Biology paper 2: inheritance, variation and evolution (patterns of inheritence).

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  • Created by: aliciasp
  • Created on: 01-02-20 17:04
Until the mid-19th century, what did most people think that sexual reproduction produced?
Most people thought that sexual reproduction produced a blend of characteristics eg. if a red flowering plant was crossed with a white flowering plant, then pink flowering plants were produced.
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How did Gregor Mendel investigate this?
He investigated this by carrying out breeding experiments on pea plants.
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What did he find that characteristics are determined by?
He found out that characteristics are deermined by 'units' that are inherited (passed on), and do not blend together.
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What was observed later in the 19th century?
The behaviour of chromosomes during cell division.
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What did scientists realise in the early 20th century?
That Mendel's 'units' and chromosomes behaved in similar ways.
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What did they then decide?
That the 'units', now called genes, were located on chromosomes.
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What did scientists work out mid-20th century?
They worked out what the structure of DNA looked like and the mechanism by which gene's work.
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Why was the importance of Mendel's discovery not recognised during his time?
He was a monk working in a monastry, not a scientist at a university. He did not publish his work in a well-known book or journal.
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What is a modern idea about characterisitics?
Some characterisitics are controlled by a single gene eg. fur colour in mice and red-green colourblindness in humans.
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What is a modern idea about genes?
Each gene may have different forms called alleles eg. the gene for the attachment of earlobes has two alleles- attached or free.
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How many alleles does an individual always have for each gene?
2.
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What is a genotype?
The combination of alleles present in a gene eg. bb.
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What is a phenotype?
How the alleles are expressed (what characteristics appear), eg. blue eyes.
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What are the 2 types of alleles?
Dominant and recessive.
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How do you determine if a person is homozygous?
If the two alleles present are the same, eg. bb or BB.
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How do you determine if a person is heterozygous?
If the alleles are different, eg. Bb.
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How are most characteristics controlled?
Most characteristics are controlled by several genes working together.
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What is it called if only one gene is involved?
It is called a monohybrid inheritance.
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What can be used to predict the outcome of a monohybrid cross?
A genetic diagram or punnett square.
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In these diagrams how do you determine which is a dominant allele and which is a recessive allele?
Capital letter for dominant allele, lower case for recessive allele.
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What are 2 examples of human disorders that can be inherited?
Polydactyll- having an extra finger or toe, is caused by a dominant allele. Cystic fibrosis- a disorder of cell membranes, is caused by a recessive allele.
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How many pairs out of the 23 chromosomes in the human body carries the genes that determine sex?
One pair.
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In females, what are the 2 chromosomes?
**.
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In males, what are the 2 chromosomes?
XY.
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What chromosomes do all offspring inherit?
One X chromosome from mother, either one X or one Y from father.
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Card 2

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How did Gregor Mendel investigate this?

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He investigated this by carrying out breeding experiments on pea plants.

Card 3

Front

What did he find that characteristics are determined by?

Back

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Card 4

Front

What was observed later in the 19th century?

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Card 5

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What did scientists realise in the early 20th century?

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