BME 80H Lecture Notes - Lecture 13: Sex Linkage, Zygosity, Reciprocal Cross

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tealantelope800

11 Jun 2018

School

UCSC

Department

Biomolecular Engineering

Course

BME 80H

Professor

Wendy Rothwell

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13th lecture

example mapping problem (test cross)

screen shot

10/100 x 100 = 10mu

c. What would be the map units if there were no recombinants

apparent in the gametes? (the answer is not 0)

-if you looked at 1,000 gametes the answer would be

<1/1000 x 100 = <0.1%

d. 50 map units represent no linkage between the genes.

Why?

-this would be the same result as if the alleles assorted

independently

IV. Violating Mendel's Law of Segregation

A. Sex-Linkage: Genes located on the X chromosome (figure 4.9, 4.10)

XX = female (homologous chromosomes)

XY = male (not homologous chromosomes)

-males with only one X chromosome cannot have

equally segregating alleles for x-linked genes

Males, having only one X chromosome, cannot be homozygous or

heterozygous for genes on the X. They are instead termed

"hemizygous" for X-linked alleles.

1. Expectations based on Mendel's work

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Document Summary

13th lecture example mapping problem (test cross) screen shot. 10/100 x 100 = 10mu: what would be the map units if there were no recombinants apparent in the gametes? (the answer is not 0) If you looked at 1,000 gametes the answer would be. <1/1000 x 100 = <0. 1: 50 map units represent no linkage between the genes. This would be the same result as if the alleles assorted independently. Violating mendel"s law of segregation: sex-linkage: genes located on the x chromosome (figure 4. 9, 4. 10) Males with only one x chromosome cannot have equally segregating alleles for x-linked genes. Males, having only one x chromosome, cannot be homozygous or heterozygous for genes on the x. hemizygous for x-linked alleles: expectations based on mendel"s work, for a cross of 2 pure breeding lines, one expressing the dominant trait and one expressing the recessive trait, the results are as follows:

Related Questions

ANSWER ALL the PARTS you can

PART1 Alleles are considered linked if recombination is less than 50% in:

a) a Px P Fl cross

b) an F1 x F1F2 cross

c) an F2 x F2F3 cross

d) an Fl x homozygous recessive cross

e) any F2 progeny x homozygous recessive cross 1.

PART2 If two loci A/a B/b are 9 map units apart, and an Ab/aB individual is testcrossed,

a) There will be 9% AB individuals

b)There will be 91% Ab individuals

c) There will be 4.5% ab individuals

d) There will be 91% recombination individuals

If two genes a and b show 50% recombination genes a and c show 35% recombination, and genes b and show 32% recombination, then

a) Genes a and b are on the same chromosome, and 50 m.u. apart

b) Genes a and b are on different chromosomes

c)Genes a and b are on the same chromosome, and 67 map units apart

d) One cannot tell if genes a and b are on the same or different chromosomes from given data.

PART4 If two genes a and b are 8.3 m.u. a part, one expects to find

a) 8.3% recombinant gametes from a double heterozygous parent

b) 91.7% recombinant gametes from a double heterozygous parent

c) A chiasma between the a and b loci in 8.3% of the meiosis

d) A chiasma between the a and b loci in 91.7% of the meiosis.

PART5 Map distances are most accurate when genes are closely linked because as genes become further apart,

a) They always show independent assortment

b)The chance of multiple crossovers increases

c) They no longer recombine

d) There is chiasma interference

PART6 In a three-point testcross, the most frequent classes of progeny were ABc and abC. The less frequent classes of progeny were AbC and aBc. Which gene is in the middle?

a) Aa

b) B/b

c)C/c

d) It is not possible to tell from just these data

PART7 In a three-point testcross with 100 progeny, there were 16 single crossovers between genes A and B, 29 single crossovers between genes B and C, and 4 double crossovers. The correct gene order was determined to be A-B-C. What is the map distance between A and B?

a) 20%

b) 0.2 m.u

c) 20 m.u.

d) 16 m.u.

e) 29 m.u.

f) 16%

What is a genome? What is a genome made of? Describe the bacterial genome. How do bacteria reproduce? What is binary fission? Distinguish between a chromosome and chromatin. Where are chromosomes located in eukaryotic cells? What is the chromosome made of? What is a centromere? What is the centromere's role? What are sister chromatids and how do they arise? Distinguish between somatic cells and germ (gametes) cells. Describe the cell cycle. What are the different phases? What occurs during S phase? What is interphase? How is the cell cycle controlled?

Describe mitosis. What are the phases of mitosis? What occurs in each of the phases of mitosis? What is cytokinesis? How does this differ between plant and animal cells? What is a kinetochore? Where does it form? What is its role? What is the role of microtubules in mitosis? What is a centriole and what is it composed of? What is a centrosome and what is its role in mitosis? What is the metaphase plate and why is this important? What is the mitotic spindle, its role and its makeup? What defines a diploid cell? How many copies of each chromosome is in a diploid cell? What about a haploid cell? Why do the daughter cells of mitosis always have the same complement of chromosomes?

Describe meiosis. What are the phases of meiosis? What occurs in each of the phases of meiosis? Distinguish between meiosis I and meiosis II and describe how each of these processes compare to mitosis. Why do animal cells undergo meiosis? What is a gamete? What is a zygote? What are recombination, crossing-over, and chiasma? When and why does this occur? What is meant by 'homologous pair of chromosomes'? Why don't the daughter cells of meiosis have the same genetic makeup? What controls the segregation of chromosomes into the gametes?

What are genetic characters? What are genetic traits? What is an allele? What is a locus? How many alleles at each locus would a human cell have and why? Distinguish between genotype and phenotype. What is meant by a dominant gene? What is meant by a recessive gene? How do these differ? What is the genotype of a homozygous dominant organism? What is its phenotype? What is the genotype of a homozygous recessive organism? What is its phenotype? What is the genotype of a heterozygous organism? What is its phenotype? What is a genetic cross? Distinguish between the P, F1, and F2 generations. What is a true-breeding line? What is the genotype and phenotype of a cross between homozygous dominant and homozygous recessive parents? If the F1 progeny are crossed, what would be the genotype and phenotype of the F2 generation? What would be the phenotypic ratio? What would be the genotypic ratio? Be ready to generate Punnet square tests or probability analyses of crosses involving more than one genetic locus. Describe a dihybrid cross where two alleles are homozygous dominant in one parent and homozygous recessive in the other. What would be the phenotypic ratio of the F2 generation from this dihybrid cross? What is meant by independent assortment? Be prepared to calculate probabilities resulting from different crosses.

Distinguish between complete and incomplete dominance. How would incomplete dominance alter the results of a hybrid cross? What would the resulting F2 generation phenotype and genotype ratios be? What is codominance? How does this affect the results of crosses? Be prepared to determine likely blood types of parents based on the blood types of their offspring. What is a polygenic trait? What is a carrier state for a genetic disease? What is meant by linked genes? How does this affect expected outcomes of genetic crosses? How is gene linkage used for chromosomal mapping? Distinguish between autosomes and sex chromosomes. What sex chromosomes are found in women? What sex chromosomes are found in men? What are sex-linked traits? Be prepared to give the results of crosses that involve sex-linked recessive traits. What is the process of nondisjunction? What are the likely results? Why is this important? What is a Barr body? Recognize the genetic abnormality of Downs Syndrome, Turner's Syndrome, and Klinefelter's Syndrome.

pucewallaby221

Question 1 Select one answer.

Two heterozygous individuals are crossed. What percentage oftheir offspring will be heterozygous?

a)50%

b)75%

c)100%

d)25%

Question 2 Select one answer.

In peas purple is dominant to white for flower color. A purpleflower is crossed with a white flower. All the offspring (over 100plants) produce purple flowers. What is the genotype of the purpleflower?

a)pp

b)Either PP or Pp

c)PP

d)Pp

Question 3 Select one answer.

A heterozygous germ cell undergoes meiosis. The gametes will

a)only have the recessive allele

b)only have the dominant allele

c)either have the dominant or the recessive allele

d)have both the dominant or the recessive allele

Question 4 Select one answer.

Sex-linked disorders

a)are always dominant are

b)always recessive

c)can be either dominant or recessive

d)are neither dominant nor recessive

Question 5 Select one answer.

A nucleus is built around chromatids which have separated. Thisoccurs during which stage of meiosis?

a)Telophase II

b)Metaphase I

c)Metaphase II

d)Telophase I

Question 6 Select one answer.

The condition of having anincorrect number of chromosomes is called ____________.

a)nondisjunction

b)aneuploidy

c)epistatis

d)trisomy

Question 7 Select oneanswer.

In humans females are

a)XY

b)YY

c)none of these

d)XX

Question 8 Select oneanswer.

Autosomal means that the gene isfound on the

a)X chromosomes

b)the Y chromosome

c)either the X or the Ychromosome

d)neither on the X nor theY

Question 9 Select oneanswer.

What organism did Mendelstudy?

a)Roses

b)Ants

c)Peas

d)Yeast

Question 10 Select oneanswer.

Huntington's disease is anautosomal dominant disorder. If two individuals who areheterozygous at this locus breed, what are the chances that theiroffspring will develop Huntington's?

a)100%

b)75%

c)50%

d)25%

Question 11 Select oneanswer.

Plum gametes have 24 chromosomes.How many chromosomes would a zygote have?

a)12

b)24

c)36

d)48

Question 12 Select oneanswer.

Hydrangeas are blue in acidicsoil with available aluminum, and they are pink in alkaline soilwithout available aluminum, but they cannot be orange under anysoil condition. The color of hydrangeas is affect by

a)genetics only

b)the environment only

c)genetics and theenvironment

Question 13 Select oneanswer.

Somatic mosquito cells have 6chromosomes. How many chromosomes do gametes have?

a)3

b)6

c)12

d)24

Question 14 Select oneanswer.

Alleles are different versions ofa

a)Gene

b)Phenotype

c)Genotype

d)Chromosome

Question 15 Select oneanswer.

A female producesgametes:

a)that have either an X or a Ychromosome

b)That have 2 Xchromosomes

c)that have a Y chromosomeonly

d)that have an X chromosomeonly

Question 16:

use the following infromation to answer the next 4 questions

In dogs, colored fur (E) is dominant to un-colored fur (e).Blackfur color (B) is dominant to brown fur color (b). The E gene isepistatic to the B gene. A yellow male dog is mated to a blackfemale. the male's parents were both brown dogs. The female'smother was yellow and her father was brown

Q1 of 4: what is the genetype of the male dog in thisexample

a)eeBb

b)eeBB

c)ee

d)eebb

Q2 of 4: What is the genotype of the female dog in thisexample?

a)EeBb

b)EEBB

c)EeBB

d)EEBb

Q3 or 4: What percentage of their puppies will be yellow?

a)100%

b)75%

c)50%

d)25%

Q4 of 4: what percentahe of the puppies will be homozygous forthe B gene.

a)100%

b)75%

c)50%

d)25%

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BME 80H Lecture Notes - Lecture 13: Sex Linkage, Zygosity, Reciprocal Cross

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