BIS 2B Lecture Notes - Lecture 11: Allele Frequency, Quantitative Genetics, Probability Distribution

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fuchsiawhale832

23 Oct 2018

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UC-Davis

Department

Biological Sciences

Course

BIS 2B

Professor

Mark Schwartz; Sharon Strauss

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BIS 2B Lecture Notes - Lecture 10: Punnett Square, Mendelian Inheritance, Gamete

BIS 2B Lecture Notes - Lecture 11: Allele Frequency, Quantitative Genetics, Probability Distribution

BIS 2B Lecture 12: Problems to HW Deviation

Document Summary

Locus 1- where or not color is expressed: expression is dominant, hence all individuals carrying two c alleles show no pigment. Locus 2- what color is expressed; b is dominant and codes for gray; so all bb individuals who also have a c allele are brown. No alleles on y chromosome, but alleles on x chromosome in humans: environmental effects on gene expression. Mendel"s characters were discrete and qualitative (red or white, smooth or wrinkled) For most traits, phenotypes vary continuously over a range- quantitative variation, or continuous. Various locations on chromosomes- can map trait to particular locations on chromosomes. Especially: quantitative genetics and polygenic traits to the rescue! Morgan- lessons from the fruit fly- notion of crossing-over and linkage of traits in organisms. Linkage and non-mendelian assortment: a vexing problem in the early 20th century. The idea arose that you could map how far apart traits were by the crossover frequency.

Related Questions

Question 1

What would be the dimensions of a Punnett square for the cross Hh x hh?

		4 x 4
		2 x 2
		2 x 1
		1 x 1

Question 2

In dogs, the gene for fur color has two alleles. The dominant allele (G) codes for grey and the recessive allele (g) codes for black fur. The female dog is heterozygous. The male dog is homozygous recessive. Figure out the phenotypes and genotypes possible in their puppies by using a Punnett Square. (provide answers on one line with commas between - xx, xx, xx, xx)

Genotypes: , ,

Phenotypes: ,

Question 3

The fundamental Mendelian process which involves the separation of alleles located at the same spot on the chromosome would be called ___.

		segregation
		independent assortment
		continuous variation
		discontinuous variation

Question 4

Using the information given on dominant and recessive traits, state the phenotype for each genotype. Purple flowers are dominant to white flowers in pea plants.

-A.B.C.	PP_____________
-A.B.C.	Pp____________
-A.B.C.	pp_______________

A.	purple flowers
B.	purple flowers
C.	white flowers

Question 5

In dogs, the gene for fur color has two alleles. The dominant allele (G) codes for grey and the recessive allele (g) codes for black fur. The female dog has black fur and the male dog is homozygous dominant. Make a Punnett square to determine the chance of getting each genotype and phenotype below.

-A.B.	Probability of GG:
-A.B.	Probability of Gg:
-A.B.	Probability of gg:
-A.B.	Probability of gray fur:
-A.B.	Probability of black fur:

A.	100
B.	0

Question 6

Using the information given on dominant and recessive traits, state the phenotype for each genotype. Round seeds are dominant to wrinkled seeds in pea plants.

-A.B.C.	RR______________
-A.B.C.	Rr _____________
-A.B.C.	rr ____________

A.	round seeds
B.	wrinkled seeds
C.	round seeds

Question 7

Using the information given on dominant and recessive traits, state the phenotype for each genotype. Hairy knuckles are dominant to non-hairy knuckles in humans.

-A.B.C.	HH_____________
-A.B.C.	Hh ___________
-A.B.C.	hh _________________

A.	non-hairy knuckles
B.	hairy knuckles
C.	hairy knuckles

Question 8

An allele is ___.

		one of the bases in DNA
		an alternate form of a gene
		another term for epistasis
		present only in males and is responsible for sex determination

Question 9

In a cross of a round hybrid pea with a true breeding round parent (Rr x RR), what genotypic proportions would be observed in the offspring?

		Half heterozygous, half homozygous dominant
		Half round, half wrinkled
		All heterozygous
		All round

Question 10

What would be the dimensions of a Punnett Square depicting a dihybrid cross?

		1 x 4
		2 x 4
		4 x 4
		2 x 2

Problem A. You cross two homozygous parents: RRYY (round yellow) and rryy (wrinkled green) to produce an F1 generation. Round seeds are dominant, yellow seeds are dominant. You cross two F1s to produce the F2 generation. In the F2 generation, you find an individual with round yellow seeds. You do a testcross to find out the genotype of this âmysteryâ dominant/dominant phenotype. In the offspring of the cross, you find 1?2 have round yellow seeds and 1?2 have wrinkled yellow seeds.

1. Based on these data what was the genotype of the mystery F2?

Problem B. You carry out a dihybrid cross between a red-flowered rose with long pollen grains (A1A1 LL) and a white-flowered rose with round pollen (A2A2 l l). The flower color gene (A) shows incomplete dominance, and long pollen is completely dominant to round pollen. The genes for these traits are on different chromosomes so assort independently

2. What would be the phenotypes of the F1 generation?

3. What fraction of the F2 generation is expected to have red flowers and long pollen? (As always when traits are independent, what rule can you apply to save time?)

Problem D. In the example of epistasis presented in class, the agouti allele in mice (A) codes for striped hairs and is dominant to the allele for all black hairs (a). A loss-of-function allele for the pigment gene (b) produces no pigment and is recessive to the normal, dominant allele (B). The recessive allele at b masks the effect of the A gene. A dihybrid cross of AABB and aabb is carried out.

5. Name all of the genotypes in the F2 generation that can produce an albino (no pigment) phenotype.

Problem E. A cross is made between homozygous fruit flies that differ for eye color (the st gene) and

body color (the e gene). The F1 double heterozygote is shown below using chromosome notation.

st+ e

--------------------------------------

st e+

st = the recessive allele for scarlet eyes; st+ = the dominant wildtype allele for red eyes e = the recessive allele for ebony body; e+ is the dominant wildtype allele for gray body

6. Are the chromosomes shown in the genotype above in cis or trans configuration?

7. Based on this notation, what were the genotypes and phenotypes of the two parents of the F1? (Think carefully here...)

8. With what phenotype would you cross this F1 to measure recombination frequency?

cyansnail823

1. If an individual has a genotype of Bb, what types of gametes (sperm/egg) could they produce?
A) B
B) b
C) B or b
D) Bb, BB, bb
E) Bb

2. Which of the following statements is true about phenotypic plasticity, i.e., phenotype variation that is the result of genotype by environment interactions?
A. Phenotypic plasticity is only favored when the parental environment is a good predictor of the offspring environment
B. Since the trait expression of a genotype varies across environments, it cannot respond to selection
C. A variable environment is required for phenotypic plasticity to be selected for
D. A single trait can only ever be plastic or non-plastic within a species
E. Phenotypic plasticity can only occur within a single generation, never across generations

3. With large numbers of genes contributing to variation for a phenotypic trait (e.g. height in humans), the population approaches what kind of distribution for that trait?
A. Mendelian
B. Exponential
C. Binomial
D. Normal
E. Continuous

4. A classic example of phenotypic plasticity is caste determination in social insects. Whether a female ant becomes a worker, soldier, or queen is determined by the food she is fed. Would you say this this an example of G, E, or GxE?

5. In an infinite population, the frequency of the A allele is 0.3 and the frequency of the a allele is 0.7. What is the frequency of heterozygotes?
A. .10
B. .21
C. .30
D. .42
E. .70

6. Blue eyes are a recessive trait caused by an autosomal allele. If there are 180 people with blue eyes in a population of 500 people, what is the frequency of the brown-eye allele? (Assume HWE)
A. .36
B. .40
C. .50
D. .60
E. .64

7. Imagine flower color in diploid roses is determined by a single gene with two alleles, white and red, which are co-dominant so that heterozygotes are pink. Frank is colorblind and can only discriminate between white and colored roses, and knows that his population has 18 white roses and 182 non-white roses. How many of Frankâs roses are pink? (Assume HWE.)
A. 18
B. 21
C. 42
D. 84
âE. 100

8. Imagine flower color in diploid roses is determined by a single gene with two alleles, white and red, which are co-dominant. If Eva's population has 250 white roses, 500 pink roses, and 250 red roses, what is true about this population?

A. It is not in Hardy-Weinberg equilibrium
B. It is under balancing selection
C. It is connected to another population by migration
D. It is in Hardy-Weinberg equilibrium
ââE. White is a recessive lethal

9. 9% of a population is unable to taste the compound PTC, which is a recessive trait. Assuming HWE, if two carriers of the non-tasting allele had a baby what is the probability that it would be unable to taste PTC?
A. 0.09
B. 0.25
C. 0.30
D. 0.50
E. 0.70

10. (Adapted from: Christensen, A. C. (2000). Cats as an aid to teaching genetics. Genetics, 155(3), 999-1004.) ss cats have no white fur, Ss cats generally have <50% white fur, and SS cats generally have >50% white fur (cats who are 100% white are scored as dominant white and can't be scored for piebald spotting). The S allele is incompletely dominant, but variably expressed, so there is a more-or-less continuous gradient of white pigmentation in populations. You and your friends score all non-white cats up for adoption: http://www.adoptapet.com/cat-adoption/search/50/miles/48824 and find there are 160 with >50% white fur, 350 with <50% white fur, and 490 with no white fur. Which of the following statements is definitely true:

A. The population is in Hardy-Weinberg equilibrium
B. The population is not in Hardy-Weinberg equilibrium
C. There is selection acting on the population
D. It is impossible to know if the population is in Hardy-Weinberg equilibrium
E. Fur color is not a heritable trait and therefore cannot evolve

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BIS 2B Lecture Notes - Lecture 11: Allele Frequency, Quantitative Genetics, Probability Distribution

BIS 2B Lecture Notes - Lecture 10: Punnett Square, Mendelian Inheritance, Gamete

BIS 2B Lecture Notes - Lecture 11: Allele Frequency, Quantitative Genetics, Probability Distribution

BIS 2B Lecture 12: Problems to HW Deviation

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