Genes And Patterns Of Inheritance Flashcards
What is a gene
A short length of DNA that codes for a polypeptide
What does genetic locus refer to
The position of a gene on a chromosome
What is an allele
An alternative form of a gene
What is a genotype
Alleles present for particular trait
Eg eye colour
What is the phenotype
The appearance of a trait
Eg blue eyes
What is the definition of hereditary
Transfer genetic factors from one generation to the next
What is mendels first law
When an individual produces gametes the alleles separate so that each gamers receives only one allele
Describe monohybrid inheritance
- Alleles separate when gametes are produced
2. Alleles combine at fertilisation when gametes fuse
Describe codominance
Alleles interact to produce a heterozygote with its own distinctive phenotype
Red x white = pink
Describe lethal allelic combinations
One allele in homozygous state causes death at early stage
What does multiple alleles mean
More than 2 alleles for a gene
Describe sex linkage
Gene and allele located in sex chromosome
When is a test cross used
To establish the genotype of unknown organisms
Describe a test cross
- Organism crossed with homozygous recessive
- because you can recognise it by its phenotype and it only passes in a recessive allele
Describe the results of a test cross if the tested organism is heterozygous or homozygous
If homo - all dominant phenotype
If hetero - mix of dominant and recessive
Describe co dominance
One allele does not completely dominate the other on a particular chromosome locus
2 alleles both expressing equally
Describe partial dominance
Between shades of complete dominance and no dominance
What do the offspring of co dominance look like in relation to parents
Look like neither parent
Intermediate between homozygous dominant and homozygous recessive
Describe multiple alleles
More than 2 alleles of a particular gene exist
Only 2 present on loci of chromosome
Describe a lethal allele
It stops producing a protein
Which prevents operation of a vital function
What are the three forms of death a lethal allele can produce
Death of zygote - no evidence
Death after reduced lifespan
Death at early stage of development - presence of allele evident
Describe x linked recessive traits (who are they inherited from)
Males inherit from female parent
Females must inherit from both parents
Describe x linked dominant traits
Expression in both sexes Female can be homo or hetero Male is hetero Positive father gives to all daughters Positive mother gives to half sons and half daughters
Describe sex linkage on the Y chromosome
Males inherit Y from father
Every son affected
Describe autosomal inheritance
Trait appears to skip a generation
Describe x linked recessive inheritance
Carrier mother gives trait to half of sons
Infected mother gives trait to all sons
For female to be infected the father must be infected
Describe autosomal dominant inheritance
One parent must have trait
Equal number of male and female
Describe x linked dominant inheritance
Not restricted to males
What is epistasis
One gene interferes with the expression of another
