Unit 7A: Inheritance Flashcards
How are chromosomes formed
- DNA wraps around associated proteins called histones, this forms a nucleosome
- nucleosome chains form chromatin, which coils to form chromosomes
What is a dominant allele
Expresses itself when with a recessive allele present
What is a recessive allele
Expresses itself only when another identical recessive allele is present
Mendel notes
- experimented from 1850 - 1870
- first person to use dominant and recessive
- known as ‘godfather of genetics’
- involved working with pea plantations
What is monohybrid inheritance
Inheriting a single pair of alleles, separation of homologous chromosomes during first division of meiosis
What is an F2 square
A punnet square of the offspring gametes
What is codominance
Alleles are equally dominant and expressed in phenotypes
What are multiple alleles
When a gene has more than two alleles that exist at a particular locus
What does alleomorphic mean
When you have several different inherited genes making up one gene
Process of dihybrid inheritance
- 2 pairs of alleles on different chromosomes
- an adult from one pair of chromosomes can enter a gamete with either allele from the other pair because of independent assortment
- for example, the four gametes from an AaBb adult are: Ab, AB, aB, ab
Process of meiosis 1 and 2
I1 - organelles double
P1 - independenr segregation, nuclear envelope disintergrates
M1 - crossing over, chromosomes line up on equator
A1 - spindle fibres pull chromosomes to either side of cell
T1 - nuclear envelope forms, cell divides
Meiosis 2 - same as 1 without I.S and C.O
What is an autosome
All chromosomal pairs which aren’t sex gametes
What is autosomal linkage
If genes have loci on a non-sex chromosome
What is sex-linkage
Any gene with loci on X or Y chromosomes
What is epistasis
- epistasis occurs when two or more genes contribute to the same phenotype.
- this arises when the allele of one gene affects or masks the expression of another in the phenotype.
