small, extra loops of DNA in some prokaryotes
1 of 134
Properties of eukaryotic chromosomes (4)
1) contains linear DNA molecule 2) associated with histone proteins 3) no plasmids 4) two or more chromosomes
2 of 134
Properties of prokaryotic chromosomes (4)
1) circular DNA molecule 2) naked (no associated proteins) 3)plasmid often present 4) one chromosome
3 of 134
Used since 1940's-technique to find radioactive substances in cells
4 of 134
Steps of autoradiography
Sections of cell coated in photographic film (left in dark for days/weeks) When view w/ microscope, structure of cell & black dots visible on photographic film. Black dot: radioactive atom
5 of 134
John Carins
adapted autoradiography by looking at chromosomes of E.Coli. Discovered DNA molecules were cirular &1,100μm long
6 of 134
Describe how John Carins adapted autoradiography
.Grew e.Coli in radioactive medium tymine (so DNA was labelled but not RNA). Placed on membrane &digested cell walls-DNA spilt.Coate mem. in photographic film& left in dark for 2 months>Lines of black dots showed DNA
7 of 134
The size of a genome
the total amount of DNA in one set of chromosomes in a species
8 of 134
Genome size of T2 phage (millions of bp)
9 of 134
Genome size of Escherichia coli (millions of bp)
10 of 134
Genome size of D.melanogaster (millions of bp)
11 of 134
Genome size of Homo sapiens (millions of bp)
12 of 134
Genome size of Paris japonica (millions of bp)
150, 000
13 of 134
homologous chromosomes
chromosomes which have the same genes in the same place but may not have the same alleles in those genes
14 of 134
Number of chromosomes in Homo sapiens (humans
15 of 134
Number of chromosomes in Pan troglodytes (chimpanzee)
16 of 134
Number of chromosomes in Canis familiaris (dog)
17 of 134
Number of chromosomes in Oryza sativa (rice)
18 of 134
Number of chromosomes in Parascaris equorum (horse threadworm)
19 of 134
Diploid nuclei
nuclei contains pairs of homologous chromosomes (46 chromosomes-2n)
20 of 134
Haploid nuclei
nuclei with only one chromosome of each type (23 chromosomes- n)
21 of 134
Examples of human haploid cells
Sperm and egg cell gametes
22 of 134
What happens to two haploid gametes during fertilisation?
gametes fuse together to produce one diploid cell (zygote)
23 of 134
Two types of sex chromosome
Larger X & smaller Y (23rd pair)
24 of 134
number & type of chromosomes present in cell or organism
25 of 134
photograph/diagram showing an organisms chromosomes in homolous pairs of decreasing lengths
26 of 134
Common uses for karyograms of humans
.Deducing sex of individual, .Diagnosing conditions due to chromosome abnormalities (i.e down syndrome or Klinefelter syndrome)
27 of 134
male & female gamete fuse to produce zygote
28 of 134
How many chromosomes do zygotes have?
Twice as many as as the gametes (46)
29 of 134
process that halves chromosome nom & allows sexual life cycle w/ gamete fusion
30 of 134
What happens to DNA before/during meiosis?
DNA of chromosomes replicated BEFORE division (each chromosome:2 sister chromatids) BUT DNA is not replicated between 1rst &2nd division of meiosis
31 of 134
Prophase 1 (4)
Chromosomes pair up, spindle microtubles grow from each pole to the equator, nuclear membrane dissolves, crossing over occurs
32 of 134
Metaphase 1 (2)
Pairs of chromosomes line across equator, Spindle microtubles attach to different chromosomes to ensure one is pulled one way & other pulled other way
33 of 134
Anaphase 1 (2)
Each chromosomes still consist of 2 chromatids, Homologous chromosomes pulled to opposite poles: halves chromosome nom
34 of 134
Prophase 2 (2)
immediately divide again, chromosomes pair up, new spindle microtubes grow from the equator, chromos
35 of 134
Anaphase 2
centromeres divided making chromatids into separate chromosomes which move to opposite poles
36 of 134
Telophase 2 (3)
Nuclear membranes reforms, cell membrane pulls inwards to divide. Each nucleus has half as many chromosomes as the parent cell nucleus, Both cells divided into 4 haploid cells
37 of 134
What are the two processes in meiosis which promote genetic variation?
1)Random orientation of pairs of homologous chromosomes in metaphase 1, Crossing over during prophase 1
38 of 134
Nom of possible combinations of chromosomes produced by random orientation
2^n in humans, n:23> over 8 million combinations per parent
39 of 134
crossing over
early stage of meiosis- homologous chromosomes pair up & parts of non-sister chromatids can be exchanged between them>produces chromatids w/ new allele combination
40 of 134
When chromosomes which are meant to separate & move to opposite poles in meiosis dont & move to the same pole>gametes produced with either one chromosomes too many or too few
41 of 134
a zygote produced with 3 chromosomes of one type instead of 2
42 of 134
What causes Down syndrome/ trisomy 21
when a child is born w/ three chromosomes of type 21 rather than two (non-disjunction during formation of sperm/egg)
43 of 134
What increases the chance of downs syndrome?
the age of parents
44 of 134
Methods for obtaining cells of unborn child for chromosome testing (2)
Amniocentesis & Chlorionic villus sampling (CVS)
45 of 134
Hypodermic needle inserted into abdomen & uterus wall. Sample of amniotic fluid removed>contains cells from the fetus
46 of 134
Chorionic villus sampling (CVS)
Hypodermic needle inserted into abdomen & uterus wall. cels from chorionic villus (fetal tissues in placenta) removed. CVS higher change of miscarriage (2%) than amniocentesis (1%) (due to risk of maternal or fetal infections)
47 of 134
George Mendel
'father of genetics'-crossed varieties of pea plants that had different characteristics & deduced the principles on which inheritance was based
48 of 134
How many seeds did Mendel encounter in the F2 generation?
7,324: 5,474 round & 1,850 wrinkled- from noms created basic ration 3:1
49 of 134
How did Medel discover the 3:1 ratio? (4)
crossed 2 varieties of pea together>F1 generation had the same characteristics as one of the parents. He allowed F1 to self fertilize> F2 generation contained both original parent types in 3:1 ratio
50 of 134
What is Mendels pea's show us?
that each pea plant has two alleles of the gene that affects the character. Parents-homologous (have 2 of the same allele- F1:heterozygous- two different alleles. F1 has same characteristics as 1 parent as that parents allele was dominant
51 of 134
the alleles po**e**ed by an organism (i.e **/**)
52 of 134
the characteristics possessed by an organism (i.e smooth/wrinkled seed)
53 of 134
P in monohybrid cross
parental generation
54 of 134
first fillia generation> offspring of P generation
55 of 134
occurs in meiosis. 2 alleles of gene on homologous chromosome move to opposite poles
56 of 134
What is the cause of large proportions of genetic diseases
recessive alleles of autosomal genes (e.g cystic fibrosis)
57 of 134
What are all chromosomes (apart from sex chromosomes)?
58 of 134
What is the cause of a small proportion of genetic diseases
dominant alleles of autosomal genes (e.g Huntington's disease)
59 of 134
Cystic Fibrosis
caused by a recessive allele of a gene coding for a chloride channel. Commonest genetic disease in parts of western Europe- 1:3,000 babies in US. Likelihood of child having cystic fibrosis from two carriers: 25%
60 of 134
Huntington's disease
neurodegenerative disease cause by dominant allele of gene coding for huntingtin (protein w/ unknown funct.) Develops in adulthood. Likelihood of parent w/ Huntington's passing it onto children:50%
61 of 134
Pedigree charts
indicate whether a disease is caused by dominant or recessive allele & allow the genotypes of some individual to be deduced
62 of 134
the association of a characteristic with the sex of the individual- gene controlling the characteristic is located only on a sex chromosome
63 of 134
How does the size of the genes on the Y and X chromosomes affect sex-linkage?
Few genes on Y chromosome. X chromosome is large & has important genes- This means sex-linkage i almost always due to genes of X chromosome.
64 of 134
Name the four ABO blood groups
A, B, AB and O
65 of 134
Co-dominant alleles
pairs of alleles that both affect the phenotype when present together in a heterozygote. Neither are recessive or dominant
66 of 134
Which blood groups are co-dominant
IA ad IB
67 of 134
multiple alleles
genes with more than two alleles
68 of 134
Example of multiple alleles
The gene for ABO blood groups- has three alleles; IA, IB and i
69 of 134
What is the genotype for blood group A?
IA i> i is recessive
70 of 134
What is the genotype for blood group B?
IB i> i is recessive
71 of 134
What is the genotype for blood group AB?
72 of 134
What is the genotype for blood group O?
73 of 134
Punnet grid
grid for predicting the outcome of monohybrid genetic crosses
74 of 134
Blood group of child with parents of O and AB
there are ii and IAIB geneotypes- could be IAi or IBi, 1:1 Group A to B ratio
75 of 134
random changes to the base sequence of a gene
76 of 134
base substitution
a mutation that replaces one base in a gene with a different base
77 of 134
Name two mutagens
. High radiation (x-rays, short/medium UV waves, gamma rays) .Mutagenic chemicals (nitrosamines in tobacco & mustard gas)
78 of 134
Name the two incidents which can be studied for the effects of radiation
The nuclear accident in Chernobyl & nuclear bombing of Hiroshima
79 of 134
What is the common feature of Chernobyl &Hiroshima?
radioactive isotopes were released into environment & people were exposed to dangerous radiation levels
80 of 134
Buclear accident in Chernobyl
Ukraine, 1986> accident caused explosions& fire in the core of a nuclear reactor.
81 of 134
What was released by the Chernobyl accident (4)
Radioactive iodien-131, caesium-134, caesium-137 & six tonnes of uranium and other radioactive materials
82 of 134
What were the consequences of the Chernobyl accident? (6)
28 workers died after 3 months & leukemia rates increased .Radioactive Iodine concentrations rose- drinking water & milk undrinkable. Iodine absorbed by thyroid-6,000 cases of thyroid cancer. High radioactive caesium levels in fish in Scandinavia,
83 of 134
Nuclear bombing of Hiroshima
1945- atomic bomb detonated & killed 90,00-166,000 (either directly or over the following months). Only few buildings remaining
84 of 134
After the nuclear bombing of Hiroshima, what long-term effect of radiation was found
.Death from cancer (leukemia &others)
85 of 134
study of variation and inheritance
86 of 134
What is the basic unit for iheritance
the gene
87 of 134
What is the current estimated nom of genes in a homo sapien (humans)
23, 000
88 of 134
What is the current estimated nom of genes in a E.coli (gut bacteria)
89 of 134
What is the current estimated nom of genes in a Drosophila melanogaster (fruit fly)
90 of 134
What is the current estimated nom of genes in a Takifugu gambiae (puffer fish)
91 of 134
What is the current estimated nom of genes in a Oryza sativa (rice)
92 of 134
What do the estimated nom of genes illustrate? (3)
.Bacteria have less genes than eukaryotes, .Some animals have less genes than humans but some have more, .plants may seem less complex but some have more genes than humans
93 of 134
different forms of the same gene
94 of 134
Sickle cell anemia
genetic disease in the beta polypeptide gene of hemoglobin (HBB) caused by base subsitiution of A to T. consists of 146 amino acids & common in parts of the world affected by malaria
95 of 134
How does the mutation causing sickle cell anemia occur
Base substitution of HBB from A to T- causes Hb^a to change into new allele Hb^s- Transcrpition- one codon in mRNA is different> one amino acid in polypeptide is altered (now glutamic acid instead of valine)
96 of 134
Advantage and disadvantage to sickle cell anemia
Advantage:Can give malaria resistance, Disadvantage: sickle cells may carry less oxygen
97 of 134
Gene locus
a genes particular position on homologous chromosomes
98 of 134
How can human gene loci be found?
using the OMIM website (Online Mendelian Inheritance in Man
99 of 134
What does the number of differences between gene base sequences of two species with a common ancestor indicate
how long ago the two species diverged from the common ancestral species
100 of 134
What does the GenBank database show?
it compares the base sequence of genes & find out how many differences there are
101 of 134
What does Polymerase chain reaction (PCR) consist of?
a cycle of stages repeatedly carried out to produce
102 of 134
What is Gel Eletrophoresis?
a method of separating mixtures of proteins or fragments of DNA, which are charged
103 of 134
Describe how Gel Eletrophoresis is carried out
Mixture of proteins/DNA fragments placed on thin gel sheet (which acts as a molecular sieve). Electric field applied to the gel bby attaching electrodes to both ends. Depending on if particles are pos or neg, they move towards one of the electrodes>
104 of 134
The Human Genome Project
Began in 1990- focused on sequencing the entire human genome> meant to take 15 yrs but tech improvements meant it finished in 2000
105 of 134
Short tandem repeats (STR)
long stretches of DNA made up of repeating bases
106 of 134
How are STR alleles used in DNA profilling? (3)
.Sample of DNA obtained (must not be contaminated by other DNA), .STR loci copied by PRC (usually from loci 11-13). Separated by gel eletrophoresis> result is pattern of bands. Two pep unlikely to have the same pattern of bands unless identical twins
107 of 134
When was DNA profiling first used in a forensic investigation & what did it show?
the Enderby double murde case. Showed that the prime suspect was not guilty despite confessing to the murders
108 of 134
How can DNA profiling be used in Paternity investigations
Children inherit half their chromosomes from each parent> all fragments produced in child should also be produced by either the mum or dad
109 of 134
Genetic modification
thhe transfer of genes from one species to another
110 of 134
Genetically modified organisms (GMO)/ transgenic organisms
Organisms that have had genes transferred into them
111 of 134
What is a vector in gene transfer?
small loop of DNA (plasmid) which are used to transfer genes between species
112 of 134
Which two enzymes are used to insert genes into plasmids in gene transfer?
Restriction endonucleases & DNA ligase
113 of 134
What does Restriction endonucleases do in gene transfer?
cuts DNA molecules at specific base sequences
114 of 134
What does DNA ligase do in gene transfer?
makes sugar-phosphate bonds link to nucleotides together & form continuous strands of nucleotides
115 of 134
What is a recombinant plasmid?
A plasmid with a gene from another species inserted
116 of 134
Outline the transfer of the human insulin gene into bacteria (Steps 1-5)
1)human pancreas mRNA coding insulin extracted, 2)DNA copies of mRNA made using enzyme reverse transcriptase, 3)Extra G nucleotides added to gene ends-makes sticky, 4)E.Coli Plasmid cut open 5)Extra C nucleotides added to plasmid ends-makes sticky
117 of 134
Outline the transfer of the human insulin gene into bacteria (Steps 6-
6)Insulin gene &plasmid mixed (linked by complementary base pairing) 7)DNA ligase seals up nicks in DNA 8)Plasmids mixed w/ host cells (e.coli) which absorbs them 9)Gm e.coli cultured in a fermenter 10)E.coli makes human insulin> extracted & purified
118 of 134
What is Bt toxin
a bacterial protein which kills insect pest which feed on crops (corn borers). This protein is code from the bacteria Bacillus Thruingiensis
119 of 134
Potential benefits of Bt maize (3)
1.Higher crop yields: more food due to less pest damage, 2.Less land needed for crop production- some areas could become wildlife conservation areas, 3.Less insecticide used- expensive &harmful to workers & wildlife.
120 of 134
What qualities are being produced in some gm crops (6)
herbicide resistance, increased vitamin content, decreased allergen/toxin content, resistance to virus diseases, increased tolerance to drought, cold or saline soils & increased shelf life
121 of 134
Possible harmful effect of Bt maize
Nonpest insects killed- Maize pollen blown onto wild plants eaten by insects (monarch butterfly) 2> Transferred gene may spread to wild plant populations by cross-pollination> makes them toxic to insects .Corn pests may devlop Bt toxin resistance
122 of 134
a genetically identical organism derived from a single original parent
123 of 134
the production of an organism that is genetically identical to another organism
124 of 134
Somatic-cell nucleus transfer
Method of cloning animals with know characteristics- nucleus from egg cell is removed & replaced by a nucleus of a differentiated somatic (body) cell.
125 of 134
What is the simplest way to clone an animal
break up an embryo into more than one group of cells (at early stage when it consists entirely of embryonic stem cells)
126 of 134
Outline the cloning of adult animals using differentiated cells, using dolly the sheep as example (5)
1.Donor udder cell taken &cultured in lab for 6 days, 2.Unfertilised egg taken from another sheep- nucleus removed. 3.Egg fused w/ donor cell using electricity pulse, 4.Embryo transferred into 3rd sheep (surrogate)-gives birth>identical to 1rst sheep
127 of 134
What are stem cuttings?
short lengths of stem that are used to clone plants artifically
128 of 134
Conditions needed for stem cuttings (3)
Compost must be well-aerated & moisture retentive, .Cutting cut just below a node, . Clear plastic bag around cutting increases humidity & decrease transcription
129 of 134
What could be the independent variables of stem cuttings (4)
How many leaves left on the cutting, whether hormone protein powder was used, how warm cutting is kept & whether plastic bag is over the cutting
130 of 134
What could be the dependent variable of stem cuttings
Whether any roots formed or not
131 of 134
Metaphase 2
Chromosomes line up across the equator, new spindle microtubles attach to chromosomes vie centromere
132 of 134
What are the stages of meosis? (8)
Prophase 1, Metaphase 1, Anaphase 1, Telophase 1+cytokinesis Prophase 2, Metaphase 2, Anaphase 2, Telophase 2+cytokinesis
133 of 134
What are the causes of genetic variation? (3)
Mutation, sexual reproduction, meosis
134 of 134

Other cards in this set

Card 2


Properties of eukaryotic chromosomes (4)


1) contains linear DNA molecule 2) associated with histone proteins 3) no plasmids 4) two or more chromosomes

Card 3


Properties of prokaryotic chromosomes (4)


Preview of the front of card 3

Card 4




Preview of the front of card 4

Card 5


Steps of autoradiography


Preview of the front of card 5
View more cards


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes and structure resources »