallest possible variance.
