Patterns of Inheritance & Variation Flashcards
Define a gene
A sequence of bases on a DNA molecules that codes for a protein
Define a allele
Different versions of the same gene
Define a genotype
An organisms genetic make up
Define a phenotype
An organisms physical characteristics determined by its genotype
Define dominant
An allele that is always expressed in the phenotype
Define recessive
An allele that is only expressed when it is homozygous in the genotype
Define locus
the specific position of a gene on a chromosome
What is monohybrid inheritance?
The transmission of one gene from parents to their offspring
What is the F1 generation?
The offspring from individuals with homozygous dominant and homozygous recessive.
All offspring are heterozygous
What is the F2 generation?
The offspring from two heterozygous F1 individuals
offspring result in a 3:1 ration of dominant to recessive
What is codominance?
Two different alleles are equally expressed in the phenotype
Both alleles are shown in the phenotype
What is sex linkage?
Genes on the X and Y chromosomes are sex linked genes
X chromosome carries the majority of these genes
Recessive alleles on the X chromosome appear on the phenotype of males
What is Haemophilia?
An X-linked recessive disorder
Caused by a recessive X-linked allele
Alters DNA sequence coding for a blood clotting protein
Causing reduced blood clotting and excessive bleeding
Explain the inheritance of Haemophilia
It mainly affects males
Doesn’t often affect females
Always inherited from the mother in males
Mainly inherited form carrier mothers
Affected fathers can only pass it on to daughters
What is a dihybrid cross
The simultaneous inheritance of 2 genes controlling separate characteristics
What is true breeding?
Organisms that are homozygous for the trait being studied
What is autosomal linkage?
Genes that are located on the same autosome are described as linked
Linked genes are inherited together in offspring
How does crossing over affect autosomal linkage?
Crossing over can separate linked genes
However, when gens are linked, fewer recombinant offspring are produced
Less genetic variation being introduced from crossing over when genes are linked
What is the chi-squared test used for?
To measure differences between observed experimental results and expected theoretical outcomes
What is epistasis?
Interaction between genes where one gene masks the expression of another
Explain recessive epistasis
One gene must be homozygous recessive to block the expression of another gene
Explain dominant epistasis
One gene is dominant and actively modifies or blocks the expression of the other gene
What is the Hardy-Weinberg principle?
An equating that calculates the frequency of alleles for a particular gene within a population
What assumptions are made when using the Hardy-Weinberg principle?
No mutations occur
No migration into or out the population
Mating is random
Population size is large
No natural selection pressures
