7.1 - Inheritance Flashcards
Define genotype
The genetic constituition of an organism
Define phenotype
The expression of an organism’s genetic constituition, combined with its interaction with the environment.
What is an allele?
Different forms of a particular gene, found at the same locus (positon) on a chromosome. A single gene could have many alleles.
How many alleles per gene do diploid organisms carry?
2
What is meant b a dominant allele?
An allele whose characteristic will always appear in the phenotype, whether one or 2 are present.
What is meant by a recessive allele?
An allele whose characteristic oly appears in the phenotype if no dominant allele is present, meaning 2 must be present.
What is meant by codominant alleles?
2 dominant alleles that both contribute to the phenotype, either by shwing a blend of both characteristics or the characteristics appearing together.
What is meant by homozygous and heterozygous?
Homozygous = both alleles are dominant or both alleles are recessive.
Heterozygous = one allele is dominant, the other is recessive.
Define monohybrid inheritance.
Where one phenotypic characteristic is controlles by a single gene.
Draw a Punnett square to show a monohybrid cross with parental genotype of GG and gg.
Should have GG on top line and gg on the side.
All middle boxes should have Gg
What % of these offspring will express te characteristic determined by allele G?
reffering to flashcard 10
100%
All potential offspring genotypes are Gg meaning none of them will express the recessive allele.
Define dihybrid inheritance.
Where 2 phenotypic characteristics are determined by 2 different genes present on 2 different chromosomes at the same time.
What is meant by sex-linkage?
Where an allele is located on one of the sex chromosomes, meaning itsexpression depends on the sex of the inividual.
Why are males more likely to express a recessive sex-linkage allele?
Most sex-linked alleles are located on the X chromosome. Therefore males only get one copy of the allele, so will express this characteristic even if its recessive. Since females get 2 alleles, this is very likely.
Which parent do males inherit sex-linked characteristics from?
Their mother, since the Y chromosome can only come from their father. Therefore, if the mother is heterozygous for sex-linked alleles, she is a carrier and may pass on the trait.
What is meant by autosomal linkage?
Where 2 or more genes are locates on the same (non-sex) chromosome. In this case, only one hoologous pair is needed for all 4 alleles to be present. For genes that aren’t linked, 2 homologous pairs are needed.
What is meant by epistasis?
Where 2 non-linked genes interact, with one gene either masking or suppressing the other gene.
Define the 2 types of epistasis
- Recessive epistasis = where 2 homozygous recessive alleles mask expression of another allele.
- Dominant epistasis = where one dominant allele masks expression of multiple other alleles.
What is the chi-squared test?
A statistical test to find out whether the difference between observed and expected data is due to chance or a real effect.
What are the criteria for the chi-squared test?
- Data placed in discrete categories
- Largw sample size
- Only raw count data allowed i.e not percentages
- No data values equal 0
How is a chi-squared test perfomed?
The formula results in a number, which is then compared to a critical value. If the number is greater than or equal to the critical value, we conclude there is a significant difference between the observed and expected data and that the results did not occur due to chance.
How can we use a chi-squared test in relation to the content of this topic?
We can compare expected phenotypic ratios with observed ratios to test our understanding of how different genes and alleles are inherited.
