Genetic Information, variation and relationships between them Flashcards
DNA function
Used to store all the genetic information (all the instructions an organism needs to grow and develop from a fertilised egg to a fully grown adult)
DNA molecule
Double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs
3 components of a nucleotide
Phosphate, deoxyribose sugar, nitrogenous base
What are the 4 nitrogenous bases in DNA?
Adenine, thymine, cytosine and guanine
Which nitrogenous bases are complementary to each other?
Adenine + thymine
Cytosine + guanine
What are the 2 types of nitrogenous bass?
Purines and pyridamines
What’s a purine and some examples?
Nitrogenous bases with 2 carbon rings such as adenine and guanine
What’s a pyridamine and some examples?
Nitrogenous base with 1 carbon ring such as thymine and cytosine
2 mononucleotides join together to make…
Dinucleotide
Nucleotides join together to form polynucleotides through what type of reaction?
Condensation reaction between the phosphate group of one and the pentose sugar of another
What type of bond is created between nucleotides after a condensation reaction?
Phosphodiester
The chain of sugars and phosphate is known as what?
Sugar phosphate backbone of the DNA molecule
Two polynucleotide strands are joined together to form what?
A double helix
Two polynucleotide strands are joined together due to what?
Hydrogen bonds between nitrogenous bases and due to complementary base pairing, adenine pairs with thymine and cytosine pairs with guanine
How many hydrogen bonds form between adenine and thymine?
2
How many hydrogen bonds form between cytosine and guanine?
3
Functions of part of DNA molecule
- sugar phosphate backbone= provides strength and stability along with protecting the more reactive organic bases inside the double helix
- DNA coiled up into double helix= compact = lots of information can be stored in the molecule
- order of nitrogenous bases= carry information for protein synthesis
- complementary base pairing= molecule replicate itself accurately
- weak hydrogen bonds between bases = can easily be broken = little energy needed = easier for replication
RNA function
Transfer genetic information from DNA to ribosome for protein synthesis (only carry information for one gene)
RNA structure
Single stranded nucleic acid that’s small enough to fit through nuclear pores- composed of phosphate group, ribose sugar, adenine, uracil, cytosine and guanine
Differences between DNA and RNA
- DNA is double stranded whereas RNA is single stranded
- DNA contains complementary base pairing between nitrogenous bases whereas RNA doesn’t contain complementary base pairing
- DNA contains the nitrogenous bases adenine, thymine, cytosine and guanine whereas RNA contains adenine, uracil, cytosine and guanine
- DNA contains deoxyribose sugar whereas RNA contains ribose sugar
- different functions- DNA is responsible for storing genetic information whereas RNA is responsible for transferring genetic information from DNA to the ribosome for protein synthesis
What is a gene?
A section of DNA at a particular position, a locus, on a DNA molecule
Function of genes?
A base sequence of DNA that codes for the amino acid sequence of a polypeptide or functional RNA, including ribosomal RNA (rRNA) and transfer RNA (tRNA)
In trying to discover how DNA bases coded for amino acids, why did scientists suggested that there must be a minimum of 3 bases that coded for each amino acid?
- only 20 amino acids regularly occur in proteins
- each amino acid must have its own code of bases on the DNA
- only 4 different bases present in DNA
- if each base coded for a different amino acid, only 4 different amino acids could be coded for
- using a pair of bases (4x4= 16) different codes are possible but inadequate
- three bases (4X4X4= 64) produces different codes, more than enough to satisfy the requirement for 20 amino acids
As the genetic code has 3 bases for each amino acid, each one is called
A triplet