Inheritance And Variation Flashcards
What is DNA?
A molecule that carries genetic information in a double-helix structure.
What is a gene?
A segment of DNA coding for a protein, determining a specific trait.
What are chromosomes?
Long strands of DNA; humans have 23 pairs (46 total).
What is an allele?
Different versions of the same gene (e.g., dominant or recessive).
What is a genotype?
The genetic makeup of an organism (e.g., BB, Bb, bb).
What is a phenotype?
The physical appearance or trait resulting from the genotype (e.g., brown eyes).
What is homozygous?
Having two identical alleles (e.g., BB or bb).
What is heterozygous?
Having two different alleles (e.g., Bb).
What is a dominant allele?
An allele that is expressed even if only one copy is present (e.g., B).
What is a recessive allele?
An allele that is only expressed if two copies are present (e.g., bb).
What is monohybrid inheritance?
Inheritance of a single characteristic controlled by one gene with two alleles.
How are Punnett squares used?
To predict genetic ratios of offspring (e.g., 3:1 for dominant:recessive traits in heterozygous crosses).
What causes genetic variation?
• Mutation: A change in the DNA sequence.
• Sexual reproduction: Mixing of alleles during fertilisation.
What causes environmental variation?
Factors like diet, climate, and lifestyle influencing characteristics.
What are mutations?
Changes in DNA that can be beneficial, harmful, or neutral.
How do mutations affect proteins?
They may change the amino acid sequence, altering protein structure and function.
What is sexual reproduction?
Involves two parents, mixing genetic material, leading to variation.
What is asexual reproduction?
Involves one parent, producing genetically identical offspring (clones).
What is meiosis?
A type of cell division that produces gametes (sperm and egg), halving chromosome number to 23.
Why is meiosis important?
It creates genetic variation through:
• Independent assortment.
• Crossing over of genetic material.
What is cystic fibrosis?
A recessive disorder causing thick mucus in lungs and digestive system (genotype: ff).
What is polydactyly?
A dominant disorder causing extra fingers or toes (genotype: PP or Pp).
What is genetic screening?
Testing embryos or individuals for genetic disorders.
What are the ethical issues of screening?
• Could lead to discrimination.
• Raises questions about “designer babies.”
