Gene Interactions, Genetic Linkage, Sex-Linked Traits

Question 1

Gene Interactions

Answer 1

Participation of 2 or more different genes in production of 1 phenotypic character (qualitative trait)

Question 2

Reciprocal Interaction

Answer 2

Interaction without change of cleavage ratio

Trait is present in more forms (phenotype); each of them encoded by 1 combination of parent alleles of genes

Question 3

Dominant Epistasis

Answer 3

Dominant allele of 1 gene suppresses expression of dominant allele of second gene
12:3:1

Question 4

Recessive Epistasis

Answer 4

Recessive homozygous constitution of 1 gene suppresses expression of dominant allele of 2nd gene
9:4:3

Question 5

Complementarity

Answer 5

Dominant allele of 2 or more genes cooperate in realisation of phenotype
Trait is expressed only if at least 1 dominant allele of both genes is present at the same time
9:7

Question 6

Compensation

Answer 6

Function of dominant alleles of 2 different genes is contradictory, their phenotype effects exclude each other
10:3:3

Question 7

Inhibition

Answer 7

Dominant allele of inhibitor gene suppresses the manifestation of dominant allele of other gene
But inhibitor gene itself HAS NO EFFECT on the phenotype
13:3

Question 8

Duplicity (Multiplicity)

Answer 8

In genes with the same effect on phenotype
Intensity of effect depends on if effects of genes cumulate or not & if there is relationship of dominance between alleles of particular gene

Question 9

Duplicity noncumulative with dominance

Answer 9

There is no cumulation of dominant alleles

15:1

Question 10

Duplicity cumulative with dominance

Answer 10

Intensity is amplified by the number of dominant alleles

9:6:1

Question 11

Duplicity cumulative without dominance

Answer 11

Intensity depends on total number of active alleles

1:4:6:4:1

Question 12

Sex-linked traits

Answer 12

Genes are located on gonosomes

Question 13

Complete sex-linked

Answer 13

Genes are located on heterologous regions of sex chromosome (crossing over is possible)

Question 14

Incomplete sex-linked

Answer 14

Genes are located on homologous (pseudoautosomal) regions of sex chromosome (crossing-over is possible, but often blocked)

Question 15

Complete sex-linked

Gene is located on gonosome Y

Answer 15

Holandric inheritance
Trait is inherited from father to son
Hair in ears

Question 16

Complete sex-linked

Answer 16

Gene is located on gonosome X

hemophilia or daltonism in human, color of eyes in fruit fly

Question 17

Complete sex-linked
Gonosome X
Uniformity of phenotype in F1 generation

Answer 17

If dominant allele is on X chromosome in FEMALE

Question 18

Complete sex-linked
Gonosome X
Cross inheritance

Answer 18

If dominant allele is on X chromosome in MALE

Question 19

Sex-Limited Traits

Answer 19

Genes are located on autosome of both sex

Trait is expressed only in 1 sex because of anatomy

Question 20

Example of sex-limited traits

Answer 20

Cryptorchism in male = absence of 1 or both testes in scrotum

Question 21

Sex-controlled traits

Answer 21

Genes are located on autosome of both sex
Trait is expressed in 1 sex
Phenotype of dominant homozygote & heterozygote is controlled by sex hormones

Question 22

Example of sex-controlled traits

Answer 22

Secondary sex traits = beard in man, size of fins in fish

Question 23

Sex-influenced traits

Answer 23

Genes are located on autosome of both sex
Trait is expressed in both sex
Phenotype of heterozygote is influenced with sex of carrier - it is due to the presence of male or female sex hormones

Question 24

Example of sex-influenced traits

Answer 24

Color of ayrshir cattle, hairlessness in man

Question 25

Genetic Linkage

Answer 25

2 or more genes are located on single chromosome & are genetically linked

Question 26

Morgan'sPrinciples Laws

Answer 26

1. Genes are located on 1 chromosome linearly running subsequently 2. Number of linkage groups equals to number of pairs of homologous chromosomes

Question 27

Centimorgan

Answer 27

Unit of genetic distance of genes on chromosome | Comonly called "map unit" or locus map unit

Question 28

Power of linkage

Answer 28

Probability of crossing-over between alleles of different genes that are in linkage

Question 29

Complete linkage

Answer 29

Small distance between genes Strong linkage Small probability of crossing over

Question 30

Incomplete linkage

Answer 30

Large distance between genes Weak linkage Large probability of crossing over

Question 31

Test crossing

Answer 31

Used to find frequency of genotypes according to phenotype ratio in offspring

Question 32

3-point cross

Answer 32

Interactions between 3 genes are observed | Is used for setting chromosome map = order of genes and their distance in centimorgans