Molecular Basis of Inheritance

Question 1

Definition of nucleoside

Answer 1

Sugar + base

Question 2

Definition of nucleotide

Answer 2

Sugar + base + phosphate

Question 3

Definition of introns

Answer 3

Non coding region of a gene

Question 4

Definition of exons

Answer 4

Coding regions of a gene

Question 5

Definition of transposon based repeats

Answer 5

DNA sequence that move to a randomly selected location in the sequence

Question 6

Definition of satellite DNA

Answer 6

V large arrays of tandemly repeating non coding DNA, main structural constituent of heterochromatin

Question 7

Definition of dosage compensation

Answer 7

Process by which the gene expression in sex genes are stopped by forming heterochromatin

Question 8

Definition of matrilineal

Answer 8

Does not follow any autosomal/sex linked inheritance patterns, only maternal DNA is passed on

Question 9

What is DNA

Answer 9

Genetic material

Question 10

Nucleotide composition

Answer 10

Deoxyribose(OHH)/ribose(OHOH)

PO4 3-

Nitrogenous bases
Purine
-Adenine NH2
-Guanine NH2, C=O

Pyramidine

• Cytosine C=O NH2
• Thymine C=O CH3
• Uracil C=O

Question 11

Nucleoside composition

Answer 11

Sugar + base = nucleoside

Adenine + deoxyribose = deoxyadenosine

Question 12

Formation of phosphodiester bonds

Answer 12

DNA polymerase forms PDB between 3C OH and PO4 3-

Releases 2 PO4 3-

Question 13

Polarity of polynucleotide chains

Answer 13

5 PO4 3- => 3 Deoxyribose

Question 14

Structure of DNA

Answer 14

RH double helix

Antiparallel strands

A=T, C=-G, perpendicular to helical axis

Question 15

Describe semiconservative replication

Answer 15

2 single template strands for base pairing

2 new strands made up of 1 old and 1 new strand

Question 16

Describe the composition of coding DNA

How does this differ between eukaryotes and prokaryotes?

Answer 16

2000 bases code for a gene
1.1% of genome codes for protein

Eukaryotes have

• promoters, coding, non coding, termination sequences
• premRNA must have introns spliced out => mRNA

Prokaryotes have
-promoters, coding, termination sequences

Question 17

What are transposon based repeats
What are the 2 consequences
What are the 2 types

Answer 17

Section of DNA => mRNA =reverse transcriptase=> DNA moves to random location

Often enters inactive regions = no effect
Enters functioning genes => cancer possible

LINES
SINES

Question 18

What is heterochromatin

How is it used?

Answer 18

Compact = transcriptionally inactive
Long arrays of tandem repeats/satellite DNA

Forensics, paternity testing

Question 19

What is snRNA

Answer 19

Small nuclear RNA

Associates with proteins = ribonucleoprotein needed to splice premRNA

Question 20

What is rRNA

Answer 20

rRNA + protein = ribosome

Question 21

Describe the structure of tRNA

Answer 21

Clover shaped

5’ HB within molecule anticodon AA binding site 3’

Question 22

What is dosage compensation

How is it used in the X chromosome

Answer 22

Xist gene in X inactivation center transcribed => ncRNA
Heterochromatin forms => inherited somatically

Only 1 X expressed per cell, both => death

Question 23

What is miRNA

How does it work

Answer 23

Types of ncRNA (regulates gene expression)

Transcribed from miRNA gene, exported into cytoplasm and processed by nuclease
Single strand base pairs with mRNA => binds and cleaves for
-translational repression
-deadenylation => unstable mRNA

Question 24

What is mtDNA
How is it inherited
What are the consequences of mutations here

Answer 24

Circular 13 polypeptides, rRNA, tRNA

Matrilineal

Mutations affect organs with high energy reqs (muscles, nerves, LHON, Ataxia)