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12 Cards in this Set

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What causes variations in populations?

Environment


Inheritance

How is inheritance of different features controlled?

Reproduction

What did Mendel discover?

Some traits show up in the offspring without the blending of parents characteristics (intermediate colours didn't appear - no colours in between). His theory overwrote this blending theory.

Techniques that made his experiment a success

(Accuracy, reliability, validity)


- Observed easily recognisable traits


- Chose common garden pea plants --> to manipulate reproduction


- before the experiment, he bred each variety for 2 years to make sure that their character was consistent


- selectively and deliberately crossbred one variety with another & observed what happened in the next generation


- Removed stamens to avoid self pollination & pollinated breeding pairs by hand


- Repetition of experiment


- Quantitative data


- Studied one character at a time so the effects of each could be confused


- Repeated the experiments, testing all the characteristics he had used in garden peas and they all have similar results

Method

- Selectively cross pollinated pure bred plants with particular traits and observed the outcome over many generations


- Have both male & female (stamen & pistil) reproductive organs --> self pollination & cross pollination

Results

f1 - All yellow


f2- 3:1, Yellow:Green


Following generations 3:1


Conclusions

1. Inheritance of each trait is determined by factors (genes) being passed down


2. One inherits a unit (gene) from each parent for each trait


3. A trait may not show up in an individual but still be passed on

Note

Parent gen: homozygous YY, yy


f1: heterozygous

What is a phenotype?

Observable characteristics

What is the principle of segregation?

- One allele from each parent passes into the offspring


- Chance / random


- Meoisis


What is the principle of independent assortment?

Different pairs of alleles are passed to offspring independent of each other. Combination of genes in neither parent are possible. e.g. a peas ability to inherit purple flowers instead of white doesn't reduce/increase/ or affect at all the ability to produce yellow peas instead of green ones.


- The inheritance of one trait doesn't affect the likelihood of the inheritance of a different trait.


- Genes for independently assorted traits are located on different chromosomes

What is the principle of independent assortment?

- The inheritance of one trait doesn't affect the likelihood of the inheritance of a different trait.


- Genes for independently assorted traits are located on different chromosomes


Different pairs of alleles are passed to offspring independent of each other. Combination of genes in neither parent are possible. e.g. a peas ability to inherit purple flowers instead of white doesn't reduce/increase/ or affect at all the ability to produce yellow peas instead of green ones.