Inheritance, Mendel's Work Flashcards
What was the first theory of inheritance and who developed it?
Lamark
* thought that changes during an organism’s lifetime would be passed on to future offspring
(eg. long necked giraffes used to have short necks, but stretched them to reach food and passed their new long neck on to offspring)
What was Gregor Mendel’s experiment on?
Peas and their traits
* he started by looking at the colour of their flowers
* but further on he looked at stalk length, wrinkles etc.
What were the variables in Mendel’s Pea Plant Experiment?
Independent, Dependent, Control
Independent: the generation tested (F1, F2)
Dependent: gene expressed (plant height, flower colour, plant texture)
Control: environment (water availability, temperature)
What was the ratio that Mendel discovered?
3:1
What were the 2 crosses that Mendel did?
- crossed two pure-breeding pea plants with a certain gene to make the Pure-breeding Generation (P1)
- crossed the results from the first generation to make the First Filial Generation (F1)
What was the importance of maths in Mendel’s experiment?
to show the inheritance patterns and their ratio
What are Mendel’s 3 Laws of Inheritance?
- law of independent assortment
- law of segregation
- law of dominance
What is the law of independent assortment?
when chromosomes line up in the middle of the cell during Metaphase, the order in which they align is different every time
ie. can go 1, 3, 7, 21, but there always has to be a mum and dad next to each other
What is the law of independent assortment?
the inheritance of one pair of genes in unrelated to the inheritance of another (independent inheritance)
ie. seperate traits are seperately inherited
What is the law of segregation?
when the chromosomes are pulled to each side of the cell in Anaphase, it occurs randomly/the way that the chromosomes go change
alleles are inherited separately (one from each parent)
What is the law of dominance
there are dominant and recessive traits
* dominant traits are expressed in the phenotype
* recessive traits are repressed
What does a Punnett Square show?
the likelihood of offspring with a specified characteristic
* multiplies the 2 alleles of both parents to result in the 4 possible allele combinations for the offspring
What is the genotypic ratio?
the ratio of all of the possible genotypes (allele pairs) in an offspring (includes all possible genotypes)
What is the phenotypic ratio?
the ratio of the possible phenotypes (external expression) in an offspring
Define homozygous
HOMO = 2 OF THE SAME
refers to a pair of alleles that are both the same
* homozygous dominant = BB
* homozygous recessive = bb
