Genetic Information And Variation Flashcards
What is a gene
Sequence of DNA bases that codes for a polypeptide and functional RNA
- determines sequence of amino acids
What is a locus
Fixed location of a gene on a chromosome
What is an allele
Different version of the same gene
(At a particular locus)
Name and describe the 3 features of the genetic code
DNA is non-overlapping: each base can only be in one triplet
Degenerate; 64 codons->20 amino acids. Multiple codons can code for the same amino acids
Universal: same codes code for the same amino acids in every organisms
How does a mutation in the genes affect the substrate
Different amino cid sequence
Different primary
Different bonding- hydrogen/ ionic
Different tertiary - active site
Substrate no longer complementary
What does diploid cell mean
Cells within the nucleus contains 2 sets of chromosomes
What does haploid cell mean
Cell that contains only a single copy of each chromosome - e.g. sex cells
Describe how a gene is a code for the production of a polypeptide
Because base/ nucleotide sequence
In triplets
Determines order/ sequence of amino acid sequence/ primary structure
What does exon mean
Base sequence coding for a polypeptide
Name the protein associates with DNA in a chromosome
Histone
Compare and contrast the DNA in eukaryotic and prokaryotic cells
Comparisons
1. Nucleotide structure is identical;
Accept labelled diagram or description of nucleatide as phosphate, deoxyribose and base
2. Nucleotides joined by phosphodiester bond:
OR
Deoxyribose joined to phosphate (in sugar, phosphate backbone):
3. DNA in mitochondria / chloroplasts same / similar (structure) to DNA
in prokaryotes:
Accept shorter than nuclear DNAlis circular not linearis not associated with protein/histones unlike
nuclear DNA:
Contrasts
Eukaryotic DNA is longer;
Eukaryotic DNA contain introns, prokaryotic DNA does not;
Eukaryotic DNA is linear, prokaryotic DNA is circular;
Eukaryotic DNA is associated with / bound to protein / histones, prokaryotic DNA is not;
What is a homologous pair of chromosomes
Carry the same genes
- same loci
- genes for the same characteristics
Suggest how the structure of the chromosome could differ along its length- in result in stain binding in different areas
Difference in base sequence
Difference since interactions with his tones
Differences in coiling/ condensation
What is the proteome
Full range of different proteins that a cell is able to produce
Range of different portions in a genome
What is the structure of an RNA nucleotide
Pentose sugar - ribose
Nitrogen containing base- uracil not thymine
Phosphate sugar
Single stranded, short
Describe the role of DNA
Carriers genetic information
Describe the role for mRNA
Transfers genetic information form DNA to ribosomes
Makes up ribosomes with proteins (involved in protein synthesis)
Describe the role for mRNA
Transfers genetic information form DNA to ribosomes
Makes up ribosomes with proteins (involved in protein synthesis)
Describe the role of tRNA
Protein synthesis
Transfers amino aid in order based on code on mRNA in translation
Describe transcription
- Hydrogen bonds (between DNA bases) break;
Ignore DNA helicase.
Reject hydrolysing hydrogen bonds. - (Only) one DNA strand acts as a template;
- (Free) RNA nucleotides align by complementary base pairing;
For ‘align by complementary base pairing’. accept align to complementary bases’ or ‘align by base pairing. - (In RNA) Uracil base pairs with adenine (on DNA)
OR
(In RNA) Uracil is used in place of thymine;
Do not credit use of letters alone for bases. - RNA polymerase joins (adjacent RNA) nucleotides;
Reject suggestions that RNA polymerase forms hydrogen bonds or joins complementary bases. - (By) phosphodiester bonds (between adjacent nucleotides):
- Pre-mRNA is spliced (to form mRNA)
OR
Introns are removed (to form mRNA):
Describe translation
- (mRNA attaches) to ribosomes
OR
(mRNA attaches) to rough endoplasmic reticulum;
(IRNA) anticodons (bind to) complementary (mRNA) codons;
- IRNA brings a specific amino acid;
- Amino acids join by peptide bonds:
- (Amino acids join together) with the use of ATP;
- RNA released (after amino acid joined to polypeptide):
- ribosome moves along to next codon - fits around 2 codons - The ribosome moves along the mRNA to form the polypeptide;
What are the different between tRNA and mRNA
Clover shaped - linear
Hydrogen bonds - no hydrogen bonds
Amino acid binding site - no
Anticodon - codon
Define the term mutagenic agent
A factor that increases the rate of mutations
What is non-disjunction mutation
In meiosis
Chromosomes not separated. Don’t form homologous pairs
What is a silent mutation
Substituting a base still does for the same amino acid a sthe original base
No effect on final polypeptide
What is a non-sense mutation
Premature ‘stop’ codon being coded for
Premature end to the synthesis of the polypeptide
What is a mis-sense mutation
Change to base- different amino acid
What is a deletion mutation
Frameshift
Nucleotide lost from DNA sequence
What are the causes of mutations
By mistake during DNA replication
Mutagenic agent- increase frequency
High energy ionised particle/ x-rays/ UV light/ high energy radiation/ uranium/ plutonium/ gamma rays/ mustard gas/ pesticides/ tobacco tar
Describe what happens to chromosomes in meiosis
- Chromosomes shorten/thicken/condense;
- Chromosomes associate in homologous/(described) pairs /formation of bivalents / tetrads;
- Crossing-over / chiasma formation;
- Join tospindle(fibres) / moved byspindle
- (At) equator/middle of cell
- (join via) centromere / kinetochore
- (Homologous) chromosomes move to opposite poles / chromosomes separate/move apart; (ALLOW‘are pulled apart’)
- (Pairs of) chromatids separated in 2nd division;
max 6(*) OR “ independent assortment” unqualified = 1 mark
Describe how meiosis causes variation and the advantages of variation
Crossing over
Independent assortment of chromosomes - meiosis 1
Independent assortment of chromatids - meiosis 2
- shuffling of maternal and paternal chromosomes
Mutation
Random fusion of gametes - new combination of alleles
Different adaptations
Some survive
To reproduce
Pass on gene
For changing environment
Describe meiosis
….
Explain the importance of genetic variation in the process of evolution
- Gene pool with wide range ofalleles;
- Random mutation results in a new allele (could bebeneficial/harmful)
- different environmental/abiotic/biotic conditions/selectionpressures;
- Selection for advantageous allele – more likely tosurvive
- Differential reproductive success/(selected) organisms surviveandreproduce;
- Leads to change inallelefrequency; over many generationsthe occurrence of the advantageous allele will increase at theexpense of the lessadvantageous.
- Occurs over a long period oftime;
- Thereforethe gene pool haschanged
What is selection pressure
Environmental factor
Leads to a greater chance of survival to reproductive age
What is a gene pool
Total number of alleles of all genes of all individuals within a population at a given time
What is directional selection
Selects against one of the extremes in a range of phenotypes
Mode shifts
Usually triggered by a change in the environment
What is stabilising selection
Favours average
Preserves characteristics of population and acts where conditions are stable
Anatomical
Structural
Increase chance of survival;
Physiological
Processes
E.g. respiring using fats to produce water
Behavioural
E.g. migration
Describe bacterial resistance
- A bacteria becomes resistant due to random mutation in DNA
- The bacteria produced a protein that makes the antibiotic ineffective
- Only the resistant bacteria survive and with less competition for resources they reproduce, passing on their antibiotic resistance
- It may have protein in its cell wall which is no longer weakened by antibiotics, an enzyme that breaks down the antibiotic, or a carrier protein that pumps antibiotics out of the cell
Who discovered penicillin
Alexander Fleming
What is classification
Grouping together of groups
What is taxonomy
Theory and practice of biological classification
What is taxonomy
Theory and practice of biological classification
What is artificial classification
Dividing organsims based on differences that are useful at the time
Same function but not the same evolutionary origins
What is phylogenetic classification
Classifies -species in groups using shared features derived from their ancestors
No overlap
What is binomial
Naming organisms
Refer to species name and genus name
What is the definition of species
Produce fertile offspring
What are the difficulties with the definition of species
Species are not fixes- change and evolve over time
Variation with species
Some species rarely reproduce
Many species came extinct with no fossil record
What did carl Woese do
Studied relationships of prokaryotic
3 domains
What are the differences between archaea, bacteria, eukarya
…
Why is courtship behaviour necessary
Ensure individual dna is passed onto the next generation
Females of species often only produce eggs at specific times
Need to ensure mating is successful, offspring will have the maximum chance of survival
Why is courtship behaviour necessary
Ensure individual dna is passed onto the next generation
Females of species often only produce eggs at specific times
Need to ensure mating is successful, offspring will have the maximum chance of survival
What does courtship enable individuals to do
Recognise members of their own species
Identify a healthy mate capable of breeding
Form a pair bond
Synchronise mating - max. Chance of conception
How does courtship work
Male carry out action
- stimulus to female
Stimulus response chain
-more likely to pass on genes
Genes for feature of display passed on
More likely to survive and reproduce
Process repeated for many generation
What is species diversity
Number of different species and the number of individuals of each species within any one community
- number of different species in a given area
-proportion of a community that is made up of up of an indivual area
-some may be small
What is genetic diversity
The variety of green possessed by individuals that make up any one species
What is ecosystem diversity
Range of different habitats within a particular area
What is species richness
Total number of species
What is biodiversity
Variety of living things in an ecosystem
What factors reduce biodiversity
- Woodland clearance - reduces number of trees and tree species while also destroying habitats. Species loose their habitats and food source so species will die or be forced to migrate
- Hedgerow removal increases the are of farmland by turning lots of small fields into fewer larger fields
- Pesticides kill organisms that feed on crops. Any species that feed on the pests will loose a food source
- Herbicides are chemicals that kill unwanted plants. Reduces plant diversity and organisms who feed on the weeds
- Monoculture is when farmers have fields containing only one type of plant. Reduces biodiversity and will support fewer organisms (e.g. as a habitat or food source), which further reduces biodiversity
What conservation methods should be used to balance
- Using hedgerows instead of fences
- Maintain and create ponds
- Reduce the draining of wetland
- Reduce the use of pesticides and herbicides - use biological control instead or genetically engineer pest resistant crop
- Crop rotation
- Intentional planting of different types of crop in different parts of the field and at different seasons in a sequential manner → ensure soil remains fertile. In crop rotation, one can also incorporate livestock in the practice when the land is left bare for a season of grazing - their waste adds nitrate
- Reduces use of fertiliser. Fertiliser which is industrially made can reduce biodiversity
- Increases soil fertile, crop yield, soil nutrients
- Intercropping
- To grow a crop among plants of a different kind. This type of organic gardening plant integration allows for greater plant diversity for increase crop production and pest control
- Creating natural meadows
All the species have the same name. What information does this tell you
Same genus
Same evolutionary origin/ common ancestor
What comparisons of genetic diversity are sued in order to generate classification y
Base sequence of DNA, mRNA,
Amino acid sequence
The student wanted to use the data from plot 1 to estimate the total number of the beetle species in the meadow.
Suggest how the student should use the data from plot 1 and other information provided to estimate the total number of the beetle species in the meadow.
- Same number of (different) species (in both plots)
OR
(Both plots) have 4 species;
(c) 1.
Determine the area of plot 1. - Calculate (total) area of meadow;
- Divide area of meadow by area of plot;
- Multiply by number of beetles (per plot)/41;
Accept multiply by incorrect figure taken from figure (eg 43)
What is the difference between species richness and index of diversity
Specie richness measures only number of different species/ doesn’t measure number of individuals
Explain how mutation of a gene canresult in an organism lacking aparticular enzyme. (4 marks)
mutation results in incorrect sequence of bases/nucleotides inDNA/frame shift of nucleotides;
incorrect codons/base triplets on mRNA;
so incorrect amino acids brought to ribosome/incorrect tRNAbring amino acids;
wrong sequence of amino acids changes tertiary structure oractive site(of enzyme)/no longer functions as enzyme/no or differentenzyme formed/protein non-functional
What is the difference between a proteome and a genome
Genome- complete set of genes in a cell, proteome is the full range of proteins that a cell can produce
- all cells with a nucelus have the same genome. Expression of proteome varies between tissue
