Inheritance Flashcards
Define diploid
An organism with a pair of homologous chromosomes, it has 2 alleles of each gene
Define gene
A sequence of DNA that codes for a certain protein
Define allele
A variation of a gene
Define genotype
The combination of alleles that an organism has
Define phenotype
The physical expression of the genotype and its interactions with the environment
What is a dominant allele?
An allele always expressed in the phenotype
What is a recessive allele?
An allele only expressed when it is homozygous
What is a codominant allele?
When both alleles are expressed in the phenotype as an intermediate
Define homozygous
Both alleles are the same
Define heterozygous
Both alleles are different
Define locus
The location/position of a gene on a chromosome, the alleles of a gene always have the same locus
What is monohybrid inheritance?
Inheritance of a characteristic controlled by a single gene
What will be the F2 Phenotypic ratio of a monohybrid inheritance from a homozygous dominant male and a homozygous recessive female?
3 : 1Dominant : Recessive
What is dihybrid inheritance?
Inheritance of two characteristics that are controlled by separate genes
What will be the F1 generation be in a dyhybrid cross between a homozygous dominant and a homozygous recessive?
100% heterozygous
What will be the ratio of the F2 generation in a dyhybrid cross between a homozygous dominant and a homozygous recessive?
9 : 3 : 3 : 19 : Both dominant 3 : Dominant allele 1, recessive allele 23 : Dominant allele 2, recessive allele 11 : Both recessive
What is codominance?
When there are multiple alleles that are dominant and can all be expressed in the phenotype as an intermediate
What is an example of codominance?
Blood group
What will be the F1 generation of a codominant cross between two different homozygous dominant patents
100% heterozygous
What will be the F2 generation phenotypic ratio of a codominant cross between two different homozygous dominant patents
1 : 2 : 11 : Homozygous allele 11 : Homozygous allele 22: Heterozygous
What is epistasis?
An interaction between genes where the expression of one gene suppresses the expression of another
How would you refer to two genes showing epistasis
gene … is epistatic to gene …
How does epistasis effect phenotypic ratios?
A dihybrid cross on epistatic genes will not result in the normal phenotypic ratio
What is the phenotypic ratio of a dihybrid cross where the epistatic gene is recessive?
9 : 3 : 4
What is the phenotypic ratio of a dihybrid cross where the epistatic gene is dominant?
12 : 3 : 1
What is an autosome?
A non-sex chromosome
How many autosomes do humans have?
44
What is an autosomal linkage?
It is where two genes are found on the same autosome and are therefore inherited together
What is autosomal linkage not affected by?
independent segregation
Does autosomal linkage affect the phenotypic ratios from a dihybrid cross?
Yes, because linked genes are inherited together they behave more like a monohybrid cross
What does an autosomal linkage mean for offspring?
They are more likely to have the same genotype and phenotype as their parents
What can affect an autosomal link?
Crossing over, however this is dependent on the loci of the two genes. The closer to two are and the closer the autosomal link the less likely they are to be separated during crossing over but it is not impossible
What will be the result of the phonotypes and genotypes of offspring after an inherited autosomal link, taking crossing over into account?
The majority of offspring will share their parents phenotypes and genotypes however a small percentage will not because of crossing over
Where are homologous pairs found?
In diploid organisms
What are homologous pairs?
Same gene but different allele
What is a sex linkage?
The expression of alleles located on sex chromosomes depends on the sex of the individual
What are the sex chromosomes of a female?
XX
What are the sex chromosomes of a male?
XY
What is different about the X and Y chromsomes?
- X chromosome is much bigger than Y- Y is missing many of the genes present on X
What is typical of a sex linkage phenotypical ratio?
1 : 1Female carrier : Male sufferer
