Chapter 17 - Inheritence Flashcards
What is meant by diploid
An organism with a pair of homologous chromosomes, it has 2 alleles of each gene
What is a gene
A sequence of DNA that codes for a protein
What is an allele
A variation or version of a gene eg A B O blood
What is a genotype
The combination of alleles an organism has
What is a phenotype
The physical expression of the genotype and it’s interaction with the environment
What is a dominant allele
An allele always expressed in the phenotype when present
What is a recessive allele
An allele only expressed when homozygous
What are codominant alleles
When both alleles are expressed in the phenotype, phenotype is intermediate
What is homozygous
When both alleles are the same
What is heterozygous
When alleles are not the same
What is the locus
The location or position of a gene on a chromosome
Alleles of a gene always have the same locus
What is mono hybrid inheritance
When inheritance of a characteristic is controlled by a single gene
What is dihybrid inheritance
Inheritance of 2 characteristics that are controlled by separate genes
What is the expected phenotypic ratio for F2 generation in dihybrid inheritance
9:3:3:1
What is an example of codominant alleles
A and B blood groups are codominant
o is recessive so not part of it
How is blood groups represented on a punnet square
Capital I to the power of whatever the blood group is
Eg I^B
What phenotypic ratios does a dihybrid cross on epistaxis genes cause
Recessive epistatic allele = 9:3:4
Dominant epistatic allele = 12:3:1
What is meant by an autosome
Non-sex chromosomes
How many autosomes does a human have
44
Describe autosomal linkage
- Genes on the same autosome are linked (the closer the lock of autosomes the more closely linked they are)
- They will stay together during independent segregation
- They will be inherited together
- Effects the expected phenotypic ratio of 9:3:3:1
- Because linked genes are inherited together they behave more like a mono hybrid cross 3:1
- Autosomal linkage means that more offspring will have the same genotype and phenotype as their parents
Why may autosomal linkage not result in more offspring having the same genotype and phenotype as their parents
- Alleles May be separated during crossing over
What is meant by a homologous pair
The pair of chromosomes a diploid organism has, one from mother and one from father
They are the same genes but different alleles
What is meant by sex linkage
The expression of alleles located on sex chromosomes depends on the sex of the individual
What are the sex chromosomes of females and males
Females XX
Males XY
Y is missing many genes present on X
Explain how haemophilia is much more common in men than women
X^H X^h Y
- Females have 2 X chromosomes, so must be homozygous to suffer
- Males only have one X chromosome, if it is recessive they will suffer
- Draw this out (in folder)
What is meant by epistasis
An interaction between genes when the expression of one gene suppressed the expression of another gene
Or
When a phenotype is controlled by more than one gene
