Topic 4 Flashcards
Give 3 differences between prokaryotic DNA and eukaryotic DNA
prokaryotic DNA
Shorter
Circular
Not associated with proteins
Eukaryotic DNA
Longer
Linear
Associated with histones
Which 2 organelles contain prokaryotic DNA
Mitochondria and chloroplasts
What is a gene
A base sequence of DNA that codes for amino acid sequence of a polypeptide or functional RNA
What is a locus
The fixed position of a gene on a chromosome
What are 3 features of genetic code
Degenerate - multiple codons can code for the same amino acid during photosynthesis
Universal - the same triplet of based codes for the same amino acid in all organisms
Non- overlapping - each base in a gene is only part of one triplet therefore each codon is read as discrete unit
What are introns
Sections of DNA that do not code for polypeptides
Where are introns found
In eukaryotic DNA not in prokaryotic
What are exons
Sequenced of DNA that DO code FOR AMINO ACIDS
What is a codon
Three bases on mRNA that code for a specific amino acid
What is a start codon
Three babes that start of every green that initiates translation
What is a stop codon
3 bases at the end of every gene that causes ribosomes to detach and therefore stop translation
What is a genome
An organisms complete set of genes in a cell
What is a proteome
The full range of proteins that a cell is able to produce
Give the properties of mRNA
(4)
short single stranded
Found in the cytoplasm and nucleus
Made during transcription complementary to DNA sequence
Give some properties of tRNA
Is clover shaped
Single stranded
Each tRNA molecule has three based called an anticodon these are complementary to codons on the mRNA molecule
tRNA is involved in translation as it carries amino acids used to make proteins to the ribosomes
What is transcription
Where one gene on the DNA is copied into mRNA
What is translation
Where the mRNA joined with a ribosome and corresponding tRNA brings the specific amino acid the codon codes for
Why is mRNA used for transcription
MRNA is much shorter than DNA And so is able to carry genetic code to ribosome in the cytoplasm
Give the 5 steps for transcription
- DNA helix unwinds to expose bases to act as template
- Only one chain of DNA acts as template
- This is catalysed by DNA helicase which breaks down the hydrogen bonds between bases
- Free mRNA nucleotides align with exposed complementary bases
- Enzyme RNA polymerase joins them together this RNA is then modified and leaves nucleus though nuclear envelope pores
In eukaryotes what is made after transcription and how
Pre mRNA made from mRNA that still contains introns so introns need it be spliced out by a protein caked a spliceosome
In 6 steps explain the process of translation
- Once modified mRNA left nucleus attached to a ribosome in the cytoplasm
- Ribosome attached at the start codon
- tRNA with the complementary anti codon to start codon aligns
- Ribosome will move along one corn on the mRNA molecule to enable another complementary tRNA to attach to the next codon on mRNA
- 2 amino acids that have been delivered by the tRNA molecule joined with a peptide bond catalysed by an enzyme and requires ATP
- This continues until ribosome reaches stop codon this stop codon does not code for an amino acid and so ribosome detached and translation ends
What is a mutation?
A change in the base sequence of DNA
What are mutagenic agents give 2 examples
Interfere with DNA replication icy as UV light, ionising radiation and chemicals and carcinogens such as cigarette smoke
What are the 2 forms of gene mutation
Deletion or substitution
What is a chromosome mutation
Changes in the number of chromosomes
What is non-disjunction
When chromosomes do no split equally during anaphase
What are the 2 forms of chromosome mutation
- Changes in whole set of chromosomes polyploidy
- Changes in the number of individual chromosomes
(Aneuploidy)
What does meiosis produce
4 haploid daughter cells that are genetically different
What happens in meiosis I
Homologous pairs of chromosomes line up opposite each other at the equator
It is random which side of the equator paternal and maternal chromosomes from each homologous pair lie
Pairs are separated so one of each homologous pair end up in daughter cell so a large number of possible combinations are possible
What is crossing over
In meiosis I when the homologous pairs are lined up the chromatids can become twisted around each other this puts tension on the chromatids causing then to break and recombine with other chromatids
What is the point of crossing over called on a chromatid
Chiazmata
Give 3 differences between meiosis and mitosis
Mitosis
One nuclear division
Creates diploid cells ( 2 sets of chromosomes)
Creates genetically identical cells
Meiosis
2 nuclear divisions
Creates haploid cells (1 set of chromosomes)
Introduces genetic variation
What was genetic diversity
The number of different alleles of genes in a population
What’s natural selection
Process that leads to evolution
What is evolution
Champagne in allele frequency over many generations in a population
In 4 stages explain how natural selection occurs
- New alleles for a gene are created by random mutations
- If the new allele increases the chances of the individual to survive in that environment so they will survive and reproduce
- This reproduction passes on the advantageous allele to the next generation
- As a result over many generations the new allele will increase its frequency in the population
What are the 3 types of selection
Directional selection
Stabilising selection
Disruptive selection
What is directional selection
Where one extreme has the selective advantage
What is stabilising selection
The middle trait has the selective advantage e.g birth weight it’s safer to be a middle weight that to be a small abby or large baby
What is disruptive selection
Where both extremes are advantageous
What is courtship behaviour
A sequence of captions unique to species how animals identify their own species to reproduce
What is the acronym for the hierarchy for biodiversity
D - do Domain
K - koalas Kingdom
P - prefer Phylum
c - chocolate class
O - or Order
F - fruit Family
G - generally Genus
S - speaking Species
What is the bionomial system
Each species universally identified using 2 names first is the genus and second is the species
What is species diversity
The number of different species and individuals within a community
What is genetic diversity
The variety of genes amongst individuals in a population do one species
What is species richness
The number of different species in a community
