MCQs on Developmental biology

1.     Stapes bone of middle ear evolved from

a)     Hyomandibular arch

b)    Jaw bone

c)     Ear bone

d)    None of the above

2.     The quadrate bone of reptilian upper jaw evolved into the mammalian  ------ bone of the middle ear & the articular bone of the reptile’s lower jaw has become our ------

a)     Malleus, incus 

b)    Incus, malleus

c)     Incus, articular

d)    None of the above

3.     Piebaldism, is due to dominant mutation in a gene (KIT) on long arm of chromosomes 4. This syndrome include

a)     Fertility, pigmentation

b)    Sterility, dumbness

c)     Anemia, sterility, unpigmented region of the skin & hair, deafness & the absence of nerve that cause peristalsis in the gut

d)    None of above

4.     Abnormalities due to exogenous agents (certain chemicals or viruses, radiation, or hyperthermia) are called disruptions. The agent responsible for these disruptions are called

a)     Teratogens

b)    Inducer

c)     External mutant

d)    All of above

5.     The study of how environmental agents disrupt normal development is called as---

a)     Abnormal developmental biology

b)    Teratology

c)     Both

d)    None

6.     Thalidomide, prescribed as a mild sedative to many pregnant woman, caused an enormous increase in a previously rare syndrome of congenital anomelies. The most noticeable of these anomalies was phocomelia , a condition in which the long bones of the limb are---

a)     Deficient or absent

b)    Highly calcified

c)     Low calcium

d)    a&c

7.     Estrogen hormone can instruct the ----- to make & secrete the yolk proteins, which are then transported through the blood into the enlarging eggs in the ovary

a)     Liver

b)    Spleen

c)     Ovarian duct

d)    Uterus

8.     Gastrulation in the frog begins at a point on the embryo surface roughly 180 degree opposite the point of sperm entry with the formation of a dimple, called the 

a)     Blastopore

b)    Archenteron

c)     Blastocyst

d)    None

9.     During amphibian development the cells that had connected the neural tube to the epidermis become the

a-   Notochord

b-   Neural crest cells

c-   Neural plate

d-   Both b & c

10.  Metamorphosis of amphibian larva is

a)     Progressive

b)    Retrogressive

c)     Neoteny

d)    None

Answer: 1-a, 2-b, 3-c, 4-a, 5-b, 6-a, 7-a, 8-a, 9-b, 10-b

Contributed by: Ms. Nargis K.

Mutiple choice questions based on restriction endonucleases

1.     Type I restriction endonuclease cleaves
a) Within the recognition sequence
b) both side of the recognition sequence
c) 20 to 30 bp away from the recognition sequence
d) 1000bp away from the recognition sequence

2.     Which of the following is not true about type II restriction endonuclease?
a) Cleavage and Methylation are by different enzymes
b) In this case the recognition sequence is asymmetric
c) It cleaves within the recognition sequence
d) It can’t cleave at methylated sequences

3.     Restriction endonucleases can recognize
a) Tandem repeats
b) Pallindromic sequences
c) both
d) No sequence specificity

4.     Which of the sequence will Dcm enzyme methylate?
a) GATC
b) GAATC
c) CCGTT
d) CCAGG

5.     Which of the following enzyme are isoschizomer?
a) SphI and BbuI
b) Not1 and HindIII
c) SmaI and XmaI
d) Pst1 and Sma1

6.     Restriction enzymes cleave the bond by which type of reaction?
a) S_N1
b) S_N2
c) S_E1
d) S_E2

7.     Which of the following enzyme are neoschizomer?
a) SphI and BbuI
b) Not1 and HindIII
c) SmaI and XmaI
d) Pst1 and Sma1

8.     If all the nucleotides are present with equal frequencies and at random, what are the chances of having a particular four nucleotide long motif?
a) 1/256
b) 1/64
c) 1/16
d) 1/8

9.     Which of the following enzymes are isocaudomer?
a) SphI and BbuI
b) Not1 and HindIII
c) Sau3A and BamH1
d) Pst1 and Sma1

10.  Zinc-finger nucleases is

a)     natural restriction enzyme

b)    type of polymerase enzyme

c)     artificial restriction enzyme

d)    type of helicase enzyme

Answers: 1. D, 2. B, 3. B, 4. D, 5. A, 6. B, 7. C, 8. A, 9. C, 10.  c

GENETIC DISORDER

Genetic disorder is an abnormal condition in individual and it is inheritable viz., transmitted from generation to generation and caused by one or more abnormality in genome. Abnormality can occur in a single base of a gene to a gross structure of chromosomes such as addition or subtraction of a segment of gene or entire chromosome. This may also occur by mutation in germ cells due to environmental effect and new mutation also inheritable if occur in germ cell. Majority of genetic disorders are rare and affect one in several thousands or millions. Occurrence of genetic disorder increases due to marriage in close relatives i.e., “consanguineous marriages”. Genetic disorders can be classified into four broad group chromosomal disorders, mitochondrial disorders, single gene disorders and multi-factorial. Chromosomal disorder occur due to change in number and arrangement of chromosomes, mitochondrial disorders occur by change in mt-DNA and can show only maternal inheritance, single gene disorder occur by single defective gene and polygenic disorders called as multifactorial.

Genetic disorders may be inherited in four way, autosomal recessive, autosomal dominant, sex linked recessive, sex linked dominant. There are a lot of example of genetic disorder, such as sickle cell anemia inherited red blood cells disorder 1 million cases occur per year in India, thalassemia a inherited type of anemia occur due to abnormal haemoglobin about 3-4%(35-45 million) thalassemia carriers are in India, spinal muscular atrophy a genetic disorder that effect nerve cells of spinal cord have approximate frequency of 1 in 10000 babies, cystic fibrosis a respiratory disorder have a frequency 1/25 live birth but survival rate is very poor, haemophilia- A a blood clotting disorder have a frequency of 1/5000, Huntington chorea a neurodegenerative disorder having a frequency of 5-10/100000 in world, in most cases Huntington chorea inherited from parent but there are 10% cases due to new mutation also & are inheritable.

Genetic disorders are rare but deleterious for human health, generally this type of disorders are incurable. Proper care and rehabilitation is necessary for patients. Genetic counseling is important to avoid the situation.

Authors: Ms. Nargis K. and Mr. Azeem Ali 

Various cloning vectors and their insert size

S.No.	Vector	Host	Insert size (in Kb)
1.	M13 vectors	E. Coli	3
2.	Plasmid vectors	E. Coli	8
3.	Phagemid vectos	E. Coli	10
4.	λgt10	E. Coli	8
5.	λZAPII	E. Coli	10
6.	λEMBL4	E. Coli	20
7.	λGEM11, λGEM12	E. Coli	25
8.	λ cosmids	E. Coli	35-45
9.	P1 derived artificial chromosomes (PAC)	E. Coli	100-300
10.	Bacterial artificial chromosomes (BAC)	E. Coli	≤300
11.	Yeast artificial chromosomes (YAC)	Sachharomyces cerevisiae	200 - 2000

Problem of quantitative genetics

Problem: Fruit colour of wild Solanum nigrum is controlled by two alleles of a gene (A and a). The frequency of A, p=0.8 and a, q=0.2. In a neighbouring field a tetraploid genotype of S. nigrum was found. After critical examination five distinct genotypes were found; which are AAAA, AAAa, AAaa, Aaaa and aaaa. Following Hardy Weinberg principle and assuming the same allele frequency as that of diploid population, the numbers of phenotypes calculated within a population of 1000 plants are close to one of the following: AAAA : AAAa : AAaa : Aaaa : aaaa

1. 409 : 409 : 154 : 26 : 2

2. 420 : 420 : 140 : 18 : 2

3. 409 : 409 : 144 : 36 : 2

4. 409 : 420 : 144 : 25 : 2                                                      (CSIR June 2016)

Solution:

Frequency of allele A = 0.8 and a = 0.2

	AA	Aa	Aa	aa
AA	AAAA	AAAa	AAAa	AAaa
Aa	AAAa	AAaa	AAaa	Aaaa
Aa	AAAa	AAaa	AAaa	Aaaa
aa	AAaa	Aaaa	Aaaa	aaaa

From above chart phenotypic ratio is,

AAAA : AAAa : AAaa : Aaaa : aaaa = 1 : 4 : 6 : 4 : 1

From Hardy-Weinberg principle:

p⁴ : 4p³q : 6p²q² : 4pq³ :q⁴

for AAAA= p⁴ x 1000 = (0.8)⁴ x 1000

= 409.6 » 409

for AAAa = 4p³q x 1000 = 4x(0.8)³x0.2x1000

= 409.6  » 409

for AAaa = 6p²q² x 1000 = 6x(0.8)²x(0.2)² x1000

= 153.6  » 154

for Aaaa = 4pq³ x 1000 = 4x0.8x(0.2)³ x1000

= 25.6  » 26

for aaaa = q⁴ x 1000 = (0.2)⁴ x1000

= 1.6 » 2

Number of phenotypes are 

AAAA : AAAa : AAaa : Aaaa : aaaa = 409 : 409 : 154 : 26 : 2

Option 1 is correct