Genetics & Heredity Flashcards
Alleles
2 alternative forms of a gene at same locus
Co dominance
Type of inheritance where both alleles are equally dominant and express themselves equally in phenotype
Complete dominance
Type of inheritance where dominant allele masks expression of recessive allele in heterozygous condition
Dihybrid cross
Genetic cross involving 2 different characteristics
Dominant allele
Allele that masks allele partner on chromosome pair and dominant characteristic is seen in homozygous and heterozygous state in phenotype
Gene
Segment of DNA/ a chromosome that codes for a particular characteristic
Gene mutation
Change in N Base/s in nuclear DNA of an organism
Genetic variation
Variety of different genes that differ from maternal and paternal genes resulting in new genotypes & phenotypes
Genotype
Total genetic composition (makeup) of organism, info present in gene alleles.
Genome
Complete set of chromosomes in cell of organism
Heterozygous
Individual having 2 non identical alleles for a characteristic
Homozygous
2 identical alleles that control a single trait (on same locus)
Incomplete dominance
Type of inheritance where both alleles express themselves in a way where intermediate phenotype is formed
Red+white flower= pink flower
Locus
Exact same position of gene on chromosome
Mendels law of dominance
2 individuals with contrasting homozygous alleles are crossed, the individuals of the first generation will all resemble parent with dominant characteristic
Mendels law of Independent Assortment
Alleles of a gene for 1 characteristic segregate independently of alleles of a gene of another characteristic. Alleles of 2 different genes will therefore come together randomly during gamete formation (random assortment)
Mendels Principle of Segregation
During gametogenesis the 2 alleles of a gene separate so each gamete will receive one allele of a gene for a specific trait
Monohybrid cross
Genetic cross involving 1 characteristic
Mutation
Sudden change in sequence of nitrogenous bases of nucleic acid
Multiple alleles
Whne there are more than 2 possible alleles for one gene locus
Phenotype
Physical appearance of an organism determined by genotype
Pedigree diagram
Diagram showing inheritance of genetic disorders over many generations
Recessive allele
Allele that is suppressed when allele partner is dominant so is only expressed if both alleles of trait are homozygous recessive
Genetics
Study of heredity & varietion in organisms
Inheritance
Transmission of genetic characteristics from parents to offspring
Variation
Changes that occur between members of population
Trait
Characteristic that can be passed from parent to offspring
Homozygous genotype
Pure Gene combination involving 2 dominant or 2 recessive genes
Heterozygous genotype
Hybrid Gene combination of one dominant & one recessive allele
Mutation
Change in amount, arrangement or structure of DNA of organism
Where mutation occurs
Somatic cell: not passed to offspring
Germinal cell : passed to offspring
How mutation affects population
Mutation may result in change in appearance of a characteristic of a population as it brings about variation in genotype =phenotype
Spontaneous mutation
Permanent changes in genome occurring without outside influence due to machinery of the cell being imperfect
Induced Mutation
Occur when mutagens causes permanent changes in DNA
Mutagen & examples
Anything causing a mutation :
Asbestos
Tar from tobacco
Pesticide
Caffeine
Types of Mutation
Chromosomal mutation
Gene /point mutation
Gene mutation
Acquired (somatic) or inherited mutation occurring through base substitution and frame shifts
Chromosome mutation
Changes in number (by time zygote develops) or structure of chromosome frequently caused by inversion, insertion, duplication, deletion of chromosomal segment.
Chromosome mutation causes explained
Inversion : Reversal in chromosomal segment
Insertion/translocation : piece of chromosome attaches itself to non homologous chromosome
Duplication: when extra chromosome appears
Deletion : Deficiency in portion of DNA
Example of results of chromosomal mutation
Trisomy 21
Extra copy of of chromosome 21 due to non dysjunction
Point mutation
Change in single base or base pair in DNA which can change the protein that has been coded for by DNA
Point mutation examples
Inversion : addition of extra nucleotide
Deletion : loss of nucleotide
Inversion : 2 nucleotides arranged in wrong order
Substitution : particular base substituted (replaced) by another.
Sickle cell anemia
A base in one of the genes involved in producing hemoglobin is substituted
How is oxygen carrying ability affected by sickle cell anemia
Hemoglobin crystallizes
Distorting red cells into sickle shape
Reducing oxygen carrying ability
Types of Mutation resulting from single point mutation
Silent mutation
Nonsense mutation : sequence of DNA results in premature codon
Missense mutation : results in substitution of one amino acid in protein for another
Frameshift mutation
Addition or deletion of a single base
Affects of frame mutations on proteins
Adding or deleting one base of DNA molecule will change every amino acid in protein which will cause protein to not function properly
How does reading frame affect protein
Changing reading frame in early gene (mRNA transcript as will change) alters majority of protein
Incorrect amino acid sequence therefore produces malfunctioning proteins
Harmful mutations
Cause change in DNA causing errors in protein sequencing resulting in partially or completing non functioning proteins
Examples of harmful mutations
Cystic fibrosis & sickle cell anemia
Dysfunctional proteins
Albinism
Cancer
Beneficial mutations & examples
Advantageous mutations :
Bacteria
RNA virus
Lactose tolerance
People with mutations have CCR5 gene making them virtually immune to HIV
Harmless mutation
No effect on structure or functioning of organism
Chin dimple
Freckles
Red hair
Stem cell
Undifferentiated cell (embryonic /adult) able to divide to produce more stem cells /cells that can differentiate into many kinds of different cells
Properties of stem cells
Unspecialized cells
Can divide :
& renew themselves for long time
& become specific specialized cell types of body
Stem cells can replace dying, old or damaged cells
Stem cells in embryo
Function to generate new organs & tissues
Stem cells in adults
Function to replace cells during natural course of cell turnover
Kinds of stem cells
Totipotent
Pluripotent
Multipotent
Totipotent
Type of stem cell found in 1-4 day old Embryo
Can develop into new individual
Pluripotent
Found in older embryos 5-14 days old
Can differentiate into any type of specialized cell
May be used to treat disease by replacing damaged cells, diabetes, repair
Multipotent
Found in foetal tissue in children & adults
Can divide & produce new cells that are needed by body
Use of stem cells
Replace damaged tissue
Studying human development
Testing new drug
Screening toxins
Testing gene therapy methods
GMO
Genetically modified organism is an organism that has altered genetic material
Transgenic organism
A GMO that gains 1/more genes by altrificial means
Process
- DNA carrying gene is taken from a cell
- The gene is inserted into DNA of another host cell
- Host cell now contains recombinant DNA
- Host cell multiplies
- Desired protein is produced
Vector
Plasmid or viruses needed to transfer a gene into a host cell
Use of genetic engineering
Make insulin for diabetic persons
Make growth hormones to treat dwarfs
Prepare vaccines
Make plants resistant to disease
Higher production of milk by cows
Make pigs less fat but have leaner meat
Gene therapy
Plants resistant to disease
Make enhanced food
Gene therapy
When gene is inserted in sick person :
Bone marrow containing stem cells is removed from hip bone
The vector is used to carry gene into stem cell
Stem cells with new gene inside are given back to patient 5 days later
How does pest resistant cabbage work
Gene that programs poison in scorpion tails combined with cabbage are genetically modified cabbages producing scorpion poison killing caterpillars when they bite leaves.
How golden rice works
Variety of rice produced through genetic engineering to produce beta carotene needed to produce vitamin a in rice. Intended to be grown & consumed in areas with shortage of dietary vitamin a. Vitamin a deficiency causes range of eye conditions (night blindness and permanent blindness)
Cloning
A clone is an organism genetically exact copy of another organism
Types of cloning explained
Reproductive
Cloning. In order to produce a genetic copy of an existing organism
Therepeutic
Cloning in order to produce a blastocyst from which stem cells can be taken & used to develop therapies for injury & disease
Steps in cloning
Haploid DNA is removed from egg cell
Egg cells DNA is replaced with diploid DNA from a body cell of the organism to be cloned
Ovum begins to divide
Blastocyst is implanted into a surrogate mother & carried to term
How Therepeutic cloning works
Instead of implanting blastocyst into a surrogate mother, stem cells are taken out of blastocyst & used to develop whatever type of cells are needed
Why we need to clone
Researchers how techniques can be used in:
Treating human diseases
Genetically altering animals for production of Han transplant organs
Cloning advantages
Produce animals with desirable traits
Increase efficiency of livestock production
Offset losses of among endangered species populations
Enable better research for finding cures to diseases
Cloning disadvantages
Decline in genetic diversity
Taking nature into our own hands
Religious & moral reasons
Physical problems (birth defects)
Clones may not live as long as other animals.
Why genetic engineering is possible
Living things use same bases & genetic code
Each codon produces same amino acid in transcription & translation regardless of species
Sequence of amino acids in polypeptide remains unchanged
Therefore we take genes from one species & insert them into genome of another species
Negative opinions on genetic engineering
Genome
All the genes that make up an organism
