MGD L1

Question 1

Describe what is meant by “central dogma” of molecular biology

Answer 1

Flow of genetic material in a biological system

Question 2

State two examples of nucleic acids

Answer 2

1. DNA (deoxyribonucleic acid)
2. RNA (ribonucleic acid)

Question 3

What is a nucleic acid?

Answer 3

Nucleic acids are polynucleotides
(linear polymers of nucleotides)

Question 4

What is a nucleotide?

Answer 4

Basic building block of nucleic acids
Consists of
1. pentose sugar (ribose, deoxyribose)
2. Phosphate group
3. Nitrogen containing base

Question 5

State the nitrogenous bases in DNA and RNA

Answer 5

Question 6

Describe the primary structure of a polynucleotide

Answer 6

1. Within nucleotide, pentose sugar + nitrogenous base are connected via glycosidic bond
2. Nucleotides are joined by phosphodiester bonds
3. Polynucleotide chain has two distinct ends and polarity: 5’ → 3’

Question 7

Describe the secondary structure of a polynucleotide

Answer 7

Two anti-parallel, complementary strands

Question 8

Describe the structure of DNA

Answer 8

1. Two complementary anti-parallel polynucleotide chains
2. Each consists of a sugar phosphate backbone + nitrogenous base
3. Nitrogenous base pairing is specific. A=T C=G
4. DNA is negatively charged

Question 9

Why is DNA negatively charged?

Answer 9

• Could be exam question

Question 10

What is the human genome?

Answer 10

Consists of info contained in DNA in one set of human chromosomes

Question 11

How many chromosomes are there in each diploid cell?

Answer 11

46 chromosomes
22 pairs of autosome chromosomes
1 pair of sex chromosomes

Question 12

How long is the DNA in each diploid cell (if stretched)?

Answer 12

2m

Question 13

What is a gene?

Answer 13

Sequence of nucleotides in DNA
Encodes synthesis of protein, RNA or gene product

Question 14

State the two types of genes

Answer 14

Protein-encoding genes
Protein non-encoding genes (most DNA is non-encoding, containing LINEs - Long Interspersed Nuclear Elements - SINEs - Short Interspersed Nuclear Elements)

Question 15

What was the Human Genome Project?

Answer 15

Human genome project
The Human Genome Project (1990 -2003) was the international research effort to determine the DNA
sequence of the entire human genome with the primary goal to discover the complete set of human
genes and make them accessible for further biological study.

Question 16

DNA packaging
How is it possible that DNA in each diploid cell, that is 2 m long, can fit in the nucleus that is 5 - 10 mm?

Answer 16

DNA PACKAGING

1. DNA in nucleus exists in complex with histones, forming chromatin that functions to package long DNA molecules into more compact, denser structures (DNA in chromatin is supercoiled)
   2.2x of the following histone proteins:
   H2A
   H2B
   H3
   H4
   These make up a histone octamer.
   This binds + wraps apporximately 1.7 turns of DNA.
   The addition of H1 histone protein leads to 2 full turns around octamer, forming chromatosome

Question 17

What is the repeating structural (and functional) unit of chromatin?

Answer 17

NUCLEOSOME (contains 8 histone proteins)

Question 18

What are chromosome territories?

Answer 18

Uncondensed chromosomes occupying regions of nucleus

Question 19

How do chromosomes reflect variations in gene expression patterns?

Answer 19

Positions of chromosomes relative to one another differs from cell to cell.

Question 20

During which stage if cel division are chromosomes most compacted?

Answer 20

Metaphase (in mitosis)

Question 21

Describe the structure of a chromosome

Answer 21

1. Each chromosome consists of a short arm and a long arm connected by a centromere
2. A chromatid is one of two identical halves of a replicated chromosome

P arm
Q arm
- pay attention to diagram