Inheritance And Pedigrees Flashcards
What is a genotype?
Your genetic make up
What is a phenotype?
Physical characteristics
What is the cycle of DNA?
DNA (nucleus), RNA (nucleus), proteins (cytoplasm).
What is the difference between a gene and an allele?
A gene is a specific stretch of DNA that codes for a genotype e.g. Eye colour - we all have it. An allele is a variation of that gene e.g. Blue eyes, brown eyes. We all have the same genes but we all have different alleles for that gene.
What is homozygous?
Where the two alleles of a gene are the same.
What is heterozygous?
Where two alleles of the same gene are different.
What is hemizygous?
Refers to X chromosome - having a gene where. Only one copy is present (in males only).
What does dominant mean?
When the dominant allele determines the phenotype i.e. If you are a carrier of that allele then you have the disease.
What does recessive mean?
The non-dominant allele. Have to have two copies of the allele to be affected.
What is co-dominance?
Two alleles that are no dominant over one another e.g. In blood types, A and B have co-dominance.
What shape is an unknown sex in a pedigree?
A diamond
How can you tell someone is deceased in a pedigree?
They have a diagonal line through them from bottom left to top right.
How can you describe the location of a person on a pedigree?
Use numbers (1,2,3) to determine which generation (going down) and roman numerals (I,II,III) to determine where in that generation (going from left to right).
What is a heterozygote?
An individual who has two different alleles on one particular gene.
Name four characteristics of autosomal recessive inheritance and one disease example.
Males and females equally affected Can skip generations Can come 'out of nowhere' Both parents must be carriers Cystic fibrosis
Name five characteristics of autosomal dominant inheritance and one example of a disease.
Males and females equally affected
Heterozygotes affected (if carrier then affected)
Does not skip generations
Rarely found in homozygous state - not viable for life
Every affected individual has a 50% chance of passing the trait on
E.g. Huntington’s disease
Name six characteristics of x-linked recessive inheritance and a disease example.
More common in males
Hemizygous males and homozygous females affected
Heterozygous females have a 50% chance of passing the trait down to their son
Affected males cannot give trait to their sons
All affected daughters must have an affected father and a carrier mother
All daughters of affected males will at least be carriers
Haemophilia A
Number three characteristics of x-linked dominant inheritance and a disease example.
Hemizygous males and heterozygous females affected
Affected females have a 50% chance of passing onto offspring
Males CANNOT give the trait to sons but WILL give the trait to daughters.
Marfans
What is mitochondrial inheritance?
Mitochondrial DNA passed down only in mother so all individuals will inherit the trait from their mothers.
What is Y-linked inheritance?
Very rare (Y chromosome is very small) Only ever passed down from father to son
What is monogenic inheritance?
Characteristic produced by a single gene or allele.
What is polygenic inheritance?
Many genes involved in the expression of the trait (phenotype) e.g. Height and weight.
What affects the probability of recombination on the same chromosome?
DISTANCE - gene close together are ‘tightly linked’ therefore recombination is more likely. Gene far apart are far less likely to recombine.
