Genetics Flashcards
What is DNA?
The hereditary material responsible for passing genetic information from cell to cell and generation to generation.
What are the 3 components of individual nucleotides?
A sugar called deoxyribose.
A phosphate group.
An organic base belonging to one of two different groups:
(a) single-ring bases- cytosine ( C ) and thymine ( T )
(b) double-ring bases- adenine ( A ) and guanine ( G )
How are the 3 components of individual nucleotides combined?
As a result of condensation reactions- to give a single nucleotide (mono nucleotide).
How is a dinucleotide formed?
A condensation reaction between the deoxyribose sugar of one mono nucleotide and the phosphate group of another.
How are polynucleotide strands formed?
Many nucleotides join together to form polynucleotide strands.
The nucleotides join up between the phosphate group of one nucleotide and the sugar of another- creating a sugar-phosphate backbone.
How do two DNA polynucleotide strands join together?
By hydrogen bonds between the bases.
Each base can only join with one particular partner- this is called specific base pairing.
Adenine always pairs with…
Thymine by means of two hydrogen bonds (they’re complementary).
Guanine always pairs with…
Cytosine by means of three hydrogen bonds (they’re complementary).
What are the structural aspects of DNA that make it suited to its function?
The double helix structure makes it very stable in the cell.
The DNA molecules are very long and are coiled up very tightly, so a lot of genetic information can fit into a small space.
It’s two separate strands are joined only with hydrogen bonds, which allow them to separate during DNA replication and protein synthesis.
By having the base pairs within the helical cylinder of the deoxyribose-phosphate backbone, the genetic information is to some extent protected from being corrupted by outside chemical and physics forces.
How do Eukaryotic cells store DNA?
They contain linear DNA molecules that exist as chromosomes- thread like structures, each made up of one long molecule of DNA which has to be wound so it can fit in the nucleus.
The molecule is wound round proteins (called histones).
Histone proteins also help to support the DNA.
The DNA (and protein) is then coiled up very tightly to make a compact chromosome.
How do prokaryotics cells store DNA?
As chromosomes- but the DNA molecules are shorter and circular.
The DNA isn’t wound around proteins- it condenses to fit in the cell by supercoiling.
What are genes?
Genes are sections of DNA.
They’re found on chromosomes.
Genes code for proteins (polypeptides)- they contain the instructions to make them.
What determines the order of amino acids in a particular protein?
The order of the nucleotide bases in a gene.
What is each amino acid coded by?
A sequence of three bases called a triplet in a gene.
The code in DNA is degenerate. What does this mean?
More than one base triplet can code for the same amino acid. That’s because there are more possible combinations of three bases than there are amino acids.
