Lecture 6: Extensions to Mendels rules

Question 1

Genetic linkage

Answer 1

The tendency of alleles that are close together on a chromosome to be inherited together during meiosis. Linked genes will segregate together and not obey mendels 2nd law

Question 2

Linkage disequalibrium

Answer 2

Non random association of alleles at different loci.
Loci are said to be in linkage disequilibrium when the frequency of association of their alleles is different than what would be expected if the loci were separating independtly

Question 3

Complex inheritance

Answer 3

Genetic traits usually dont follow simple inheritance pattern.

Question 4

Polygenic traits

Answer 4

Traits that are produced by the interplay of many sets of genes

Question 5

Is it possible for a recessive phenotype to be displayed given a dominant genotype

Answer 5

Yes, in the case of hermaphrodite snails, there is a maternal effect that can override genotype.
Mother produces a substance that causes the phenotype of her offspring to reflect her genotype, regardless of the offsprings actual genotype

Question 6

One of the earliest and most important events during embryological development is

Answer 6

Establishing polarity

Question 7

Medels traits exhibit what type of dominance

Answer 7

Complete dominance

Question 8

Complete dominance

Answer 8

Phenotype of the heterozygote is the same as the phenotype of one of the homozygotes

Question 9

Incomplete dominance

Answer 9

Phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes

Question 10

Codominance

Answer 10

Phenotype of heterozygote includes phenotypes of both homozygotes

Question 11

Penetrance

Answer 11

The percentage of individuals having a particular genotype that express the expected phenotype

Question 12

Expressivity

Answer 12

The degree to which the character is expressed

Question 13

Complete penetrance

Answer 13

Everyone who inherits the disease causing allele has same symptoms

Question 14

Incomplete penetrance

Answer 14

Some individuals do not express the phenotype even though they inherit the alleles

Question 15

Variable expression

Answer 15

Symptoms vary in intensity in different people

-for example, two extra digits vs three extra digits in polydactyly

Question 16

Lethal allele and affects

Answer 16

Causes death at an early stage of development, some some genotypes do not appear among the progeny
-Affects the mendelian genotypic and phenotypic rates in progeny

Question 17

Factors that affect penetrance

Answer 17

Sex and the parent who contributed the mutation affect the risk of expression of the phenotype

Question 18

Type O

Answer 18

Can donate to any recipienct

Question 19

Type AB

Answer 19

Can receive from any donor

Question 20

Type A genotype

Answer 20

AO

AA

Question 21

Type B genotype

Answer 21

BO

BB

Question 22

Type AB genotype

Answer 22

AB

Question 23

Type O genotype

Answer 23

OO

Question 24

Gene interaction

Answer 24

Effects of gene at one locus depend on the presence og genes at another locus

• Gene interaction with epistasis- one gene masks the effect of another
• Gene interaction can produce novel genotypes

Question 25

Recessive epistasis

Answer 25

Genotypes at both the H locus and the ABO locus determine the ABO blood type

Question 26

Bombay phenotype

Answer 26

People with homozygous recessive hh genotype fail to convert the intermediate into H.
Blood type O can result from the absence of a terminal sugar on compound H, or from the absence of compound H.