PCB 4674 Lecture Notes - Lecture 27: Mutation, Gamete, Panspermia

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orchidbeaver616

21 Dec 2016

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Stabilizing selection: that which occurs when individuals with intermediate values of a trait have higher fitness; can result in reduced phenotypic variation in a population and can prevent evolution in the mean value of the trait. Sexual dimorphism: a difference between the phenotypes of females versus males within a species. Sexual selection: a difference, among members of the same sex, between the average mating success of individuals with a particular phenotype versus individuals with other phenotypes. Fecundity: the number of gametes produced by an individual; usually used in reference to the number of eggs produced by a female. Ecotypes of a species: thought to be phenotypically divergent groups in the process of speciation. Secondary contact: when two populations that have diverged in isolation from a common ancestor are reunited geographically. Reproductive isolation: occurs when populations of organisms fail to hybridize regularly in nature, or fail to produce fertile offspring when they do hybridize.

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1) Ants are haplodiploid organisms. This means females are diploid (2n) and males are haploid (n). The gametes produced by both males and females are haploid (n). There is no homologous recombination in males during gamete formation. There is no sex chromosome. In an ant species, it is known that wings formation (F) and setae density (D) are each controlled by a different, simple-Mendelian locus/gene. Individuals which are homozygous recessive for both genes have no wings (f) and no setae (d). Previous experiments also indicated that both loci/genes are on the same chromosome.

a. Design a test cross to map the genetic distance of the genes, by writing the genotype of the tester and its mate. (2 pts) Genotype of tester: Genotype of testerâs mate:

b. In order for the test cross to produce offspring with non-parental phenotypes, the tester has to be of a specific sex. What sex must the tester be? Briefly explain your choice in your own words. (Hint: what is a test cross?) (2 pts) Sex of tester:

c. 100 offspring were produced from a particular test cross. The phenotypic ratio of these offspring is observed to be the following:

Normal wings and setae density40

Wings and setae both absent 47

Normal wings but no setae 4

Normal setae density but no wings 9

Calculate and describe in words the genetic distance between the two loci/genes of interest. Remember to include the unit of measurement (6 pts).

carminecaribou726

1. An animal (called a Box) is diploid, and has 5 types of chromosomes (4 autosomes, 1 pair sex chromosomes). Box sex chromosomes are designated W and Z. Box males are heteromorphic (WZ), and Box females are homomorphic (WW).

Boxes are covered in a thick coat of hair. There is a disease in Box, called hairlessness, that has an inheritance pattern that is W-linked and recessive. The allele used to designate this disease is h. Haired Box are wild-type (allele = h+) and hairless Box are mutant (allele = h). In general (not thinking about Box and hairless) when we say that an inheritance pattern is recessive, we automatically know some things about the genotype of affected/diseased individuals.

A) Is the trait simple, or some other type?

B) Does the presence of one diseased allele cause disease, or are two needed?

C) What other name do we use to describe a heterozygous individual?

In the case of Box and the hairless phenotype, what are all the possible genotypes for a hairless female? What are all the possible genotypes for a hairless male? (You do not need to use complete sentences here)

A heterozygous female is mated with an affected male. Indicate what gametes these two individuals can produce. (You donât need to use complete sentences here)

D) Draw a Punnett square for all the possible offspring that these two Box can create. Place the female gametes across the top of the square, and the male gametes down the left side. Insert a picture of your drawing below.

E) What is the ratio of unaffected to affected female offspring for these parents? For male offspring?

F) Choose one female offspring and one male offspring from the F1 and draw a Punnett Square for a mating between those two individuals (F2). Place the female gametes across the top and the male gametes down the left side. Take a picture of the square and insert it below.

Kindly write a one page summary of the data below.

A crucial assumption underlying most models of sexual selection is that sexual advertisements honestly reflect the phenotypic and/or genetic quality of their bearers (1). Here we show that experimental activation of the immune system is rapidly mirrored in the expression of a carotenoid-based secondary sexual trait in male blackbirds (Turdus merula). This result shows that sexual advertisement honestly signals male health and can be reliably used by conspecifics as a cue of individual quality during intra- and/or intersexual interactions. Male blackbirds exhibit a black plumage with a yellow to orange bill, whereas females are brownish with a brown bill. Recent studies have suggested that bill color is a sexually selected trait in blackbirds (2, 3). For example, resident male blackbirds are more aggressive to mounts with orange bills than to mounts with yellow bills (2). Bill pigmentation might therefore provide a signal used during contests between males (2). In addition, male blackbirds with orange bills are mated with females in better body condition and fledge more offspring than males with yellow bills (3). Overall, these results suggest a role for bill color in sexual selection, possibly as an indicator of male phenotypic quality. Carotenoids are common components of colored signals used in animal communication (4). They are also important in the up-regulation of various aspects of the immune functioning (5) and cellular protection against free radicals (6). This suggests that a trade-off may exist between allocation of carotenoids to sexual signaling versus immune defenses (4). Using an autosampler high-performance liquid chromatographer, we determined the presence of carotenoids deposited in the bill of male blackbirds [see note (S1)] (7). The analysis of the absorption spectrum revealed the presence of - and -carotene, -cryptoxanthin, zeaxanthin, and lutein (Fig. 1A). To investigate whether bill color reflects immune status, we immunized captive male blackbirds with a suspension of sheep red blood cells (SRBC) in both spring 1999 (n 19) and spring 2002 (n 13). A control group (n 15) was injected with a phosphate-buffered saline solution (PBS) for control in 2002. Only the 2002 birds were used as a direct test of the hypothesis that immune activation reduces the expression of the secondary sexual trait, by comparing changes in bill color for SRBC and PBS males. Birds immunized with SRBC in both years (n 32) were used to assess the effect of anti-SRBC immune response on bill color [see note (S2)] (7). The humoral immune response against SRBC was determined 7 days after the challenge with a haemagglutination technique. Birds immunized with SRBC displayed a significant decrease in bill color [repeated measurements analysis of variance, F(1,26) 14.34, P 0.0008; Fig. 1, B, C, and D], which was independent of initial bill color and was not associated with a decrease in body mass (P 0.1). In addition, among immunized males, the likelihood of becoming duller was significantly correlated with the intensity of the anti-SRBC response as determined from the haemagglutination test (logistic regression, Wald 2 5.12, P 0.023, n 32), whereas neither year nor initial bill color entered the logistic regression model (P 0.1). Overall, these results demonstrate the existence of a trade-off between sexual advertisement and immune activation in male blackbirds. This finding has important consequences for both the evolution of secondary sexual traits and the cost of immune function. Assessment of opponent quality during male-male competition or mate quality during female choice based on a dynamic trait, such as bill color, might have evolved if it honestly reflects health status of the individual (1). The activation of the immune system by an infectious process is rapidly mirrored in the color of the bill. Contrary to feather ornaments that are produced during the annual molt, dynamic traits might therefore convey a continual update on male health. Carotenoids, such as astaxanthin, lutein, and -carotene, used for sexual signaling have been shown to enhance in vitro and in vivo antibody production to SRBC (8) and to provide protection against free radicals (6). Our results suggest that the activation of the immune system withdraws carotenoids to enhance immune functioning as well as to deal with free radicals produced during the immune response, at the expense of sexual signaling.

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PCB 4674 Lecture Notes - Lecture 27: Mutation, Gamete, Panspermia

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