8th grade cells, genetics and evolution

Example

What is a gene?

1. A gene is a short section of DNA carrying the code for one protein.
2. So the answer is: a section of DNA that codes for a protein

Answer: a section of DNA that codes for a protein

Example

A potato cylinder had a mass of 3.2 g. After 30 minutes in a sugar solution its mass was 3.04 g. What is the percentage change in mass? (Use a minus sign for a loss.)

1. 3.04 − 3.2 = −0.16 g
2. −0.16 ÷ 3.2 × 100 = −5 %
3. So the answer is: −5 %

Answer: -5 %

Example

Which process is this: urea passing from cells into the blood?

1. Diffusion: particles move down a concentration gradient with no energy needed.
2. So the answer is: diffusion

Answer: diffusion

Example

A cell is 0.05 mm long. How long is it in micrometres (µm)? (1 mm = 1000 µm)

1. 0.05 × 1000 = 50
2. So the answer is: 50 µm

Answer: 50 µm

Example

Which word means: a different version of a gene, such as B or b?

1. Alleles are different versions of the same gene.
2. So the answer is: allele

Answer: allele

Example

Cuttings from one geranium plant (clones with identical genes) were grown in sun and in shade. Mean height after 8 weeks: sun 49 cm, shade 32 cm. What can you conclude?

1. Same genes, different conditions: the 17 cm difference is environmental.
2. So the answer is: The difference in height was caused by the environment (light).

Answer: The difference in height was caused by the environment (light).

Example

A cube-shaped cell model has sides of 3 cm. What is its surface area to volume ratio, written as ? : 1?

1. surface area = 6 × 3 × 3 = 54 cm²
2. volume = 3³ = 27 cm³
3. 54 ÷ 27 = 2
4. So the answer is: 2

Answer: 2