genetics - storing genetic info, chromosomes, mutations etc Flashcards
how many bases are there per turn in the helix of DNA?
10
what does the way the way the helix is wound result in structurally?
a major and minor groove
which direction does the double helix spiral?
clockwise (right-handed)
what are chromosomes?
a single piece of DNA containing many genes, regulatory elements and other nucleotide sequences
what is chromatin?
a mixture of DNA, proteins and RNA that package DNA within the nucleus
name the condensed and extended forms of chromatin?
condensed - heterochromatin
extended - euchromatic
which two mechanisms make chromatin more accessible for transcription/replication?
- histones can be enzymatically modified
- histones can be displaced by chromatin modelling complexes
Which end of the growing strand can DNA polymerase add new nucleotides to during replication?
3’
What are formed on the lagging strand, which are joined together by DNA ligase to form one continuous strand?
Okazaki fragments
which specialised enzyme replicates the 5’ ends of the lagging strand?
telomerase
In which phase of mitosis are chromosomes most compacted and visible?
metaphase
Most amino acids are encoded by more than one codon. What is this referred to?
degeneracy
what is the third base of the codon referred to as?
the wobble position
which amino acid is termed the initiation codon and is also one of two to be coded by one codon?
methionine
name the three types of RNA
messenger
transfer
ribosomal
what is alternative splicing?
a process where the exons of the RNA produced by transcription of a gene are reconnected in multiple ways during RNA splicing, resulting in multiple proteins
what does rRNA do?
combines with proteins to form a ribosomes
what’s the difference between the centromere and the kinetochore?
centromere is a constricted region joining sister chromatids whereas the kinetochore is a protein complex tat binds to microtubules
does the heterochromatin or euchromatin contain active genes?
euchromatin
how many histone proteins are in a nucleosome?
8
roughly how many nucleosomes per turn of chromatin?
6
What does karyotyping test?
the number and appearance of chromosomes in the nucleus
what is the chromosome described as when the petite arm is tiny and has basically no coding?
acrocentric
what are the four types of FISH probes?
- unique sequence probes
- centromeric probes (useful for determining chromosome number)
- telomeric probes (useful for detecting subtelomeric rearrangements and often present in children with unexplained mental retardation)
- whole chromosome probes (cocktail of probes covering different parts of a particular chromosome, used with different fluorescent dyes, spectral karyotype, useful for detecting translocations and rearrangements)
