Top4-Ch5-P105-117Reverse

Question 21

ABO bloodgroup contains three alleles

• IA for A antigen
• IB for B antigen
• i for O antigen
• A and B are codominant, both are dominant over O

Remember: An antigen is any substance that causes your immune system to produce antibodies against it.

Answer 21

Explain ABO bloodgroup

Question 22

genes at different loci contribute to the determination of a single phenotypic characteristic. Interactions among genes at three, four or more loci are common as well as two which will be focussed on .

See peppers example below

Answer 22

What is gene interaction?

Question 23

one gene masks (hides) the effect of another gene at a different locus.

Similar to dominance but between genes at different loci

Answer 23

Gene interaction with epistasis is?

Question 24

in epistasis the gene that does the masking

Epistatic genes may be recessive or dominant in their effects.

Answer 24

What is an epistatic gene?

Question 25

in epistasis the gene whose effect is masked.

Epistatic genes may be recessive or dominant in their effects.

Answer 25

What is a hypostatic gene

Question 26

No ABO blood groups made because no substrate produced

See picture below on P108. How it works is that dominant H allele (top half) encodes enzyme that converts intermediate compound into compound H. A and B antigen produce terminal blood sugar on end which determines the blood type. O on top has no terminal sugar on compound H to produce O but the Bombay phenotype also has no terminal blood sugar but it didn’t even have compond H, but just the intermediate compound

Answer 26

See recessive epistasis in Bombay phenotype for ABO blood groups

Question 27

inhibits the expression of an allele at a different locus.

Answer 27

In recessive epistasis the presence of two recessive alleles (homozygous phenotype) does what?

Question 28

Only a single copy

Answer 28

In dominant epistasis how many copies of an allele is required to inhibit the expression of the allele at a different locus.

Question 29

two recessive alleles at either of two loci are capable of suppressing a phenotype which is illustrated by albinism in snails.

Answer 29

What is duplicate recessive epistasis?

Question 30

Answer 30

See chart of phentypic ratios due to gene interaction on p111 and in answers.

Question 31

one mutant allele is ‘repaired’ by a mutation in another allele on another chromosome.

or

the reappearance of wild-type characteristics in a cell or organism that has had two distinct mutations on the same chromosome. 2. Two normal versions of two different mutant genes on different chromosomes affecting the same phenotype which, when inherited together, results in the wild-type phenotype despite the presence of mutant copies of the gene.

Wild type (or wildtype abbreviated wt) refers to the phenotype of the typical form of a species as it occurs in nature

Answer 31

Complementation occurs when

Question 32

wild type

Answer 32

Double mutant exhibit a ____ _____ phenotype

Question 33

alleles are at the same locus

Answer 33

Complementation does not occur when

Question 34

denoting an autosomal trait that is expressed differently, either in frequency or degree, in males and females, as for example, male-pattern baldness.

or textbook: is determined by autosomal genes and are inherited according to Mendel’s principles, but they are expressed differently in males and females.

Answer 34

Sex influenced characteristics is what

Question 35

In male goats the beard is expressed with the B^b allele which is dominant in males but it is recessive in females. So, for male goat to have a beard it just needs one B^b allele but for female she must have two B^b to have a beard.

Answer 35

Explain how beards on goats is an autosomal sex influenced trait?

Question 36

It is an extreme form of sex influenced inheritance and is encoded by autosomal genes that are expressed in only one sex; the trait has zero penetrance in the other sex.

Answer 36

What is a sex limited characteristic?

Question 37

In chickens there is cock feathering which is an autosomal recessive trait that is sex limited to males. Because the trait is autosomal the genotypes of males and females are the same but the phenotypes differ in males and females. So males must have both cock feathering alleles to have cock feathering while a female never gets cock feathering even if she has two cock feathering alleles.

Answer 37

Explain cock feathering in domestic chickens and how this is a sex limited characteristic.

Question 38

Autosomally inherited, males need one allele to become bald, females need two alleles to become bald (expressed weakly in females as well)

Answer 38

Explain sex influenced baldness?

Question 39

one

Answer 39

Sex-limited traits only occur in ___ sex

Question 40

sex influenced characteristics are encoded by autosomal genes that are more readily expressed in one sex. Sex limited characteristics are encoded by autosomal genes whose expression is limited to one sex.

Answer 40

Explain difference between sex influenced characteristics and sex limited characteristics.

Question 41

Many types of precocious puberty (pp) but male limited precocious puberty is genetic. Pp for males is dominate for precocious puberty but not for females. See graph below where females never get it but males do.

Answer 41

Explain male limited precocious puberty