Monogenetic inheritance Flashcards
What is monogenetic inheritance?
inheritance from a single gene
What did Mendel do?
experiments on pea pods- come in 2 colours= green and yellow
green= dominant
What is codominance?
2 different alleles occur for a gene, both of which are equally dominant
As a result, both alleles f the gene are expressed in the phenotype of the organism if present
What happens when a gene has more than 2 alleles?
this is called multiple alleles
an organism can only carry 2 of these alleles= one on each chromosome
EG. blood group has multiple alleles, the immunoglobulin gene codes for production of diff antigens present on surface of RBCs
groups A and B are codominant, and O is recessive so…
What are the sex chromosomes?
the 23rd pair is different between males and females
females= XX
males= XY
x chromosome= large and contains lots of genes not involved in sexual development
y chromosome= small, containing almost no genetic information, but does carry a gene that causes the embryo to develop as a male
How is the sex of offspring determined?
whether the sperm fertilising the egg contains a Y or X chromosome
What is sex linkage?
some characteristics are determined by genes carried on the sex chromosomes- these genes are sex linked
Y chromosome is much smaller than the X, there are number of genes on X that males only have one copy of, meaning that any characteristic caused by a recessive allele on the section of the X chromosome, which is missing the Y chromosome, occurs more frequently in males, as many females will also have a dominant allele present in their cells
What is haemophilia?
sex-linked genetic disorder
causes people to have blood which clots very slowly due to absence of protein blood-clotting factor
injury can result in prolonged bleeding= potentially fatal
If a male inherits the recessive allele that codes for haemophilia, they cannot have corresponding dom allele on their Y chromosome = develop the condition
Females can be sufferers if they are homozygous recessive for this alleles, and therefore can also pass it on to their children through this way also
when showing a sex linked
disease on genetic cross use letters X and Y to represent gender…
If there are no alleles attatchted to the Y chromosome, it doesnt carry the gene
Male offspring only inherit their X chromosome form their mother, if their mother carries a recessive allele for a disease on this X, and it doesnt exist on a Y, then the male offspring will also be sufferers
A faulty male (recessive) can pass on this to his daughter and them not be affected, only carriers, as they have another X chromosome, which may be dominant stopping them from suffering from the recessive condition
