B: Topic 6 – Inheritance, Variation and Evolution

What is the definition of a genome?

The entire genetic material of that organism, including the DNA in the chromosomes and the mitochondria.

Describe the structure of DNA.

A polymer made up of two strands forming a double helix. It is contained in structures called chromosomes.

How does meiosis differ from mitosis in terms of daughter cells?

Meiosis leads to four non-identical daughter cells (gametes), each with half the number of chromosomes (23 in humans), whereas mitosis produces two identical diploid cells.

Explain the process of meiosis.

1. DNA duplicates its columns.
2. The cell divides twice.
3. Four genetically different haploid gametes are formed.

Define homozygous and heterozygous.

• Homozygous: Having two identical alleles for a particular gene (e.g., BB or bb).
• Heterozygous: Having two different alleles for a particular gene (e.g., Bb).

What is the cause of Cystic Fibrosis and is it dominant or recessive?

It is caused by a recessive allele, meaning an individual must inherit two copies (ff) to have the disorder. It affects cell membranes.

What is polydactyly and how is it inherited?

A condition characterized by having extra fingers or toes. It is caused by a dominant allele (P), meaning only one copy is needed to express the phenotype.

State the four main stages of evolution by natural selection.

1. Variation: Occurs due to mutations.
2. Survival: Individuals with characteristics better suited to the environment are more likely to survive.
3. Reproduction: Survivors pass on their advantageous alleles.
4. Inheritance: The frequency of the advantageous allele increases in the population over generations.

What is selective breeding and what is its main drawback?

The process by which humans breed plants and animals for particular genetic characteristics. A major drawback is inbreeding, which reduces the gene pool and increases the risk of genetic defects or disease susceptibility.

How is genetic engineering performed?

A gene is cut out of the DNA of one organism using enzymes and inserted into a vector (like a plasmid or virus), which then inserts the gene into the cells of another organism.

What are the three ways fossils can form?

1. From gradual replacement of body parts by minerals.
2. From casts and impressions (like footprints or burrows).
3. From preservation in places where no decay happens (e.g., amber, ice, or peat bogs).

Explain why antibiotic resistance in bacteria is evidence for evolution.

Bacteria reproduce rapidly and can mutate. Mutations may lead to resistance. When treated with antibiotics, non-resistant strains die while resistant ones (MRSA) survive and reproduce, increasing the resistant population via natural selection.

What is the definition of a genome?

The entire genetic material of that organism, including the DNA in the chromosomes and the mitochondria.

Describe the structure of DNA.

A polymer made up of two strands forming a double helix. It is contained in structures called chromosomes.

How does meiosis differ from mitosis in terms of daughter cells?

Meiosis leads to four non-identical daughter cells (gametes), each with half the number of chromosomes (23 in humans), whereas mitosis produces two identical diploid cells.

Explain the process of meiosis.

1. DNA duplicates its columns.
2. The cell divides twice.
3. Four genetically different haploid gametes are formed.

Define homozygous and heterozygous.

• Homozygous: Having two identical alleles for a particular gene (e.g., BB or bb).
• Heterozygous: Having two different alleles for a particular gene (e.g., Bb).

What is the cause of Cystic Fibrosis and is it dominant or recessive?

It is caused by a recessive allele, meaning an individual must inherit two copies (ff) to have the disorder. It affects cell membranes.

What is polydactyly and how is it inherited?

A condition characterized by having extra fingers or toes. It is caused by a dominant allele (P), meaning only one copy is needed to express the phenotype.

State the four main stages of evolution by natural selection.

1. Variation: Occurs due to mutations.
2. Survival: Individuals with characteristics better suited to the environment are more likely to survive.
3. Reproduction: Survivors pass on their advantageous alleles.
4. Inheritance: The frequency of the advantageous allele increases in the population over generations.

What is selective breeding and what is its main drawback?

The process by which humans breed plants and animals for particular genetic characteristics. A major drawback is inbreeding, which reduces the gene pool and increases the risk of genetic defects or disease susceptibility.

How is genetic engineering performed?

A gene is cut out of the DNA of one organism using enzymes and inserted into a vector (like a plasmid or virus), which then inserts the gene into the cells of another organism.

What are the three ways fossils can form?

1. From gradual replacement of body parts by minerals.
2. From casts and impressions (like footprints or burrows).
3. From preservation in places where no decay happens (e.g., amber, ice, or peat bogs).

Explain why antibiotic resistance in bacteria is evidence for evolution.

Bacteria reproduce rapidly and can mutate. Mutations may lead to resistance. When treated with antibiotics, non-resistant strains die while resistant ones (MRSA) survive and reproduce, increasing the resistant population via natural selection.