11. Genotype, Phenotype and Inheritance Flashcards
What is genotype?
• A genotype is an individual’s collection of genes
What is phenotype?
• the set of observable characteristics of an individual resulting from the interaction of it’s genotype with the environment.
What influences phenotypes?
Genotype and environment
Can the environment affect our genotype?
Yes - radiation, mutagenic chemicals, smoking
How many alleles are there of a gene?
2
How many allele of a gene are there in the population
Many
Define homozygous
Two alleles of a gene are the same
Define heterozygous
Two alleles of a gene are different
Define hemizygous
Only one allele of the gene on the X chromosome (Males only)
Define dominant
The dominant allele in heterozygote determines the phenotype (only one allele is needed to be expressed)
Define recessive
The non-dominant allele in a heterozygote is called recessive (Two of these alleles need to be present for the characteristic to be expressed)
Define co-dominance
When both alleles are expressed (neither is dominant or recessive)
What are the three alleles for blood type?
A B O
Which two alleles of blood type are codominant?
A and B
What are the different types of inheritance patterns?
Autosomal / sex-linked (Mendelian)
Mitochondrial
Polygenic / Complex or multifactorial
Give an example of an autosomal recessive disease
Cystic fibrosis
Give an example of an autosomal dominant disease
Huntington’s disease
Why are diseases rarely found in the dominant homozygous state?
Diseases with dominant homozygous are very bad that its not viable for life
What’s the chance that an affected individual has an affected offspring in an autosomal dominant disease?
50%
Can an autosomal dominant disease skip a generation?
No
Who are affected by x-linked recessive diseases?
Hemizygous males and homozygous
females affected
Who are x-linked recessive diseases more common in?
Males
What’s the chance of a heterozygous female carrier having affected sons of an x-linked recessive disease?
50%
What’s the chance of an affected male carrier having affected sons of an x-linked recessive disease?
0%
What is an example of an x-linked recessive disease?
Haemophilia A
Who are affected in x-linked dominant diseases?
Hemizygous males and heterozygous
females affected
Will affected males of x-linked dominant diseases give the trait to sons and daughters?
Affected males cannot give trait to sons,
but will give it to all their daughters
Who do all individuals inherit their mitochondria and mitochondrial DNA from?
From their mothers
What is the chance of children of a mother with a mitochondrial disease inherit the disease?
All the children will inherit it
What is the chance of children of a father with a mitochondrial disease inheriting the disease?
None of the children will be affected
What does polygenic mean?
When more than one gene is involved in producing a phenotype
Is albinism inherited in a dominant or recessive manner?
Recessive manner
When considering polygenic inheritance, what does linked and not linked mean?
• Genes on the same chromosome are
said to be ‘linked’
• Genes on different chromosomes are
said to be ‘not linked’
What types of genes do not show independent assortment at meiosis?
Linked genes
What is the recombinant frequency?
How often crossing over occurs
What is the recombinant frequency between two linked genes dependent on?
The instance between the genes
If two genes are close together, what is it called and what does t mean?
Tightly linked - the genes are more likely to travel together - less affected by crossing over
What happens if two genes on the same chromosome are far apart?
They almost behave as unlinked genes
Describe the effect of distance between genes on crossing over occurring
The further linked genes are apart, the more likely that crossing over occurs and more likely that new combinations are made
