Genetics: DNA, Genes & Chromosomes - DNA Flashcards
1
Q
What is the role of DNA?
A
- To store genetic information
2
Q
What are the components of a DNA nucleotide?
A
• Pentose sugar
- Deoxyribose
• Phosphate group
• One organic base
- Adenine, cytosine, guanine or thymine
3
Q
Describe the general structure of DNA
A
- Double helix shape
- Composed of two polynucleotides joined together by hydrogen bonds between complementary bases
4
Q
Describe the structure of eukaryotic DNA
A
- Linear
- Long molecule
- DNA double-helix wound around histone proteins
5
Q
What is a chromosome?
A
- A thread like structure made up of one long DNA molecule
6
Q
What is a nucleosome?
A
- A segment of DNA wound around eight histone proteins
- Looks like a bead
7
Q
Describe how DNA forms chromosomes in eukaryotes
A
- DNA double-helix wound around histone proteins, forming nucleosomes
- Nucleosomes coiled up to form chromatin
- Chromatin further organised into chromosomes
8
Q
Describe the structure of prokaryotic DNA
A
- Circular
- Shorter molecule
- DNA isn’t wound around histones
- DNA condenses to fit in cell by supercoiling
9
Q
Where is prokaryotic DNA found?
A
- Found in chromosome (nucleoid) and in smaller structures called plasmids
10
Q
What is a gene?
A
- A gene is a sequence of DNA bases that codes for either a polypeptide or functional RNA (tRNA, rRNA)
11
Q
What is a sequence of three DNA bases called?
A
- A triplet
- Codes for a specific amino acid
- 20 different amino acids
12
Q
What are the features of genetic code?
A
- Universal
- Degenerate
- Non-overlapping
13
Q
What does universal mean?
A
- The same specific base triplet codes for the same amino acid in all living organisms
14
Q
What does degenerate mean?
A
- More than one triplet codes for the same amino acid
- Reduces number of mutations
15
Q
What does non-overlapping mean?
A
- Each triplet is read once and triplets don’t share bases
