genetic inheritance Flashcards
Who is Gregor Mendel and what was his contribution to the understanding of genetics?
Gregor Mendel was an Austrian monk, who crossed pea plants in a garden of a monastery. His experiments were published and soon became the foundation of genetics today.
What was Mendel’s first cross?
He crossed a dwarf pea plant (homozygous recessive) with a tall pea plant (homozygous dominant). The offspring were all tall pea plants.
What was Mendel’s second cross?
Then, he crossed these two tall offspring (heterozygous) together - the offspring included 3 tall pea plants, and one dwarf pea plant.
3:1 = phenotypic ratio
What were Mendel’s 3 important conclusions?
- characteristics determined by hereditary units
- hereditary units can be dominant or recessive
- hereditary units passed on from parents to offspring unchanged
Why was Mendel’s work initially not recognised?
- published in a ‘not very well-known’ journal
- scientists didn’t have the background knowledge to properly understand Mendel’s findings
what are alleles?
alternative forms of the same gene, every gene has 2 alleles in the body
What is a homozygous trait?
If both alleles for the gene are the same, it is called homozygous.
What is a heterozygous trait?
If both alleles for a gene are different, it is called heterozygous.
What does dominant mean?
A dominant allele only needs one allele present for the trait to be expressed.
It is represented by a capital letter.
E.g. Tt = heterozygous dominant
What does recessive mean?
A recessive allele needs two to be expressed, otherwise its traits are masked by a dominant allele.
It is represented by a lowercase letter.
E.g. tt = homozygous recessive
What is monohybrid inheritance?
Inheritance of a single characteristic which can be shown on a monohybrid cross
- it can also be shown on a punnett square
