7.1 Inheritance Flashcards
Define genotype
The genetic constitution of an organism
Define phenotype
The expression of the genotype, and it’s interaction with the enviroment
Define Dominant Allele
Always expressed in the phenotype
Expected offspring phenotype ratio for heterozygous monohybrid cross
3:1
Expected offspring phenotype ratio for heterozygous dihybrid cross
9:3:3:1
How to produce gametes for dihybrid cross
All combinations possible for each parent
Expected offspring phenotype ratio for pure white and pure red co-dominant cross
100% roan
What sex chromosomes do female humans have
XX
What sex chromosomes do male humans have
XY
Where are sex-linked genes located
Non-homologous section of the X chromosome
Why are males more likely to show recessive sex-linked characteristics than females
- Chromosomes are homologous in females
- Male has one allele for sex gene
- Recessive allele is always expressed in males
- Females need two recessive alleles for allele to be expressed
Why do X and Y chromosomes not form a typical bivalent
- X and Y chromosomes are different sizes
- Chromatids are unable to line up and form bivalent
- Short pairing reigon means most of length not homologous
Draw a cross and expected offspring phenotype ratio for RECESSIVE SEX-LINKED cross, with female carrier and unaffected male
What is autosomal linkage
Two genes located on the same chromosome (genes are linked)
What is epistasis
When the allele of one gene may mask the expession of another gene in the phenotype
What does it mean when p < 0.05 in a chi-squared test
- Reject the null hypothesis
- Is a significant difference btween the observed and expected values
What does it mean when p > 0.05 in a chi-squared test
- Accept the null hypothesis
- There is no significant difference between the observed and expected values
What reasons are there for why the observed phenotypic ratios are not the same as expected ones
- Lethal genotypes / lethal alleles
- Epistasis
- Random fertilisation of gametes
- Small populations
