Genetics Topic 4 Flashcards
What are the 3 features of genetic code
- Degenerate
- Universal
- Non over lapping
What does degenerate mean
There are more than one triplet bases which code for each amino acid
What are exons and introns
Exons : sequences of DNA that do code for amino acid
Introns : section which does not code for amino acid
What is a codon
Three bases on MRNA which code for a specific amino acid
Start codon -the three bases at the start of every gene which intimates translation
Stop codon - three bases at the end of every gene where ribosomes detach at end of translation
What is a genome
An organisms complete set of genes in a cell
What is transcription
Is the production of mRNA from DNA
What is translation
Where the mRNA joins with a ribosome, and corresponding tRNA molecules bring the amino acids the codons code for
Describe-what happens before transcription
A complementary mRNA copy of a gene is created in nucleus
mRNA is shorter than DNA so is able to carry the genetic code to the ribosome
Describe transcription
1.DNA helix unwinds exposing DNA bases
2.) unwinding is catalysed by DNA helicase are which breaks hydrogen bonds between bases
3.) free mRNA nucleotides in nucleus align opposite exposed complementary DNA bases
4.)RNA polymerase joins together RNA nucleotides to create RNA polymer chain.
5.in eukaryotic cells ,pre-mRNA introns are spliced out , then the mRNA moves out of the pore and attaches to a ribosome in the cytoplasm
what is non disjunction
when chromatids or chromosomes do not split equally during anaphase
what is polyploidy
changes in the whole set of chromosomes occur when organisms have two or three more chromosomes rather than usual two
what is aneuploidy
changes in the number of individual chromosomes
define meiosis
is a form of cell division which gives rise to four genetically different daughter cells. produces haploid cells
what is courtship behaivour
Members of the same species share similar physical and
behavioural characteristics. Courtship behaviour takes place before mating.
What happens during meiosis one
1.) the homologous pairs for bivalvents
2.crossing over of chromosomes (exchange of genetic material)happens during chiasma
3.) cell divides into two ,homologous chromosomes separate randomly
What happens during meiosis 11
1.)Independent segregation of sister chromatids
2.)each cell divides again ,producing haploids
Give two ways meiosis produces genetic variation
1.) crossing over during meiosis one
2. Independent segregation
Results in New combinations of alleles
What is genetic diversity
The total number of different alleles in a population
What is directional selection
-occurs when environmental conditions change
-individuals with phenotypes suited to the new conditions will survive and pass on genes
-overtime the mean will move towards the characteristic
How does antibiotic resistance in crease directional selection
Bacteria with the mutation is able to survive and reproduce.
This increases the allele frequency and the population will shift to have greater anti biotic resistance
What is stabilising selection
When environmental conditions stay the same
Individuals closest to the mean are favoured
And any new selection is selected against
Define species
A group of organisms which can breed to make fertile offspring
Define classification
The process of arranging organisms into groups
Define biodiversity
The variety of living organisms
Measured in species diversity
Genetic diversity
Ecosystem diversity
Community
All the different species live in the same area and interact with one another
What is the difference in DNA between eukaryotes and prokaryotes
Eukaryotes
Linear DNA
Associated with protein
Contained in nuclear membrane
Prokaryotes
Circular DNA
Not associated with proteins
Not contained in a membrane
Describe the DNA in mitochondria and chloroplast
Have circular DNA
Describe the link between DNA and genes and bases with amino acids
DNA contains genes
Genes are sequences of DNA that code for an amino acid
Every three bases in the DNA code for a different amino acid
What does universal mean
The same base sequence codes for the same amino acid in different organism
What does non-overlapping mean
Base triplets don’t overlap or share their bases
What is the proteome
The full range of proteins that a cell is able to produce
What is translation
The production of polypeptides from the sequence of codons carried by mRNA
Describe the process of translation
- the mRNA attaches itself to a ribosome and the tRNA brings the amino acid
2.A tRNA molecule that has a complementary anticodon for the first codon on the amino acid binds to it
3.Another tRNA that is complementary for the second codon binds - The amino acids they carry are joined by the ribosome
- This continues until the ribosome meets a codon called a “stop” codon and the signals for translation to stop and the polypeptide to detach
What is genetic diversity
The number of different alleles in a population
How can you improve genetic diversity
New mutations
Through migration of a new population
What are the steps of natural selection
- Random mutations result in new alleles
2.individuals may have an allele that gives them a reproductive advantage - These individuals are more likely to survive and pass on their gene whereas individuals with a different allele is less advantageous will be less likely to survive
- Overtime allele frequency in population increases
What is biodiversity
Refers to the variety of different organisms
What is species richness
Is a measure of the number of different species in a community
What is the index diversity
DI=N(n-1)/(n-1)
N=the total number of organisms
n=the total number of organisms of each species
How can biodiversity be reduced
Monocultures -only a small number of organisms can be supported
Using pesticides -to kill insects reduces number of insects and animals which feed on the insects could die
Using herbicides -reduces the number of weeds ,organisms which feed on weeds could die
Removing hedgerows - destroys habitat for organisms that live there
How can we improve agriculture whilst conserving biodiversity
Protect endangered species
Provide subsidies
Restrict development of areas
How are organisms classified according
Phylogenic classification system
What is hierarchies for phylogenic system
domain, kingdom, phylum, class, order, family, genus, and species
What are the humans genus and species
Genus :Homo
Species:Sapiens
What is courtship behaviour
Courtship behaviours are used to help classify species
Organisms use courtship behaviour to attract a mate from the right species
What does courtship behaviour tell you about a species
The more closely related species are, the more similar their courtship behaviour
