DNA, Genes And Chromosomes Flashcards
(103 cards)
1
Q
Introns
A
Non coding DNA
2
Q
Extrons
A
Coding DNA
3
Q
What is splicing
A
Removal of a section of DNA
4
Q
How does splicing occur
A
When introns are removed and exons are fused together
5
Q
When does splicing happen
A
Before pre MRNA exits nucleus
6
Q
What is pre-mRNA
A
A mRNA copy that contains introns and exons
7
Q
universal
A
all organisms use the same genetic code for proteins
8
Q
non overlapping
A
each triplet code is separate from each other in the chromosome
9
Q
degenerate
A
a single amino acid may be coded for by more than one codon
10
Q
nucleoid
A
chromosomal dna, 1 huge structure in prokaryotic cells
11
Q
histone
A
protein associated with dna- allows high amount of dna to be stored, as it wraps around
12
Q
chromatin
A
tightly coiled dna and histone, what chromatids and chromosomes are made of
13
Q
cell quiescence
A
cells life span
14
Q
telomeres
A
many adenine joined, protective structure on end of chromosomes
15
Q
replication of linear dna.. mitosis or binary?
A
mitosis
16
Q
replication of circular dna.. mitosis or binary
A
binary
17
Q
produces 2 daughter cells.. mitosis or binary?
A
both
18
Q
happens in prokaryotic cells.. mitosis or binary
A
binary
19
Q
happens in eukaryotic cells… mitosis or binary
A
mitosis
20
Q
what is mRNA
A
base sequence used by ribosomes to form polypeptides
21
Q
what is tRNA
A
transfer rna, decodes mRNA sequence into a protein, synthesises protein
22
Q
what is rRNA
A
reads order of amino acids and links them together
23
Q
types of mutation
A
insertion, deletion (everything downstream is affected), substitution
24
Q
what is the starting codon of every mrna sequence
A
AUG
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mutagenic factors
UV light, nitrous acid, gamma rays, viruses
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silent mutation
no change to primary structure of polypeptide despite change in a nucleotide base
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how is it possible to have a silent mutation?
when a change in the DNA sequence of a gene does not affect the subsequent amino acid sequence of the protein it codes for.
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frameshift mutation
everything codons downstream of mutation are affected
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how does base deletion affect amino acid sequence?
ex of frameshift mutation
due to non-overlapping nature of the genetic code, as soon as the nucleotide base is removed, every reading frame from that point of the mutation is shifted
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inversion mutation
when a gene breaks away and reattaches to the chromosome in a reversed order.
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substitution mutation
exchanges one base for another
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insertion mutation
when new nucleotides are added to the sequence
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non dysfunction
a pair of homologous chromosomes has failed to separate or segregate at anaphase so that both chromosomes of the pair pass to the same daughter cel
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duplication
one or more copies of a dna segment are produced
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haploid
have single celled chromosomes
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diploid
have 2 sets of chromosomes
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matching copies of chromosomes in diploids are called...
homologous
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meiosis process
prophase 1
metaphase 1
anaphase 1
telophase 1
prophase 2
metaphase 2
anaphase 2
telophase 2
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what happens in prophase 1
chromosones condense and become visible, undergoes chiasmata
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metaphase 1
homologous chromosomes move to equator of the cells
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anaphase 1
chromosomes move to opposite sides of the cell
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telophase 1
chromosomes gather and cytoplasm divides
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prophase 2
spindle fibres form around chromosomes
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metaphase 2
chromosomes line up at equator again
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anaphase 2
chromatids moved to opposite poles
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telophase 2
nuclear envelope reforms around chromosomes
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what is produced from meiosis
4 genetically unidentical daughter cells
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chiasmata
chromosomes wrap/twist around each other
section breaks off and rejoins the other one (variation)
49
Translation process
mRNA binds to ribosome in cytoplasm
One molecule of tRNA binds to codon in ribosome. Anticodon allows correct tRNA to bind
Each tRNA molecule carries specific amino acid into ribosome
tRNA molecule binds to 2nd codon and the 2 amino acids form a peptide bond
Ribosome moves along mRNA strand so new codon enters ribosome for complementary tRNA, process repeats
When ribosome reaches the stop codon polypeptide chain is released
50
Transcription process
RNA polymerase binds to locus of target gene to be transcribed
RNA polymerase binds to dna, breaking hydrogen bonds to separate dna strands, leaving bases exposed
RNA polymerase binds free nucleotides to the template strand of dna to form complementary mRNA
Phosphodiester bonds form between nucleotides in condensation reaction to form complete mRNA
RNA polymerase reaches stop codon
mRNA strand is separated from template strand by RNA polymerase. Hydrogen bonds join the 2 strands of DNA again.
mRNA strand leaves nucleus and enters cytoplasm
Splicing- introns leave and exons are fused together
51
What is gene mutation
Change in sequence of base pairs
Could occur in dna replication
Happens continuously and spontaneously
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How does gene mutation occur
Nucleotide- insertion, deletion, substitution
Section of gene- inversion, duplication, translocation
53
Substitution of nucleotides
Occurs when a base in dna is randomly swapped for a different one
Only changes amino acid for the triplet in which the mutation occurs
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3 forms of substitution in nucleotides
Silent mutation- mutation doesn’t alter amino acid sequence (certain codons may code for same amino acids- degenerate)
Missense mutations- mutation alters a SINGLE amino acid
Nonsense mutation- creates a premature stop codon causing polypeptide to be incomplete and change the function
55
Insertion
When a nucleotide is randomly inserted
Changes amino acid
Knock on effect- frame shift mutation
May change sequence produced and ability of polypeptide chain to function
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Deletion
Nucleotide is randomly deleted
Changes amino acid Knock
Frame shift mutation
Changes sequence and polypeptide to function
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Inversion of gene section
Occurs during cross over of meiosis
DNA of single gene is cut into 2 pieces
Cut peice is turned 180 then rejoined
Amino acid affected- different or non functional protein
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Duplication of gene
Gene is duplicated so 2 copies of gene on same chromosome
Original gene Isn’t a harmful mutation as intact
2nd copy undergoes mutation- new function
Important source of evolutionary change
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Translocation of gene
Gene is cut into 2 places
Section of gene attaches to separate gene
Cut gene - non functional
Gene with translocated section- non functional
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Causes of mutations
Exposure to mutagenic agents:
-high energy ionising radiation can increase mutations
-chemicals
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Effect of gene mutation on phenotype
Polypeptide/ protein affect phenotype via cellular mechanisms
E.g. phenotype of human affected by lack of melanin= albinism
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Effect of gene mutation on polypeptides
Most don’t alter polypeptide chain or only alter it slightly
Small number of mutations code for completely altered polypeptide with a different shape
May effect ability of protein to perform function
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How does altered polypeptide chain affect ability of protein to perform its function
Shape of active site changes so substrate cannot bind
Structural protein (collagen) may loose strength if shape changes
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3 components of a nucleotide
pentose sugar
phosphate group
organic base
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describe the structure of DNA
deoxyribose sugar, phosphate group, one of the organic bases, .
double stranded, hydrogen bonds between bases form a helix.
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role of dna
carries genetic info, determines inherited characteristics
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structure of rna
ribose sugar
phosphate group
one of the four bases (u,c,a,g)
single stranded
68
role of rna
transfers genetic info from dna to ribosomes for protein synthesis
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how is dna in eukaryotic cells different from dna in prokaryotic cells
eukaryotic cells- found in nucleus, long and linear, associated with histone proteins to form chromosones
prokaryotic- short and circular, not associated with proteins
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locus
the fixed position on a dna molecule occupied by a gene
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where are introns found
between exons
within genes
72
genome
full set of dna found in an organism
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proteome
full range of proteins that can be synthesised by a genome
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biodiversity
variety of organisms in a certain area
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species richness
measure of the number of different species in a community
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index of diversity
measure biodiversity taking into account species richness and the number of individuals in each species
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index of diversity calculation
(N(N-1)/εn(n-1)
n= total number of organisms of each species
N= total number of organisms of all species
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genetic diversity
number of different alleles of genes in a population
factor which enables natural selection to occur
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natural selection
mechanism of evolution by which individuals better adapted to their environment, tend to survive reproduce successfully and then pass on their alleles
80
what is the process of natural selection
random mutation can result in new alleles of a gene
new mutation of a gene might benefit organism
survival of the fittest
reproduce
alleles passed on
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direction selection
selective force that favours individuals with an extreme form of a trait and selects against phenotypes at the opposite extreme
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stabilizing selection
selective force that favours the phenotype closest to the mean value of the trait
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disruptive selection
selective force that favours both extreme phenotypes
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3 types of adaptations
behavioural
psychological
anatomical
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biological species concept
a species contains all organisms that are capable of breeding together to produce fertile offspring
86
courtship behaviour
enables individuals to identify same member species and identify mates capable of breeding
87
classification
sorting living things into groups
88
what are the 8 levels of classification
domain
kingdom
phylum
class
order
family
genus
species
89
how does the binomial naming system work
names species by their genus and species name
90
transects
lines created with tape measure across a habitat, use quadrats at different equal points along the transect.
91
why do we use transects
allows you to see how distribution is changing
92
species diversity
no. of different species and the no. of individuals of each species within one community
93
genetic diversity
variety of the genes possessed by individuals that may make up one species
93
ecosystem diversity
the range of different habitats within a particular area
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