3A1 Structure and Function of Chromosomes

Question 1

What are the five nitrogenous bases discovered by Albrecht Kossel?

Answer 1

• Adenine
• Thymine
• Guanine
• Cytosine
• Uracil

Received the Nobel prize in 1910 for his work.

Question 2

What is a purine?

Answer 2

A nitrogenous base that has a 2 ring structure.

Question 3

What are the purines in DNA?

Answer 3

• Adenine
• Guanine

Question 4

What is a pyrimidine?

Answer 4

A nitrogenous base that has a single ring structure.

Question 5

What are the pyrimidines in DNA?

Answer 5

• Cytosine
• Thymine

Question 6

What is the structure of a nucleotide composed of?

Answer 6

• A Nitrogenous base
• A Sugar
• A Phosphate group

Question 7

How many nucleotides can a single DNA molecule contain?

Answer 7

Hundreds - even millions.

Question 8

What is the sugar-phosphate backbone of DNA typically compared to?

Answer 8

The sides of a ladder.

Question 9

What does adenine pair with in DNA?

Answer 9

Thymine

Adenine and thymine are bonded with 2 hydrogen bonds.

Question 10

What does cytosine pair with in DNA?

Answer 10

Guanine

Cytosine and guanine are bonded with 3 hydrogen bonds.

Question 11

What is the role of hydrogen bonds in DNA?

Answer 11

Hold the two strands of DNA together throughout the entire length of the molecule.

Question 12

How do nucleotides connect in a strand of DNA?

Answer 12

The phosphate group of one nucleotide connects to the sugar of its neighbor by a phosphodiester bond.

Question 13

What is the function of DNA in cells?

Answer 13

DNA stores genetic information that tells cells how to make proteins necessary for various life functions.

Question 14

What is complementary base pairing?

Answer 14

The specific bonding between cytosine and guanine (3 hydrogen bonds) and adenine and thymine (2 hydrogen bonds) in DNA.

Question 15

What does antiparallel mean in terms of DNA strands?

Answer 15

That the strands in a DNA molecule are parallel but oriented in opposite directions.

The 5’ end of one strand pairs with the 3’ end of the other strand.

Question 16

Why must DNA strands be antiparallel?

Answer 16

To allow hydrogen bonding between the nitrogenous bases, which can only fit together in a specific orientation.

Question 17

What are the four nitrogenous bases found in DNA?

Answer 17

• Guanine (G)
• Adenine (A)
• Thymine (T)
• Cytosine (C)

Question 18

What are the main differences between DNA and RNA?

Answer 18

• DNA:
  
  • Double-stranded helix
  • Contains the sugar deoxyribose
  • Thymine (T) as one of its bases
• RNA:
  
  • Single-stranded
  • Contains the sugar ribose
  • Uracil (U) replaces thymine (T)

Question 19

List the similarities between DNA and RNA.

Answer 19

• Both contain nucleotide, phosphate, and pentose sugar structures.
• Both use adenine, guanine, and cytosine nucleotides.
• Both carry genetic information.

Question 20

Where is DNA stored and processed within the eukaryotic cell?

Answer 20

Within the nucleus of the cell.

Question 21

What is the structure of DNA?

Answer 21

Double-helix structure

DNA’s double-helix structure allows it to be easily replicated and preserved during cellular division.

Question 22

What are the nitrogenous bases found in RNA?

Answer 22

• Guanine (G)
• Cytosine (C)
• Adenine (A)
• Uracil (U)

Question 23

Where are chromosomes located?

Answer 23

In the nucleus.

Question 24

What is the difference in the number of chromosomes between gametic and somatic cells in humans?

Answer 24

• Gametic cells: 23
• Somatic cells: 46

Question 25

What are **chromatids**?

Answer 25

These are the **two symmetrical structures** of a chromosome, each containing a single DNA molecule.

Question 26

What is a **centromere**?

Answer 26

It holds together the two sister chromatids in a chromosome.

Question 27

What is a **chromosome**?

Answer 27

A **single molecule of DNA** representing a specific subset of information in a genome.

Question 28

What are **homologous chromosomes**?

Answer 28

Pairs of chromosomes that **carry the same set of genes**.

Question 29

What are **heterologous chromosomes**?

Answer 29

Chromosomes that carry a **different set of genes** of a particular characteristic.

Question 30

What are the **three parts** of a chromosome?

Answer 30

* Centromere * Arm * Telomere

Question 31

What is the **chromosome arm**?

Answer 31

The segment of the chromosome **found on either side of the centromere**.

Question 32

What is the **telomere**?

Answer 32

The portion of the **chromosome tip that protects the chromosomal DNA from degradation** and interactions with other chromosomes.

Question 33

What is a **sister chromatid**?

Answer 33

One of the two copies of a single chromosome produced during replication.

Question 34

What is a **diploid** organism?

Answer 34

An organism that has **two copies of each chromosome**, called homologous chromosomes or homologs.