Biology Chromosome and DNA MCQs Chapter 6 Class 12

Biology Chromosome and DNA for Second Year Entry Tests and FSC Board Exams

Chromosome and DNA is a crucial chapter in Second Year Biology that explains how genetic material is organized, transmitted, and expressed in living organisms. This topic is highly important for students preparing for MDCAT, NUMS, AKU, NUST, UET ECAT, and FSC Second Year board exams. Key concepts include structure of DNA, replication, transcription, translation, chromosomes, karyotypes, and mutations, which are frequently tested in both MCQs and conceptual questions.

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Created on March 02, 2022 By Ali Durrani

Biology Ch 6 Class 12 Chromosomes and DNA

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1 / 62

Transfer of genetic material from one cell to another that can alter the genetic makeup of recipient cell is called

Mutation

Transuction

Replication

Variation

2 / 62

An anticodon is the sequence of the nitrogenous bases on the:

NTS 2014
Biology
Chromosomes and DNA
Elimination Tool:

A) complementary strand of DNA which codes for one amino acid

B) complementary strand of mRNA which codes for one amino acid

C) tRNA molecule where the amino acid is attached

D) tRNA molecule which recognizes the appropriate sequence of bases on the mRNA

3 / 62

Evolutionary relationship among species are reflected in their ________.

NUMS 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) DNA and proteins

B) Only DNA

C) Only proteins

D) RNA

4 / 62

Which is incorrect?

Chromosomes 1st observed by walther Fleming

Chromosomal theory of inheritance 1st formulated by Walter Sutton

1st evidence of hereditary nature of DNA provided by Friedrich Meischer

. Sex chromosomes discovered by Thomas Hunt Morgan

5 / 62

An individual has an additional sex chromosome. Which syndrome does he have?

NUMS 2014
Biology
Chromosomes and DNA
Elimination Tool:

A) Down's syndrome

B) Turner's syndrome

C) Jacob's syndrome

D) Klinefelter's syndrome

6 / 62

A typical human chromosome contains _________ nucleotides in its DNA

240 million

140 million

150 million

160 million

7 / 62

Y chromosome in humans:

NUMS 2015
Biology
Chromosomes and DNA
Elimination Tool:

A) Is completely inert

B) Carries few genes

C) Carries many genes

D) Contains genes for hemophilia and color blindness

8 / 62

Histones have abundance of amino acids

Valine and lysine

Arginine and lysine

Valine and arginine

Histidione and threonine

9 / 62

Haploid and monoploid numbers of chromosomes of hexaploid wheat are:

NTS 2014
Biology
Chromosomes and DNA
Elimination Tool:

A) 21 and 42

B) 7 and 21

C) 21 and 7

D) 42 and 21

10 / 62

What would be the number of nucleotides for a protein molecule of about 142 amino acids?

NUMS 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) 430

B) 142

C) 426

D) 460

11 / 62

A fern has _____ pairs of chromosomes.

NTS 2012
Biology
Chromosomes and DNA
Elimination Tool:

A) 23

B) 40

C) 500

D) 13

12 / 62

What is the effect of enzyme DNA ligase?

PMC 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) DNA is broken up at specific sites

B) DNA fragments are joined together

C) DNA replication occurs

D) DNA transcription occurs

13 / 62

Mutations can occur in:

NUMS 2016
Biology
Chromosomes and DNA
Elimination Tool:

A) DNA

B) Protein

C) RNA

D) A and C

14 / 62

Gene mutations take place in:

NUMS 2014
Biology
Chromosomes and DNA
Elimination Tool:

A) Ribosomes

B) Chloroplasts

C) Deoxyribonucleic acids

D) None of them

15 / 62

Central dogma is

Transfer of information from DNA to mRNA

Basic mechanism of reading and expressing genes

Transfer of information from RNA to proteins

Synthesis of all three types of RNA

16 / 62

DNA has a helical shape with the diameter of

3 nm

4 nm

2 nm

5 nm

17 / 62

Phenylketonuria is

NTS 2016 DUHS & JSMU
Biology
Chromosomes and DNA
Elimination Tool:

A) Sex linked dominant trait

B) Sex linked recessive trait

C) Autosomal dominant trait

D) Autosomal recessive trait

18 / 62

Which of the following enzymes is used to join DNA fragments?

NTS 2016 DUHS & JSMU
Biology
Chromosomes and DNA
Elimination Tool:

A) DNA polymerase

B) Ligase

C) Primase

D) Endonuclease

19 / 62

Which of the following statements correctly describes homologous chromosomes?

NTS 2016 DUHS & JSMU
Biology
Chromosomes and DNA
Elimination Tool:

A) They are formed during meiosis.

B) They are held together by centromeres.

C) They are chromatids of the same chromosome.

D) They carry both morphologically similar members with same set of genes.

20 / 62

The particular array of chromosomes that an individual possesses is called its:

PMC 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) Genotype

B) Phenotype

C) Karyotype

D) Allele

21 / 62

Highly condensed portions of the chromatin are called:

NTS 2011
Biology
Chromosomes and DNA
Elimination Tool:

A) Euchromatin

B) Heterochromatin

C) Nucleosome

D) Super coils

22 / 62

During DNA replication ______ attaches the fragment to the lagging strand.

NUMS 2019 Reconduct
Biology
Chromosomes and DNA
Elimination Tool:

A) Ligase

B) Invertase

C) Helicase

D) Topoisomerase

23 / 62

Bacteria were grown in a medium containing heavy isotope of nitrogen (N15) for many generations and all their DNA contained many heavy nitrogen only. A bacterium of this type was transferred to normal medium and allowed to duplicate. After two divisions of heavy DNA is likely to be that:

NTS 2012
Biology
Chromosomes and DNA
Elimination Tool:

A) Only one daughter cell will have heavy DNA

B) Two daughter cells have normal DNA and other two have heavy DNA

C) All daughter cells have heavy DNA

D) Half daughter cells have heavy DNA and other half have normal DNA

24 / 62

Chromosomes are composed of

40% protein and 60% DNA

50% protein and 50% DNA

70% protein and 30% DNA

60% protein and 40% DNA

25 / 62

Locus is defined as:

NUMS 2019 Reconduct
Biology
Chromosomes and DNA
Elimination Tool:

A) Position of a gene on the chromosome

B) Appearance of a trait in an individual

C) Partner of a gene pair

D) Gene in an individual for a trait

26 / 62

The total of all the alleles in a population is called a:

NUMS 2014
Biology
Chromosomes and DNA
Elimination Tool:

A) Genetic drift

B) Genotype

C) Gene pool

D) Gene mutation

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Within the chromosomes, each chromatid contains ______ DNA molecule:

NUMS 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) One

B) Two

C) Three

D) Half

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Chromosome is made of

2 chromatids +1 centromere +secondary constriction

1 chromated + 1 centromere + primary constriction

2 chromatids + 1 centromere + primary constriction

2 chromatids + 2 centromere + secondary constriction

29 / 62

Genetic information in the DNA is encoded as:

NTS 2018
Biology
Chromosomes and DNA
Elimination Tool:

A) Deoxyribose sugar

B) Ribose sugar

C) Phosphate group

D) Sequence of nitrogenous bases

30 / 62

The genotype of a normal male in humans is ______ chromosomes.

NTS 2012
Biology
Chromosomes and DNA
Elimination Tool:

A) 44 + XX

B) 44 + XY

C) 44 + XXY

D) 44 + XO

31 / 62

In alkaptonuria

Patient's urine contains homogenetisic acid

Urine becomes black

Both a and b

Urine contains phenylalanine

32 / 62

The number of base pairs in a complete helical turn is/are:

NUMS 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) 1

B) 5

C) 10

D) 15

33 / 62

Who discovered DNA?

P.A.Levene

Frederick Griffith

Friedrich Miescher

Rosalind Franklin

34 / 62

Part of the amino acid sequences In normal and sickle cell hemoglobin are shown.

Normal haemoglobin

Thr – pro – glu – glu

Sickle cell haemoglobin

thr – pro – val – glu

mRNA codons for these amino acids are

Glutamine (glu) GAA GAG

Threonine (thr) ACU ACC

Proline (pro) CCU CCC

Valine (val) GUA GUG

Which transfer RNA molecule is Involved in the formation of this part of the sickle cell haemoglobin?

NTS 2016 DUHS & JSMU
Biology
Chromosomes and DNA
Elimination Tool:

A) GUG

B) CAU

C) UGC

D) GAG

35 / 62

The sequence of nucleotides that determines the amino acid sequence of a protein is

Chromosome

DNA

RNA

Gene

36 / 62

The biochemical analysis of a sample of DNA shows that 32% of the nitrogenous bases are cytosine. What is the total % of adenine and uracil in RNA transcribed from this DNA?

NTS 2015 SMBBMC
Biology
Chromosomes and DNA
Elimination Tool:

A) 16%

B) 18%

D) 36%

C) 32%

37 / 62

The Meselson and Stahl experiment confirmed that DNA replicates in _____ manner.

NUMS 2019 Reconduct
Biology
Chromosomes and DNA
Elimination Tool:

A) Conservative

B) Semi – conservative

C) Dispersive

D) New synthesis

38 / 62

In a typical nucleotide, the nitrogenous base is attached to _______ carbon of pentose sugar.

NTS 2010
Biology
Chromosomes and DNA
Elimination Tool:

B) 5th

C) 4th

D) 3rd

E) 1st

39 / 62

Particular array of chromosomes that an individual processes is called its:

NUMS 2019 Reconduct
Biology
Chromosomes and DNA
Elimination Tool:

A) Nucleosome

B) Gene pool

C) Karyotype

D) Centromere

40 / 62

Which of the following can be blocked, if one wants to stop translation of mRNA?

NUMS 2019 Reconduct
Biology
Chromosomes and DNA
Elimination Tool:

A) RNA polymerase

B) Helicase

C) Elongation factor

D) Primase

41 / 62

Which statement is correct?

Leading strand elongates away from the replication fork

Lagging strand elongates towards the replication fork

Lagging strand is constructed discontinuously.

Both a and b

42 / 62

“Law of independent assortment” states:

PMC 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) That each pair of alleles assort independently of other pairs of alleles during gamete formation

B) That alleles of each pair of contrasting trait have unequal probability to assort with the alleles of other pair

C) That the two coexisting alleles for each trait segregate (separate) from each other at meiosis so that each gamete receives only one of the two alleles

D) That pertain to inheritance of single trait (monohybrid cross)

43 / 62

In Maxam – Gilbert method, DNA threads are:

NUMS 2015
Biology
Chromosomes and DNA
Elimination Tool:

A) Chemically synthesized

B) Synthesized from mRNA

C) Synthesized by using terminating nucleotides

D) Chemically cut into pieces

44 / 62

A tortion of chromatin that is condensed only during cell division is

Euchromatin

Heterochromatin

Biochromatin

Nucleochromatin

45 / 62

Rate of DNA replication by DNA polymerase is

2000 nucleotides / sec

1000 nucleotides / sec

150 nucleotides / sec

1050 nucleotides / sec

46 / 62

The diploid human chromosome set has:

NTS 2016 SMBBMC
Biology
Chromosomes and DNA
Elimination Tool:

A) 22 pairs of autosomes and 1 pair of sex chromosomes

B) 22 pairs of autosomes and XY chromosomes

C) 22 pairs of autosomes and XX chromosomes

D) Haploid somatic cells and diploid germinal cells

47 / 62

Genetic code is a ______ code and out of 64 codons, _____ are nonsense codons.

NUMS 2019 Reconduct
Biology
Chromosomes and DNA
Elimination Tool:

A) Single ; two

B) Single ; three

C) Triplet ; two

D) Triplet ; three

48 / 62

In DNA A.

A forms two bonds with T

G forms three bonds with C

A forms three bonds with T

Both a and b

49 / 62

What will be the approximate length of a DNA strand having 500 nucleotides?

NUMS 2015
Biology
Chromosomes and DNA
Elimination Tool:

HIDE ELIMINATED OPTIONS

A) 100 nm

B) 130 nm

C) 170 nm

D) 150 nm

50 / 62

Which statement correctly describes the transcription of DNA?

PMC 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) It produces amino acids

B) It produces messenger RNA

C) It results in increased DNA synthesis

D) It is a semi conservative process

51 / 62

Phenotype is:

PMC 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) The genetic component i.e. the genes in an individual for a particular trait

B) Partner of gene pair

C) The form of appearance of a trait

D) The position of a gene on the chromosome

52 / 62

Diameter of DNA double helix is:

NUMS 2015
Biology
Chromosomes and DNA
Elimination Tool:

A) 3.4 nm

B) 0.3 nm

D) 0.2 nm

C) 2 nm

53 / 62

The true E.Coli replicating enzyme is

DNA polymerase I

DNA polymerase II

DNA polymerase III

All of these

54 / 62

DNA contains

Purines (A and G) pyrimidines (U and (c)

Purines (T and (c) pyrimidines (A and G)

Purines (A and (c) pyrimidines (U and G)

Purines (A and G) pyrimidines (T and (c)

55 / 62

In semi-conservative replication

. Sequence of original duplex is conserved after one round of replication

Gererate DNA copies of entirely new molecules

Parental DNA become completely dispersed

Each strand of daughter molecules will be a mixture of old and new

56 / 62

The combination of XXY (47) chromosomes results in:

NTS 2012
Biology
Chromosomes and DNA
Elimination Tool:

A) Down's Syndrome

B) Turner's Syndrome

C) Klinefelter's Syndrome

D) Sickle cell anemia

57 / 62

The chromosomes with equal arms are called:

NTS 2018
Biology
Chromosomes and DNA
Elimination Tool:

A) Metacentric

B) Submetacentric

C) Acrocentric

D) Telocentric

58 / 62

The phenomenon known as crossing-over occurs during:

NTS 2017
Biology
Chromosomes and DNA
Elimination Tool:

A) Mitosis

B) Meiosis

C) Geographic distribution

D) Active transport

59 / 62

Which of the following is NOT the part of RNA?

NTS 2018
Biology
Chromosomes and DNA
Elimination Tool:

A) Nitrogenous bases

B) Ribose Sugars

C) Deoxyribose Sugars

D) Phosphate groups

60 / 62

Which of the following RNA sequences would be transcribed from the DNA sequence ATGGCTAGGAC?

NTS 2017
Biology
Chromosomes and DNA
Elimination Tool:

A) TACGGATCCTG

B) UAGCGAUCCUG

C) AUGCCUAGGAC

D) UACCGAUCCUG

61 / 62

The length of okazaki fragments in eukayotes is

150–250 nucleotides long

200-300 nucleotides

1000-2000 nucleotde

100-200 nucleotides

62 / 62

Transcription is the process in which an RNA copy of the DNA sequence and coding the gene is produced with the help of an enzyme called:

PMC 2020
Biology
Chromosomes and DNA
Elimination Tool:

A) DNA polymerase

B) RNA polymerase

C) DNA transcriptase

D) RNA transcriptase

Your score is

The average score is 58%

Importance of Chromosome and DNA in Competitive Biology

A strong understanding of Chromosome and DNA helps students explain genetic inheritance, cell division, gene expression, and chromosomal disorders. Topics such as Mendelian genetics, DNA structure and function, mutation types, and human karyotypes are commonly asked in entry tests. Practicing chapter-wise MCQs, diagrams, and topic-wise exercises improves accuracy, conceptual clarity, and confidence during exams.

Effective Preparation and Practice Resources for Second Year Students

Effective preparation for Chromosome and DNA includes systematic revision, MCQ practice, and mock testing. Solving past papers and exam-focused questions helps students identify frequently tested areas and strengthen weak concepts. PLS Academy provides structured learning resources that allow students to master Chromosome and DNA and perform confidently in medical entry tests and FSC Second Year board examinations.

JazakAllah.