BIOL1003 Study Guide - Final Guide: Population Genetics, Genotype Frequency, Allele Frequency

105 views3 pages

goldraven829

16 May 2018

School

Department

Course

Professor

For unlimited access to Study Guides, a Grade+ subscription is required.

Population Genetics

Probabilities

In a cross between pea plants that are heterozygous for seed colour (Yy), what is the probability the

offspring will be heterozygous?

• p(Yy) = 0.5 x 0.5 = 0.25

• p(yY) = 0.5 x 0.5 = 0.25

• P(Yy or yY) = 0.25 + 0.25 = 0.5

Plants homozygous for round, yellow seeds (RRYY) were crossed with plants homozygous for

wrinkled green seeds (rryy).

• The resulting F1 dihybrid progeny (RrYy) had round, yellow seeds – the dominant

phenotypes.

If these two characters segregate independently, what is the probability of the F2 progeny having

green, wrinkled seeds?

• 9 (Round Yellow): 3 (Round Green): 3 (Wrinkled Yellow): 1 (Wrinkled Green).

• P(yy) = 0.5 x 0.5 = 0.25

• P(rr) = 0.5 x 0.5 = 0.25

• Therefore, probability of yyrr = p(yy) x p(rr) = 0.25 x 0.25 = 0.0625

• Selection happens at the level of the individual but evolution occurs at the level of the

population.

• Population – localised group of freely interbreeding organisms that belong to the same

species.

• Gene flow – the movement of genes between populations as a result of migration or

gamete dispersal.

• Gene pool – the sum total of all genes and their alleles present in a population.

• Eg: Snapdragons: incomplete dominance → RR, RW, WW.

• Genotype frequency: 0.26 (RR): 0.50 (RW): 0.24 (WW).

• p = frequency of dominant allele.

• q = frequency of recessive allele.

• p + q = 1

The Hardy Weinberg Law

• The genotype frequency of a given population is determined by the allelic frequency of the

previous generation (not by the genotype frequency).

Genotype

Genotype Frequency

2pq

• p2 + 2pq + q2 = 1.0

• A population is only in HW equilibrium if these gene frequencies are met.

• Assumptions behind H-W Law:

1. Population is large – the smaller the population, the more likely it is that allele

frequencies will fluctuate by chance from one generation to the next.

2. No migration or gene flow – by moving alleles into or out of populations, gene flow can

alter allele frequencies.

3. No mutations – the gene pool is modified if mutations alter alleles or if entire genes are

deleted or duplicated.

4. Random mating – if individuals tend to mate within a subset of the population, random

mixing of gametes does not occur, and genotype frequencies change.

5. No natural selection – differences in the survival and reproductive success of individuals

carrying different genotypes can alter allele frequencies.

find more resources at oneclass.com

Unlock document

This preview shows page 1 of the document.
Unlock all 3 pages and 3 million more documents.

Already have an account? Log in

Document Summary

Plants homozygous for round, yellow seeds (rryy) were crossed with plants homozygous for wrinkled green seeds (rryy): the resulting f1 dihybrid progeny (rryy) had round, yellow seeds the dominant phenotypes. The hardy weinberg law: the genotype frequency of a given population is determined by the allelic frequency of the previous generation (not by the genotype frequency). aa q2. Genotype frequency: p2 + 2pq + q2 = 1. 0, a population is only in hw equilibrium if these gene frequencies are met, assumptions behind h-w law: Evolution and genetics: evolution is a change in the frequency of alleles in a population, things that result in change in allelic frequency over time: Now a large proportion of the population are colour blind: occurs when a new colony is started by a few members of the original population, changes allelic frequencies eg: makes genetic diseases more common.

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

1. Characters that show a continuous range of variation, such as height and eye color, usually are controlled:

a.	by a single gene with two alleles that are codominant.

b.	by many genes with an additive effect.

c.	by epistatic interactions between two genes.

d.	mainly by the environment, with only a small genetic component.

2. In humans, red-green colorblindness is inherited as a sex-linked recessive trait. In order for a woman to be red-green colorblind, which of the following statements must be true.

a.	Her mother must be red-green colorblind.

b.	All of her brothers must be red-green colorblind.

c.	Her father must be red-green colorblind.

d.	All of the above statements must be true if a woman is red-green colorblind.

3. The x-ray crystallography data collected by Rosalind Franklin suggested to Watson and Crick that the:

a.	structure of DNA is a double helix.

b.	two strands of the DNA molecule are joined by hydrogen bonds between the bases.

c.	four bases within DNA pair in a specific way.

d.	two strands of the DNA molecule are joined by covalent bonds between the bases.

4. In the genetic code, _________ one amino acid.

a.	one nucleotide specifies

b.	two nucleotides specify

c.	three nucleotides specify

d.	four nucleotides specify

5. During Meiosis I, a homologous pair of chromosomes may not separate, resulting in daughter cells that have extra chromosomes or are missing chromosomes. This can lead to genetic disorders, including Down Syndrome. This phenomenon is called:

a.	independent assortment.

b.	nondisjunction.

c.	segregation.

d.	crossing over.

6. You are a human geneticist studying the incidence of retinitis pigmentosa in the residents of Tristan de Cunha, a group of small islands in the middle of the southern Atlantic Ocean. The allele for retinitis pigmentosa, which causes a form of blindness, is inherited as an autosomal recessive. You have determined that the frequency of this allele (r) in the population is 0.4 (40%). Using the principles of the Hardy-Weinberg rule, you would estimate the frequency of individuals who are heterozygous for this allele (Rr) in the population to be:

a.	0.16 (16%)

b.	0.24 (24%)

c.	0.36 (36%)

d.	0.48 (48%)

7. Natural selection acts at the level of the:

a.	phenotype.

gene.

c.	population.

d.	nucleotide.

8. You are working with pea plants, trying to recreate the experiments that Mendel performed. You are doing a dihybrid cross with a plant that is heterozygous for both seed shape and seed color, with the genotype RrYy. Which allelic combinations would you expect to find in the gametes produced by this plant?

a.	This plant would produce only RY and ry gametes.

b.	This plant would produce only RrYy gametes.

c.	This plant would produce RY, Ry, rY, and ry gametes.

d.	You cannot determine which gametes this plant can produce without knowing the genotypes of its parents.

9. Biochemist Erwin Chargaff found that in DNA there is a special relationship between the four bases that we now call Chargaff's rule. His observation was that, in an organism's genome the:

a.	percentage of A nucleotides = the percentage of T nucleotides, and the percentage of C nucleotides = the percentage of G nucleotides.

b.	four bases all occur in an equal frequency (25%) within each organism.

c.	percentage of A nucleotides = the percentage of G nucleotides, and the percentage of C nucleotides = the percentage of T nucleotides.

d.	genetic material is composed of proteins, not DNA.

10. During DNA replication:

a.	each strand of the double helix acts as a template for the synthesis of a new strand.

b.	the enzyme DNA polymerase adds nucleotides to the strand being synthesized.

c.	the bases A,C,G and T are required.

d.	All of the above are true of DNA replication.

11. During translation, amino acids are joined by peptide bonds to make polypeptides. The formation of these peptide bonds is catalyzed by:

12. If an allele (R) at a gene with two alleles shows complete dominance, individuals with the genotypes ______ will have the same phenotype.

a.	RR and rr.

RR and Rr

Rr and rr

d.	Each of the three possible genotypes will have a different phenotype.

mauvefox570

BIOL1003 Study Guide - Final Guide: Population Genetics, Genotype Frequency, Allele Frequency

Document Summary

Get access

Related Questions