Genetic Info and Variation Flashcards
(26 cards)
Where is Prokaryotic DNA
Cytoplasm
As no nucleus
Describe Prokaryotic chromosomes
Short, circular
Nucleoid - single, circular
Plasminds - very small circular
Contain only few genes, more accessible for proteins for gene expression, genes required often
Describe Eukaryote’s DNA
Lon, Linear, Condensed
Tightly wrapped around histones
Ends of chroatids sealed with telomeres
What is a chromatin
Combination of tightly coiled DNA and proteins
What is the endosymbiotic theory
bacterial cells were engulfed by a large cell during evolution
Bacteria and host cell formed beneficial symbiotic relationship
What are genes
sequences of bases in DNA that code for amino acid sequence of a single polypeptide or functional RNA molceule
Whats a locus
Specific location of a gene in DNA
Which out of DNA and mRNA has a codon and whihc has a triplet
DNA triplet
mRNA codon
What are introns
Non coding regions of the gene
How are Introns removed
splicing, when gene is translated for protein synthesis
It’s in pre-mRNA
not in prokaryotes
What are exons
coding regions
Describe the genetic code
Non-overlapping
Degenerate - code for same, limits effect of mutation
Universal - same codons=same amino acids
What is the genome
complete set of genes in individual’s DNA
What is the proteome
Full range of proteins an individual can produce
Larger than the genome, as the exons can be sliced in dif ways (alt splicing)
Which comes first: Transcription or Translation
Transcription
Describe the process of transcription
RNA polymerase binds to locus of target gene, cuases H bonds to break, separating the strands
RNA polymerase then binds free floating RNA nucleotides to template strand, mRNA formed is copy of gene
RNA polymerase catalyses the condensayion reaction forming phosphodiester bonds
When reaches stop codon, stops separating DNA and producing mRNA, strands join back up.
mRNA leave nucleus through pore
Describe the process of Translation
mRNA binds to ribosome, 6 bases at a time
1 molecule tRNA binds to first codon, via complementary anticodon, bringing in specific amino acid, bound to it using ATP
2nd tRNA binds to second codon in ribosome, corresponding aino acid bought in, they form peptide bond using ATP
Ribosome then moves along mRNA strand, so new codon enters ribosome, adds to polypeptide chain.
When reaches stop codon, no correspinding tRNA molecule, chain released
Describe sturtcure of tRNA
Single stranded nucelic acid molecule,
Clover like shape
Has anticodon, complementary
What are mutations
Changes to base sequence in DNA
Why do most mutations not lead to a change in polypeptide function
In introns
Degenerate code
Not in functional region
Which types of mutation lead to a frameshift mutation
Addition/ insertion
Deletion
What are the three forms of substitution
Silent - doesn’t alter amino acid sequence (degenerate)
Missense - alters single amino acid
Nonsense - premature stop codon, polypeptide chain incomplete, affects final protein structure
What are 3 causes of mutation
Replication: erros in replication process when DNA read and copied, spontaneous
Mutagenic Agents: environemtnal factors increase rate of mutations, ionisng radiation (x Rays) UV (high E radiation) toxic chemicals
Chromosome mutations: spontaneous in meiosis, affect number of chromosomes in devloping zygote- “aneuploidy”, if pairs of chromosomes don’t separate properly “Non-disjunction”, extra chromosome/none
What does meiosis produce from what?
produced: Haploid gametes (4 genetically dif daughter cells
From: diploid
