Download Assignment 1

Human Molecular Genetics
Assignment 1 (Week 1) with Answers
Q1: With reference to the central dogma of biology, the statement “DNA goes to RNA”
refers to the process of ______________
(a) Protein synthesis
(b) DNA replication
(c) Transcription
(d) Translation
Answer 1: C (Transcription),
Biological process of copying DNA into RNA is termed “Transcription”, making another
copy of DNA from DNA is termed “Replication” and making protein from RNA is termed
“Translation”.
Q2: With reference to the central dogma of biology, the statement “RNA goes to protein”
refers to the process of ______________
(a) RNA synthesis
(b) DNA replication
(c) Transcription
(d) Translation
Answer 2: D (Translation)
Explanation stated in the first answer.
Q3: What is the maximum length of a polypeptide encoded by an mRNA that is 60 nucleotide
long?
(a) 60 amino acid long
(b) 40 amino acid long
(c) 30 amino acid long
(d) 20 amino acid long
Answer 3: D ( 20 amino acid long):
Taking into account that 3 nucleotides (termed codon), codes for 1 amino acid, therefore
60/3= 20
Q4: Replicated copies of each chromosome are called _____________ and are joined at the
___________.
A. homologues/centromere
B. sister chromatids/spindle fiber
C. sister chromatids/centromere
D. homologues/ spindle fiber
Answer 4: C (sister chromatids/centromere)
Replicated copies of each chromosome are called sister chromatids and they are joined at the
centromere. Homologues are referred to pair of chromosome, which might be non-identical
and we receive one from mother and the other from father. Spindle fibres are protein in
nature (microtubules) and are formed during cell division.
Q5: An allele is
a. present only in males and is responsible for sex determination
b. an alternate form of a gene
c. a mutant form of a RNA
d. A DNA made in the lab
Answer 5: B (An alternate form of gene)
There are many variants of a gene, each of which is termed an allele. For each gene we have
two alleles, since we are diploids.
Q6. Shown below is a karyotype of an individual suspected to have a genetic disorder. Based
on our understanding on the chromosomal basis of disorders, identify the disorder that the
karyotype represents.
(a) Down syndrome
(b) Prader–Willi syndrome
(c) Turner syndrome
(d) Klinefelter syndrome
Answer 6: A (Down syndrome)
This karyotype shows trisomy for chromosome 21, and hence the disorder is Down
syndrome.
Q7. Examine the karyotype given below and identify the possible cause for the defect.
a. translocation
b. chromosomal breakage
c. non-disjunction
d. gene deletion
Answer 7 : C ( Non-disjunction)
This karyotype as represent trisomy for chromosome 21, which could occur due to nondisjunction during meiosis.
Q8. Which one the following statements accurately explain the relationship between the parts
of genetic materials discussed.
A. Each DNA molecule contains many genes
B. Each DNA molecule contains many chromosomes
C. Each chromosome contains many DNA
D. Each gene contain many genes
Answer 8: A (Each DNA molecule contains many genes)
This is the only correct statement. All other options are incorrect.
Q9 and 10:
Shown below is an 80 base pair segment of a hypothetical gene. It includes the promoter and
the first codon of the gene. The sequences of both strands of the DNA duplex are shown: the
top strand reads 5’ to 3’, left to right (1 to 80); the bottom, complimentary, strand reads 5’ to
3’ right to left (80 to 1). Assume that the synthesis of mRNA starts from the base shown in
the box (A-T), the start point of the arrow. The arrow also identifies the direction of mRNA
synthesis.
Q9: Which one of the following options correctly lists the second, third and fourth amino
acids of the polypeptide that would result from the translation of the mRNA? You may
consult the genetic code from the text book or in the video file.
a. Cys-Glu-Trp
b. Asp-Asn-Asn
c. Val-Trp-Thr
d. Met-Asp-Asn
Answer 9: B (Asp-Asn-Asn),
This is the only ORF that shows no in-frame stop codon in the sequence given. And these are
three amino acids following the first Met amino acid for this ORF.
Q10. If the third base (U) of the resulting mRNA is mutated to G, then what would be the
effect of the mutation on the polypeptide being synthesized? Assume that this mutation does
not affect the mRNA synthesis.
a. Polypeptide will be synthesized, but the amino acid coded in that place would be Lys.
b. Due to the change, the polypeptide will not be synthesized.
c. Protein will be synthesized without any change in the sequence of the polypeptide being
made.
d. The mutation will introduce a stop codon, thus, truncating the synthesis.
Answer 10: C (Protein will be synthesized without any change in the sequence of the
polypeptide being made).
If the ORF discussed above for Question No 8 is correct, then this mutation is less likely to
alter the protein coding potential of the resulting mRNA as the change would be present
upstream of the initiation codon.