Biology A2 Chapter 17 - Inherited Change Flashcards
Define the term genotype
The genetic constitution of an organism, it describes all the alleles the organism has
Define the term phenotype
The observable or biochemical characteristics of an organism - it is the result of the interaction between the expression of the genotype and the environment
Define the term gene
A length of DNA, that is, a sequence of nucleotide bases, that normally code for a particular polypeptide
Define the term allele
One of the different forms of a gene
What does it mean if an organism is homozygous for a charcateristic?
If the alleles on each of the homologous chromosomes is the same, then the organism is homozygous for that characteristic
What does it mean if an organism is heterozygous for a characteristic?
If the two alleles on homologous chromosomes are different then the organism is heterozygous for that characteristic
What is a homozygous dominant organism?
An organism with two dominant alleles for a named characteristic
What is a homozygous recessive organism?
An organism with two recessive alleles for a names characteristic
Define the term codominant
When two dominant alleles are both expressed in the phenotype of an organism, meaning the phenotype is either a blend of the features, or both features are represented
What does it mean if an organism has multiple alleles?
When a gene has more than two alleles, of which only two may be present at the loci of an individuals homologous chromosomes
What is monohybrid inheritance?
The inheritance of a single gene
What does the law of segregation state?
In diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete
What is dihybrid inheritance?
When two characteristics, determined by two different genes located on different chromosomes, are inherited together
What is the expected ratio for dihybrid inheritance?
9:3:3:1
What does Mendel’s Law of Independent Assortment state?
Each member of a pair of alleles may combine randomly with either of another pair
Define the term sex linked
Any gene that is carried on either the X or Y chromosome is said to be sex linked
Why are sex linked diseases such as haemophilia more common in males?
The X chromosome is longer than the Y chromosome so there may be no equivalent homologous portion of the Y chromosome for certain characteristics. Heamophilia is caused by a recessive allele only present on the X chromosome and hence males only need to inherit one recessive allele to have the disease, but females need to inherit two recessive alleles which is less likely
What is an X-linked genetic disorder?
A disorder caused by a defective gene on the X chromosome
Define the term autosomal linkage
When two or more genes are carried on the same autosome
What is an autosome?
All the chromosomes that are not sex chromosomes
What is epistasis?
When the allele of one gene affects or masks the expression of another in the phenotype
In epistasis, what are the names of the genes:
1. Doing the suppressing
2. Being suppressed
- Epistatic gene
- Hypostatic gene
When is the chi squared test used?
It is used to test the null hypothesis. It is a means of testing whether any deviation between the observed and the expected numbers is significant or not
What criteria must be met for the chi squared test to be used?
- The sample size must be relatively large, that is, over 20
- The data must fall into discrete categories
- Only raw counts and not percentages can be used
- It is used to compare experimental results with theoretical ones
