20.2 Monogenetic inheritance Flashcards
What’s monogenetic inheritance
The inheritance of a single gene
What do you need to include in a genetic cross
- State parents phenotype
- State parents genotype
- State parents gametes, circle them.
- Use a punnett square
- State the proportion of each genotype.
- State the phenotypes for the genotype.
What’s codominance
When two different alleles occur for a gene both of which are equally dominant, as a result both alleles of the gene are expressed in the phenotype of the organism
How is codominace show in the colour of snapdragon flowers
There are two equally dominant alleles one codes for an enzyme that produces a red pigment and one codes for an enzyme that does not produce the red pigment so the flower stays white
The snapdragon can now be three colours red white or pink (when the plant is heterozygous )
How are codominace genes written
A capital C or other letter and then a higher second letter (subscript)
What happens when there’s multiple version of a gene eg. In blood types
Your blood group is determined by a gene with multiple alleles the immunoglobulin gene codes for the production of different antigens on RBC there’s I^A and I^B are codominant and I^O is recessive so the blood groups are A, B, AB or O
What’s are the chromosome pairs 1 to 22 known as
Autosomal Chromosomes - both genes in the pair are identical
What are the features of the Y chromosome
Very small
• Contains little to no genetic information
• Does contain a gene that causes the embryo to develop as a male
What are the features of the X chromosome
• Large
• Contains many genes not involved in sexual development
How is sex determined
By if the sperm that fertilised the egg has an X or Y chromosome
What’s sex linkage
occurs when certain traits are determined by genes on sex chromosomes
Why are any characteristics that are caused by a recessive allele on the X chromosome more frequent in males than females
As males only have one copy of the X. Chromosome as females can also have a dominant allele present in their cells
Why is colour blindness more common in males
As its caused by a recessive allele on the X chromosome
What’s haemophilia
It’s a sex linked genetic disorder where blood clots very slowly so it can cause prolonged bleeding and therefore be fatal
Why’s haemophilia more common in males than females
As if a male inherits their recessive allele they can’t have the corresponding dominant allele so the develop the condition whereas females who are heterozygous for haemophilia are carriers and don’t suffer but can pass on the allele, a male can only inherit an X chromosome from their mother
How are sex gametes written
Y and X with a subscript other letter capital or lowercase depending if its dominant or recessive
