Genetic Variation

Question 1

What is mutation?

Answer 1

Change in DNA sequence leads to genetic variation known as mutation

Question 2

What is alleles?

Answer 2

Different types of a gene or variation in a gene

Question 3

What is locus:

Answer 3

Location of a gene in chromosome

Question 4

Homozygote

Answer 4

Having the same allele on both chromosomes of a pair

Question 5

Heterozygote

Answer 5

Having different alleles on both chromosomes of a pair

Question 6

Genotype

Answer 6

The combination of alleles presents at a locus on chromosome of a pair

Question 7

Phenotype

Answer 7

Physically expressed feature of a genotype is called phenotype

Question 8

Polymorphism

Answer 8

DNA sequence variants that are more common in population are conventionally known as polymorphism. Loci that contain multiple alleles are called polymorphic.

Question 9

point mutation and its types

Answer 9

In which base pair are exchanged or replaced.
Silence mutation, Missense mutation and nonsense mutation

Question 10

Silence mutation

Answer 10

Replacement of base pair is not changing the amino acid sequence

Question 11

Missense mutation

Answer 11

Replacement of base pair changes the amino acid in final protein

Question 12

Nonsense mutation or nonsense mediated RNA decay

Answer 12

Replacement of base pair produces one of the three STOP codons in mRNA and protein chain terminates earlier.

Question 13

Frameshift mutation

Answer 13

Deletion or insertion of one or more base pair leads to alteration of downstream codons known as frameshift mutation.

Question 14

Splice site mutation and location of splice site mutation

Answer 14

Occurs at intron - exon boundaries and can alter splicing response that is necessary for proper excision of an intron.
Location: GT sequence (5’ splice site - donor site) or AG sequence (3’ splice site - Acceptor site).

Question 15

Promoter mutation

Answer 15

Leads to reduce affinity for RNA polymerase for the promoter site leads to reduce synthesis of mRNA and protein

Question 16

Loss of function, gain of function and dominant negative mutation

Answer 16

1. Loss function: results in protein product eliminated or reduced that leads to haploinsufficiency (50% protein is not enough for normal body functioning)
2. Gain function - produces novel or excess protein product
3. Dominant negative: produces altered protein which affects with the normal protein produced by other alleles

Question 16

Protein electrophoresis steps and application

Answer 16

• Tissue sample loaded on to electrically charged gel
• Due to difference in charge amino acids travels to different poles
• Staining step produces bands that reflects molecules with different electrical charges and therefore different amino acid sequences, are visible
  Application: to detect genetic variation

Question 17

Southern Blotting steps and application

Answer 17

• DNA sample separated from the blood and digested with restriction enzyme
• Loaded onto gel electrophoresis to produce DNA fragments according to the sizes
• DNA denatured by alkaline solution
• transferred from gel to solid membrane (called southern blot) to fix their position
• hybridization with radioactive probe
• exposed to X ray film (autoradiography)
• Produces different bands indicating different sizes of fragments (AA)

Application: to detect insertion, deletion and rearrangements of DNA, restriction fragment length polymorphism

Question 18

PCR steps and application

Answer 18

• Tissue sample is heated at 95 degrees to denature and produce single strands
• Primer annealing phase - sample cool down to 55 degrees and hybridize with primers to flank the sequence of interest.
• again, heated to intermediate temperature at 72 degrees where DNA polymerase adds nucleotides to 3’ position and starting at the primer
• this blunt copy of DNA serves as a template for repeat cycle of heating and cooling
• multiple copies of DNA are produced by this method bounded on each end of the primer

Application: to detect genetic variations (insertion, deletion, rearrangement) and forensic investigation

Question 19

Components required for PCR

Answer 19

• Two primers
• DNA polymerase
• Free nucleotides
• DNA sample

Question 20

Gene and genotype frequencies

Answer 20

specify the proportions of each allele and each genotype, respectively, in a population.

Question 21

Codominance

Answer 21

Where effect of both the alleles is observed in heterozygote.

Question 22

Conservative and radicle substitution

Answer 22

Conservative: one amino acid replaced by the mutant amino acid, but they share the common chemical and physical properties which does not affect the final protein function.
Radicle: amino acids differ in their chemical and physical properties which affects the function of final protein.