A1.2 Nucleic Acids Flashcards
What is a nucleotide?
A monomer unit of nucleic acids
What is the backbone of DNA made up of?
The backbone is formed by covalent bonds between deoxyribose and phosphate molecules
What is the meaning of complimentary base pairing?
Nitrogenous bases align with each other in a specific way; complementary bases are held together by hydrogen bonds
How is complimentary base pairing important in the replication of DNA as the genetic material?
When the two strands of a DNA molecule are separated each one is used as a template to build a new strand; Complimentary base pairing ensures that new strands of DNA have the same sequence as the original molecule.
What are the four bases found in DNA?
- Adenosine
- Thymine
- Cytosine
- Guanine
What are the four bases found in RNA?
- Adenosine
- Uracil
- Cytosine
- Guanine
How is it possible for universal DNA molecules to store varied genetic information both within species and
between species?
There are a huge number of different base sequences possible which provides variety in the genomes
Different lengths of DNA, or different sequences of the bases causes variation in the genetic information stored in a genome
Within species each organism has many genes with a lot of similarity in the DNA sequence and this gives the species it’s recognizable characteristics
There is some variation in the sequence of DNA in some genes within species creating variation in characteristics
Between species there are more differences in the DNA sequence, which gives more variation in characteristics
How did Hershey and Chase use radioactive labelling in viral bacteriophages to demonstrate that DNA is the genetic material?
Radioactive labelling allows specific molecules to be observed
Phosphorus is found in DNA but not protein
Bacteriophage DNA was labelled with radioactive phosphorus
The radioactive label showed that the DNA part of the virus entered the bacterial cell
The radioactive labelled DNA was used to make new virus particles showing that DNA was the genetic material and not protein
What is the structure of a nucleosome?
Core made from 8 histone proteins
DNA molecule wrapped twice around the core
Additional histone protein holds the core and DNA together
What are the main differences between RNA & DNA?
DNA has two antiparallel strands of nucleic acids; RNA has one strand
What is a phosphodiester bond?
The linkage between the 3’ carbon atom of one sugar molecule and the 5’ carbon atom of another
What is a gene?
A length of DNA that codes for a protein
What is a chromosome?
A length of DNA that carries specific genes in a linear sequence
Each chromosome is a linear series of genes
What is the locus?
The particular position of a gene on homologous chromosomes
Genes for a characteristic are found at the same position ona chromosome
What is an allele?
Different versions of the same gene
What is a homologous chromosome?
Pairs of chromosomes, one from each parent that carry the same sequence of genes (but not necessarily the same alleles)
What is a condensation reaction?
The formation of larger molecules involving the removal of water from smaller component molecules
What are the three components of a nucleotide?
1) A nitrogenous base
2) A pentose sugar
3) A phosphate group
How is a nucleotide formed?
The three components are combined by an enzyme-controlled condensation reaction
What is a polynucleotide?
A long, unbranched chain of nucleotides
What forms the genetic code?
Information in DNA lies in the sequence of the nitrogenous bases
What is a codon?
Three consecutive bases in DNA
(or RNA) which specify an amino acid
What is the relationship between the four-letter DNA code and the 20 letter amino acid code?
The genetic code lies in the sequence in one of the DNA strands, the coding strand. The other strand is complementary to it. The code is a three-letter or triplet code, meaning that each sequence of three bases stands for one of the 20 amino acids
What is a polymer?
A large, organic molecule made up of repeating subunits (monomers)
What is messenger RNA (mRNA)?
A single-stranded ribonucleic acid, formed by the process of transcription of the genetic code in the nucleus, that then moves to ribosomes in the cytoplasm
What is transfer RNA (tRNA)?
Short lengths of RNA that combine with specific amino acids prior to protein synthesis
What is ribosomal RNA (rRNA)?
A molecule that forms part of the protein-synthesizing ribosome
What are the three functional types of RNA?
1) Messenger RNA (mRNA)
2) Transfer RNA (tRNA)
3) Ribosomal RNA (rRNA)
How is RNA formed?
RNA is formed by the condensation of many nucleotides. Links are formed between pentose sugar and phosphate groups of adjacent nucleotides
