DNA Flashcards
What is DNA?
DNA is a molecule that contains all the instructions (genetic information) to put an organism together and make it work
Where is DNA found?
DNA is found in the nucleus of living cells
In really long molecules called chromosomes
(Chromosomes are made up of coiled up DNA)
What is uncoiled DNA known as?
- CHROMATIN
How many metres of DNA does every cell in the body contain?
Every cell in the body contains about 2 metres of DNA therefore it has to be coiled and tightly packed
What does DNA stand for?
Deoxyribonucleic-acid
What gives a DNA molecule its spiral double helix shape?
- the DNA molecule consist of 2 ‘polynucleotide strand’ that look like a twisted ladder
Why do all of the body’s cells contain exactly the same DNA?
- all of the body’s cells contain exactly the same DNA because the DNA is copied exactly every time the cell divides
What are the sides of DNA made up from?
The sides (backbone) is made of sugar (deoxyribose) and phosphate
What are the 4 bases that make the ‘steps’ of the double helix ladder?
- ADENINE (A)
- THYMINE (T)
- CYTOSINE (C)
- GUANINE (G)
Bases are the basic building blocks of DNA
What do all of the ORGANIC bases contain?
All 4 bases contain nitrogen hence their other name NITROGENOUS BASES
How many classes can the 4 bases be split into? And what are the names of the two classes?
The 4 bases can be split into 2 classes PURINES and PYRIMIDINES
Name 2 purines:
- ADENINE
- GUANINE
THINK OF ‘OH PURE ADELAIDE’
Name 2 pyrimidines:
- THYMINE
2. CYTOSINE
What are purines?
- bases that form double rings
What are pyrimidines?
- bases that have one ring
Why is DNA a polymer?
- DNA is a polymer because it’s made up of many repeated units called nucleotides
What groups do ALL nucleotides contain:
- Phosphate group
- Pentose - 5 carbon sugar
- Nitrogenous base e.g. A T C G
What do nucleotides form?
- nucleotides form the MONOMERS of nucleic acids DNA and RNA
In DNA what is the nucleotide pentose sugar?
- in DNA the nucleotide pentose sugar is DEOXYRIBOSE
In RNA what is the nucleotide pentose sugar?
- in RNA the nucleotide pentose sugar is RIBOSE
What reaction joins nucleotides together and what is the product of this reaction?
- Nucleotides join together by a CONDENSATION reaction to form a POLYNUCLEOTIDE chain
What is the covalent bond between the sugar residue and phosphate group in a nucleotide known as?
- The covalent bond between the sugar residue and the phosphate group in a nucleotide is called a PHOSPHODIESTER group
Why are the 2 polynucleotides strands described as ANTIPARALLEL?
- The 2 strands run in opposite directions so they are described as ANTIPARALLEL
What is the direction of a polynucleotide based on?
- the ‘opposite direction’ of the 2 strands refers to the direction that the 3rd and 5th carbon molecule on the 5 carbon sugar, deoxyribose are facing
What is the 5’end of the molecule referring to?
- the 5’end of the molecule is referring to where the phosphate group is attached to the 5th carbon atom of the deoxyribose sugar
What is the 3’end of the molecule referring to?
- the 3’end of the molecule is referring to where the phosphate group is attached to the 3rd carbon atom of the deoxyribose sugar
What do the 2 polynucleotide strands twist around one another to form?
- the 2 polynucleotide stands twist around one another to form the double helix
Why do the 4 bases join together and form complementary pairs?
- they form complementary pairs because they always join in a very specific way
What base does the PURINE ADENINE always join to? And how many hydrogen bonds form between them?
- ADENINE always joins to the PYRIMIDINE THYMINE
- 2 hydrogen bonds
Which base does the PURINE GUANINE always form with? And how many hydrogen bonds form between the bases?
Guanine always forms with the PYRIMIDINE CYTOSINE
3 Hydrogen bonds
Why do hydrogen bonds join the bases in DNA?
- because the hydrogen bonds are very weak and so can easily be broken for transcription and DNA replication
What bonds hold the 2 antiparallel polynucleotide strands together?
- the two antiparallel strands are held together by hydrogen bonds
Are there other types of nucleotide molecules?
YES
What do you call a nucleotide which contains more than 1 phosphate?
When nucleotides contain more than 1 phosphate they are said to have become PHOSPHORYLATED - phosphor y lated - nucleotides
Give 2 examples of 2 phosphoylated nucleotides:
- ATP
2. ADP
What does ATP stand for?
ATP = ADENOSINE TRIPHOSPHATE
What is Adenosine triphosphate?
- Adenosine triphosphate is an energy-rich END PRODUCT of most energy releasing bio chemical processes
- and it is used in many energy requiring metabolic processes
What does ADP stand for?
ADENOSINE DIPHOSPHATE
What is adenosine diphosphate?
- Adenosine diphosphate is another molecule that plays an important role in the process in which CELLS GENERATE ENERGY
What makes an adenosine?
ADENINE + RIBOSE = ADENOSINE
