Storing and Using Genetic Information Flashcards
define phenotype
physical manifestation of an organism ( physical appearance)
define genotype
full hereditary information of an organism (even if not expressed physically)
what are components of a nucleotide?
- sugar (5-carbon sugar)
- base
- phosphate group
what are components of a nucleoside?
-sugar (5-carbon sugar)
- base
(NO phosphate group)
how many bases are there for every turn of the helix?
10 bases
what are 2 most common sugars used in DNA?
- deoxyribose (lacking oxygen)
- ribose
is deoxyribose or ribose less resistant to enzymes?
deoxyribose
does DNA or RNA break down quicker?
RNA
how do polynucleotide chains run against each other? (in what way)
anti-parallel (from 5’ to 3’ which makes it stable)
what structures are present for interactions of proteins with the DNA molecule?
major and minor grooves (many binding sites found on major groove)
what volume of nucleus is the nucleolus?
approx. 25%
what is the function of the nucleolus?
site of transcription and assembly of rRNA and creates ribosomes
when are chromosomes visible?
when the cell is dividing
what structures does DNA coil around?
histones
how many proteins make up a histone?
9 proteins
What is DNA around a histone called?
a nucleosome
what part of mitosis, does coiling of DNA occur?
metaphase
what is chromatin?
mixture of DNA, proteins and RNA that packages DNA within the nucleus
what 2 types of chromatin are there?
- heterochromatin
- euchromatin
what is heterochromatin?
condensed, non-functional part of the DNA
what is euchromatin?
extended form, functional part of the DNA
what are 2 major mechanisms which make chromatin more accessible?
- histones can be enzymatically modified
2. histones can be displaced by chromatin remodelling complexes
is DNA folding and unfolding reversible?
yes
what does structure of chromatin/DNA depend on?
varies depending on the access required to the DNA
what are 2 main characteristics of DNA replication?
- semi-conservative
2. bi-directional
what is meant by DNA being semi-conservative?
one half of each new molecule of DNA is old and one half is new
what bonds are broken when DNA is “unzipped”?
hydrogen bonds
DNA polymerase can only add new nucleotides to which end of the growing strand?
3’ end of growing strand
what does DNA ligase do?
joins DNA strands together by catalysing the formation of double bonds.
what are Okazaki fragments?
formed on the lagging strand (small newly synthesised segments DNA) which join together by DNA ligase to form a continuous strand
(Okazaki fragments form short double-stranded DNA sections which are complementary to lagging template strand)
In what direction does DNA polymerase work in?
(5’–> 3’) and adds to the 3’ end
does new strand grow in the opposite direction to the old strand?
yes
what are exons?
part of the code for a particular gene (CODING regions)
what are introns?
doesn’t code for anything, “junk” of the DNA strand (NON-CODING regions)
how many bases make up a codon?
3 bases
how many amino acids are there?
20 amino acids
what is the degeneracy/ redundancy of the genetic code?
Many (more than one) codons can code for the same amino acid (exceptions; methionine and tryptophan)
what is the name given to codons which refer to the same amino acid?
synonyms
where is the most common location for variations between synonyms to occur?
at third base of the codon(wobble position)
what is the point of degeneracy in a genetic code?
- minimises the effect of genetic mutations
- alterations to the base sequences are less likely to alter the protein being coded for
- prevent alteration to protein structure and hence function
what is the initiation codon?
methionine
what is a common example of a single point mutation?
sickle cell anaemia
what is mRNA?
transcribed from DNA in nucleus during transcription, carries information for protein synthesis
what is alternative splicing?
- process by which exons of the RNA produced by transcription of a gene (primary gene transcript of pre-mRNA) are reconnected in multiple ways.
- resulting different mRNAs can be translated into different protein forms
- therefore a single gene may code for multiple proteins
what is tRNA?
- acts as an adapter molecule between coded amino acid and mRNA
- anti-codon on tRNA will bind to the codon on mRNA
what is rRNA?
- component of ribosomes (produced in nucleus)
- transported to cytoplasm where they combine with proteins to form ribosomes
- susceptible to enzyme degradation
