Skills & Applications Ch 3 Flashcards
1
Q
Findings & benefits of Human Genome Project
A
- humans share most of their DNA sequences
- number, location, size, & sequence of human genes was established
- medicine –> discovery of new proteins
- improved treatments
- ancestry –> origins, evolution, migratory patterns
- cooperation + collaboration
2
Q
Causes & consequences of sickle cell anemia
A
- single nucleotide (base substitution) mutation
- GAG –> GTG
- mutation of the 6th gene of haemoglobin
- mRNA copies the mutation of DNA
- glutamic acid is substituted by valine
- distorted haemoglobin protein (HbS)
- sickling + blocks capillaries
- can give resistance to malaria
3
Q
Genome size of:
- T2 phage = ?
- E coli - ?
- D melanogaster = ?
- Homo sapiens = ?
- Paris japonica = ?
A
- T2 phage = 0.18
- E coli - 5
- D melanogaster = 140
- Homo sapiens = 3,000
- Paris japonica = 150, 000
4
Q
Chromosome numbers
- Homo sapiens =
- chimpanzee =
- dog =
- rice =
- horse threadworm =
A
- Homo sapiens = 46
- chimpanzee = 48
- dog = 78
- rice = 24
- horse threadworm = 4
5
Q
Cairn’s Technique of Autoradiography
A
- measured lengths of DNA molecules
- grew E coli in medium containing radioactively labelled thymine, so DNA ONLY was labelled not RNA
- he placed cells on membrane & digested their walls –> DNA spilled out over the membrane
- coated membrane with photographic film & left it in the dark for 2 months
- lines of black dots appeared showing the position of DNA molecules
- DNA molecules were circular & 1,100 micrometers long
6
Q
Explain how non-disjunction (Down syndrome) is caused
A
- non-separation of chromosomes can occur in anaphase I or II
- gametes with an abnormal number of chromosomes are produced
- at anaphase I –> 4 affected cells
- at anaphase II –> 2 affected cells
- can lead to zygotes/individuals with an extra chromosome / individual has 47 chromosomes;
- in Down syndrome this would be trisomy 21/extra chromosome 21;
- increased probability with increased age of mother/ages of parents;
CENTROMETES NOT DIVIDING / INCORRECT SPINDLE ATTACHMENT
7
Q
Describe 2 examples of codominance.
A
- Inheritance of ABO blood groups (involves more than 2 alleles being expressed together, e.g. AB)
- inheritance of sickle-cell anemia (heterozygous individuals have milder symptoms due to the MODERATING INFLUENCE of normal allele (HbA HbS)
8
Q
Identify two examples of X-linked recessive diseases.
A
- Red-green colour blindness –> caused by recessive allele of gene for one of the photoreceptor proteins
- Hemophilia –> inability to control blood clotting leads to bleeding
- inability to make Factor VII (protein)
9
Q
Provide an example of an autosomal recessive disease.
A
Cystic Fibrosis
- autosomal recessive allele on CFTR gene, chromosome 7
- produces sticky mucus, clogs airways
- clogs secretory ducts of the digestive system
- respiratory failure
- pancreatic cysts
10
Q
Provide an example of an autosomal dominant disorder.
A
Huntington’s disease
- mutation to the HTT gene, chromosome 4
- degenerative changes in the brain’s nerve cells
- changes to behaviour, cognition
- heart failure, pneuomonia, symptoms emerge b/w 40-50 years of age
11
Q
GMO Benefits
A
- pest-resistance, less insecticides needed
- longer shelf-life
- less fuel for farming (reducing ploughing/spraying)
- increased nutritional value
- resistance to drought, cold, salinity, disease
- lack known allergens
- improved food supply in poor countries
- less need for land clearing –> reduced costs + carbon footprint
12
Q
GMO Risks
A
- non-target organisms affected
- reduced biodiversity
- antibiotic resistance genes –> bacteria
- adverse health reactions
- cross pollination –> super weeds
- conflicting regulatory standards
13
Q
DNA profiling
A
- DNA of person from a selection of short tandem repeat loci is copied by PCR
- DNA cut using restriction enzymes
- gel electrophoresis used to separate DNA fragments
- pattern of bands is produced in gel
- analysed for matches b/w child with mother & possible father
- about half of child’s bands will match father, half will match mother
- paternity + forensic investigations
14
Q
Describe amniocentesis.
A
- sample of amniotic fluid removed from amniotic sac around fetus
- hypodermic needle inserted into wall of mother’s abdomen + uterus
- amniotic fluid drawn into syringe
15
Q
Describe chorionic villus sampling.
A
- Cells removed from fetal tissues in placenta called chorionic villi
- higher risk of miscarriage
- both have risk of infections
16
Q
Explain the use of karyotyping in human genetics.
A
- karyotype is number + type of chromosomes in cell
- karyogram is photograph of chromosomes in cell arranged in homologous pairs
- cells collected from chorionic villus OR by amniocentesis
- requires cells in METAPHASE
- chromosomes are burst + spread & a photo is taken
- the chromosomes are organised according to size/structure/banding pattern
- karyotypes are used to identify sex, abnormal chromosome numbers
- down syndrome is due to the extra chromosome 21
- may lead to a decision to abort the fetus
17
Q
Describe somatic cell nuclear transfer
A
- a cell is taken from the udder of a donor sheep
- diploid nucleus removed
- unfertilised (haploid) egg taken from another sheep
- the nucleus was removed
- fused together w/ pulse of electricity –> zygote
- embryo implanted in uterus of surrogate
18
Q
Bt Crops
A
- GMO maize (has insecticide-producing gene from bacterium Bacillus thuringiensis)
- makes the plant toxic to insects
- pollen dusts milkweeds
- affects monarch butterflies
19
Q
Nuclear Accident at Chernobyl
A
- explosion at nuclear plant in USSR
- radioactive metals (iodine, caesium) were released
- spread to dif parts of Europe
- uranium broken up into particles and escaped
- thyroid cancer due to radioactive iodine in milk/water
- leukemia, livestock death, forests affected, fish & caesium
20
Q
Nuclear Bombing of Hiroshima
A
- atomic bomb
- leukemia, cancer, mutations, stillbirths
- people stigmatised
- long-term effects of radiation were studied
- most deaths occurred in the first ten years after the bombing
21
Q
Non-Mendelian ratios
A
- polygenic (e.g. height, skin colour)
- linked genes
- recombinant phenotypes due to crossing over
- codominance of specific alleles (pink flowers)
- sex-linked effects (colourblindness)
- environmental influence on inheritance –> epigenetics, methylation
22
Q
Causes of Mutation
A
- high energy radiation e.g. X-rays, UV, gamma, alpha particles from radioactive isotopes
- mutagen chemicals e.g. benzene
- biological e.g. bacteria or viruses
23
Q
Explain the process of gel electrophoresis
A
- separating mixtures of proteins / fragments of DNA which are charged
- mixture placed on thin sheet of gel (Acts like molecular sieve)
- electric field applied to gel by attaching ELECTRODES to both ends
- particles move based on charges
- rate of movement depends on SIZE of particles
24
Q
Explain the key stages of PCR
A
- DENATURATION –> DNA sample heated + strands separated
- ANNEALING –> cooling + DNA primers attached to 3’ end of target sequence
- ELONGATION –> heat tolerant TAQ polymerase binds to primers & copies strands
25
Q
Genetic Transfer
A
- mRNA coding for insulin extracted from human pancreas cells
- DNA copies of mRNA made using enzyme reverse transcriptase
- sticky ends made by adding extra G nucleotides to ends of gene
- plasmids cut open using restriction enzymes –> sticky ends of plasmid = more C
- insulin gene + plasmid mixed together (base pairing)
- DNA ligase seals nicks (sugar-phosphate bonds)
- recombinant plasmids are mixed w/ host ells
- E coli absorbed
- E coli cultured in fermenter - makes insulin which is extracted & purified for diabetics
