topic three Flashcards
(162 cards)
1
Q
what is the genome
A
all the genetic info in the body
2
Q
what is a gene
A
a short stretch of dna that influences a specific characteristic
3
Q
locus
A
the specific position of a gene on a chromosome.
4
Q
alleles
A
the various, specific forms of a gene that usually vary from each other by one or a few bases.
5
Q
gene
A
a heritable factor that consists of a length of DNA and influences a specific characteristic.
6
Q
having a pair of each kind of chromosome is called
A
the diploid state
7
Q
having one copy of each chromosome is
A
the haploid state
8
Q
homozygous
A
two copies of the same allele
9
Q
heterozygous
A
two copies of different alleles
10
Q
gneotype is
A
homozygous for red eg
11
Q
phenotype is
A
erd petals
12
Q
What is always different between the alleles of a gene?
A
Their base sequence.
13
Q
A particular gene has three alleles across the human population. At maximum, how many different alleles can you, an individual human, have for that gene?
A
2
14
Q
no genes in e.coli (bacteria)
A
4 000
15
Q
no genes in humasn
A
20000
16
Q
no genesin rice
A
35,000
17
Q
what is the sense strand
A
the dna strand that is not transcribed
has the same sequence of bases as the mRNA molecule except for thymine being replaced by uracil.
18
Q
what is the antisense strand
A
the antisense strand and is complementary to the mRNA molecule.
19
Q
how does sickle cell anaemia come about
A
When the HBB locus is transcribed, the mRNA from Hb A has G A G for the 6th codon, which translates to the amino acid called glutamic acid . The mRNA copied from Hb S has the codon G U G, which codes for the amino acid valine
20
Q
You should be able to recall that one specific base substitution causes glutamic acid to be substituted by valine as the WHAT NUMBER amino acid in the beta hemoglobin polypeptide.
A
sixth
21
Q
precise base sub mutation
A
(from GAG→ GTG in sense DNA), the change to the base sequence of mRNA transcribed (from GAG→ GUG), and the corresponding change to the sequence of a polypeptide in hemoglobin (from glutamic acid to valine in the sixth position).
22
Q
what forms hemogolobin
A
2 beta subunits
2 alpha subunits
23
Q
how does hemoglobin behae differently under low o2 levels
A
Under normal conditions, hemoglobin formed using either Hb A or Hb S is equally good at carrying and transporting oxygen. However, in specific situations like low oxygen levels in cells, they behave differently. The glutamic acid in Hb A interacts well with water, keeping hemoglobin molecules dissolved within red blood cells. In contrast, the valine in Hb S is hydrophobic, causing the beta subunits to come together and form long fibers. This leads to two problems: the ability to carry oxygen is significantly reduced, and the long fibers distort the cell membrane, resulting in the characteristic “sickle” shape of red blood cells.
24
Q
problems of sickle cell
A
They can get stuck and clog blood vessels anywhere in the body, causing intense pain as blood supply fails. If this happens in the brain, the person could have a stroke. Sickled cells must be broken down and eliminated from the body, which strains the liver and causes a shortage of functioning red blood cells (anemia). New red blood cells must be made in the bone marrow to replace the cells lost, and the extra work can damage bone structure.
25
Sickle cell anemia occurs when a person is homozygous for what
Hb S
all of their hemoglobin contains the alternate beta subunit.
26
When a person’s alleles are Hb A Hb A , their hemoglobin will never
polymerise and their erythrocytes will never sickle.
27
waht happens with HbA and HbS
cells will only sickle when infected by plasmodium falciparum
28
why is it advantageous to have one HbS allele
Because the body eliminates sickled red blood cells, the malarial infection is eliminated along with them.
29
waht does hemoglobin do with logn fibres
Hemoglobin proteins polymerise into long fibres. There are hundreds of millions of hemoglobin molecules in each red blood cell. `
30
what is the ident column in genome databases
gives the percentage of identical nucleotides.
31
why is prokaryotic dna called naked dna
not organised around associated histone proteins
32
shape of prokaryotic dna
circualr dna double heliz molecule
33
plasmids can be easily what between bacteria
exchanged, providing a mechanism by which antibiotic resistance spreads
34
what do homologous chromosomes do
carry the same set of genes in the same locations
35
what are autosomes
not sex hormones
36
Which of the following statements about homologous chromosomes is correct?
A particular gene will be found at the same locus on homologous chromosomes.
, Correct answer
Your answer
They are two identical copies of a parent chromosome which are attached to one another at the centromere.
They are chromosomes that have identical genes and alleles.
They always produce identical phenotypes.
A particular gene will be found at the same locus on homologous chromosomes.
37
genome sizes in order
e. coli
drosophilia melanogaster
homo sapiens
paris japonica
38
what chromosomes does an egg cell have
22 autosomes and one copy of the x chromosome
39
wat chromosomes does a sperm have
22 autosomes and one X or Y
40
whcih chromosomes are which gender
XX female
XY male
41
each chromosome in a homologus pair is referred to as a
homologue
42
what is a tetrad
two homologues
43
what is the best mitotic phase for viewing
metaphase
44
how are homologus chromosomes aligned in karyotyping
by length, location of the centromere and by bands of colour differences (striations) induced using dyes.
45
non disjunction
failure of a pair of homologous chromosomes or sister chromatids to seperate
46
trisomy 21
down syndrome
47
Two important uses of karyograms are:
To deduce the sex of an individual.
To diagnose for chromosomal abnormalities such as Down syndrome in humans
48
what is autoradiography
a technique that uses X-ray film to visualise the two-dimensional distribution of a radioactively labelled substance. The image formed through autoradiography is called an autoradiograph.
49
how did cairns first produce images of DNA molecules using autoradioagraphy
He produced thymidine (the nucleotide containing thymine) labelled with radioactive hydrogen ( 3 H).
Next, he grew E. coli bacteria in a medium containing the radioactive thymidine. When the E. coli cells replicated their DNA, they used the radioactive thymine, creating radioactive DNA.
He then lysed the cells (ruptured their cell walls and membranes) to release the cell contents, including the intact bacterial DNA, onto slides.
Next, he covered the slides with photographic emulsion and stored them in the dark for two months.
During that period, high energy electrons emitted by the radioactive decay of 3 H within the DNA caused the appearance of dark spots on the photographic emulsion.
The pattern of dark spots indicated the presence of labelled DNA (as shown in Figure 1 ).
The length of the E. coli chromosome could then be measured and was worked out to be about 1 mm, nearly 1 000× longer than the typical E. coli cell.
50
What creates the dark spots seen on the photographic emulsion in an autoradiograph?
High energy electrons released from the DNA itself
51
Cairns used autoradiography as a technique to measure the length of:
DNA molecules
52
what is meiosis
a form of nuclear division that produces four haploid nuclei from one diploid nucleus.
53
prophase I
Chromosomes become visible due to supercoiling. The replicated chromosomes form closely-linked homologous pairs (called tetrads or bivalents), which have two chromosomes and four total chromatids.
At this stage, non-sister chromatids may cross over at points called chiasmata and exchange equivalent segments of DNA.
Centrioles, if present, migrate to opposite poles and spindle fibres start to form. The nucleolus and nuclear membrane disintegrate.
54
metaphase I
Homologous pairs move together along the metaphase plate, which lies halfway between the two poles. Maternal and paternal homologues show random orientation towards the poles.
The spindle fibres attach to the centromeres of each chromosome and gently pull to align them along the equatorial metaphase plate.
Spindle fibres connect each centromere to one pole only.
55
anaphase I
Spindle microtubules shorten, pulling homologous chromosomes apart towards opposite poles. Unlike mitosis, sister chromatids remain connected at the centromere and move to the same pole.
56
telophase I
The first meiotic division effectively ends when the chromosomes arrive at the poles. Note that each chromosome still consists of a pair of chromatids.
The chromatids partially uncoil and a nuclear membrane then reforms around each nucleus formed.
Although technically not part of meiosis, cytokinesis usually occurs during telophase I. Cytokinesis results in two daughter cells with haploid nuclei from meiosis.
57
prophase II
Chromosomes condense again. Centrioles, if present, migrate to opposite poles and spindle fibres start to form. The nucleolus and nuclear membrane disintegrate.
58
metaphase II
The spindle fibres attach to the centromere and connect each centromere to both poles. They exert a gentle pull to align the sister chromatids at the equator.
59
anaphase II
Centromeres divide and chromatids are moved to opposite poles by spindle fibres.
Once sister chromatids are separated, they are called chromosomes.
60
telophase II
Chromosomes reach opposite poles and uncoil. This is followed by nuclear envelope formation and cytokinesis.
Meiosis is now complete, resulting in four haploid daughter cells. Note that each of the four cells are genetically distinct.
61
meiosis I
Reduction division – Cells begin with two copies of each chromosome and end with only one;
Diploid (2n) → Haploid (n)
62
meiosis II
Separation of chromatids in haploid cells (n → n)
63
Meiosis results in the formation of haploid gametes. this means the number of chromosomes
halves
64
when does crossing over occur
prophase I
65
how do chromosomes condense
by supercoiling
66
what is a chromatid
a long, single strand of double-helical DNA organised by histone proteins.
67
sister chromatids
identical and joined at the centromere
68
what is chiasmata
the points at which crossing over occurs
69
what does crossing over do
new combinations of alleles that were not present in either original chromosome
70
after crossin gover,
the tetrads complete the process of condensation and move toward the equatorial plate.
71
what does prophase I involve
Pairing of homologous chromosomes
Crossing over followed by condensation of DNA into highly organised chromosomes.
72
The two chromatids that are connected together by the centromere are called
sister chromatids
73
Between which structures does crossing over typically occur?
Between non-sister homologous chromatids
74
A tetrad includes which of the following?
Two pairs of sister chromatids
75
what are bivalents/tetrads
the pairs of homologous chromosomes
76
compare metaphase of mitosis with metaphase I
77
reduction division
Daughter cells contain only half of the chromosomes that were present in the parent cell. In this case a parent cell has four chromosomes; the daughter cell has two. The parent cell is diploid. The daughter cells will be haploid, having only one version of each chromosome.
78
random orientation
When pairs of homologous chromosomes line up at the equator of the cell, the paternal copy, for example, has an equal chance of facing either pole. The orientation of one pair (e.g. maternal facing north) does not impact the orientation of any other pair. Each gamete gets one copy of each chromosome, but a random assortment of the maternally and paternally inherited versions.
79
Two important changes will result from the chromosomes arranging themselves in pairs instead of individually:
reduction division. daughter cells haploid and only have one version of each chromosome
random orientation. maternal and paternal chromosomes could have gone either pole
80
Reduction division occurs during:
Meiosis I
81
what increases genetic variation
sexual reproduction
meiosis: crossing over, random orientation
Fusion of gametes from different parents.
82
how many combinations based off chromosome number
The number of possible combinations is equal to 2 to the power of the number of haploid chromosomes.
For a diploid organism where 2n = 16 (i.e. 8 pairs of chromosomes), the number of combinations would be 2^8 = 256 different combinations.
83
trisomy 13
patau syndrome
84
During the first 10 weeks of a 40-week pregnancy, the developing human is called an
embryo
85
after week 10 the aby is
a fetus
86
Amniocentesis
s the fetus develops in the uterus, it is cushioned by amniotic fluid, as seen in Figure 2. Amniocentesis is usually performed between weeks 14 and 20 of pregnancy. A doctor uses ultrasound imagery to guide a syringe needle through the abdomen and uterine wall without piercing the fetus. The needle is then used to withdraw a small amount of amniotic fluid. Fetal cells floating in the fluid are cultured and karyotyped.
87
Chorionic villus sampling (CVS):
Early in pregnancy there is not enough amniotic fluid to perform amniocentesis safely; however, during weeks 10–13, CVS can be used. As in amniocentesis, ultrasound imaging is used to guide the medical professional during the sampling and avoid harm to the developing embryo or fetus. Fetal cells are sampled by inserting a suctioning tool (often a catheter or syringe) through the vagina or abdomen to reach the fetal cells in the chorion, as seen in Figure 3. The chorion is a membrane that surrounds the fetus and develops into part of the placenta.
88
what is the law of segregation
To segregate means to divide and separate. The inheritance of each characteristic is controlled by a pair of alleles in an individual. The two alleles are separated during meiosis so that each gamete contains only one allele for each gene. Alleles are passed from one generation to the next as distinct units.
89
the law of independent assortment
The allele inherited for one trait does not affect which allele will be inherited for any other trait. A gamete contains one copy of each gene; which copy it receives during meiosis is the result of random orientation of homologous chromosomes during metaphase I.
90
the law of dominance
In an organism with two different alleles, one allele will determine the trait. The allele that determines the trait is dominant; the unexpressed allele is recessive.
91
P/F1/F2
A specific breeding test in which two parents homozygous for different forms of a trait (e.g. purple flowers and white flowers) are mated. Their offspring (F1 generation) are heterozygous for that trait and are mated with each other to produce the F2 generation.
92
P
parental generation, homoxygous
93
F1
First filial (offspring) generation – offspring of the parental generation, heterozygous.
94
F2
Second filial generation – offspring of a cross of the F1 generation.
95
phenotype
An organism's observable characteristics or traits, including its morphology and biochemical properties.
Example: pea colour or hemoglobin structure.
96
Genotype
The two alleles present in an organism for a particular gene
97
co dominant alleles
Alleles that jointly affect the phenotype when present together, creating an intermediate or combined phenotype.
The alleles CR and CW that will produce red petals when the genotype is CRCR and white when CWCW, but pink petals when CRCW
98
A gene has three possible alleles. How many different genotypes can be found for this gene?
6 because alleles
99
What is true of the law of segregation?
It refers to the fact that a parent has a pair of alleles for each gene, and will pass on only one to an offspring.
100
what determines whether a blood group is positive or negative
determined by the RHD gene and indicates whether a particular Rh factor protein is present
101
A blood group
|A|A or |Ai
102
B blood group
|B|B or |Bi
103
AB blood group
|A|B
104
O blood group
ii
105
which blood groups are co dominant with eachother
alleles IA and IB are co-dominant with respect to each other. They are both dominant with respect to allele i – the latter being recessive to both IA and IB.
106
how many alleles in the ABO blood group ene
3
107
what does the i in the alleles stand for
isoagglutinogen
108
All three alleles produce the same base molecule, but IA and IB make different additions to the molecule. These modified molecules are called
antigens becaue they can generate an immune response in an individual to whom they are foreign
109
which blood group does not produce an antigen
i
110
whcih alleles are recessive and which are codminant in bood groups
the i allele is recessive and why IA and IB are co-dominant.
111
why is O bood the universal donor
he product of the ‘i’ allele does not trigger an immune response
112
Which of the following blood group phenotypes always has a homozygous genotype?
O
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what is OMIM
Online Mendelian Inheritance in Man
114
what does recessive refer to
the interaction of an allele in a diploid state
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Some diseases are autosomal co-dominant, such as
sickle cell anemia
116
autosomal recessive disease such as
cystic fibrosis
117
what are sex linked diseases
a disease causing gene on the sex chromosome. can be x linked or y linked
118
most genes are on the x rather than y chroomsoome
Since males have one X and one Y chromosome, they have only one copy of each of these genes. Females, with two copies of the X chromosome, have two copies of these genes (and no copies of genes on the Y chromosome).
119
pattern of y linked genes
he gene is passed from the father only, to all sons and no daughters.
120
pattern of x linked genes
Females can be unaffected carriers of recessive alleles on the X chromosome, but since males have only one copy of the gene, they cannot be carriers.
121
examples of x linked diseases
red green colour blindness and hemophilia
122
cycstic fibrosis cause
The recessive allele was formed by a mutation in the CFTR gene, which codes for a chloride channel in mucous membranes.
123
huntingtons disease
a neurodegenerative disorder that usually starts to affect people between 30 and 50 years of age. It is caused by a dominant allele that has developed through the mutation of the HTT gene found on chromosome 4.
124
what is huntingtons caused by
caused by a dominant mutation of a gene on an autosome, so the occurrence of only one copy of the mutated allele is enough to cause the disease.
125
The recessive allele for red-green colour blindness codes for
a non-functional copy of one type of photoreceptor protein in the retina of the eye
126
what is hemophilia
a disease in which a protein needed for blood clotting, most commonly factor VIII, is not made. The gene for clotting factor VIII is on the X-chromosome and the allele that causes hemophilia is recessive. For hemophilia, the normal allele has the notation XH and the allele for hemophilia has the notation the Xh.
127
pedigree chart conventions
Females are represented by circles.
Males are represented by squares.
When a circle or a square is cross-hatched or shaded, it means that an individual is affected by the disease/disorder that is being studied.
Parents and children are connected by a 'T' shape.
Sometimes a circle or square is half shaded or a dot is placed inside to show that an individual is a carrier (in the case of recessive alleles); however, charts often show only the phenotypes of the individuals.
Individuals of the same generation are shown in the same row where possible.
Roman numerals identify generations, and Arabic numerals are used to identify individuals within each generation, e.g. III-1 is the first (born) person of the third generation. Usually, the individuals are numbered left to right.
128
what is radiation
when energy, in the form of waves (e.g. radio waves) or particles (e.g. electrons), is emitted.
129
Which is NOT known to damage DNA?
Mutagenic chemicals like nitrites
Non-ionising radiation like microwaves
UV (ultraviolet) rays
Gamma radiation
Non-ionising radiation like microwaves
130
why is predicted not actual outcome in ounnet squares
However, if you were to actually carry out these crosses, the predicted outcome would almost never be an exact match for your actual data. The main reason is that reproduction involves events that occur randomly, though with a known probability. For example, the specific assortment of alleles formed in meiosis and the particular gametes that fuse to form a zygote are events with random components.
131
gel electrophoresis is a technique used to
separate proteins or fragments of DNA according to size.
132
in order to get fragments of an appropriate size for gel electrophoresis what happens
dna is diested with special enzymes called restriction endonucleases
133
waht do restriction endonucleases do in gel electrophoresis
These enzymes cut the backbone of the DNA double helix at highly specific sequences, producing shorter DNA segments and distinctive fragment patterns
134
what is the next step in gel electrophoresis following restriction endonucleases
Samples with fragments of DNA are loaded into small depressions, called wells, on one end of the gel (a jelly-like polymer). The gel is submerged in a buffer solution, and an electric current is run through the gel. The DNA samples must begin near the negative pole, so that they can spread out as they are drawn toward the positive pole.
135
waht does teh consistency of the gel allow for in gel elec
separation of the DNA fragments by size
136
what is the gel in gel elec made from
often the polysaccharide agarose
137
what must dna do in gel elec
travel through the spaces betwen the polymers. Smaller pieces can slip through the spaces more easily, allowing them to travel further along the gel in a given amount of time. By using higher concentrations of polymer, the average size of the pore can be reduced, and smaller pieces of DNA can be separated.
138
summarise/state the steps of gel elec
Samples are placed in a block of gel and an electric current is applied which causes the samples to move through the gel
Smaller samples are less impeded by the gel matrix and hence will move faster through the gel
This causes samples of different sizes to separate as they travel at different speeds
139
how is dna seperation conducted
DNA may be cut into fragments using restriction endonuclease – different DNA samples will generate different fragment lengths
Fragments separate because DNA is negatively charged due to the presence of a phosphate group (PO43–) on each nucleotide
DNA samples are placed into an agarose gel and fragment size calculated by comparing against known industry standards
Specific sequences can be identified by incorporating a complementary radiolabelled hybridisation probe, transferring the separated sequences to a membrane and then visualising via autoradiography (Southern blotting)
140
how is protein seperation conducted
Proteins may be folded into a variety of shapes (affecting size) and have positive and negative regions (no clear charge)
Proteins must first be treated with an anionic detergent (SDS) in order to linearise and impart a uniform negative charge
Protein samples are placed into a polyacrylamide gel and sizes compared against known industry standards
Separated proteins are transferred to a membrane and then target proteins are identified by staining with specific monoclonal antibodies (Western blotting)
141
DNA and proteins can be separated through gel electrophoresis due to the fact that:
they are both charged molecules
142
PCR
143
are the hydrogen bonds between dna strands broken in pcr
yes
144
To find a match between DNA evidence and an individual (suspect or victim), every band in the gel must be
an identical match.
145
To determine paternity,
start by matching the DNA fragments from the child with the mother’s profile. For the child, every band that does not match the mother must have a match in the father’s profile.
146
steps of gene transfer
Isolate the desired gene from the original species using restriction endonucleases.
Isolate an appropriate plasmid (a small loop of DNA containing a few genes that is often traded between bacteria).
Cut the plasmid with the same restriction endonuclease that was used to remove the desired gene. This will open the loop of the plasmid, forming a string with two ends.
Mix many copies of the target gene and cut plasmid together to allow their complementary unpaired sequences to join together, thus adding the gene into the plasmid.
Use the enzyme DNA ligase to covalently bond the DNA backbones of the gene and plasmid together, permanently sealing the gene into the plasmid loop.
Transfer the plasmid with the target DNA (called a recombinant plasmid) back into the bacterium.
Grow colonies of the genetically modified bacteria that now produce a eukaryotic protein.
147
Why are plasmids useful in genetic modification of bacteria
They are easily transferred between bacterial cells and are small enough to manipulate easily.
148
What is used to seal a target gene into a bacterial plasmid?
DNA ligase
149
For any GMO you can do a risk/benefit analysis. Questions that are used to assess risk include:
How likely is a harmful or beneficial consequence?
If the consequence occurs, how much harm or benefit will it cause?
150
benefits of gmo crops
introduction of new positive traits to the crop
econ advantages
environmental advantages
151
risks of gmo crops
ecosystem damage
increasing monoculture
corporate control over food supply
human health concerns
152
advantages of naturla cloning
The individuals do not need to find a mate, and they pass all their genetic information to each offspring. If an individual is well adapted and in a stable environment, its cloned offspring will have all the advantages of its parent.
153
Scientists have also developed the means of deliberately cloning animals in two different ways:
Splitting or fragmentation of an embryo to clone an animal before the cells have differentiated.
Using differentiated cells and somatic cell nuclear transfer to clone adult animals.
154
cloning by fragmentation of an embryo
155
clonigng via somatic cell nuclear transfer
Donor somatic (body) cells are taken from the organism that will be cloned and cultured in the lab.
Somatic cells with the least DNA inactivation should be chosen. In this case, cells were taken from the udder of the donor sheep.
The cell is starved so that the amount of cellular material other than the nucleus is reduced.
An unfertilised egg is taken from another individual.
The unfertilised egg is enucleated (the nucleus is removed).
In this case, the nucleus was removed using a tiny pipette.
The enucleated egg is fused with a donor cell.
In this case, the cells were placed next to each other and an electrical current was used to disrupt the cell membranes enough so that they would fuse together.
The fused cell is allowed to divide until a small embryo has formed.
The embryo is transplanted into the uterus of a surrogate mother.
The pregnancy and birth of the offspring proceed normally.
156
What happens to the unfertilised egg used in somatic-cell nuclear transfer?
Its nucleus is replaced by the nucleus of the differentiated body cell.
157
GM maize has been modified so that it produces a protein called
Bt toxin from Bacillus thuringiensis bacteria.
158
what does bt toxin allow
farmers to apply less pesticide because the Bt toxin within the maize is already eliminating the corn borers.
159
bt toxin is in pollen so there were concenrs
that it woluld blow over to milkweed, primary food source for monarch butterfly larvae
160
Some internal plant factors affecting rooting include:
Position of the cutting on the plant
Age of the starting plant
Nutritional status of the stem cutting
Number or surface area of leaves on the stem cutting
161
Some external factors affecting rooting include:
Length and intensity of light exposure
Temperature at which the cutting is allowed to root
Type and concentration of rooting hormones used
Type and concentration of nutritional supplements used
Type of growth medium (water, agar, soil, etc.)
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