Genetics And Genetic Engineering notes include:
- Gregor Mendel and his experiment
- Genes and alleles
- Monohybrid and test crosses
- Sex chromosomes
- Sex linked alleles and diseases
- Polygenetic inheritance
- Genomes and Human Genome Project
- Gene mutations
- Neutral, beneficial an...
Genetics
Branch of biology that studies heredity and variation in organisms
Father of genetics
● Gregor Mendal
● Australian monk
● First major breakthrough in study of heredity by investigating transfer of characters from one generation to the
next
● Discovered genes
Genes and alleles
- Chromatid = DNA molecule
- DNA molecule = series of genes
- Gene = section of DNA
- Alleles = versions of a gene
Genes:
- Somatic cells = exact copy of genes in organism
- Each cell = 2 of each kind of gene (maternal & paternal)
- Gene pool = set of all genes/ genetic info in a population
Activeness:
● Only needed genes are activated (others suppressed) = creates specific proteins for characteristics (eg. skin
cells)
● Play role in early embryo development
● ‘Housekeeping genes’ → basic functions
● Many are non-coding
Alleles:
- Control different versions of a trait in same locus on homologous chromosomes
- 2 or more forms of a gene
Represented:
● Capital letter = dominant
● Lowercase letter = recessive
Passed on:
● By chromosomes in gametes in sex organs (meiosis)
Gametes:
● Fertilization = diploid zygote
● Divides by mitosis = new organism
● Same set of chromosomes & alleles
Genotype All genes in an organism
Phenotype Appearance of an organism
Homozygous Pair of alleles same on locus
Heterozygous Pair of alleles different on locus
Dominant Trait expressed in offspring
, Recessive Trait suppressed by dominant allele/ not expressed in offspring
Monohybrid cross
- Cross between parents with different alleles for a single gene
1. Genetic diagrams:
- P1 = parent generation
- F1 = first generation offspring
- F2 = second generation offspring
2. Punnett square
3. Pedigree diagram/ family tree
Mendel’s experiment:
- “What happens to the alternative forms of traits when they are combined together to form a hybrid?”
Experiment:
● Transferred pollen grains from tall pea plant to short pea plant
● Collected and sowed the seeds
● Resulting F1 generation = tall and self pollinate
● F2 generation = ¾ tall, ¼ short
Complete dominance:
● Dominant allele overrides recessive allele in phenotype
● Heterozygous phenotype = homozygous phenotype with dominant alleles (eg. TT and Tt both tall)
● Masked characteristic (heterozygous) = recessive & only expressed when homozygous (eg. tt)
Principles/ results:
1. Principle of segregation → pairs of alleles separate when gametes form (meiosis)
2. Principle of independent assortment → alleles separate randomly/ independently
3. Principle of dominance → dominant allele appears in phenotype
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