unit 4 Flashcards
i odnt want to so this
Gene
a section of DNA that contains a
code for making a polypeptide
and functional RNA
Allele
a different version of the same
gene
Locus
the location of a particular gene
on a chromosome
Prokaryotic
DNA
DNA molecules are shorter and
circular
DNA is not wound around
histones. Instead, it supercoils
to fit in the cell
What is the advantage
of the genetic code
being degenerate?
if a substitution mutation
occurs, the new triplet of bases
may still code for the same
amino acid
therefore the mutation will have
no impact on the final protein
produced
Chromosome
threadlike structure
composed of tightly coiled DNA
wrapped around histones (if it
is a eukaryotic cell)
Homologous
chromosome
a pair of chromosomes that
have the same genes
therefore, they are the same
size
Stop codon
3 bases at the end of every gene
that do not code for an amino
acid
this causes ribosomes to
detach
and therefore stops translation
Eukaryotic
DNA
DNA is stored as chromosomes
inside the nucleus
linear chromosomes
DNA is tightly coiled and
wrapped around proteins called
histones
Codon
3 bases on mRNA that code for
an amino acid
Start codon
3 bases at the start of an mRNA
sequence which help to initiate
translation
Genetic code
an amino acid is coded for by 3
DNA bases which are described
as the “triplet code”
What is meant by
‘the genetic code
is degenerate?
each amino acid is coded for by
more than one triplet of bases
What is the advantage
of the genetic code
being universal?
genetic engineering is possible
a human gene can be inserted
into another organism
e.g human gene for insulin
inserted into bacteria to make
insulin
What is the advantage
of the genetic code
being nonoverlapping?
f a point mutation occurs, it
will only affect one codon and
therefore one amino acid
Triplet code
an amino acid is coded for by 3
bases
Mutation
a change in the DNA
can be a gene or chromosome
mutation
What is meant by
‘the genetic code
is universal?
the same triplet of bases codes
for the same amino acid in all
organisms
What is meant by
‘the genetic code is
non-overlapping?
each base in a gene is only part
of one triplet of bases that
codes for one amino acid
therefore each codon is read as
a discrete unit
Exons
sequences of DNA that code for
amino acids
Introns
non-coding sequence of DNA
Genome
the complete set of genes in a
cell
What is
splicing?
post-transcription modification
removing introns
Proteome
The full range of proteins that a
cell is able to produce
Translation
the second stage in protein
synthesis
the polypeptide chain is
created using both the mRNA
base sequence and the tRNA
occurs on ribosomes in the
cytoplasm
tRNA
structure
single-stranded, folded to
create a cloverleaf shape
held in place by hydrogen bonds
has an anticodon and amino
acid binding site
Anticodon
3 bases on the tRNA which are
complementary to the codon on
mRNA.
mRNA
function
a copy of a gene from DNA
created in the nucleus, and it
then leaves the nucleus
to carry the copy of the genetic
code of one gene to a ribosome
in the cytoplasm
mRNA
structure
single-stranded
made up of codons
a copy of one gene
tRNA
function
a specific amino attaches at the
binding site
transfers this amino acid to the
ribosome to create the
polypeptide chain
Transcription
the first stage in protein
synthesis
one gene in DNA is copied into
mRNA
occurs in the nucleus
DNA
helicase
catalyses the breaking of
hydrogen bonds between the
two strands of DNA
Which enzymes
are involved in
transcription?
DNA helicase
RNA polymerase
pre-mRNA
mRNA in eukaryotes that still
contains the introns
RNA
polymerase
joins adjacent RNA nucleotides
together
forming a phosphodiester bond
Haploid
one copy of each chromosome
in a cell
Diploid
two copies of each chromosome
in a cell
How is premRNA
modified?
the introns are removed by a
protein called a spliceosome
this leaves just the exons
What is ATP
used for in
translation?
forming the peptide bond
between amino acids
Meiosis
cell division that creates
genetically different gametes
there are two nuclear divisions
in this process
results in four haploid daughter
cells
Crossing over
homologous pairs of
chromosomes line up opposite
each other at the equator in
meiosis 1
parts of the chromatids twist,
break and recombine with
another chromatid
results in new combinations of
alleles in the gametes
Substitution
mutation
a gene mutation
a base is swapped for a
different one
Gametes
sex cells (sperm and egg)
Independent
segregation
homologous pairs of
chromosomes randomly line up
opposite each other at the
equator of the cell
when they separate it creates a
large number of possible
combinations of chromosomes
in the daughter cells produced
Genetic
diversity
he number of different alleles
in a population
How does meiosis
introduce
variation?
crossing over
independent segregation
Chromosome
mutation
change in the number of
chromosomes
occurs during meiosis
What is a
frameshift?
the removal of one base
changes all of the subsequent
codons
all the bases shift back one
position
Types of gene
mutations
deletion
substitution
Deletion
mutation
a gene mutation
a base is removed from a
sequence
causes a frameshift
Evolution
he change in allele frequency
over many generations in a
population
Polyploidy
changes in whole sets of
chromosomes
e.g. when organisms have three
or more sets of chromosomes
mainly occurs in plants
Aneuploidy
a change in the number of
individual chromosomes
e.g 3 copies of chromosome 21
Non-disjunction
the chromosomes or
chromatids do not split equally
during anaphase
Natural
selection
the process that leads to
evolution in populations
results in species becoming
better adapted to their
environment
Down’s
syndrome
causes by a chromosome
mutation
an example of aneuploidy
3 copies of chromosome 21
Types of
selection
stabilising
directional
Gene pool
all the genes and alleles in a
population at a particular time
Allele
frequency
the proportion of organisms
within the population carrying a
particular allele
Selection
pressure
factors that affect the survival
of an organism
the driving force of natural
selection
Directional
selection
one of the extreme traits has a
selective advantage
occurs when there is a change
in the environment
the modal trait changes
An example of
directional
selection
antibiotic resistance
Stabilising
selection
the middle (median) trait has a
selective advantage and
continues to be the most
frequent in the population
represented by a normal
distribution graph
range decreases as the extreme
traits are lost over time
An example of
stabilising
selection
a group of similar organisms
that can breed to make fertile
offspring
Binomial
system
a universal naming system
individuals are named after
their genus and species
e.g. Homo sapiens
Courtship
behaviour
different sequences of
behaviours that animals
demonstrate to attract a mate
each species demonstrates its
own unique behaviour
essential for successful mating
Taxon
the term for each group in
classification
Importance of
courtship
helps to synchronise mating
behaviour so that the animals
are more likely to mate when
the female is releasing eggs
increases the likelihood of
successful mating
enables individuals to
recognise members of the same
species and opposite sex
What is meant
by a hierarchy?
smaller groups arranged within
larger groups
there is also no overlap between
groups
Common
ancestor
the species from which another
species evolved
Species
richness
the number of different species
in a particular area at the same
time
Phylogenetics
the study of species’
evolutionary origins and
relationships
Community
all the species in a particular
area at a particular time
Biodiversity
a measure of the range of
habitats
from a small local habitat to the
entire Earth
a measure of species diversity
a measure of genetic diversity
Species
diverstity
the number of different species
and the number of individuals
within each species in a
community
What are the taxa in
the Linnaeus
classification
system?
domain
kingdom
phylum
class
order
family
genus
species
Habitat
The range of physical, biological
and environmental factors in
which a species can live
Environment
the abiotic (non-living) factors
in an area
Index of diversity
a measure of species diversity
a calculation to measure the
relationship between the
number of species in a
community and the number of
individuals in each species
Which farming
techniques reduce
biodiversity?
destruction of hedgerows
selective breeding
monocultures
over-grazing
filling in ponds and draining
wetlands
Genetic
diversity
the mesure of how many
different alleles there are for
each gene
How do you make
sure your sampling is
representative of the
population?
take a large sample (at least
30)
randomly sample to avoid bias
How is standard
deviation more
useful than a mean?
it gives you the spread of data
(variance) around the mean\
overlaps in standard deviation
indicate no significant
difference in the means
How can you
measure genetic
diversity?
by comparing the base
sequence of DNA, mRNA and the
amino acid sequence of the
protein
Formula for
Index of Diversity
D = N(n - 1) / n(n - 1)
N = total number of organisms of all species
n = the population size of one species
D = simpsons index of diversity
Compare the DNA in
chloroplast/
mitochondria to
prokaryotic DNA
the DNA is similar to
prokaryotic DNA, in that it is:
short
circular
not histone bound
What is the role
of tRNA in
translation?
it carries a specific amino acid
anticodons align opposite
complementary codons on the
mRNA
Gene
mutations
a change in the base sequence
of DNA
substitution or deletion
How does
transcription differ
between prokaryotes
and eukaryotes
Transcription in prokaryotic
organisms results in mRNA
that requires no modification
because prokaryotic DNA does
not contain any introns
eukaryotic transcription results
in pre-mRNA that needs introns
removed
When in the cell
cycle do gene
mutations occur?
interphase (s phase)
this is when DNA is replicated
What is the role
of ribosomes in
translation?
it holds two tRNA molecules
to enable peptide bonds to form
between the amino acids
