A1.2 Flashcards
Nucleic acids
What are nucleic acids?
The information molecules of cells which can be split into two types, deoxyribonucleic acid (DNA) or ribonucleic acid (RNA)
What is genetic code?
the code containing the information in the nucleic acids which is universal (in all organisms)
Where is DNA found?
chromosomes of the nucleus (and chloroplasts and mitochondria)
Where is RNA found?
in the cytoplasm and more specifically in the ribosomes
What is a nucleotide made of?
A nitrogenous base, a pentose sugar, a phosphate group
What are the 4 nitrogenous bases for DNA?
Adenine, thymine, cytosine and guanine
What reaction forms a nucleotide?
condensation reaction
What is the sugar phosphate backbone?
Alternating sugar and phosphate molecules, each base is attached to a pentose sugar that alternates with a phosphate molecule.
Where does the genetic code lie?
in the coding strand
How many different combinations are there?
64 (4x4x4)
What is a codon?
a three-letter or triplet code with each sequence standing for one of the 20 amino acids
What are the 4 nitrogenous bases for RNA?
adenine, uracil, cytosine, guanine
What are the 3 functional types of RNA?
Messenger RNA( mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA)
What is the bond in RNA formed between adjacent nucleotides called?
3’-5’ phosphodiester bond
How is RNA formed?
the condensation of nucleotide monomers
What is the DNA double helix?
two antiparallel polynucleotide strands paired together and held by hydrogen bonds
What are the sections that code for proteins called?
genes
What is a gene?
A heritable factor that influences a feature of an organism such as height
Where are genes located?
each gene occupies a specific position on a chromosome hence each chromosome is a linear series of genes
What is a locus?
the point where a gene for a particular characteristic is found every time
What is an allele?
Each gene had two or more forms called alleles
What is a homologous chromosome?
chromosomes of eukaryotic cells that occur in pairs
What us complementary base pairing?
the combinations that fit together on the helix since they only form hydrogen bonds with each other, adenine and thymine, cytosine and guanine
what are conserved sequences?
sequences that remain unchanged or only slightly changed
What are the most highly conserved genes?
The ones that can be found in all organisms
How is DNA packed into chromosomes?
by coiling the DNA double helix and looping it around protein beads called nucleosomes
What is a nucleosome made of?
eight histone molecules make one bead
What was the Hershey and Chase experiment?
an experiment to prove that DNA was the holder of information in the cell and not protein
How did Hershey and chase conduct the experiment?
They labeled two different bacteriophages, one with DNA and one with protein and let them infect cultures of e coli. They observed that only the bacteriophage marked with DNA was transferred to the next generation
