Session 1: Chromosomes, DNA and Nucleotides

Question 1

What is molecular biology?

Answer 1

Flow of genetic information within a biological system

Question 2

What is a polynucleotide?

Answer 2

Linear polymer of nucleic acid monomers

Question 3

What sugar is found in DNA?

Answer 3

Deoxyribose

Question 4

What sugar is found in RNA?

Answer 4

Ribose

Question 5

What is a nucleotide?

Answer 5

Basic building block of nucleic acids that consists of a pentose sugar molecule (ribose in RNA or deoxyribose in DNA) attached to a phosphate group and a nitrogen-containing base

Question 6

What is a nucleoside?

Answer 6

Nitrogenous base + sugar

Question 7

What is the difference between deoxyribose and ribose structure?

Answer 7

Ribose sugar has a hydroxyl (OH) group at position 2, whereas deoxyribose sugar has a hydrogen (H) atom at position 2

Question 8

What are purines?

Answer 8

Bases with a double-ring structure. Adenine (A) and Guanine (G)

Question 9

What are pyrimidines?

Answer 9

Bases with a single-ring structure. Cytosine (C), Thymine (T), Uracil (U)

Question 10

What bond joins the pentose sugar and nitrogenous base within a nucleotide?

Answer 10

Glycosidic bond

Question 11

What type of bonds join nucleotides?

Answer 11

Phosphodiester

Question 12

By convention, how is polynucleotide primary structure read?

Answer 12

From the 5’ to 3’ end

Question 13

What is the secondary structure of DNA?

Answer 13

Double helix

Base pairs form the rungs of the ladder; Sugar phosphate backbone

Question 14

What bonds join the DNA double helix?

Answer 14

Hydrogen

Question 15

Why is DNA negatively charged?

Answer 15

Phosphate groups

Question 16

Describe some features of DNA’s double-helix secondary structure.

Answer 16

• Two anti-parallel, complementary strands from 5’ to 3’
• Right-handed helix
• Negatively-charged
• Sugar phosphate backbone

Question 17

What is the diameter of DNA?

Answer 17

2nm

Question 18

What is the length of one turn of DNA?

Answer 18

3.4nm

Question 19

What is the structure of RNA?

Answer 19

Single-stranded

Question 20

What bases bind in RNA?

Answer 20

Adenine and Uracil; Guanine and Cytosine

Question 21

What types of secondary structure can RNA form?

Answer 21

The RNA stem can loop to produce…
- Hairpin structure
- Clover-leaf structure (e.g., t-RNA)

Question 22

Where does DNA exist in the nucleus?

Answer 22

In complex with histone proteins

Question 23

What is chromatin?

Answer 23

DNA + histones

Question 24

What is the function of chromatin?

Answer 24

Efficiently package long DNA into a small volume (compact, condensed) to fit into the nucleus of a cell and protect the DNA structure and sequence

Question 25

What is the basic repeating structural and functional unit of chromatin?

Answer 25

Nucleosome

Question 26

What is a chromatosome?

Answer 26

Consists of a nucleosome and an H1 histone protein.

Question 27

What is a histone octamer?

Answer 27

Two each of H2A, H2B, H3, and H4 form the protein complex which DNA wraps around (wraps around 1.7 turns of DNA - 146 base pairs)

Question 28

When are chromosomes most compacted and visible under a light microscope?

Answer 28

During metaphase

Question 29

What is heterochromatin?

Answer 29

Tightly packed DNA, transcriptionally inactive

Question 30

What is euchromatin?

Answer 30

Loosely packed DNA, transcriptionally active

Question 31

How many chromosomes are in each diploid cell of our body?

Answer 31

46

Question 32

How many pairs of chromosomes do humans have?

Answer 32

23 pairs

Question 33

How many pairs of autosomes do humans have?

Answer 33

22 pairs of autosomes; 1 pair of sex chromosomes (XX = Female; XY = Male)

Question 34

What is a karyotype?

Answer 34

A display of the chromosome pairs of a cell arranged by size and shape.

Question 35

What are chromosome territories?

Answer 35

Regions of the nucleus preferentially occupied by particular chromosomes

Question 36

What type of arrangements do chromosomes have?

Answer 36

Non-random

Question 37

Why is the spatial localization of chromosome territories important?

Answer 37

For gene expression

Question 38

What does the position of chromosomes relative to one another reflect?

Answer 38

Variation in gene expression pattern

Question 39

What is a chromatid?

Answer 39

One of two identical halves of a replicated chromosome

Question 40

Why is it important for chromosomes to replicate before cell division?

Answer 40

This allows each daughter cell to receive a complete set of chromosomes

Question 41

What is the structure of a chromosome?

Answer 41

2 sister chromatids attached by a centromere; identical DNA

Question 42

Where is the CFTR mutation located for cystic fibrosis?

Answer 42

Chromosome 7

Question 43

What is DiGeorge Syndrome?

Answer 43

Deletion in chromosome 22

Question 44

What is Down Syndrome?

Answer 44

Additional copy of chromosome 21, Trisomy 21

Question 45

What is a gene?

Answer 45

Basic unit of heredity that consists of a segment of DNA that encodes a gene product, either protein or RNA

Question 46

What are some examples of non-coding regions of DNA?

Answer 46

- Introns - LINEs (Long Interspersed Nuclear Elements) - SINEs (Short Interspersed Nuclear Elements) - Regulatory DNA sequences