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63 terms

Topic 4: Genetics

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Eukaryote chromosomes contain:
DNA and assorted proteins
Gene
A heritable factor that controls a specific characteristic
Allele
1. A specific form of a gene
2. Differing from other alleles by 1 or a few different bases
3. Occupying the same locus as alleles of the same gene.
Genome
The whole genetic info of an organism
Gene mutation
Change in the base sequence of a gene
Consequences of base substitution in relation to the processes of translation and transcription, using sickle cell anemia.
Base substitution (gene mutation):
1. From A to T in the triplet coding of a sixth amino acid.
2. Mutation changes HbA (hemoglobin) into HbS (sickle hemoglobin)
3. Valine replaces hemoglobin
4. Valine may = sickle shaped cells
5. Sickle cells = increased cloting, lack of oxygen in body tissues.
Meiosis
A reduction division of diploid nucleus to form a haploid nucleus.
Homologous chromosomes
Chromosomes that have the same arrangement of genes as each other (base seq. may differ = alleles)
Explain how non-disjunction can lead to changes in chromosome number, using Down's Syndrome
Non-disjunction = failure of chromatids to separate during the division of the nucleus.
Result = gametes (sex cells) with more or less than a haploid number of chromosomes
DS = non-disjunction of chromosome pair 21
Result = embryo having 3 copies of 21 (trisomy 21)
Chromosomes are arranged in pairs according to size and structure in:
Karyotyping
Karyotype
The chromosome complement of a cell or whole organism
Amniocentesis
1. Remove amniotic fluid surrounding the fetus
2. Syringe inserted through abdominal wall
3. Used for diagnosing: neural tube disorder (i.e. spina bifida)
Karyotype of a normal healthy male:
1. Has two chromosomes for each number
2. Has a Y chromosome
Karyotype of a Down syndrome male:
1. Has 3 chromosomes in the 21st
Genotype
The alleles of an organism
Ex: AaBb
Phenotype
The characteristics of an organism
Ex: AABB (AaBb)
allele
the different forms of a gene. Each organism must have 2 of these from each trait, one from Mom's and Dad's.
Dominant allele
Allele that has the same effect on the phenotype whether it is homozygous or heterozygous
Recessive allele
Allele that only has effect on the phenotype when it is homozygous.
Co-dominant alleles
Pair of alleles that both affect the phenotype when present together in heterozygous.
p generation
parent generation.
f₁ generation
offspring of the p generation.
f₂ generation
offspring of the f₁ generation.
Locus
The position on homologous chromosomes of a gene.
Homozygous
Having two identical alleles of a gene
example HH or hh
Heterozygous
Having two different alleles of a gene
example Hh
Carrier
Individual that has one copy of a recessive allele that = disease in individuals with homozygous for this disease.
Test cross
Testing a suspected heterozygous with a known homozygous recessive.
Describe ABO blood groups as an example of multiple alleles
ABO blood group = 3 different alleles
A and B = co-dominant
I = Immunoglobin.
O = ii,
A= IAIA or IAi,
B= IBIB or IBi,
AB = IAIB
Explain how sex chromosomes control gender, using inheritance of X and Y chromosomes.
Gender is determined by sex chromosome inherited by the parents.
Males = heterogametic XY , Females =homogametic XX
Some genes present on X chromosome is missing from Y chromosome because:
Y chromosome is shorter than X chromosome
Sex linkage
Sex linkage: association of a characteristic with gender, because the gene controlling the chromosome is located on a sex chromosome.
Describe the inheritance of color blindness as an example of sex linkage
CB:
1. Produced by a sex-linked, recessive allele
2. Loci on non-homologous part of X chromosome
3. Males must inherit it from mother (not father)
4. Women carry gene and do not express it
Predict outcome of colorblind carrier XBXb and male recessive XbY, where b = colorblind
Female: XBXb Male: XbY

Female: carrier XBXb and colorblind XbXb
Male: normal XBY and colorblind XbY
A human female can be what? with respect to sex-linked genes?
Heterozygous and Homozygous
Female carriers are:
Heterozygous for X-linked recessive alleles.
Outline use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA
PCR:
1. DNA sequencing
2. DNA profiling
3. Diagnosing diseases
4. Amplify small samples
Gel Electrophoresis
The separation of nucleic acids or proteins, on the basis of their size and electrical charge, by measuring their rate of movement through an electrical field in a gel.
What are restriction enzyme
is an enzyme that cuts DNA in specific places and is an essential tool in gene splicing, for cloning a gene as well as in Gel-electrophoresis.
In gel electrophoresis, fragments of DNA:
1. Move in an electric field
2. Are separated according to their size, electric charge and physical properties
Gel electrophoresis of DNA is used in:
DNA profiling
Describe the application of DNA profiling to determine paternity
1. DNA sample from mother, child and potential fathers
2. All DNA fragments from the child must match with either father or mother
Describe the application of DNA profiling in forensic investigations
1. DNA taken from victim, crime scene and suspect
2. Bands are compared to associate the suspect and to eliminate the victims
Outline three outcomes of the sequencing of the complete human genome
1. A knowledge of the number of human genes
2. The location of specific genes
3. Allowed for the discovery of protein and their specific functions
When genes are transfered from species to species, the amino acid:
Remains unchanged because genetic code is universal
Pro for the selective breeding of animals
The creation of a more useful organism that can survive better
Con for the selective breeding of animals
1. The loss of genetic diversity
2. The possibility of animals suffering as a result of genetic modification
What does DNA ligase do?
links pieces of DNA together
What property of the genetic code makes it possible for a gene to be transferred between species?
DNA code is universal (the same codons code for the same amino acids in all species.)
Outline the basic technique used for gene transfer involving host cell, plasmids and DNA ligase
1. Plasmids are removed
2. Plasmids are cleaved by restriction enzymes
3. DNA fragments from another organism is also cleaved by the same enzymes.
4. These pieces are added to the open plasmids and spliced together by ligase.
5. Recombinant plasmids are inserted into host cell
State two examples of uses of genetically modified crops or animals
1. Added retinol in rice
2. Herbicide resistance in crop plants
Added retinol in rice
Why? = Vitamin A deficiency in 3rd world countries
How? = By using beta-carotene molecules in rice
Herbicide resistance in crop plants
Why? = Weeds use soil nutrients that crops need
Competition for soil = lack of productivity/efficiency
How? = Herbicides are used to kill weeds before planting of crops
Benefits of salt tolerance in tomatoes
Tomato can grow in regions with high salinity = can grow in remote and "unfarmable" areas
Disadvantages of salt tolerance in tomatoes
1. Transgene spreading
2. Outclassing indigenous plants (due to pollen)
3. Outclassing indigenous business
4. Does not solve the problem of WH, WH = the unequal distribution of food, not the production.
Benefits of genetic modification
1. Increased food production and crop yields
2. Improved health of humans, less dependence of medicines
3. Decreased use of pesticides, herbicides
4. Greater nutritional value
5. Extended shelf life
Disadvantages of genetic modification
1. People with allergies to transgenic foods
2. Little real economic benefit = Large corporations outclassing smaller ones.
3. Possible uncontrolled spread of transgenes = unfair advantage to "real" plants
4. Accumulation of toxins in plants from herbicides
Clone
A genetically identical organism or a group of cells, derived from a single parent cell.
Reproductive cloning Pro
1. Parents with genetic diseases are able to have children without passing on that disease (removing the issue of aborting child with genetic defect)
2. Infertile couples able to have biological children
Reproductive cloning Con
1. May lead to the rise of a "superior race"
2. Clones may have fewer rights than "real" people
3. Clones may lack sense of personhood/identity
Therapeutic cloning Pro
1. Patients able to have new organs w/out risk of rejection
2. Provides new genetic treatments
Therapeutic cloning Con
1. Humans used for "spare parts"
What are the outcomes of the complete sequencing of the human genome? (Human Genome Project) knowledge of the number of human genes
knowledge of the numbers of human genes and what they maybe used for,