12 Why did the improvement of microscopy techniques in the late 1800s set the stage for the emergence of modern genetics It revealed new and unanticipated features of Mendels pea plant varieties ID: 816122
Download The PPT/PDF document "The Chromosomal Basis of Inheritance" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
The Chromosomal Basis of Inheritance
12
Slide2Why did the improvement of microscopy techniques in the late 1800s set the stage for the emergence of modern genetics?
It revealed new and unanticipated features of Mendel’s pea plant varieties.
It allowed the study of meiosis and mitosis, revealing parallels between behaviors of the
Mendelian concept of the gene and the movement/pairing of chromosomes. It allowed scientists to see the nucleotide sequence of DNA. It led to the discovery of mitochondria. It showed genes functioning to direct the formation of enzymes.
© 2016 Pearson Education, Inc.
Slide3Why did the improvement of microscopy techniques in the late 1800s set the stage for the emergence of modern genetics?
It revealed new and unanticipated features of Mendel’s pea plant varieties.
It allowed the study of meiosis and mitosis, revealing parallels between behaviors of the
Mendelian concept of the gene and the movement/pairing of chromosomes. It allowed scientists to see the nucleotide sequence of DNA. It led to the discovery of mitochondria. It showed genes functioning to direct the formation of enzymes.
© 2016 Pearson Education, Inc.
Slide4Morgan and his colleagues worked out a set of symbols to represent fly genotypes. Which of the following are representative?
AaBb
AaBb 46 or 46w
w or w on X 2 3
© 2016 Pearson Education, Inc.
Slide5Morgan and his colleagues worked out a set of symbols to represent fly genotypes. Which of the following are representative?
AaBb
AaBb 46 or 46w
w or w on X 2 3
© 2016 Pearson Education, Inc.
Slide6Imagine that Morgan had chosen a different organism for his genetics experiments. What kind of species would have made a better choice than fruit flies?
© 2016 Pearson Education, Inc.
Slide7Imagine that Morgan had used a grasshopper (2n
24, and sex is determined as follows: male has X, and female has XX) to study sex linkage. Predict where the first mutant would have been discovered.
on the O chromosome of a maleon the X chromosome of a maleon the X chromosome of a femaleon the Y chromosome of a male
© 2016 Pearson Education, Inc.
Slide8Imagine that Morgan had used a grasshopper (2n
24, and sex is determined as follows: male has X, and female has XX) to study sex linkage. Predict where the first mutant would have been discovered.
on the O chromosome of a maleon the X chromosome of a maleon the X chromosome of a femaleon the Y chromosome of a male
© 2016 Pearson Education, Inc.
Slide9Think about bees and ants, which have no X and Y sex chromosomes. Males are haploid, whereas fertilization results in females, as diploid cells become females. Which of the following are accurate statements about bee and ant males when they are compared to species in which males are XY and diploid for the autosomes?
Bee males have half the DNA of bee females, whereas human males have nearly the same amount of DNA that human females have.
Considered across the genome, harmful (deleterious) recessives will negatively affect bee males more than
Drosophila males.Human and Drosophila
males have sons, but bee males do not.Inheritance in bees is like inheritance of sex-linked characteristics in humans.none of the above© 2016 Pearson Education, Inc.
Slide10Think about bees and ants, which have no X and Y sex chromosomes. Males are haploid, whereas fertilization results in females, as diploid cells become females. Which of the following are accurate statements about bee and ant males when they are compared to species in which males are XY and diploid for the autosomes?
Bee males have half the DNA of bee females, whereas human males have nearly the same amount of DNA that human females have.
Considered across the genome, harmful (deleterious) recessives will negatively affect bee males more than
Drosophila males.Human and
Drosophila males have sons, but bee males do not.Inheritance in bees is like inheritance of sex-linked characteristics in humans.none of the above© 2016 Pearson Education, Inc.
Slide11Determination of sex in Drosophila is similar to that in humans. In some species of Drosophila
, there are genes on the Y chromosome that do not occur on the X chromosome. Imagine that a mutation of one gene on the Y chromosome reduces the size by half of individuals with the mutation. Which of the following statements is accurate with regard to this situation?
This mutation is transmitted to all offspring of a male with the mutation.
This mutation is transmitted to all male but no female offspring of a
male with the mutation. This mutation is transmitted to all offspring of a female with the mutation.This mutation is transmitted to all male but no female offspring of a female with the mutation.This mutation is transmitted to all offspring of both males and females with the mutation.
© 2016 Pearson Education, Inc.
Slide12Determination of sex in Drosophila is similar to that in humans. In some species of Drosophila
, there are genes on the Y chromosome that do not occur on the X chromosome. Imagine that a mutation of one gene on the Y chromosome reduces the size by half of individuals with the mutation. Which of the following statements is accurate with regard to this situation?
This mutation is transmitted to all offspring of a male with the mutation.
This mutation is transmitted to all male but no female offspring of a male with the mutation.
This mutation is transmitted to all offspring of a female with the mutation.This mutation is transmitted to all male but no female offspring of a female with the mutation.This mutation is transmitted to all offspring of both males and females with the mutation.
© 2016 Pearson Education, Inc.
Slide13In cats, a sex-linked gene affects coat color. The O allele produces an enzyme that converts
eumelanin
, a black or brown pigment, into
phaeomelanin, an orange pigment. The o allele is recessive to O and produces a defective enzyme, one that does not convert eumelanin into phaeomelanin. Which of the following statements is/are accurate?
The phenotype of o-Y males is black/brown because the nonfunctional allele o does not convert eumelanin into phaeomelanin.The phenotype of OO and Oo males is orange because the functional allele O converts eumelanin into phaeomelanin.The phenotype of Oo males is mixed orange and black/brown because the functional allele O converts eumelanin into phaeomelanin in some cell groups (orange) and because in other cell groups the nonfunctional allele o does not convert
eumelanin
into
phaeomelanin
.
The phenotype of
O-Y
males is orange because the nonfunctional allele
O does not convert eumelanin into phaeomelanin, while the phenotype of
o-Y
males is black/brown because the functional allele
o
converts
eumelanin
into
phaeomelanin
.
© 2016 Pearson Education, Inc.
Slide14In cats, a sex-linked gene affects coat color. The O allele produces an enzyme that converts
eumelanin
, a black or brown pigment, into
phaeomelanin, an orange pigment. The o allele is recessive to O and produces a defective enzyme, one that does not convert eumelanin into phaeomelanin. Which of the following statements is/are accurate?
The phenotype of o-Y males is black/brown because the nonfunctional allele o does not convert eumelanin into phaeomelanin.The phenotype of OO and Oo males is orange because the functional allele O converts eumelanin into phaeomelanin.The phenotype of Oo males is mixed orange and black/brown because the functional allele O converts eumelanin into phaeomelanin in some cell groups (orange) and because in other cell groups the nonfunctional allele o does not convert eumelanin into
phaeomelanin
.
The phenotype of
O-Y
males is orange because the nonfunctional allele
O
does not convert
eumelanin into phaeomelanin, while the phenotype of o-Y
males is black/brown because the functional allele
o
converts
eumelanin
into
phaeomelanin
.
© 2016 Pearson Education, Inc.
Slide15Imagine a species with three loci thought to be on the same chromosome. The recombination rate between locus A and locus B is 35%, and the recombination rate between locus B and locus C is 33%. Predict the recombination rate between A and C.
The recombination rate between locus A and locus C is either 2% or 68%.
The recombination rate between locus A and locus C is probably 2%.
The recombination rate between locus A and locus C is either 2% or 50%.The recombination rate between locus A and locus C is either 2% or 39%.The recombination rate between locus A and locus C cannot be predicted.
© 2016 Pearson Education, Inc.
Slide16Imagine a species with three loci thought to be on the same chromosome. The recombination rate between locus A and locus B is 35%, and the recombination rate between locus B and locus C is 33%. Predict the recombination rate between A and C.
The recombination rate between locus A and locus C is either 2% or 68%.
The recombination rate between locus A and locus C is probably 2%.
The recombination rate between locus A and locus C is either 2% or 50%.The recombination rate between locus A and locus C is either 2% or 39%.The recombination rate between locus A and locus C cannot be predicted.
© 2016 Pearson Education, Inc.
Slide17Chromosomal rearrangements can occur after chromosomes break. Which of the following statements is most accurate with respect to alterations in chromosome structure?
Chromosomal rearrangements are more likely to occur in mammals than in other vertebrates.
Translocations and inversions are not deleterious because no genes are lost in the organism.
Chromosomal rearrangements are more likely to occur during mitosis than during meiosis.An individual that is homozygous for a deletion of a certain gene is likely to be more damaged than one that is homozygous for a duplication of that same
gene because loss of a function can be lethal.
© 2016 Pearson Education, Inc.
Slide18Chromosomal rearrangements can occur after chromosomes break. Which of the following statements is most accurate with respect to alterations in chromosome structure?
Chromosomal rearrangements are more likely to occur in mammals than in other vertebrates.
Translocations and inversions are not deleterious because no genes are lost in the organism.
Chromosomal rearrangements are more likely to occur during mitosis than during meiosis.An individual that is homozygous for a deletion of a certain gene is likely to be more damaged than one that is homozygous for a duplication of that same gene because loss of a function can be lethal.
© 2016 Pearson Education, Inc.
Slide19Imagine that you could create medical policy for a country. In this country it is known that the frequency of Down syndrome increases with increasing age of the mother and that the frequency of schizophrenia and autism increases with the age of the father. In both
schizophrenia and autism
, the severity of characteristics varies enormously and unpredictably among affected individuals. Furthermore, financial resources are severely limited, both for testing of pregnant women and for supplemental training of children with Down syndrome. What kind of policy regarding fetal testing would you implement?
© 2016 Pearson Education, Inc.
Slide20Recall that in Drosophila, white eyes are due to an X-linked recessive allele (Xw). Describe a genetic cross that
could
result in white
–eyed female Drosophila.no possible crosswhite-eyed females with red-eyed males
heterozygous red-eyed females with white-eyed malesheterozygous red-eyed females with red-eyed males© 2016 Pearson Education, Inc.
Slide21Recall that in Drosophila, white eyes are due to an X-linked recessive allele (Xw). Describe a genetic cross that
could
result in white
–eyed female Drosophila.no possible crosswhite-eyed females with red-eyed males
heterozygous red-eyed females with white-eyed malesheterozygous red-eyed females with red-eyed males© 2016 Pearson Education, Inc.
Slide22Which statement best describes the relationship between recombination frequency and the physical distance of genes on chromosomes?
There is no relationship. All genes have random recombination frequencies.
There is no relationship. All genes have the same, fixed recombination frequencies.
The farther apart two genes are, the higher the recombination frequencyThe closer together two genes are, the higher the recombination frequency© 2016 Pearson Education, Inc.
Slide23Which statement best describes the relationship between recombination frequency and the physical distance of genes on chromosomes?
There is no relationship. All genes have random recombination frequencies.
There is no relationship. All genes have the same, fixed recombination frequencies.
The farther apart two genes are, the higher the recombination frequencyThe closer together two genes are, the higher the recombination frequency© 2016 Pearson Education, Inc.
Slide24What is the expected recombination frequency for a testcross between the black and cinnabar loci?
9%
48.5%
50%57.5%© 2016 Pearson Education, Inc.
Slide25What is the expected recombination frequency for a testcross between the black and cinnabar loci?
9%
48.5%
50%57.5%© 2016 Pearson Education, Inc.
Slide26What is the expected recombination frequency for a testcross between the black and brown loci?
48.5%
50%
56%100%© 2016 Pearson Education, Inc.
Slide27What is the expected recombination frequency for a testcross between the black and brown loci?
48.5%
50%
56%100%© 2016 Pearson Education, Inc.
Slide28In tomatoes, a heterozygous plant with yellow flowers and red fruit is crossed with a recessive plant having white flowers and yellow fruit. The following distribution of offspring is observed:
yellow flowers, red fruit 42.5% white flowers, yellow fruit 42.5%
yellow flowers, yellow fruit 7.5% white flowers, red fruit 7.5% What conclusion can be made regarding the loci for flower color and fruit color?
The loci may be on the same chromosome more than 50 map units apart, or they may be on separate chromosomes.The loci are on separate chromosomes.The loci are on the same chromosome, at an unknown distance from each other.The loci are on the same chromosome 15 map units apart.© 2016 Pearson Education, Inc.
Slide29In tomatoes, a heterozygous plant with yellow flowers and red fruit is crossed with a recessive plant having white flowers and yellow fruit. The following distribution of offspring is observed:
yellow flowers, red fruit 42.5% white flowers, yellow fruit 42.5%
yellow flowers, yellow fruit 7.5% white flowers, red fruit 7.5% What conclusion can be made regarding the loci for flower color and fruit color?
The loci may be on the same chromosome more than 50 map units apart, or they may be on separate chromosomes.The loci are on separate chromosomes.The loci are on the same chromosome, at an unknown distance from each other.The loci are on the same chromosome 15 map units apart.© 2016 Pearson Education, Inc.
Slide30In tomatoes, a heterozygous plant with purple stems and normal leaves is crossed with a recessive plant having green stems and broad leaves. The following distribution of offspring is observed:
purple
stems, normal leaves 25% green stems, broad leaves 25% purple
stems, broad leaves 25% green stems, normal leaves 25% What conclusion can be made regarding the loci for stem color and leaf shape?The loci may be on the same chromosome more than 50 map units apart, or they may be on separate chromosomes.The loci are on separate chromosomes.The loci are on the same chromosome, at an unknown distance from each other.The loci are on the same chromosome 25 map units apart.© 2016 Pearson Education, Inc.
Slide31In tomatoes, a heterozygous plant with purple stems and normal leaves is crossed with a recessive plant having green stems and broad leaves. The following distribution of offspring is observed:
purple stems, normal leaves 25%
green stems, broad leaves 25%
purple stems, broad leaves 25% green stems, normal leaves 25% What conclusion can be made regarding the loci for stem color and leaf shape?
The loci may be on the same chromosome more than 50 map units apart, or they may be on separate chromosomes.The loci are on separate chromosomes.The loci are on the same chromosome, at an unknown distance from each other.The loci are on the same chromosome 25 map units apart.© 2016 Pearson Education, Inc.
Slide32Which of the following diagrams best depicts the karyotype of a trisomy?
© 2016 Pearson Education, Inc.
Slide33Which of the following diagrams best depicts the karyotype of a trisomy?
© 2016 Pearson Education, Inc.
Slide34Nondisjunction can happen in either meiosis I or meiosis II. Consider an n + 1 gamete that is formed from nondisjunction and compare the origin of the extra (+1) chromosome between the two types of nondisjunction. Select the best comparative statement.
There is no inherent difference between the two.
The +1 chromosome resulting from meiosis I nondisjunction was a homolog of its partner, while that from meiosis II was a sister chromatid of its partner.
The +1 chromosome resulting from meiosis I nondisjunction was a sister chromatid of its partner, while that from meiosis II was a homolog of its partner.The +1 chromosome resulting from meiosis I nondisjunction results in syndromes, while that from meiosis II does not
.© 2016 Pearson Education, Inc.
Slide35Nondisjunction can happen in either meiosis I or meiosis II. Consider an n + 1 gamete that is formed from nondisjunction and compare the origin of the extra (+1) chromosome between the two types of nondisjunction. Select the best comparative statement.
There is no inherent difference between the two.
The +1 chromosome resulting from meiosis I nondisjunction was a homolog of its partner, while that from meiosis II was a sister chromatid of its partner.
The +1 chromosome resulting from meiosis I nondisjunction was a sister chromatid of its partner, while that from meiosis II was a homolog of its partner.The +1 chromosome resulting from meiosis I nondisjunction results in syndromes, while that from meiosis II does not
.© 2016 Pearson Education, Inc.