Patterns of Inheritance Flashcards
What does the genotype influence?
The phenotype
What is the phenotype?
What it looks like
What does the environment influence?
The genotype and the phenotype
Give 5 environmental factors
- Radiation
- Mutagens
- Chemicals affecting cell growth
- Diet
- Life style
Give an example of how an environmental factor can influence the DNA
Radiation can damage DNA
Give an example of a disease that is purely genetic
Cystic fibrosis
Give an example of a disease that is purely environmental
Infection
Give 2 examples of diseases that are a mixture of genetic and environmental factors
NAME?
What are genetics down to?
NAME?
What is variation caused by?
NAME?
How many genes does each human have?
25,000
How many copies of each gene does each individual have?
2
Where do the 2 copies of each gene come from?
One maternal, one paternal
What does each individual have of each gene?
2 alleles
How many alleles of a gene are there within a population?
Many
What does homozygous mean?
Two alleles of a gene are the same
What does heterozygous mean?
Two alleles of a gene are different
What does hemizygous mean?
Only one allele of a gene on the X chromosome
What does dominant mean?
The allele that determines the phenotype in heterozygote
What does recessive mean?
The non-dominant allele
Is the heterozygote affected in an autosomal recessive disease?
No
Are males or females more affected in an autosomal recessive condition?
Equal
What is the chance of two heterozygotes having a child affected with an autosomal recessive condition?
25%
What is chance of two individuals affected by an autosomal recessive condition having affected children?
100%
Are heterozygotes affected with an autosomal dominant condition?
Yes
Is an autosomal dominant disease usually found in the homozygous state?
No
Why is an autosomal dominant disease not usually found in the homozygous state?
Often, disease is so important, that the homozygous state is incompatible with life
What is the chance of an affected individual having affected offspring in the case of an autosomal dominant disease?
50%
What does every individual affected with an autosomal dominant condition have?
At least 1 affected parent
Can an autosomal dominant disease skip a generation?
No
Who is affected with an X-linked recessive disease?
Hemizygous males and homozygous females
Who is a X-linked recessive disease more common in?
Males
What is the chance of a heterozygous female carrier or an X-linked recessive disease having an affected son?
50%
Can a male affected with a X-linked recessive disease give the trait to their sons?
No
Why can’ta male affected with a X-linked recessive disease give the trait to their sons?
Because the trait is on the X chromosome, but males can only give the Y chromosome to their songs
What does every female affected with an X-linked recessive disease have?
A carrier mother and an affected father
What is the genotype of daughters of males with an X-linked recessive condition?
Heterozygous
What is co-dominance?
When both alleles contribute to the phenotype
Give an example of where co-dominance is shown?
In blood types
What is complementation?
When more than one gene contributes to the phenotype
Give an example of where complementation is found?
Albinism
How does complementation work?
A gene may code for an enzyme that converts the substrate to an intermediate. Another gene may code for a different enzyme that converts the intermediate to the product. Therefore, both genes have contributed
What is said of genes on the same chromosome?
They are ‘linked’
Do linked genes show independent assortment at meiosis?
No
Why don’t linked genes show independent assortment at meiosis?
Because they are carried together
Why do you only have two combinations of gametes with linked genes?
As the alleles are carried together
How can you get other combinations with linked genes?
If crossing over between locus of the linked genes
Why is the ratio of gametes for linked genes not 1:1:1:1?
Because dependant on how often crossing over occurs
What is recombination frequency between two linked genes dependant on?
The distance between two genes
What is said of genes close together?
They are ‘tightly linked’
How do genes far apart on the same chromosome behave as?
Almost as unlinked genes
