Inherited Change (Chapter 17) Flashcards
Define Gene
Section of DNA that codes for a polypeptide
Define Allele
A version of a gene
Define Genotype
The genetic makeup of an organism
Define Phenotype
Person’s appearance due to their environment and genotype
Define Homozygous
When the alleles of a particular gene are identical
Define Heterozygous
When the alleles of a particular gene are different
Define Haploid
When cells have one copy of each chromosome
Define Diploid
When cells have two copies of each chromosome
What is the difference between dominant and recessive alleles?
Dominant are always shown in the phenotype but recessive are only shown in the phenotype if there are no dominant alleles.
Define Co-Dominance
When both alleles are expressed in the phenotype
How are co-dominant alleles shown?
Using superscript letters
Define Multiple Alleles
A gene with more than two possible alleles
Define Sex-Linked Genes
Any gene found on X or Y chromosome
What causes sex-linked conditions?
Mutation of a gene on X chromosomes. The mutation usually leads to a non-functional protein being made. Males will only have one X chromosome so only needs one allele that codes for non-functional [roetins so more likely to have the condition.
Why are drosophila used in experiments?
- Short lifecycle
- Small space needed
- Lays lots of eggs
- Not endangered
What are some of the assumptions of the Hardy Weinberg technique?
- Random mating
- No mutations
- Large population
- Population genetically isolated
- No migration
What is some evidence that proves a gene is recessive?
2 parents don’t have the condition but their child does - parents must be carriers/both parents have the condition, so all their children must too
What is some evidence that proves a gene is dominant?
2 parents have the condition but their child does not
What is some evidence that proves a gene is sex-linked?
- Dad always passes X chromosome to daughter, so if dad has a dominant condition, daughter will have it too (
- Mum gives son X chromosome so if mum has a recessive allele, she always gives to son.
What is Weinburg’s prediction?
Frequency of alleles will stay constant from one generation to next.
What is the Hardy-Weinberg equation?
p2 + 2pq + q2 = 1
Describe monohybrid inheritance
- One gene
* Dominant and recessive in 3:1 ratio with heterozygous parents
Describe dihybrid inheritance
- Two genes on different chromosomes
- Independent characteristics - one does not control the other
• Heterozygous parents produce gametes in 9:3:3:1
9 = two dominant alleles e.g. BbNn
3 = 1 dominant and 1 recessive e.g. Bbnn or bbNN
1 =2 recessive e.g. bbnn
Describe multiple alleles
Three or more phenotypes present
