unit 4. DNA, genes and chromosomes Flashcards
(38 cards)
what is a gene
a gene is a sequence of DNA bases that codes for the specific amino acid sequence of a polypeptide.
what are chromosomes
DNA coiled further and wrapped around histones
difference between prokaryotes and eukaryotes
what does it mean for a code to be. degenerate
more than one triplet code codes for the same amino acid
what is a genome
complete set of genes (and non coding DNA) in a cell
what is a pretome
full range of proteins a cell is able to produce
what is transcribing
occurs in the nucleus involves rewriting part of the DNA code into a strand of messenger RNA
what is translation
occurs in the cytoplasm and involves ribosome synthesising proteins where the sequence of codons on the mRNA strand is used to determine the sequence of amino acids in a polypeptide
what is splicing
splicing of pre RNA involves the removal of introns and the joining together of the exons to form mRNA
what are exons and introns
exons- sections of the gene that code for the polypeptide
introns- sections of the gene that do not code
what is genetic diversity
the number of alleles in a population
what causes genetic diversity
meiosis
gene mutation
random fission of gametes during fertilisation
chromosome mutation
what are gene mutations
changes in the sequence of nucleotide bases in DNA which may result in the formation of a different protein.
what can mutations result it
it can result in a different amino acid sequence in the encoded polypeptide due to the altered base sequence for a different sequence of amino acid
what is substitution and what can it result in
the replacement of one or more bases in a triplet code by one or more different bases
results:
change in triplet code causes change in amino acid which may result in a non-functional protein
what is deletion and what does it result in
removal of on or more bases
result:
it results in a frame shift which is alteration of all the triplet code from the point of mutation forms aa non functional protein
what is addition and what does it result in
addition of one or more bases
result:
also results in a frame shift which results in a non functional protein.
what is duplication and what does it result in
where one or more bases is repeated
results:
results in a frame shift
what is inversion
sequence of bases is reversed
what is translocation
where the sequence of bases is moved from one location in the DNA molecule to another part of the genome
what is meiosis
type of nuclear division that produces cells that are genetically different
what is the product of meiosis
four genetically different haploid daughter cells
what occurs in meiosis I
it separation of the members of each homologous pairs
what occurs in meiosis II
separates the chromatids of each chromosome
