Genetics Flashcards
Define Gene
A gene is a hereditary unit composed of a DNA section. They determine the characteristics of an organism by forming a protein.
Define gene locus
a fixed point on a chromosome for a gene
Define allele
variation of a gene at a particular gene locus
Define genotype
the allele combination of an individual
Define phenotype
the physical, behavioral or physiological characteristics of an organism which are a result of the combination of the genotype and the environment.
Define dominant
Allele will be expressed in the heterozygous genotype
Define recessive
Only expressed in the phenotype when the genotype is homozygous.
Define homozygous
Two of the same alleles for a gene at a specific gene locus
Define heterozygous
Two different alleles for a gene at a specific gene locus
Define a chromosome
A long thread-like structure
Composed of DNA
Carries genes
Define autosomal
To do with any chromosome except the sex chromosomes
Write the mode of inheritance statement for a DOMINANT trait
The mode of inheritance is dominant because every affected individual () at least one affected parent ()
Write the mode of inheritance statement for a RECESSIVE trait
The mode of inheritance is recessive because an affected individual () has two unaffected parents( and _)
How do you determine if a recessive trait is X-linked?
X-linked if an affected mother () passes the trait to all of her sons ()
(otherwise autosomal)
How do you determine if a dominant trait is X-linked?
X-linked if an affected father () passes the trait to all of his daughters ()
State the mode of inheritance of huntingtons and provide alleles
Autosomal dominant
H = huntingtons
h = unaffected / no huntingtons
State the mode of inheritance of cystic fibrosis and provide alleles
Autosomal recessive
A = unaffected / no cystic fibrosis
a = cystic fibrosis
State the mode of inheritance of haemophilia and provide alleles
X - linked recessive
X^H = unaffected
X^h = haemophilia
State the mode of inheritance of sickle-cell anemia and provide alleles
Codominant
Hb^A = normal cells
Hb^S = sickle cells
State the F1 genotype ratio when two heterozygous individuals are crossed
1:2:1
or 25% : 50% : 25%
State the F1 phenotype ratio when two heterozygous individuals are crossed
3:1
or 75% : 25%
What is the scaffold for Explain questions
Because, then, therefore
What is the scaffold for Compare questions?
Whereas
What is the scaffold for Describe questions
This means that
Define co-dominant
Alleles are equally expressed in the phenotype (e.g. in sickle cell trait HBA and HBS are expressed)
