Inherited Changes Flashcards
Define fertilisation
When the nucleus of a sperm cell fuses with the nucleus of an ovum
Resulting in a zygote which has 46 chromosomes
How are the 46 chromosomes in your body divided up
22 pairs of chromosomes and one pair of sex chromosomes
What is an allele
Alternating forms of the same gene
Where are homologous pairs for same characteristics found
At the same loci
What is mono hybrid inheritance
Inheritance of a single gene
What is dihybrid inheritance
Investigating two characteristics at the same time
What is the expected ratio for a dihybrid cross
9:3:3:1
What is co dominance
Both alleles are dominant and both are expressed in the phenotype
How do you write a co dominant cross
Using super script letters
Why is sex inheritance different to other types of inheritance
Sex is determined by a chromosome not a gene
Explain sex linkage
Any gene carried on the X or the Y
There is no equivalent homologous portion on the Y chromosome and most of the alleles are recessive
Which gender are characteristics more likely to appear in
Males because the X chromosome is much longer than the Y
There is no equivalent homologous portion of the Y so recessive characteristics on the X appear in phenotype
Why is haemophilia almost always inherited by the mother
Faulty allele carried on X chromosome
No equivalent region of Y chromosome
Males always inherit X chromosome from the mother
What is an autosome
The other 22 chromosomes that aren’t sex linked
What is autosomal linkage
Two genes are on the same chromosome at the same loci and gametes aren’t produced equally
they are likely to be inherited together
No independent segregation
