Inheritence/genes Flashcards
What is the law of segregation?
In diploid organisms, characteristics are determined by alleles that occur in pairs.
-only applies for monohybrid inheritance
-only one of each pair of alleles can be present in a single gamete
What does homologous mean? (In homologous chromosomes)
Pair of chromosomes, one from each parent, that have the same genes
What are multiple alleles
When there is more than two allelic forms
Why do you NOT get the expected ratio when carrying out genetic crosses
-each fertilisation is independent
-mutation can occur
What is the Chi-squared test and what are the rules for using it?
-statistical test to potentially show a relationship between observed and expected data
-must have
-large sample size
-discrete data (categorical)
-raw numbers only
How to calculate degrees of freedom?
Number of categories - 1
What is dihybrid inheritance?
Inheritance of two different characteristics controlled by two different genes
What is co-dominance
Where both alleles are expressed in the phenotype if present
What is an example of multiple alleles and its definition
-more than two allelic forms for a characteristic (however only two can be present in an individual)
-blood type, A B AB and O
What is autosomal linkage
when there are two gene loci found on the same autosomal chromosome
What is an autosome
A chromosome that isnt a sex chromosome
What is epistasis
the interaction between two non-linked genes which causes one gene to mask the expression of the other in the phenotype
Why is a male more likely to develop haemophilia than a female?
-the condition is caused by a gene on the X chromosome (recessive)
-Male chromosomes only contain one ALLELE as they only have one X chromosome.
-only needs one recessive allele present to develop condition whilst female needs both recessive alleles, which is more unlikely
EQ: in fruit flies, the genes for body colour (G and g) and wing length (N and n) are linked.
Crossing fruit flies heterozygous to both genes with fruit flies homozygous recessive to these traits produces majority:
-heterozygous for both or homozygous recessive for both
Explain why these are more common than homozygous or heterozygous for only one of the two traits
-autosomal linkage
-GN and gn are linked
-produce mainly GN and gn gametes
-crossing over produces a few Gn and gN gametes
-so fewer Ggnn or ggNn individuals
