Genetic Information Flashcards
What are the three sources of genetic variation?
Meiosis
Mutation
Random fertalisation
What stages of meosis can cause genetic variation?
Independent assortment
Crossing over
How can independent assortment during meiosis cause genetic variation?
The genes from mother and father are distributed randomly
How can crossing over during meiosis cause genetic variation?
Enzymes cut and join different bits of chromasomes together
How can mutations be a cause of genetic variation?
There are slight changes in the DNA of the organism
How can random fertalisation cause genetic variation?
Each sperm carries a different combination of alleles and the process determining which sperm fertalises he egg is completely random.
What is a phenotype?
The physical and chemical characeristics that make up the appearance of an organism.
Result of genetics and environment
How many chromasomes do humans have?
46 (28 pairs)
What is an allele?
A different variation of the same gene
What is a homozygote?
A person where their two alleles code for the same characteristic
eg: both coding for blue eyes
What is a heterozygote?
A person where their two alleles code for different characteristics
eg: one allele is brown eyes and the other is green
What is a dominant allele?
The allele is expressed, even when it’s heterozygus
What is a recessive allele?
Both alleles must be the same in order for it to be expressed (homozygus recessive)
What are polygenic traits?
Traits determined by a number of alleles
Why are the ratios seen in punnet squares never the same as a real-life experiment?
It happens at random so there is still the element of chance
Some offspring may die before they are sampled
Insufficent techniques like an organism escaping
What is Mendell’s law of segregation?
The idea that one allele is inherited from each parent to give a total fo 2 alleles for that trait. Some alleles are dominant over others
What does it mean when a trait has multiple alleles?
There are more than two possible variants of the trait but two of them are still inherited.
What does it mean when an allele is codominant?
Both alleles are dominant and expressed, acting independantly of each other and not mixing.
eg: AB blood group
What does the chi squared test do?
Compare the differences between two sets of data and evaluate if they differ from each other significantly
What affects how closely two genes are linked?
How close together they are on a chromasome
What is a crossover value?
Shows how closely linked genes are. More closely linked genes will give smaller values
What is a recombintant phenotype?
Where the offspring have different phenotypes to the parents due to recombination of the chromasomes during sexual reproduction
How do you work out the crossover value?
total number of offspring
What sex chromasomes are there in female mammals?
XX
