Genetic Screening Flashcards
What are Pedigree charts used for ?
To analyse patterns of inheritance in genetic screening and counselling
How can a pattern of inheritance be revealed?
By collecting information about a particular characteristic from the family members or the information used to construct a family tree
When can most genotypes be determined ?
Once phenotypes are know
What does a genetic counsellor do?
Construct a family tree
Uses information from the family tree to advise parents of the possibility of passing a genetic condition to their child
What do pedigree charts show ?
Sex Matings Siblings Affected individuals Twins Heterozygotes Carrier of sex linked allele Deceased
What does autosomal inheritance mean?
genes carried by normal body cells
What does recessive mean ?
A gene whose effect does not show it there is a dominant allele too, a recessive characteristic only shows if there are two recessive genes , traditionally represented by small letters.
What does the term dominant mean?
A gene whose effect always shows, they are normally represented by capital letters
What is an example of autosomal recessive inheritance ?
Cystic fibrosis
What does homozygous mean?
Both genes for a particular characteristic are the same
What does heterozygous mean?
The two alleles are different, one dominant, one recessive
What appears in every generation?
Autosomal dominant inheritance
What is an example of autosomal dominant inheritance?
Huntington’s chorea
What is incomplete dominance ?
Where the recessive gene still has an effect and there is an intermediate phenotype
What is an example of autosomal incomplete dominance ?
Sickle cell anaemia
What is an example of sex linked recessive trait?
Haemophillia
How are sex linked genetic problems different ?
Only the X chromosomes carry an effective gene
Female chromosomes?
They have Two X chromosomes
Male chromosomes?
They have an X chromosome and a much shorter Y chromosome which has fewer genes
What is likely to happen if one female X chromosome has a recessive gene?
The other X chromosome will have a dominant gene to prevent the recessive condition having an effect
What will happen if a male has a recessive gene on their only X chromosome?
There will be no allele in the shorter Y chromosome and so the condition will show in their phenotype
Which chromosomes do males receive from their parents?
Y from their father
X from their mother
What will sons always inherit from their mothers if there is any recessive genes on their X chromosome?
The sex linked condition
What are females who are normal for a given characteristic and heterozygous known as?
A carrier
