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Flashcards in 8.23.16 Lecture Deck (37):
1

Genetic variation defines ___ (phenotypic variation) and ethnic differences, provides us with markers of ___, and defines susceptibility to disease.

Inter-individual differences; disease

2

What is the general format of mutation notation?

Type of sequence, nucleotide number, nucleotide, > replacement nucleotide

3

What are the abbreviations for the 5 types of sequence?

g: genomic
c: cDNA
m: mitochondrial
r: RNA
p: protein

4

The nucleotide is capitalized for which type of sequence? Lowercase for which type of sequence?

Genomic; RNA

5

In introns, a mutation is noted as ___#, where the donor splice site G is assigned position ___.

IVS (Intervening Sequence); +1

6

How are deletions and insertions notated?

By start and stop nucleotide # separated by _ then del or ins followed by affected nucleotides

7

How are translated mutant sequences notated?

Original aa in 3 letter code, position in protein, replacement aa or X for stop codon

8

What are polymorphisms?

Variant sequences (not necessarily deleterious) occurring at an allele frequency >1%

9

What are the 5 types of typical polymorphisms?

1. Single nucleotide polymorphisms (SNP; 2 alleles)
2. Simple insertions or deletions (indols; 2 alleles)
3. Short tandem repeat sequences (STRP; 5+ alleles)
4. Variable number tandem repeat sequences (VNTR; 5+ alleles)
5. Copy number polymorphisms (CNP; 2 alleles)

10

What are three examples of polymorphisms?

ABO, Rh, and MHC

11

How are ABO blood groups defined?

By glycosyltransferase that adds either N-acetylgalactosamine residues (A) or D-galactose residues (B) or no sugars (O) to the H-antigen on RBC.

12

What are the phenotypes, attached sugars, inheritances modes, and antibodies in serum for the 4 blood groups?

O - no sugar - recessive inheritance - anti-A, anti-B
A - N-acetylgalactosamine - dominant inheritance, anti-B
B - galactose - dominant inheritance, anti-A
AB - both types of sugar - co-dominant inheritance - neither

13

What is the universal blood donor?

O

14

What is the universal blood recipient?

AB

15

The Rhesus factor, expressed on RBC, is encoded on chromosome ___. Mutations are inherited ___.

1; autosomal recessive

16

What are the two Rhesus phenotypes, the corresponding presence of Rh-D polypeptide on RBC surface, mode of inheritance, and antibodies Rh-D in serum?

Rh negative - Rh-D polypeptide absent - recessive inheritance - antibodies to Rh-D present

Rh positive - Rh-D polypeptide present - dominant inheritance - antibodies to Rh-D absent

17

What are MHC class I and class II and what do they do?

Major histocompatibility complexes; define expression of human lymphocyte antigen (HLA) needed to present antigen to specific T-cells.

18

MHC complexes are encoded on which chromosome?

6p

19

Matching ___ is pivotal for transplants.

HLA

20

The MHC cluster is inherited as a haplotype - what does this mean?

These genes are mapped in close proximity to another another and are thus inherited together; very dense part of the genome, highly polymorphic, many alleles

21

Disregarding crossing over, siblings have a ___ chance of sharing both alleles of the MHC haplotype.

25%

22

Knowing ___ and ___ frequencies in a population allows us to calculate risk.

Genotype; allele

23

What does the Hardy-Weinberg equilibrium do?

Describe the relationship between allelic frequencies and genotype frequencies in a stable population

24

What is the Hardy-Weinberg equilibrium equation?

(p+q)^2 = p^2 + 2pq + q^2; p and q must remain constant, p + q = 1

25

What is the Hardy-Weinberg equilibrium equation for 3 possible alleles?

(p+q+r)^2

26

Disease frequency = ?

q^2

27

How does the Hardy-Weinberg equilibrium change for sex-linked diseases?

Genotype frequency = allele frequency in males

28

What are the 4 conditions necessary for Hardy-Weinberg Equilibrium?

1. Large population (not influenced by chance fluctuations)
2. Random mating (no preference based on phenotype similarities)
3. No mutation (no conversion of P allele to Q allele)
4. No selection (all genotypes are equally capable of mating/producing offspring)

29

Generally, random mating means what 3 things?

1. No stratification (subpopulation exists that remains genetically separate)
2. No assortative mating (choice of mate determined by common trait)
3. No consanguinity

30

What are the three major exceptions to Hardy-Weinberg equilibrium?

1. Gene flow: slow movement of genes between populations
2. Genetic drift: chance changes with the environment favoring a genetically defined subpopulation
3. Founder effect: small population with different allele frequency breaks away from general popualtion

31

What is fitness?

Ability to procreate

32

Reduced fitness occurs in conditions that affect the ability of diseased individuals to ___.

Procreate

33

f (fitness) usually = ___ in dominant disease

34

For a population in equilibrium, the new mutation rate (mu) = ?

sq; s (selection coefficient selection against mutation) = 1-f

35

What is positive selection of heterozygotes?

In a balanced polymorphism, forces exist to remove affected alleles from the population as well as to maintain them. In this situation, equilibrium is affected by a heterozygous advantage favoring viability over homozygotes.

36

What is an example of positive selection of heterozygotes?

Heterozygosity for sickle cell allele offers protection from malaria and beta-thalassemia

37

What are AIMs?

Ancestry Informative Markers - alleles that show large differences among populations of different geographic origins