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#	Question	Answer
1	Which branch of biology developed as a consequence of studying genetic material?	Molecular biology.
2	Name some scientists who contributed majorly to molecular biology according to the text.	Watson, Crick, Nirenberg, Khorana, Kornbergs, Benzer, Monod, and Brenner.
3	Which parallel biological problem was being tackled along with molecular genetics?	The mechanism of evolution.
4	Which areas enriched our understanding of the molecular basis of evolution?	Molecular genetics, structural biology, and bioinformatics.
5	What topics are examined in this unit?	Structure and function of DNA, and the story and theory of evolution.
6	What common scientific interest united Watson and Crick?	Solving the DNA structure.
7	When was the complementary double-helical configuration of DNA proposed?	Early in March 1953.
8	What led Watson and Crick to the successful DNA model?	More experimental evidence and better appreciation of nucleic acid literature.
9	Which proposal made by Watson and Crick in 1953 became historic?	The double-helical structure for DNA and the replication scheme.
10	Which branch of biology deals with inheritance and variation?	Genetics.
11	What does Genetics study?	Inheritance and variation of characters from parents to offspring.
12	Define inheritance.	Inheritance is the process by which characters are passed on from parent to progeny.
13	What is the basis of heredity?	Inheritance.
14	Define variation.	Variation is the degree by which progeny differ from their parents.
15	During which period did humans recognize that sexual reproduction causes variation?	Around 8000–1000 B.C.
16	How did humans exploit naturally occurring variations?	By selective breeding and domestication.
17	Which Indian cow breed is mentioned as an example of artificial selection?	Sahiwal cows of Punjab.
18	What did ancient humans lack regarding inheritance and variation?	Scientific understanding of these phenomena.
19	During which century was major progress made in understanding inheritance?	Mid-nineteenth century.
20	Who conducted hybridisation experiments on garden peas?	Gregor Mendel.
21	For how many years did Mendel conduct pea plant experiments?	Seven years (1856–1863).
22	What did Mendel propose from his experiments?	Laws of inheritance in living organisms.
23	What type of traits did Mendel study in pea plants?	Opposing contrasting traits.
24	Give examples of contrasting traits studied by Mendel.	Tall/dwarf plants and yellow/green seeds.
25	What is a true-breeding line?	A line that shows stable trait inheritance and expression after continuous self-pollination for several generations.
26	How many true-breeding pea plant varieties did Mendel select?	14 varieties.
27	What was special about the pea plant varieties selected by Mendel?	They differed in only one character with contrasting traits.
28	Name the seven contrasting characters studied by Mendel in pea plants.	1. Stem height – Tall/Dwarf, 2. Flower colour – Violet/White, 3. Flower position – Axial/Terminal, 4. Pod shape – Inflated/Constricted, 5. Pod colour – Green/Yellow, 6. Seed shape – Round/Wrinkled, 7. Seed colour – Yellow/Green
29	What kind of pollination experiments did Mendel perform?	Artificial pollination/cross-pollination experiments.
30	Which plants did Mendel cross in his monohybrid experiment?	Tall pea plants and dwarf pea plants.
31	What did Mendel call the units responsible for inheritance?	Factors.
32	Define genes according to the text.	Genes are units of inheritance containing information required to express a trait.
33	What are alleles?	Slightly different forms of the same gene controlling contrasting traits.
34	Which symbols are used for tall and dwarf traits in pea plants?	T for tall and t for dwarf.
35	What are the possible allele combinations for height in pea plants?	TT, Tt, and tt.
36	What is a homozygous condition?	A condition where both alleles are identical, such as TT or tt.
37	What is the genotype of a true-breeding tall pea plant?	TT.
38	What is the genotype of a true-breeding dwarf pea plant?	tt.
39	What is genotype?	The allelic composition of an organism.
40	What is phenotype?	The observable expression of a trait, such as tall or dwarf.
41	What is the phenotype of genotype Tt?	Tall.
42	What did Mendel conclude from the appearance of Tt plants?	One factor dominates over the other.
43	Which allele is dominant in pea plant height?	T (tallness).
44	Which allele is recessive in pea plant height?	t (dwarfness).
45	Why are capital and small letters used for alleles?	To represent dominant and recessive forms of the same gene.
46	Why should T and d not be used together for tall and dwarf?	Because they may not clearly indicate alleles of the same gene.
47	What is a heterozygous condition?	A condition where the two alleles are different, such as Tt.
48	Why is the cross between TT and tt called a monohybrid cross?	Because it involves one character (height).
49	What is a monohybrid?	An organism heterozygous for genes controlling one character.
50	What is a monohybrid cross?	A cross between TT and tt involving one character.
51	During which process do alleles segregate from each other?	Meiosis.
52	How many alleles of a gene are transmitted to a gamete?	Only one allele.
53	Is segregation of alleles random?	Yes, segregation is a random process.
54	What is the probability of a gamete containing either allele in a heterozygote?	50 percent.
55	Which allele is present in gametes of tall TT plants?	T allele.
56	Which allele is present in gametes of dwarf tt plants?	t allele.
57	What genotype is formed when T and t alleles unite during fertilisation?	Tt.
58	Why are Tt plants called heterozygous?	Because they contain contrasting alleles.
59	What is a Punnett Square?	A graphical representation used to calculate possible genotypes in a genetic cross.
60	Who developed the Punnett Square?	Reginald C. Punnett.
61	How are possible gametes represented in a Punnett Square?	Along the top row and left columns.
62	What is the probability of T pollen fertilising T eggs?	50 percent.
63	What proportion of fertilisations produce TT genotype?	1/4.
64	What proportion of fertilisations produce Tt genotype?	1/2.
65	What proportion of fertilisations produce tt genotype?	1/4.
66	What is the phenotypic appearance of Tt plants?	Tall.
67	Why can TT and Tt plants not be distinguished externally?	Both show the tall phenotype.
68	What is the genotype of dwarf plants according to Mendel?	Homozygous tt.
69	Why can phenotype alone not determine genotype in dominant traits?	Because both TT and Tt show the same dominant phenotype.
70	What is a test cross?	A cross between an organism showing dominant phenotype and a recessive parent to determine genotype.
71	Why is a test cross performed?	To determine whether a dominant phenotype organism is homozygous or heterozygous.
72	Which example is given for a test cross in the text?	Violet flower colour (V) dominant over white flower colour (v).
73	Which two laws did Mendel propose based on monohybrid crosses?	Law of Dominance and Law of Segregation.
74	State the first point of the Law of Dominance.	Characters are controlled by discrete units called factors.
75	State the second point of the Law of Dominance.	Factors occur in pairs.
76	State the third point of the Law of Dominance.	In a dissimilar pair of factors, one dominates over the other.
77	What happens to alleles during gamete formation according to the Law of Segregation?	Alleles separate so each gamete receives only one factor.
78	What type of gametes does a homozygous parent produce?	Similar gametes.
79	What type of gametes does a heterozygous parent produce?	Two kinds of gametes in equal proportion.
80	Which plant is used as an example of incomplete dominance?	Snapdragon (Antirrhinum sp.).
81	What was crossed in the snapdragon experiment?	True-breeding red-flowered (RR) and white-flowered (rr) plants.
82	What was the genotype of pink-flowered snapdragon plants?	Rr.
83	What is the genotype ratio in incomplete dominance?	1 RR : 2 Rr : 1 rr.
84	What does every gene contain?	Information to express a particular trait.
85	How many copies of each gene are present in diploid organisms?	Two copies.
86	Why may alleles in a heterozygote differ from each other?	Due to changes modifying the information in one allele.
87	What example is used to explain dominance at the molecular level?	A gene coding for an enzyme.
88	What does the normal allele produce in the enzyme example?	A normal enzyme required for substrate transformation.
89	What are the three possible effects of a modified allele?	1. Normal/less efficient enzyme, 2. Non-functional enzyme, 3. No enzyme at all
90	When are two alleles considered equivalent?	When both produce the same phenotype.
91	Which allele is generally dominant in enzyme-related inheritance?	The functioning or unmodified allele.
92	Why is a recessive trait expressed?	Due to non-functional enzyme or absence of enzyme production.
93	Which human trait is given as an example of co-dominance?	ABO blood grouping.
94	Which gene controls ABO blood groups in humans?	Gene I.
95	What is present on the plasma membrane of red blood cells in ABO blood groups?	Sugar polymers.
96	What does allele i produce?	No sugar.
97	Why do humans possess only two alleles of the ABO gene at a time?	Because humans are diploid organisms.
98	How many different genotypes are possible in human ABO blood groups?	Six genotypes.
99	What is multiple allelism?	Presence of more than two alleles governing the same character.
100	Why can multiple alleles be observed only at the population level?	Because an individual can possess only two alleles at a time.
101	Which trait in pea seeds is controlled by a single gene with alleles B and b?	Starch synthesis.
102	Which genotype produces large starch grains in pea seeds?	BB homozygotes.
103	Which genotype produces small starch grains in pea seeds?	bb homozygotes.
104	What is the seed shape of BB seeds after maturation?	Round.
105	What is the seed shape of bb seeds after maturation?	Wrinkled.
106	What type of dominance is shown by starch grain size in Bb seeds?	Incomplete dominance.
107	Why is dominance not considered an autonomous feature of a gene?	Because it depends on gene product and phenotype expression.
108	Which symbols are used for seed colour alleles in the dihybrid cross?	Y for yellow and y for green.
109	Which symbols are used for seed shape alleles in the dihybrid cross?	R for round and r for wrinkled.
110	How is the 9:3:3:1 ratio derived?	By combining 3:1 ratio for seed shape with 3:1 ratio for seed colour.
111	On which type of crosses was the Law of Independent Assortment based?	Dihybrid crosses.
112	What does the Punnett Square help explain in a dihybrid cross?	Independent segregation of two pairs of genes during meiosis.
113	Which alleles are considered for seed shape in the dihybrid cross?	R and r.
114	Which alleles are considered for seed colour in the dihybrid cross?	Y and y.
115	What proportion of gametes carries allele R?	50 percent.
116	What proportion of gametes carries allele r?	50 percent.
117	What proportion of gametes carries allele Y?	50 percent.
118	What proportion of gametes carries allele y?	50 percent.
119	Why is segregation of R/r independent of Y/y?	Because alleles assort independently during meiosis.
120	What are the four types of gametes produced by RrYy plants?	RY, Ry, rY, and ry.
121	What is the frequency of each gamete type in a dihybrid cross?	25 percent or 1/4th.
122	How many total boxes are formed in the Punnett Square of a dihybrid cross?	16 boxes.
123	What advancement helped scientists observe chromosomes clearly?	Advancements in microscopy.
124	What structures were observed doubling and dividing before cell division?	Chromosomes.
125	What important similarity exists between chromosomes and genes?	Both occur in pairs and segregate during gamete formation.
126	What important observation was made about chromosomes during meiosis?	Chromosomes occur in pairs and segregate during gamete formation.
127	Where are alleles located according to chromosomal theory?	On homologous sites of homologous chromosomes.
128	During which stage of meiosis do chromosome pairs align independently?	Anaphase I of meiosis.
129	What does independent alignment of chromosome pairs explain?	Independent assortment of genes.
130	What did Sutton and Boveri conclude from chromosome behaviour?	Pairing and separation of chromosomes lead to segregation of factors (genes).
131	Who proposed the Chromosomal Theory of Inheritance?	Walter Sutton and Theodore Boveri (though Sutton specifically united the knowledge and named it).
132	What did Sutton combine to formulate the Chromosomal Theory of Inheritance?	Chromosomal segregation and Mendelian principles.
133	Which scientist experimentally verified the Chromosomal Theory of Inheritance?	Thomas Hunt Morgan.
134	Which organism did Morgan use for genetic experiments?	Drosophila melanogaster (fruit fly).
135	Why was Drosophila melanogaster suitable for genetic studies?	It could be grown easily in the laboratory on simple synthetic medium.
136	What is the life cycle duration of Drosophila melanogaster?	About two weeks.
137	Why did Drosophila produce useful experimental data quickly?	A single mating produced a large number of progeny.
138	Why were male and female Drosophila easy to study?	Because the sexes are clearly distinguishable.
139	What advantage did hereditary variations in Drosophila provide?	Variations could be observed easily with low-power microscopes.
140	What type of crosses did Morgan perform in Drosophila?	Dihybrid crosses involving sex-linked genes.
141	Which female Drosophila traits were crossed by Morgan?	Yellow body and white eyes.
142	Which male Drosophila traits were crossed by Morgan?	Brown body and red eyes.
143	Why did Morgan conclude that genes did not assort independently?	Because parental combinations appeared more frequently than non-parental combinations.
144	On which chromosome were the studied genes located?	X chromosome.
145	What is linkage?	Physical association of genes on the same chromosome.
146	What is recombination?	Formation of non-parental gene combinations.
147	What did Morgan discover about tightly linked genes?	They showed very low recombination.
148	What did Morgan discover about loosely linked genes?	They showed higher recombination.
149	Which gene pair in Drosophila showed only 1.3% recombination?	White and yellow genes.
150	Which gene pair in Drosophila showed 37.2% recombination?	White and miniature wing genes.
151	Which student of Morgan mapped gene positions on chromosomes?	Alfred Sturtevant.
152	On what basis did Sturtevant map genes?	Frequency of recombination between gene pairs.
153	What are genetic maps used for today?	As starting points in sequencing whole genomes.
154	Which major project used genetic maps extensively?	Human Genome Sequencing Project.
155	Which scientist carried out several dihybrid crosses in Drosophila?	Thomas Hunt Morgan.
156	Why did Morgan perform dihybrid crosses in Drosophila?	To study sex-linked genes.
157	On which chromosome were the studied genes located?	X chromosome.
158	Define linkage.	Physical association of genes on the same chromosome.
159	Define recombination.	Generation of non-parental gene combinations.
160	What did Morgan discover about genes located on the same chromosome?	Some genes are tightly linked while others are loosely linked.
161	What is the characteristic of tightly linked genes?	Very low recombination frequency.
162	What is the characteristic of loosely linked genes?	Higher recombination frequency.
163	Which gene pair showed only 1.3% recombination in Drosophila?	White and yellow genes.
164	Which gene pair showed 37.2% recombination in Drosophila?	White and miniature wing genes.
165	Who used recombination frequency to map genes?	Alfred Sturtevant.
166	What did Sturtevant use as a measure of distance between genes?	Frequency of recombination.
167	What is a genetic map?	A map showing positions of genes on chromosomes.
168	Why are genetic maps important in modern biology?	They are used in sequencing whole genomes.
169	Which project extensively used genetic maps?	Human Genome Sequencing Project.
170	Why does Cross A show stronger linkage?	Because recombination frequency is lower.
171	What causes non-parental gene combinations?	Recombination.
172	What type of gene combinations appear more frequently in linked genes?	Parental gene combinations.
173	Which organism became a major model for linkage studies?	Drosophila melanogaster.
174	What key concept did Morgan establish through his experiments?	Genes located on the same chromosome show linkage and do not assort independently.
175	What are polygenic traits?	Traits controlled by three or more genes.
176	Why do polygenic traits show continuous variation?	Because multiple genes and environmental influence affect them.
177	Which human trait is given as an example of polygenic inheritance?	Human skin colour.
178	How is phenotype determined in polygenic inheritance?	By the additive effect of each allele.
179	Which genes are assumed to control human skin colour in the text?	A, B, and C.
180	Which alleles are responsible for dark skin colour?	Dominant alleles A, B, and C.
181	Which alleles are responsible for light skin colour?	Recessive alleles a, b, and c.
182	Which genotype produces the darkest skin colour?	AABBCC.
183	Which genotype produces the lightest skin colour?	aabbcc.
184	What type of skin colour results from three dominant and three recessive alleles together?	Intermediate skin colour.
185	What is pleiotropy?	A condition where a single gene affects multiple phenotypic traits.
186	What is a pleiotropic gene?	A gene showing multiple phenotypic expressions.
187	What usually causes pleiotropy?	Effect of a gene on metabolic pathways contributing to different phenotypes.
188	Which human disease is given as an example of pleiotropy?	Phenylketonuria.
189	Which enzyme gene is mutated in phenylketonuria?	Phenylalanine hydroxylase.
190	What are the phenotypic effects of phenylketonuria?	Mental retardation and reduced hair and skin pigmentation.
191	Which major topic begins after pleiotropy?	Sex determination.
192	What did Henking observe about sperm formation in insects?	50% sperm received the X body and 50% did not.
193	What is the XO type of sex determination?	A mechanism where males have one X chromosome and females have two X chromosomes.
194	In XO sex determination, what do all eggs contain?	An X chromosome besides autosomes.
195	In XO sex determination, what types of sperm are produced?	Some with X chromosome and some without X chromosome.
196	Which offspring develop from sperm carrying an X chromosome in XO system?	Females.
197	Which offspring develop from sperm lacking an X chromosome in XO system?	Males.
198	Why is the X chromosome called a sex chromosome?	Because it determines sex.
199	What are autosomes?	Chromosomes other than sex chromosomes.
200	Which organism is an example of XO type sex determination?	Grasshopper.
201	What chromosome composition do male grasshoppers have?	One X chromosome plus autosomes.
202	What chromosome composition do female grasshoppers have?	Two X chromosomes plus autosomes.
203	What is the XY type of sex determination?	A system where males are XY and females are XX.
204	Which chromosome is smaller in XY type sex determination?	Y chromosome.
205	Which organisms are mentioned as having XY sex determination?	Humans and Drosophila.
206	What chromosome combination is present in human males?	XY.
207	What chromosome combination is present in human females?	XX.
208	What is male heterogamety?	A condition where males produce two different types of gametes with respect to sex chromosomes.
209	What are the two types of gametes produced in male heterogamety?	Gametes with X chromosome and gametes with Y chromosome (or without X in XO type).
210	Which organisms are examples of male heterogamety?	Humans and Drosophila.
211	What type of sex determination occurs in birds?	Female heterogamety.
212	What sex chromosomes are present in female birds?	ZW chromosomes.
213	What sex chromosomes are present in male birds?	ZZ chromosomes.
214	Which sex produces two types of gametes in birds?	Females.
215	What is the sex determining mechanism in humans?	XY type.
216	How many pairs of autosomes are present in humans?	22 pairs.
217	Which chromosomes determine male characteristics in humans?	X and Y chromosomes.
218	What type of gametes are produced during human spermatogenesis?	50% X-bearing sperm and 50% Y-bearing sperm.
219	What type of ova are produced in human females?	Only X-bearing ova.
220	What determines the sex of a child in humans?	Genetic makeup of the sperm.
221	What is the probability of having a male or female child in each pregnancy?	50 percent each.
222	What is the basis of sex determination in honey bee?	Number of sets of chromosomes received by the individual.
223	How is a female honey bee produced?	By fertilisation of egg with sperm.
224	How is a male honey bee (drone) produced?	From an unfertilised egg by parthenogenesis.
225	What is the chromosome number in female honey bees?	Diploid, 32 chromosomes.
226	What is the chromosome number in male honey bees?	Haploid, 16 chromosomes.
227	What is the sex determination system in honey bee called?	Haplodiploid sex determination.
228	How do male honey bees produce sperms?	By mitosis.
229	What is mutation?	Alteration in DNA sequence causing changes in genotype and phenotype.
230	Besides recombination, what else produces variation in DNA?	Mutation.
231	What chromosomal changes occur due to deletion or duplication of DNA segments?	Chromosomal aberrations.
232	In which cells are chromosomal aberrations commonly observed?	Cancer cells.
233	What is a point mutation?	Change in a single base pair of DNA.
234	Which disease is a classical example of point mutation?	Sickle-cell anaemia.
235	What are frame-shift mutations caused by?	Insertions or deletions of DNA base pairs.
236	What are mutagens?	Chemical and physical factors that induce mutations.
237	Which radiation is mentioned as a mutagen?	UV radiation.
238	What is pedigree analysis?	Study of inheritance of traits over several generations in a family.
239	Why is pedigree analysis important in human genetics?	It helps trace inheritance of specific traits, abnormalities, or diseases.
240	Why are controlled crosses not possible in humans?	Ethical and biological limitations.
241	What does a pedigree chart represent?	Family history of inheritance of a particular trait across generations.
242	What is the carrier of genetic information?	DNA.
243	Where are genes located?	On DNA present in chromosomes.
244	What is a mutation?	An alteration or change in genetic material.
245	Into which two categories are genetic disorders broadly classified?	Mendelian disorders and chromosomal disorders.
246	What causes Mendelian disorders?	Mutation or alteration in a single gene.
247	How are Mendelian disorders transmitted?	According to Mendelian principles of inheritance.
248	Which method helps trace inheritance patterns of Mendelian disorders?	Pedigree analysis.
249	Name some common Mendelian disorders mentioned in the text.	Haemophilia, cystic fibrosis, sickle-cell anaemia, colour blindness, phenylketonuria, and thalassemia.
250	Can Mendelian disorders be dominant or recessive?	Yes.
251	Which disorder is mentioned as an X-linked recessive trait?	Haemophilia.
252	How is an X-linked recessive trait usually transmitted?	From carrier female to male progeny.
253	What causes colour blindness?	Defect in red or green cone cells due to mutation in genes on the X chromosome.
254	Which colours cannot be distinguished in red-green colour blindness?	Red and green.
255	What is the frequency of colour blindness in males?	About 8 percent.
256	What is the frequency of colour blindness in females?	About 0.4 percent.
257	Why is colour blindness more common in males?	Males have only one X chromosome.
258	What is the probability that the son of a carrier mother will be colour blind?	50 percent.
259	Why is a carrier mother usually not colour blind?	Because the normal dominant allele masks the recessive allele.
260	Under what condition can a daughter become colour blind?	If the mother is a carrier and the father is colour blind.
261	What type of disease is haemophilia?	Sex-linked recessive disease.
262	What is affected in haemophilia?	A protein involved in blood clotting.
263	What happens in a haemophilic individual after a simple cut?	Non-stop bleeding occurs.
264	Can a heterozygous female transmit haemophilia?	Yes, to her sons.
265	Why is haemophilia rare in females?	The mother must be a carrier and the father haemophilic.
266	What type of inheritance does sickle-cell anaemia show?	Autosomal recessive inheritance.
267	Which alleles control sickle-cell anaemia?	HbA and HbS.
268	Which genotype shows sickle-cell disease?	HbSHbS.
269	What is the condition of heterozygous individuals (HbAHbS)?	They are carriers but usually unaffected.
270	What is the probability that a carrier parent transmits the mutant HbS gene?	50 percent.
271	Which amino acid substitution causes sickle-cell anaemia?	Glutamic acid is replaced by valine at the sixth position of β-globin chain.
272	Which codon change causes sickle-cell anaemia?	GAG changes to GUG.
273	What happens to mutant haemoglobin under low oxygen tension?	It polymerises.
274	How does sickle-cell anaemia affect RBC shape?	RBCs change from biconcave discs to elongated sickle-shaped structures.
275	What type of inheritance does phenylketonuria show?	Autosomal recessive inheritance.
276	Which enzyme is absent in individuals with phenylketonuria?	Enzyme that converts phenylalanine into tyrosine.
277	What accumulates in phenylketonuria due to enzyme deficiency?	Phenylalanine.
278	Into what compounds is excess phenylalanine converted?	Phenylpyruvic acid and other derivatives.
279	What effect does accumulation of phenylalanine derivatives have on the brain?	Mental retardation.
280	Why are phenylalanine derivatives excreted in urine?	Due to poor absorption by the kidney.
281	What type of disease is thalassemia?	Autosomal-linked recessive blood disease.
282	How is thalassemia transmitted to offspring?	From heterozygous carrier parents.
283	What causes thalassemia?	Mutation or deletion affecting globin chain synthesis.
284	Which globin chains are affected in thalassemia?	Alpha (α) and beta (β) globin chains.
285	What is the main effect of abnormal globin synthesis in thalassemia?	Formation of abnormal haemoglobin causing anaemia.
286	What is α-thalassemia?	Disorder caused by reduced production of α-globin chains.
287	Which genes control α-thalassemia?	HBA1 and HBA2 genes.
288	On which chromosome are HBA1 and HBA2 located?	Chromosome 16.
289	What causes α-thalassemia?	Mutation or deletion of one or more α-globin genes.
290	What happens when more α-globin genes are affected?	Fewer alpha globin molecules are produced.
291	What is β-thalassemia?	Disorder caused by reduced production of β-globin chains.
292	Which gene controls β-thalassemia?	HBB gene.
293	On which chromosome is the HBB gene located?	Chromosome 11.
294	What causes β-thalassemia?	Mutation in one or both HBB genes.
295	How does thalassemia differ from sickle-cell anaemia?	Thalassemia is a quantitative defect, while sickle-cell anaemia is a qualitative defect.
296	What causes chromosomal disorders?	Absence, excess, or abnormal arrangement of chromosomes.
297	What is aneuploidy?	Gain or loss of one or more chromosomes due to failure of chromatid segregation.
298	What is polyploidy?	Increase in a whole set of chromosomes due to failure of cytokinesis.
299	In which organisms is polyploidy commonly observed?	Plants.
300	How many chromosomes are present in a normal human cell?	46 chromosomes.
301	How many pairs of autosomes are present in humans?	22 pairs.
302	What is trisomy?	Presence of an additional copy of a chromosome.
303	What is monosomy?	Absence of one chromosome from a pair.
304	What is genetics?	A branch of biology dealing with principles of inheritance and its practices.
305	Who first systematically studied inheritance?	Gregor Mendel.
306	What did Mendel call the units controlling characters?	Factors.
307	What are alleles?	Pairs of factors regulating the same character.
308	Which law states that dominant characters are expressed in heterozygous condition?	Law of Dominance.
309	In which condition are recessive traits expressed?	Homozygous condition.
310	Do characters blend in heterozygous condition according to Mendel?	No, characters do not blend.
311	Which law explains separation of alleles during gamete formation?	Law of Segregation.
312	Which types of dominance other than complete dominance are mentioned?	Incomplete dominance and co-dominance.
313	Which law states that factors assort independently during inheritance of two characters?	Law of Independent Assortment.
314	What is a Punnett Square?	A square tabular representation showing theoretical combinations of gametes.
315	What is genotype?	Genetic constitution or factors controlling characters.
316	What is phenotype?	Physical expression of characters.
317	What are linked genes?	Genes located on the same chromosome.
318	What happens to closely located linked genes?	They assort together.
319	What causes distantly located linked genes to assort independently?	Recombination.
320	What are sex-linked genes?	Genes linked to sex chromosomes.
321	What are autosomes?	Chromosomes other than sex chromosomes.
322	What are the sex chromosomes in human females?	XX.
323	What are the sex chromosomes in human males?	XY.
324	What are the sex chromosomes in male birds?	ZZ.
325	What are the sex chromosomes in female birds?	ZW.
326	What is mutation?	Change in genetic material.
327	What is a point mutation?	Change in a single base pair of DNA.
328	Which disease is caused by a point mutation in β-globin gene?	Sickle-cell anaemia.
329	What is pedigree analysis used for?	Studying inheritance of traits and disorders in families.
330	What causes polyploidy?	Increase in a whole set of chromosomes.
331	Which disorder is caused by mutation in phenylalanine hydroxylase gene?	Phenylketonuria.
332	Which blood disorder is a quantitative defect in globin synthesis?	Thalassemia.
333	Which blood disorder is a qualitative defect in globin function?	Sickle-cell anaemia.
334	Which scientist proposed the Chromosomal Theory of Inheritance?	Walter Sutton and Theodore Boveri (though Sutton specifically united the knowledge and named it).
335	Which organism did T.H. Morgan use for genetics experiments?	Drosophila melanogaster.