genetics and diversity Flashcards
what is prokaryotic DNA like
single, circular chromosomal DNA
plasmids containing a few genes like antibiotic resistance
not associated with histones
what is Eukaryotic DNA like
-long condensed chromosomal DNA
- associated with histones
- has introns
what is mitochondrial DNA like
circular, shorter no associated with proteins
what is chloroplast DNA like
small, circular pieces of DNA
what is a gene
a base sequence of DNA that codes for a specific amino acid sequence to form a polypeptide strand or a functional RNA molecule
what is the Loci
the position of a gene on a chromosome is its locus
what is a codon
a sequence of three bases coding for an amino acid
what does degenerate mean
more possible combinations of triplets than amino acids
what does universal mean
every organism uses the same code and this means that the same codons code for the same amino acid in all living things
what does non-overlapping mean
DNA is read in triplets so no bases are read again
what is the genome
the complete set of genes in a cell
what is the proteome
the full range of proteins that a cell is able to produce
what are homologous chromosomes
chromosomes that are the same size and have the same gene but different alleles
what is mRNA
a single stranded molecule that is made of a sugar phosphate backbone and exposed unpaired bases U, A, C, G
what is the structure of tRNA
single stranded molecule with a folded shape due to hydrogen bonds
- has a specific anticodon complementary to specific codon
describe transcription
- The DNA unwinds and the hydrogen bonds break
- The exposed gene is used as a template and a complementary copy of the code from the gene is made called mRNA made from free RNA nucleotides with complementary bases to DNA sequence
- RNA polymerase bonds the RNA nucleotides together to form a sugar-phosphate backbone
- mRNA molecule then leaves the nucleus via a pore in the nuclear envelope
when, where and what happens in splicing
before the pre-mRNA leaves the nucleus splicing occurs which is the removal of introns and the coding sections called exons are joined together resulting in mRNA coding only for the genes
what is alternative splicing and what does it result in
when the exons of genes can be spliced in many ways to reproduce different mature mRNA molecules
a single eukaryotic gene can code for more than one polypeptide chain
what happens in translation
- mRNA molecule attaches to a ribosome and tRNA molecules carry amino acids to it and the amino acid bond with the tRNA molecule requires ATP
- a tRNA molecule with an anticodon that’s complimentary to the first codon on mRNA and they attach by complimentary base pairing
- the two amino acids attached to the tRNA molecules are joined by a peptide bond and the first tRNA molecule moves away leaving its amino acid behind
how do you calculate the number of amino acids in a protein
divide the number of coding nucleotides by 3 and minus one for the stop codon
what is a gene mutation
change in the sequence of base pairs in a DNA that occurs randomly that may results in an altered polypeptide
what are the three types of mutations
insertion mutations, deletion mutations and substitution mutations
what is an insertion mutation, what does it cause and what is changed in the big picture do to it
when a nucleotide is randomly inserted into the DNA sequence which changed the amino acid that is coded for as it creates a new different triplet of bases due to the knock off effect by changing the triplets further on in the DNA sequence.
what is a deletion mutation
mutation occurs when a nucleotide is randomly deleted from the DNA sequence which changed the amino acid that would have been coded for as there is a knock-on effect by changing the groups of three bases further on in the DNA sequence. This may dramatically change the amino acid sequence produced from this gene and therefore the ability of the polypeptide to function.
what is a substitution mutation
is when a base in the DNA sequence is randomly swapped for a different base. The mutation will only affect the amino acid triplet the substitution has happened in so there is no large knock-on effect
what are the three types of substitution mutations
Silent mutations which is when the mutations doesn’t alter the amino acid sequence.
Missense mutations is when the mutation alters a single amino acid.
Nonsense mutations is when the mutations creates a premature stop codon causing the polypeptide chain produced to be incomplete and therefore effecting the final protein structure and function.
what is a mutagenic agent and the examples
Mutagenic agents are environmental factors that increase the mutation rate of cells.
Examples of mutagenic agents are UV light, x-rays and toxic chemicals.
what is the mutation that happens in chromosome number called and when does it happen
Non-disjuction mutation
Non-disjunction occurs when chromosomes fail to separate during meiosis and this occurs spontaneously.
what do mutations in the chromosome number cause in haploids and what are the consequences of this
The gametes may end up with one extra copy of a chromosome or no copies of one and this means the gametes will have a different number of chromosomes then the haploid number.
If the abnormal gamete, then takes part in fertilization, then a chromosome mutation occurs.