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Term 3 Biology Recap
| Term | Definition |
|---|---|
| Gene | A segment of DNA which specifies the structure of a protein and contains an RNA molecule. Codes for an overall characteristic. |
| Allele | Alternate form of a gene/characteristic |
| Dominant gene | A gene for a particular characteristic that completely hides or masks the alternate gene |
| Recessive gene | A gene for a particular characteristic that is masked by the alternate gene |
| Phenotype | Physically displayed characteristic |
| Genotype | Types of gene in an organism |
| Homozygous | Genotype is two copies of the same allele |
| Heterozygous | Genotype is two copies of two different alleles |
| Phenotypic ratio for monohybrid cross | 3:1 |
| Four conditions for a monohybrid cross | Variation in trait is controlled by single gene Gene is on an autosome Two alleles of a gene One phenotype is dominant |
| Phenotypic ratio for dihybrid cross | 9:3:3:1 |
| Five conditions for a dihybrid cross | Two genes control two distinct traits Two different alleles for each of the genes For each trait one phenotype is dominant Both genes are autosomes Two genes assort independently |
| Incomplete Dominance | When genes for a particular characteristic are neither dominant nor recessive but combine to produce an intermediate colour/characteristic. E.g. Pink snapdragons |
| Co-dominance | Both alleles are expressed. E.g. roan cows |
| What should you do in exam when doing sex-linked inheritance? | Draw a key! |
| What types of females will be affected by an x-linked recessive disorder? | Only females who have homozygous recessive alleles |
| What is a female who is heterozygous x-linked recessive? | A carrier |
| Will males be affected? | Male is always affected if they inherit the gene |
| Pattern of inheritance typical of x-linked recessive disorders? | Female parent to male offspring |
| What females will be affected by x-linked dominant disorder? | Females who are homozygous dominant and heterozygous. |
| Will male offspring be affected if their father is affected by x-linked dominant? | No |
| Pattern of inheritance in y-linked disorders? | If trait is passed from father to son and never observed in females it is y-linked |
| Sex-limited inheritance | Only occurs in one sex because the feature is unique to that sense |
| What are pedigrees used for? | To follow inheritance of traits through a family over generations |
| If the condition is NOT observed in each generation of a family and the daughters have the condition and their father does NOT have the condition what pattern of inheritance is it? | Autosomal recessive |
| If the condition is NOT observed in each generation of a family and the daughters have the condition and their father DOES have the condition what pattern of inheritance is it? | X-linked recessive |
| If the condition is observed in each generation of a family and only the males have the condition what pattern of inheritance is it? | Y-linked |
| If the condition is observed in each generation of a family and both males and females have the condition and affected males mate with a normal female and have no sons with the condition what pattern of inheritance is it? | X-linked dominant |
| If the condition is observed in each generation of a family and both males and females have the condition and affected males mate with a normal female and have sons with the condition what pattern of inheritance is it? | Autosomal dominant |
| What creates a phenotype? | Genotype + environmental factors |
| How can meiosis go wrong? | When chromosomes don't separate |
Created by:
ceekayb
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