4A Flashcards
What is an allele?
A variation of a gene
What is the genetic code?
The sequence of base triplets in the mRNA sequence that codes for amino acids
What are the features of the genetic code?
It’s non overlapping none of the bases in each triplet overlap
Degenerate one amino acid can be coded for by more than one set of triplets
They have stop signals that ends proteins production
Universal as same base sequences make up same amino acids in all organisms shows evolution as all evolved from one common ancestor
What is a homologous chromosomes?
A pair of identical chromosomes, have same genes and same size but have different alleles st same locus
Differences in prokaryotic and eukaryotic DNA?
Both contain chromosomes Prokaryotic Shorter Super coiled DNA loop in cytoplasm Not wound around histones No nucleus Eukaryotic Longer In nucleus Wound around histones
What is genome?
The complete set of genes in a cell
That is proteome?
The full range of proteins that a cell is able to produce
What is the structure of RNA?
Single polynucleotide strand not two
Shorter
Contains uracil not thymine
Ribose sugar not deoxyribose
Describe transcription
DNA helicase break the H bonds holding that bases in the DNA strand together p, exposing the bases.
Free RNA nucleotides in the nucleus complimentary bases pair with the exposed bases in either strand. Uracil and not thymine using DNA as template
RNA polymerase joins the lined up RNA nucleotides forming strands
The helix recoils and bonds reformed after RNA polymerase passed
Stop signals inhibit polymerase
mRNA moves out of nucleus through nuclear pore into cytoplasm to the ribosomes
Describe structure of tRNA molecule
Singer strand
Folded into clover shape
H bonds between complimentary base pairs hold shape
At end has specific sequence of three bases called anticodon
At top has amino acid binding site
Describe translation
The mRNA strand moves into the ribosome
The tRNA molecules anticodon complimentary base pairs to first triplet in mRNA sequence
Another tRNA molecule complimentary base pairs with the next triplet and their amino acid binding site are joined by a petite bond
The first tRNA moves away leaving he amino acids contest until the protein is made
When mRNA first made why does it need splicing?
The mRNA is called pre mRNA as it contains introns as well as exons the introns are non coding parts of the sequence that codes for non functional RNA as has no role so splicing removes this.
What is a gene?
A section of DNA made up of triplets bases that codes for proteins
Give two reasons why meiosis is necessary
Genetic variation among organisms
As have haploid number of chromosomes means that when gametes fuse get right amount of chromosomes as would get double
