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MISS ESTRUCH FLASHCARDS > TOPIC 4: GENETIC INFORMATION, VARIATION, AND RELATIONSHIPS BETWEEN ORGANISMS > Flashcards

TOPIC 4: GENETIC INFORMATION, VARIATION, AND RELATIONSHIPS BETWEEN ORGANISMS Flashcards

1
Q

Gene

A

a section of DNA that contains a
code for making a polypeptide
and functional RNA

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2
Q

Locus

A

the location of a particular gene
on a chromosome

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3
Q

Allele

A

a different version of the same
gene

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4
Q

Chromosome

A

threadlike structure
composed of tightly coiled DNA
wrapped around histones (if it
is a eukaryotic cell)

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5
Q

Homologous
chromosome

A

a pair of chromosomes that
have the same genes
therefore, they are the same
size

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6
Q

Eukaryotic
DNA

A

DNA is stored as chromosomes
inside the nucleus
linear chromosomes
DNA is tightly coiled and
wrapped around proteins called
histones

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7
Q

Prokaryotic
DNA

A

DNA molecules are shorter and
circular
DNA is not wound around
histones. Instead, it supercoils
to fit in the cell

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8
Q

Codon

A

3 bases on mRNA that code for
an amino acid

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9
Q

Start codon

A

3 bases at the start of an mRNA
sequence which help to initiate
translation

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10
Q

Stop codon

A

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

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11
Q

Genetic code

A

an amino acid is coded for by 3
DNA bases which are described
as the “triplet code”

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12
Q

What is meant by
‘the genetic code
is degenerate?

A

each amino acid is coded for by
more than one triplet of bases

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13
Q

What is the advantage
of the genetic code
being degenerate?

A

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

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14
Q

What is the advantage
of the genetic code
being universal?

A

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

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15
Q

What is the advantage
of the genetic code
being nonoverlapping?

A

if a point mutation occurs, it
will only affect one codon and
therefore one amino acid

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16
Q

Triplet code

A

an amino acid is coded for by 3
bases

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17
Q

Mutation

A

a change in the DNA
can be a gene or chromosome
mutation

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18
Q

What is meant by
‘the genetic code
is universal?

A

the same triplet of bases codes
for the same amino acid in all
organisms

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19
Q

What is meant by
‘the genetic code is
non-overlapping?

A

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

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20
Q

Introns

A

non-coding sequence of DNA

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21
Q

Exons

A

sequences of DNA that code for
amino acids

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22
Q

What is
splicing?

A

post-transcription modification
removing introns

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23
Q

Genome

A

the complete set of genes in a
cell

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24
Q

Proteome

A

The full range of proteins that a
cell is able to produce

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25
Anticodon
3 bases on the tRNA which are complementary to the codon on mRNA.
26
mRNA structure
single-stranded made up of codons a copy of one gene
27
tRNA structure
single-stranded, folded to create a cloverleaf shape held in place by hydrogen bonds has an anticodon and amino acid binding site
28
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
29
tRNA function
a specific amino attaches at the binding site transfers this amino acid to the ribosome to create the polypeptide chain
30
Transcription
the first stage in protein synthesis one gene in DNA is copied into mRNA occurs in the nucleus
31
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
32
Which enzymes are involved in transcription?
DNA helicase RNA polymerase
33
DNA helicase
catalyses the breaking of hydrogen bonds between the two strands of DNA
34
RNA polymerase
joins adjacent RNA nucleotides together forming a phosphodiester bond
35
pre-mRNA
mRNA in eukaryotes that still contains the introns
36
How is premRNA modified?
the introns are removed by a protein called a spliceosome this leaves just the exons
37
What is ATP used for in translation?
forming the peptide bond between amino acids
38
Haploid
one copy of each chromosome in a cell
39
Diploid
two copies of each chromosome in a cell
40
Meiosis
cell division that creates genetically different gametes there are two nuclear divisions in this process results in four haploid daughter cells
41
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
42
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
43
Gametes
sex cells (sperm and egg)
44
How does meiosis introduce variation?
crossing over independent segregation
45
Types of gene mutations
deletion substitution
46
What is a frameshift?
the removal of one base changes all of the subsequent codons all the bases shift back one position
47
Chromosome mutation
change in the number of chromosomes occurs during meiosis
48
Deletion mutation
a gene mutation a base is removed from a sequence causes a frameshift
49
Substitution mutation
a gene mutation a base is swapped for a different one
50
Non-disjunction
the chromosomes or chromatids do not split equally during anaphase
51
Polyploidy
changes in whole sets of chromosomes e.g. when organisms have three or more sets of chromosomes mainly occurs in plants
52
Aneuploidy
a change in the number of individual chromosomes e.g 3 copies of chromosome 21
53
Down's syndrome
causes by a chromosome mutation an example of aneuploidy 3 copies of chromosome 21
54
Genetic diversity
the number of different alleles in a population
55
Natural selection
the process that leads to evolution in populations results in species becoming better adapted to their environment
56
Gene pool
all the genes and alleles in a population at a particular time
57
Allele frequency
the proportion of organisms within the population carrying a particular allele
58
Evolution
the change in allele frequency over many generations in a population
59
Selection pressure
factors that affect the survival of an organism the driving force of natural selection
60
Types of selection
stabilising directional
61
Directional selection
one of the extreme traits has a selective advantage occurs when there is a change in the environment the modal trait changes
62
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
63
An example of directional selection
antibiotic resistance
64
An example of stabilising selection
human birth weight
65
Definition of a species
a group of similar organisms that can breed to make fertile offspring
66
Binomial system
a universal naming system individuals are named after their genus and species e.g. Homo sapiens
67
Courtship behaviour
different sequences of behaviours that animals demonstrate to attract a mate each species demonstrates its own unique behaviour essential for successful mating
68
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
69
What is meant by a hierarchy?
smaller groups arranged within larger groups there is also no overlap between groups
70
Phylogenetics
the study of species' evolutionary origins and relationships
71
Common ancestor
the species from which another species evolved
72
Taxon
the term for each group in classification
73
What are the taxa in the Linnaeus classification system?
domain kingdom phylum class order family genus species
74
Species diverstity
the number of different species and the number of individuals within each species in a community
75
Species richness
the number of different species in a particular area at the same time
76
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
77
Community
all the species in a particular area at a particular time
78
Environment
the abiotic (non-living) factors in an area
79
Habitat
The range of physical, biological and environmental factors in which a species can live
80
Which farming techniques reduce biodiversity?
destruction of hedgerows selective breeding monocultures over-grazing filling in ponds and draining wetlands
81
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
82
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
83
How do you make sure your sampling is representative of the population?
take a large sample (at least 30) randomly sample to avoid bias
84
How can you measure genetic diversity?
by comparing the base sequence of DNA, mRNA and the amino acid sequence of the proteins
85
Genetic diversity
the mesure of how many different alleles there are for each gene
86
Formula for Index of Diversity
D=N(N-1)/E n(n-1) N= the total number of organisms of all the species n=the population size of one species D=simpson's index of diversity
87
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
88
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
89
What is the role of ribosomes in translation?
it holds two tRNA molecules to enable peptide bonds to form between the amino acids
90
What is the role of tRNA in translation?
it carries a specific amino acid anticodons align opposite complementary codons on the mRNA
91
Gene mutations
a change in the base sequence of DNA substitution or deletion
92
When in the cell cycle do gene mutations occur?
interphase (s phase) this is when DNA is replicated

MISS ESTRUCH FLASHCARDS (8 decks)

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