D3.2 Inheritance
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What is inheritance?
The transmission of genetic information (genes) from one generation to the next.
Where is genetic material located in eukaryotes?
In chromosomes in the nucleus.
What is the difference between diploid and haploid?
Diploid (2n): Two sets of chromosomes (body cells) Haploid (n): One set (gametes)
How does meiosis and fertilization ensure genetic inheritance?
Meiosis → produces haploid gametes Fertilization → restores diploid number → ensures genetic variation + stability across generations
How did chromosomes support Mendel’s laws?
Genes exist on chromosomes Chromosomes occur in pairs → matches allele pairs Separation during meiosis explains segregation
What is a gene?
A unit of heredity that codes for a trait.
What are alleles?
Different versions of the same gene.
Define genotype.
The combination of alleles an organism has.
Define phenotype.
The observable characteristics resulting from genotype + environment.
Homozygous vs heterozygous?
Homozygous: same alleles (AA or aa) Heterozygous: different alleles (Aa)
What are homologous chromosomes?
Pairs of chromosomes with same genes at same loci, one from each parent.
Why are alleles important?
They create genetic variation, enabling evolution and diversity.
What is a monohybrid cross?
A cross involving one gene.
F₁ vs F₂ generation?
F₁: offspring of parent cross F₂: offspring of F₁ cross
What is a true-breeding organism?
Homozygous for a trait.
Why is F₁ all dominant phenotype?
All offspring are heterozygous → dominant allele expressed.
Why does recessive trait reappear in F₂?
Two recessive alleles can combine (aa) → trait expressed.
Expected ratios in monohybrid cross (Aa × Aa)?
Genotype: 1 AA : 2 Aa : 1 aa Phenotype: 3 dominant : 1 recessive
Why aren’t real ratios exactly 3:1?
Due to chance, small sample size, environmental factors.
What determines phenotype?
Genotype + environment + epigenetics.
Give an example of environmental influence.
Skin tanning (UV → melanin production).
Why are twin studies useful?
Same genotype → differences show environmental effects.
What is phenotypic plasticity?
Ability of one genotype to produce different phenotypes in different environments.
Advantage of phenotypic plasticity?
Increases survival and adaptability in changing environments.