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Genes Flashcards

1
Q

GENES AND THE GENETIC CODE

chromosone
histone
gene definition

A

chromosone = length of DNA associated with histone proteins

histone = a protein that DNA wraps around to package up into a chromosone

gene = region of DNA that codes for polypeptides and functional RNA

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2
Q

GENES AND THE GENETIC CODE

allele
gene locus
genome
proteone

A

allele = different versions of the same gene

gene locus = position of a gene on a chromosone

genome = complete set of genes in a cell

proteone = full range of proteins a cell is able to produce

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3
Q

GENES AND THE GENETIC CODE

whats coding dna and non coding dna called

A

coding = exons
non coding = introns

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4
Q

GENES AND THE GENETIC CODE

4 bases for dna, whats the basis for the genetic code

A

4*3

three bases = 1 amino acid =. 64 amino acids

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5
Q

GENES AND THE GENETIC CODE

feature sof the genetic code (5)

A
  1. DEGENERATE TRIPLET CODE = triplet codes can code for more then 1 amino acid
  2. READ IN 1 DIRECTION ONLY
  3. PUNCTUAL = has start an stop codons
  4. NON OVERLAPPING
  5. UNIVERSAL = the same triplet codes for the same amino acid in all organisms
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6
Q

GENES AND THE GENETIC CODE

universal
degenerate
non overlapping definition

A

universal - same codon will always code for the same amino acid

degenerate - more then one codon can code for the same amino acids

non overlapping - each codon is read in descreet triplet bases

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7
Q

GENES AND THE GENETIC CODE

what do histones do

A

dna wrapps around the histones creating a DNA protein complex ( chromatin )
allows supercoiling to form a chromasome in metaphase

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8
Q

GENES AND THE GENETIC CODE

whats a homogolous chrromasone

A
  • pair of one material and one paternal chromosone which pair up during meiosis
  • they have the same genes in the same locus
  • they may have diffeent versions of the genes ( allelle ) due to a different base sequence
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9
Q

GENES AND THE GENETIC CODE

prokaryotic vs eukaryotic dna

A

prokaryotic

  • no histones
  • made in Nucleus but found all in the cell
  • no introns
  • circular
  • smaller
  • all coding

Eukaryotic

  • histones
  • found in nucleus
  • some introns
  • linier dna
  • larger
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10
Q

GENES AND THE GENETIC CODE

how many chromosones

A

23 pairs of chromosomes in each cell

apart from in gametes they have half due to being haploid cells

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11
Q

GENES AND THE GENETIC CODE

codon and anticodon definition

A

codon - sequence of 3 bases on Mrna that codes for a single amino acid

anticodon - sequence of 3 bases on Trna that codes for a single amino acid

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12
Q

GENES AND THE GENETIC CODE

Mrna characteristics

A
  • no hydrogen bonds
  • A,U,G,C
  • ribose sugar
  • single helix structure
  • smaller then DNA larger then Trna
  • most unstable = individual mollecules ususally broke down in a few days
  • manufactured in nucleus found throught cell
  • qualtity in cell varies depending on metabolic activity
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13
Q

GENES AND THE GENETIC CODE

Trna characteristics

A
  • singles stranded
  • smallest
  • clover shape
  • A,U,C,G
  • ribose sugar
  • hydrogen bonds
  • quantities vary cell to cell depending on metabolic activity
  • made in nucleus, found all in cell
  • more stable then Mrna
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14
Q

GENES AND THE GENETIC CODE

DNA characteristics

A
  • double helix stranded
  • Largest
  • A,T,C,G
  • deoxyribose sugar
  • same amount in each cell
  • hydrogen bonds
  • made and found in nucleus
  • most stable
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15
Q

GENES AND THE GENETIC CODE

Why is it important that Mrna is unstable

Why is it important that DNA is most stable

A
  1. stops translation, controlls comcentration of proteins produced
  2. lets it withstand thermal and chemical damage so can be transferred from generation to generation
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16
Q

MEIOSIS

meiosis vs mitosis definition

A

meiosis - produces 4 daughter cells with half the number of chromasones ( haploid ) which are genetically different

mitosis - produces 2 daughter cells with the correct number of chromasomes ( diploid ) which are genetically similar

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17
Q

MEIOSIS

what occours in meiosis 1 and meiosis 2

A

meiosis 1

  • homogolous chromasomes pair up by independent assortment, this means that the combinations of maternal and paternal chromasones are a matter of chance

meiosis 2

  • sister chromatids are seperated, to different poles via spindle fibres as the centrimere splits.
  • this creates 4 daughter cells with 1/2 chromasomes and are genetically different
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18
Q

MEIOSIS

how do you calculate how many combinations of chromasomes in Meiosis 1

A

2*n

2= 1 chromosome is two sister chromatids
n = how many sister chromatids

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19
Q

MEIOSIS

what causes variation (2 )

A
  • independent assortment = homologous chromosomes pair up randomly
  • Crossing over = chromatids cross over in meiosis 1 at the chiasmata. Equal portions of the sister chromatids are broken off and recombine with another chromatid, creation a new combination of alleles
  • this means some genes are inherited together due to being close together on a chromasome and both included when crossing over occured
  • normal meiosis 1 and 2
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20
Q

MEIOSIS

why is changing diploid to haploid important in gamete production

A
  • at fertalisation, diploid numbers are restored
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21
Q

MEIOSIS

whats crossing over

A

Crossing over = chromatids cross over in meiosis 1 at the chiasmata. Equal portions of the sister chromatids are broken off and recombine with another chromatid, creation a new combination of alleles
- this means some genes are inherited together due to being close together on a chromasome and both included when crossing over occured

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22
Q

MEIOSIS

how can genetic variation be introduced

A
  • fertalisation is random, random gametes to create a zygote
  • mutations occour creating new alleles
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23
Q

TRANSCRIPTION

process

A

DNA - MRNA in the nucleus

  • dna helicase breaks the H bonds causing the section of DNA to unwind
  • One strand acts as a template
  • Rna nucleotides join by complimentary base pairings
  • RNA polymerase secures nucleotides by createing a phosphodiester bond and a sugar phosphate backbone
  • DNA triplets converted into MRNA codons ( pre RNA )
  • Non coding sections are spliced out ( introns )
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24
Q

why is prokaryotic gene expression quicker ( DNA to proteins )

A
  • Prokaryotes dont have nucleus, can go traight to ribosome
  • No introns = splicing doesnt occour
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25
TRANSLATION
- Mrna - proteins in the cytoplasm - Mrna moves through the cytoplasm to the ribosome to the start codon - Trna carries a specific amino acid - Mrna read in codons - the anticodon of Trna nd Codon of Mrna join - ATP used to join amino acids via complimentry base pairnings - Only space for 2 Rna in a ribosome - Trna can be reused - Sequence of codons codes for the sequence pf amino acids - Ribosome moves along Mrna to form the polypeptide chain until it reaches the stop codon
26
POLYLOIDY
having a greater then normal diploid number - caused during errors in cell division, leading to whole genome duplication - often used to increase size of frruit eg : strawberrys
27
CHROMASOMR NON DISFUNCTION
- gametes can end up with and extra or too few chromasomes - eg: Trisomy 21 = downsyndrome - this can occour dueing Meiosis 1 leading to trisomic and monosomic cells - or can occour in Meiosis 2 leaving to disomic, trisomic and monosomic cells
28
Gene mutations
- changes in the sequence of base pairs in DNA that result in a non functional polypeptide - they can occour continuously or spontaniously = often occour in dna replication
29
Mutagenic Agents
- these increase the rate of mutations that occour caused by: 1. high energy ionising radiation eg; Xrays = ionises bases and doesnt form correct pairs 2. chemicals ( carcinogenic ) eg : tar = interferese with transcription 3. chemicals eg: mustard gas binf to dna = seperating double helix 4. visuses = chnage in base sequence
30
CLASSIFICATION Species definition
- a group of organisms that have a similar anatomical, biochemical and behavioural characteristics and can interbreed to produce live and fertile offspring
31
CLASSIFICATION Species occupy the same ecological niche and belong to same gene pool What does this mean
Ecological niche = role and posterior a species has on an environment Gene pool = total amount of different genes in an interbreeding population
32
CLASSIFICATION What are the 3 domains
Eukarya Bacteria Archaea
33
CLASSIFICATION What are the 4 kingdoms in Eukarya
- fungi - plantae - anamalia - Protista
34
CLASSIFICATION Hierarchy of Taxonomic groups Anagram
DEMON - domain KINKY - kingdom PENGUINS - phylum CANT - class ORGASM - order FROM - family GOOD - genus SEX - species
35
CLASSIFICATION How do we name a species
Genus + species
36
MUTATION whats mutation
change in structure or arrangement or qualntity of DNA leading to new alleles
37
MUTATION two types of mutation
somatic = occour in body cells = not passed on Germinal = occours in reproductive tissue = passed on
38
MUTATION substitution ( 3 )
1. silent mutation = when only affects one amino acid, has no affect due to being degenerate 2. non sense mutation = causing a premature stop codon = protein incomplete and non functional 3. mis sense mutation = different amino acid = alters polypeptide structure
39
MUTATION deletion and insertion
these cause more serious affects due to frame shift mutation - deletion shifts to left - insertion shifts to right - all amino acids down stream of mutation are incorrect and protein non functional
40
NATURAL SELECTION definitions of population genetic diversity allele frequency
population = group of interbreeding organisms of the same species living in one place genetic diversity = total amount of different alleles in a popualtion allele frequency = how often a particular allele occours within a gene pool
41
NATURAL SELECTION How can genetic diversity be affected ( 4)
- introduction of new individuals in a close population - selective breeding - natural disasters - Isolation
42
NATURAL SELECTION how does it occour
- random mutation = different alleles - can give a competitative advantage - better able to survive and reproduce sucessfully passing on alleles - allele frequency increased
43
NATURAL SELECTION whats selection pressure
change in environment that selects for particular characteristics
44
NATURAL SELECTION directional selection and example
- one extreme characteristic is favoured - other extreme isnt favoured eg: antibiotic resistance - random mutation = new allele - highest antibiotic resistance selected for - new allele has competative advantage = reproduces sucessfully - high allele frequency - normal distribution curve shifts direction
45
NATURAL SELECTION stabelising selection and example
- envionment stays the same for a long time = selection favours average - extremes are selected against eg: human birth weight - random mutation = new alleles - alleles selected which are closest to average - extremes arent selected - competitative advantage = more likely for sucessful reprodcution - alleles passed on increaseing allele frequency - normal distribution curve = less standard deviation and is higher and thinner
46
BIODIVERSITY community habitat biodiversity ecosystem
community - all living organisms present in an ecosystem at a given time habitat - the place where an organism normally lives, characterised by physical conditions biodiversity - the range and variety of genes, species and habitats in a particular region ecosystem - all living and non living components of a particular area
47
BIODIVERSITY species diversity genetic diversity ecosystem diversity species richness
species = number of differnt species and number of individual in each species in a cimmunity genetic = number of differnet alleles of genes in a population ecosystem = variety of habitats within an area species richness = measure of species in a community
48
BIODIVERSITY how to measure
d = species diversity index N = total number of organisms of all species n = total number of organisms in each species higher value the greater the species diversity
49
BIODIVERSITY positive and negative impacts humans have on species diversity
pos - conservation - rewilding - desegnated protected area neg - deforestaion - hunting and poaching - pollution - eutrification
50
BIODIVERSITY Farming decreasing and increasing biodiversity
dec - loss of habitat - loss of range of food sources which support a variety of organisms - organisms cant be supported so reduce numbers Inc - wild flower seeds - hedge rows - organic fertalisers - crop rotation increases habitats and range of food sources, can support more species
51
COURTSHIP BEHAVIOUR what does it insure and how
helps insure sucessful mating by... - recognising memembers of own species - identify mates capable of breeding - synchranise mating - places individual of opposite sex into a physiological state which allows breeding to occour - form a pair bond so that both parents are their to raise the young
52
INVESTIGATING DIVERSITY 5 factors
- comparing frequency of measurable or observable characteristics - comparison of DNA base sequences - comparison of MRNA sequences - comparison of amino acid sequences - use of immunological advances
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INVESTIGATING DIVERSITY comparing frequency of measurable or observable characteristics
- comparing how many have a particular trait - however many characteristics are polygenic and hard to distinguish one varient from another - solution is modern dna technology and dna sequencing
54
INVESTIGATING DIVERSITY comparison of dba base sequences
compare dna - mutation occours over time so the similar the dna the closer related the species is
55
INVESTIGATING DIVERSITY comparison of Mrna species
- Mrna is drvived from the dna base sequence during transcription - so more similar Mrna the closer related
56
INVESTIGATING DIVERSITY comaprison of amino acid sequence
- determined by dna of organisms
57
INVESTIGATING DIVERSITY use of immunological advances to clarify evolutionary relationships
- idea behind this method is that antibodies of one species will respond to antigens found on another species - the greater the number of similar antigens the more precipitate is formed and more closely species are related process : - species A blood into B - produces antibodies for all antigen sites from species A - extracted from B into C - antibodies respond to corresponding antigens in C - the more precipitate is found the similar the antigens = closely related
58
CAUSES OF VARIATION - genetic factors
- different alleles ( discreet data ) - polygenic = continious data - sexual reproduction = offspring inherit different characteristics - asexual = no genetic variation
59
CAUSES OF VARIATION - environmental factors
- nutrition, temp, sunlight, physical forces
60
two types of variation
inter specific = between species intra specific = between members of same species
61
RANDOM SAMPLING
- taking meausurements of individuals selected from a population of organisms which is being investigated - important that it is representative by avoiding sampling bias, reduce limitations of chance
62
RANDOM SAMPLING removing bias
- use a grid with numbered lines - use random numbers to obtain coordinates - cannot remove chnage but minimise effects by: - use large enough sample sizes to reduce probability that chance will influence result - use statistical analysis
63
RANDOM SAMPLING purpous of repeat methods
- more representative - reduces chance - data more reliable - can cauc mean - larger the standard deviation the less reliable e
64
standard deviation and normal distribution curve tells us
idea about the range

Biology A Level (5 decks)

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