BIO 2133 Lecture Notes - Lecture 3: Intron, Chromosome, Nondisjunction

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16 Mar 2017

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Mutations in regulatory regions and introns: do(cid:374)"t affe(cid:272)t protei(cid:374) itself, (cid:271)ut affe(cid:272)ts the rate a(cid:374)d if a ge(cid:374)e will (cid:271)e tra(cid:374)s(cid:272)ri(cid:271)ed. The mutant version stays on and expresses lactase. The graph would be between the two but it would most likely remain above threshold, may still go slightly below but would only be mildly intolerant. Female jaw line larger breasts: (cid:374)o ada(cid:373)"s apple, high pitched voice, vagina, wider hips, dat ass, no facial hair, behavior, generally shorter, smaller stature, makeup and hair, smell better, pregnancy the way they stand. Male testes: penis, herculean physique, deeper voice, more body hair, broad shoulders, higher testosterone levels, quick to anger, bigger hands and feet, deeper voice lower body fat facial hair. Not necessarily good indications of actually being male or female. All phe(cid:374)ot(cid:455)pes, (cid:271)ut does(cid:374)"t (cid:373)ea(cid:374) the(cid:455) i(cid:374)di(cid:272)ate (cid:373)ale or fe(cid:373)ale (cid:272)o(cid:373)pletel(cid:455) Oft (cid:373)arkers: (cid:373)a(cid:455) (cid:271)e i(cid:374)di(cid:272)atio(cid:374)s of ge(cid:374)ot(cid:455)pes, (cid:271)ut do(cid:374)"t tell the whole stor(cid:455)

Related Questions

Homozygous recessive loss of function mutations in any one of 4 different genes in C. elegans worms (genes A, B, C, or D) results in female worms that don't form proper egg-laying structures, called vulvas, as shown in Lines 2-5 of the data table below. In vulvaless females, the fertilized eggs hatch and baby worms develop inside the mother, killing her in the process.

	genotype	phenotype
1	AA BB CC DD (wild type)	normal vulva
2	aa BB CC DD	No vulva
3	AA bb CC DD	no vulva
4	AA BB cc DD	no vulva
5	AA BB CC dd	no vulva

You would like to figure out the order in which these genes act during the creation of the vulva (you cannot assume it will be A--->B--->C--->D as the gene names are arbitrary). Your friend tells you to perform epistasis analysis by making double mutants between the different homozygous recessive mutants and analyzing the phenotype of the double mutant. For example, she asks you to examine the phenotype of aabbCCDD (double mutant of genes A and B) and compare this to the single mutants to figure out whether gene A acts earlier than gene B, or vice versa. You know this won't work. Why not? Pick the ONE BEST choice:

a. The phenotype of the single mutant is already pretty severe. The double mutant will most likely be dead, therefore epistasis analysis won't be possible.

b. Each of the single mutants (aaBBCCDD) and (AAbbCCDD) has the same mutant phenotype i.e., no vulva. Epistasis analysis between any 2 genes is only possible when the mutant phenotypes for each gene is different.

c. Epistasis analysis involves making triple mutants (such as aabbccDD) in order to learn something about how the genes are ordered.

d. Epistasis analysis can never be carried out with null loss of function mutations. The mutations being analyzed all have to be dominant gain of function alleles.

To address your concern, you first generate overactive alleles of either gene A (denoted as A*) or gene B (denoted as B*). As shown in lines 6-7 of the table below, C. elegans that have one of these overactive alleles produce multiple vulvas.

	Genotype	Phenotype
6	A*A BB CC DD	multiple vulvas
7	AA B*B CC DD	multiple vulvas

To find out the order in which these genes act, you combine the overactive alleles with different loss of function alleles and observe the phenotype in double mutants (see Lines 8-11).

	Genotype	Phenotype
8	A*A bb CC DD	multiple vulvas
9	A*A BB cc DD	multiple vulvas
10	A*A BB CC dd	no vulva
11	AA B*B cc DD	multiple vulvas

Based on the data in the table, what is the order in which these 4 genes normally act in wild-type C. elegans in order to produce a wild-type/normal vulva?

a. A----> B----->C----->D ---> Vulva

b. D----> B----->C----->A----> Vulva

c. B----> C----->A----->D----> Vulva

d. C----> B----->A----->D----> Vulva

e. C----> B----->D----->A----> Vulva

f. don't have enough data to make any conclusions

Based on the vulva formation phenotype of the double mutants, which of the following statement(s) accurately describes the genetic interactions between the A* allele and alleles of other genes affecting vulva formation? Pick ALL that apply:

a. The A* allele is epistatic to homozygous recessive loss of function mutations in gene B

b. A homozygous recessive loss of function mutation in gene B is epistatic to the A* allele

c. Homozygous recessive loss of function mutation in gene D is epistatic to the A* allele

d. The A* allele is epistatic to homozygous recessive loss of function mutation in gene D

e. The A* allele enhances the homozygous recessive loss of function mutation in gene D

BIO 2133 Lecture Notes - Lecture 3: Intron, Chromosome, Nondisjunction

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