Molecular Basis of Inheritance

Question 1

Name the 3 components of a nucleotide.

Answer 1

Deoxyribose sugar

Nitrogenous base

Phosphate group

Question 2

What distinguishes deoxyribose sugar from ribose?

Answer 2

It contains a hydrogen only at position C2 as opposed to an OH group.

Question 3

What 2 groups are the nitrogenous bases categorised into?

Answer 3

Purines

Pyramidines

Question 4

What are the X2 purines?

Answer 4

Adenine

Guanine

Question 5

What are the X2 pyramidines?

Answer 5

Cytosine

Thymine

Question 6

Which base is replaced in RNA and which base does it replace?

Answer 6

Thymine is replaced by Uracil.

Question 7

Are the purines single or double ring structures?

Answer 7

Double.

Question 8

Are the pyramidines single or double ring structures?

Answer 8

Single.

Question 9

A sugar + base makes a…

Answer 9

NucleoSIDE

Question 10

DNA nucleotides have how many phosphate groups?

Answer 10

X3, they are nucleotide TRIphosphates.

Question 11

What type of bonds do nucleotides form?

Answer 11

Phosphodiestser bonds.

Question 12

Which part of the nucleotide is the 5-prime end?

Answer 12

The phosphate group.

Question 13

Which part of the nucleotide is the 3-prime end?

Answer 13

The hydroxyl (OH) group.

Question 14

What is the name given to the inorganic molecule consisting of X2 phosphates (PPi) released when nucleotides bond.

Answer 14

An inorganic pyrophosphate.

Question 15

What is the name of the enzyme which catalyses the formation of DNA molecules from deoxyribonucleotides?

Answer 15

DNA polymerase.

Question 16

Describe the complementary base pairings.

Answer 16

A - T (X2 hydrogen bonds)

C - G (X3 hydrogen bonds)

Question 17

What is the orientation of the X2 DNA strands and their base pairings?

Answer 17

The X2 strands run ANTIPARALLEL with the bases PERPENDICULAR to the helical axis.

Question 18

What is semi-conservative DNA replication?

Answer 18

The process whereby X2 new daughter DNA strands are produced from a single DNA helix, each retaining X1 strand of the original DNA helix due to complementary base pairing.

Question 19

What are INTRONS and EXONS?

Answer 19

INTRONS = non-coding regions of DNA which are lost during transcription.

EXONS = coding regions of DNA.

Question 20

45% of the human genome consists of transposing based repeats such as retrotransposable elements, what are these and how do they work?

Answer 20

Sequences of DNA are transcripted into RNA before being reversely transcribed back to a DNA sequence and inserted back into the genome at a different site.

Examples include:
LINES (Long interspersed elements)
SINES (Shirt interspersed elements)

Question 21

6.6% of the human genome is heterochromatin. What is this?

Answer 21

Chromatin that is so tightly compact it is transcriptionally inactive.

Question 22

What is the name of the gene which is responsible for x-chromosome inactivation in females?

Answer 22

Xist

Question 23

What is it called when one X chromosome in females is transcriptively inactive in order to prevent over transcription?

Answer 23

Dosage compensation.

Question 24

What is the name of the X inactivation centre on the X chromosome which causes mass compression of the X chromosome into heterochromtin?

Answer 24

XIC.

Question 25

What has its own circular genome?

Answer 25

Mitochondria.

Question 26

Is mitochondrial DNA (mtDNA) inherited from the mother only, father only, or both parents?

Answer 26

Mother only.

Question 27

How many polypeptides does mtDNA encode for?

Answer 27

13.

Question 28

Does mtDNA contain introns only, exons only or both?

Answer 28

Exons only.

Question 29

What is the name for the non-Mendelian method of inheritance of mtDNA from mother to progeny?

Answer 29

Cytoplasmic extra-nuclear inheritance.