AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Students should be able to: • describe the development of our…
Full specification wording
The understanding of genetics (biology only): Students should be able to: • describe the development of our understanding of genetics including the work of Mendel • understand why the importance of Mendel’s discovery was not recognised until after his death. In the mid-19th century Gregor Mendel carried out breeding experiments on plants. One of his observations was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged. In the late 19th century behaviour of chromosomes during cell division was observed. In the early 20th century it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways. This led to the idea that the ‘units’, now called genes, were located on chromosomes. In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out. This scientific work by many scientists led to the gene theory being developed.
Our understanding of genetics developed in stages.
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Study notes
From the checked teaching notes for this specification point.
The idea
Our understanding of genetics developed in stages. In the mid-19th century Mendel bred pea plants and concluded that characteristics are determined by 'units' passed to offspring unchanged, now called genes. His work was published but ignored. In the late 19th century scientists observed how chromosomes behave during cell division. In the early 20th century they noticed that chromosomes and Mendel's 'units' behaved similarly, so genes were located on chromosomes. In the mid-20th century the structure of DNA was determined and gene function worked out, producing gene theory. Mendel's importance was not recognised until after his death because his findings were ahead of their time, chromosomes and DNA were unknown, his work was published in a little-read journal, and few scientists connected his 'units' to heredity.
What earns the marks
- Describe Mendel's mid-19th century breeding experiments on plants and his conclusion that 'units' pass to descendants unchanged.
- State that chromosomes were observed during cell division in the late 19th century.
- Explain that in the early 20th century chromosomes and Mendel's 'units' were seen to behave similarly, leading to genes being located on chromosomes.
- Describe that in the mid-20th century the structure of DNA was determined and gene function was worked out.
- Explain that many scientists contributed over time to develop gene theory.
- Explain why Mendel's work was unrecognised: it was ahead of its time, chromosomes and DNA were unknown, and his paper was not widely read.
Common mistakes and how to put them right
Saying Mendel discovered DNA.
Put it right: He proposed 'units' of inheritance, later called genes.
Believing Mendel's work was immediately accepted.
Put it right: Its importance was recognised only after his death.
Confusing the order of discoveries.
Put it right: Mendel, then chromosomes, then DNA structure and gene function.
Exam tips
- Use a timeline approach: mid-19th century Mendel, late 19th century chromosomes, early 20th century genes on chromosomes, mid-20th century DNA.
- When explaining why Mendel was unrecognised, refer to the lack of knowledge of chromosomes and DNA at the time.
- Link each stage to the evidence it provided rather than listing names without explanation.
Try the lesson
The start of the The understanding of genetics (biology only): Students should be able to: • describe the development of our understanding of genetics including the work of Mendel • understand why the importance of Mendel’s discovery was not recognised until after his death. In the mid-19th century Gregor Mendel carried out breeding experiments on plants. One of his observations was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged. In the late 19th century behaviour of chromosomes during cell division was observed. In the early 20th century it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways. This led to the idea that the ‘units’, now called genes, were located on chromosomes. In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out. This scientific work by many scientists led to the gene theory being developed. lesson, made from checked teaching notes for this specification point.
Have a go first
In the mid-19th century, Gregor Mendel carried out breeding experiments on plants. What did he propose was passed on to descendants unchanged to determine inherited characteristics?
Listen
Our understanding of genetics developed in stages. In the mid-19th century Mendel bred pea plants and concluded that characteristics are determined by 'units' passed to offspring unchanged, now called genes. His work was published but ignored. In the late 19th century scientists observed how chromosomes behave during cell division. In the early 20th century they noticed that chromosomes and Mendel's 'units' behaved similarly, so genes were located on chromosomes. In the mid-20th century the structure of DNA was determined and gene function worked out, producing gene theory. Mendel's importance was not recognised until after his death because his findings were ahead of their time, chromosomes and DNA were unknown, his work was published in a little-read journal, and few scientists connected his 'units' to heredity. A strong answer earns marks for these points. Describe Mendel's mid-19th century breeding experiments on plants and his conclusion that 'units' pass to descendants unchanged. State that chromosomes were observed during cell division in the late 19th century. Explain that in the early 20th century chromosomes and Mendel's 'units' were seen to behave similarly, leading to genes being located on chromosomes. Describe that in the mid-20th century the structure of DNA was determined and gene function was worked out. A common slip: Saying Mendel discovered DNA. Instead, he proposed 'units' of inheritance, later called genes. Exam tip: Use a timeline approach: mid-19th century Mendel, late 19th century chromosomes, early 20th century genes on chromosomes, mid-20th century DNA.
See it
Put it in order
Put these steps in the order they happen.
- 1. Gene theory developed by many scientists
- 2. Mid-20th century: structure of DNA determined and gene function worked out
- 3. Late 19th century: chromosomes observed during cell division
- 4. 'Units', now called genes, located on chromosomes
- 5. Mid-19th century: Mendel's breeding experiments on plants
- 6. Mendel's conclusion: 'units' passed to descendants unchanged
- 7. Early 20th century: chromosomes and Mendel's 'units' behave similarly
Key words
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Development of genetics
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Mendel's experiments
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Chromosomes and genes
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DNA structure and function
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See every definition
- Development of genetics
- Our understanding developed in stages, from Mendel's 'units' to chromosomes, then DNA structure and gene function, leading to gene theory.
- Mendel's experiments
- In the mid-19th century breeding experiments on plants showed that inheritance of each characteristic is determined by 'units' passed to descendants unchanged.
- Chromosomes and genes
- In the early 20th century chromosomes and Mendel's 'units' behaved in similar ways, leading to the idea that the 'units', now called genes, were located on chromosomes.
- DNA structure and function
- In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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Test your understanding of The understanding of genetics (biology only): Students should be able to: • describe the development of our understanding of genetics including the work of Mendel • understand why the importance of Mendel’s discovery was not recognised until after his death. In the mid-19th century Gregor Mendel carried out breeding experiments on plants. One of his observations was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged. In the late 19th century behaviour of chromosomes during cell division was observed. In the early 20th century it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways. This led to the idea that the ‘units’, now called genes, were located on chromosomes. In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out. This scientific work by many scientists led to the gene theory being developed.
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