Introduction to Morgan's Experiments

Q. In maize, coloured endosperm (C) is dominant over colourless (c) and full endosperm (R) is dominant over shrunken (r). When a dihybrid of $F_1$ generation was test crossed, it produced four phenotype in the following percentage
Coloured and Full = 45%
Coloured - Shrunken = 5%
Colourless - Full = 4%
Colourless - Shrunken = 46%
From these data what would be distance between the two allelic genes

1. 48 units
2. 9 units
3. 4 units
4. 12 units

Q.

Briefly mention the contribution of TH Morgan in genetics.

Q. Which statement is not true for Drosophila melanogaster?

1. They complete their life cycle in about two weeks
2. Single mating produce large number of progeny flies
3. It has few hereditary variation that can be seen with high power microscope
4. It has clear differentiation of the sex

Q. Fruit flies were used as experimental material by Morgan as

1. they have life cycle of about 10 weeks
2. single mating produces a large number of progeny flies
3. all the characteristics exhibited by flies can only be viewed under a microscope
4. female flies are smaller in size than male flies and hence are easily distinguishable

Q. Study the pedigree given below. What is the most likely mode of inheritance for this disease?

1. Autosomal recessive
2. Y linked disorder
3. Autosomal dominant
4. X-linked recessive

Q. (a) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with them for their experiments. Explain the correlation between linkage and recombination with respect to genes as studied by them.
(b) How did Sturtevant explain gene mapping while working with Morgan ? [5]

Q. In haploids, both recessive and dominant alleles are expressed because

1. two alleles are present for each gene
2. more than two alleles are present for each gene
3. only one allele for each gene is present in the individual organism
4. alleles do not have dominant recessive relationship

Q. Mendel failed to get linkage because

1. genes selected by him were discrete and stable
2. genes of seven types of traits selected by him were located on four different chromosomes and behaved independently
3. genes selected by him were located on seven non homologous chromosomes
4. pea plant does not show linkage

Q. Fruit flies were used as experimental organism by Morgan because

1. they have a life cycle of about 15 weeks
2. single mating produces a large number of progeny flies
3. all the characteristics exhibited by flies cannot be viewed under a microscope
4. female flies are smaller in size than male flies and hence are easily distinguishable

Q. Thomas Hunt Morgan got a Nobel prize for his work on which organism?

1. C. elegans
2. Pea plant
3. Zebrafish
4. Fruit fly

Q. Which of the following is the source of polymorphism in DNA?

1. Crossing over
2. Inbreeding
3. Mutation
4. Both a and b

Q. Who is regarded as the father of genetic engineering

1. Cohen
2. Boyer
3. Paul Berg
4. Smith

Q. In a dihybrid cross between two heterozygotes, AaBb $\times$ AaBb, if we get a 3 : 1 ratio among offspring, the reason would be ___________.

1. Polygenes
2. Linked genes
3. PIeiotropic genes
4. Hypostatic genes.

Q.

The model organism that T.H. Morgan used in his genetic studies was

1. Pisum sativum

2. Lathyrus odoratus

3. Mirabilis jalapa

4. Drosophila melanogaster

Q. The change of chromosomal parts between non homologous pairs of chromosome is

1. Crossing over
2. Translocation
3. Inversion
4. Transition

Q. Read the following statements and find out the incorrect statement.
A) Genetics deals with the inheritance as well as variation of characters from parents to offspring
B) Variation is the process by which characters are passed on from parent to progeny
C) Inheritance is the basis of heredity
D) Inheritance is the degree by which progeny differ from their parents
E) Human knew from as early as $8000-10000B.C.$ that one of the causes of variation was hidden in sexual reproduction

1. B, D and E only
2. A, C and E only
3. B and D only
4. E only

Q. Linkage map of X-chromosome of fruitfly has $66$ map units with yellow body gene(y) at one end and bobbed hair(b) at the other. The recombination frequency between y and b gene would be

1. $100\%$
2. $66\%$
3. $\le 50\%$
4. $>50\%$

Q. Give one significant contribution of each of the following scientists:
T.H. Morgan

Q. (a) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiments. Explain the correlation between linkage and recombination with respect to genes as studied by them.
(b) How did Sturtevant explain gene mapping while working with Morgan?

Q. The fruit fly Drosophila melanogaster was found to be very suitable for experimental verification of chromosomal theory of inheritance by Morgan and his colleagues because

1. It completes life cycle in about two weeks.
2. It reproduces parthenogenetically.
3. A single mating produces two young flies.
4. None of the above.

Q. What do you call the inheritance pattern of skin colour in humans?

1. Monogenic inheritance
2. Mendelian inheritance
3. Polygenic or quantitative inheritance
4. Codominance

Q. Differentiate between.
Linkage and crossing over

Q. What do you call the inheritance pattern of skin colour in humans?

1. Monogenic inheritance
2. Mendelian inheritance
3. Polygenic or quantitative inheritance
4. Codominance

Q. A geneticist interested in studying variations and pattern of inheritance in living beings prefers to choose organisms for experiments with a shorter life cycle. Provide a reason.

Q. The regulation of gene expression is more complex in eukaryotic cells because the:

1. Operons are controlled by more than one promoter region.
2. The chromosomes are linear and more numerous.
3. Inhibitory or activating molecules may not help to regulate transcription.
4. Gene expression differentiates specialised cells.

Q. Fruitfly Drosophila melanogaster was found to be very suitable for experimental verification of chromosome theory of inheritance by Morgan and his colleagues because.

1. Smaller female is easily distinguishable from large male
2. It reproduces parthenogenetically
3. A single mating produces two young flies
4. It completes life cycle in about two weeks

Q. Assertion :GM salmon was the first transgenic animal for performing vaccine safety tests. Reason: For the production of GM salmon, genetically modified ova were fused with normal sperms of the same species.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
3. Assertion is correct but Reason is incorrect
4. Both Assertion and Reason are incorrect

Q.

Mendelian recombinations are mainly due to

1. Linkage

2. Independent assortment of genes

3. Mutations

4. Dominant characters

Q. Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiment. Explain the correlation between linkage and recombination with respect to genes as studied by them.

Q. Three Mark Questions :
During his studies on genes in Drosophila that were sex linked, T. H. Morgan found $F_2$ population phenotypic ratios deviated from expected 9 : 3 :3 :1. Explain the conclusion he arrived at.