Unit 4 Flashcards
Genetic Information and Variation
describe the similarities between DNA and RNA
- nucleotides
- four nitrogenous bases (adenine, cytosine, guanine)
- phosphate group
- have hydrogen and phosphodiester bonds
describe differences between DNA and RNA
- DNA has deoxyribose and thymine, RNA has ribose and uracil
- DNA is a double helix and RNA is a single helix
- DNA is longer
define codon
three bases (triplet) that code for an amino acid
name for a location of a gene
locus
are introns or exons removed
introns are removed in splicing to form mRNA from pre-mRNA
how many amino acids do we have
20 - 64 possible triplets
features of the genetic code
- non-overlapping - triplets only read once
- degenerate - more than one triplet codes for the same protein
- universal - same codon always codes for the same amino acid
- start/stop codons - initiates and terminates the translation process
differences between DNA in prokaryotic and eukaryotic cells
- prokaryotic; nucleoid free in cytoplasm, short, circular and not associated with proteins, no introns.
- eukaryotic; chromosome membrane bound in nucleus, long, linear and associated with proteins (histones), introns (longer)
does translation or transcription come first
transcription
describe the structure of mRNA
- single stranded helix
- complementary to dna
- pre-mrna contains introns, removed in spicing (shorter than DNA)
describe the structure of tRNA
single polypeptide in a clover shape, smaller then mRNA
describe transcription - breaks H bonds between between A-T and C-G bases…
- RNA polymerase attach complementary nucleotides to the DNA template strand A-U, T-A, C-G in a condensation reaction forming phosphodiester bonds
- splicing - removing introns from mRNA to become mRNA that diffuses through nuclear pores
describe translocation - mRNA associates with ribosomes, tRNA collects amino acids and takes them to the ribosome…
- tRNA attaches to the mRNA by complementary base pairing
- amino acids by peptide bonds in a condensation reaction, ATP used
- this repeats until a stop-codon is reached, tRNA dissociates as ribosomes moves along mRNA
define mutation
change in the base sequence
define genome
all the genes in an organism
define proteome
all of the proteins that an organism can produce
describe substitution
one nucleotide is replaced by another
describe deletion
nucleotide is removed causing a frame shift meaning multiple different amino acids
variation - describe independent assortment
chromosomes line up in pairs at random
variation - describe crossing over
when homogenous chromosomes become bivalent they swap genes
describe meiosis I
- nuclear membrane breakdown. synapsis
- chromosomes move together and touch so their bivalent
- crossing over - swapping genes
describe meiosis II
- chromatids move apart and the cell divides into four then divides again by mitosis
finish the order - Kingdom, Phylum, class…
…order, family, genus, species
describe natural selection
- environmental change occurs causing selection pressure
- individuals with advantageous alleles survive and reproduce
- advantageous alleles are passed onto the offspring
- increased frequency of allele in population
define selection
process in which individuals are better suited to their environment
define gene pool
the total number of different allele in the population
when naming animals the genus is always written…
…with a capital letter
define niche
species with a specific role in an environment
describe directional selection
environmental condition change the favourable allele best suited to the new conditions. those with the allele are more likely to survive and reproduce
describe stabilising selection
environment stays the same as one characteristic is favoured genes are lost
name ways to increase biodiversity
hedgerows, intercropping, reduce pesticides and herbicides, preserving wetlands
limitation to not using amino acid sequence to compare species
- could be degenerate
- characteristics could be influenced by environment
how does agriculture effect biodiversity
only one species grown, reduces biodiversity - less habitats and food sources for other species
index of diversity=…
…N(N-1) of the total organisms/the sum of n(n-1) of the separate species
