Inheritance (17) Flashcards
What is the genotype?
genetic construction of an organism
What is the phenotype?
expression of an organisms genetic constitution combined with its interaction with the environment
What is an allele?
different forms of a particular gene found at the same locus on a chromosome
How many alleles could a single gene have?
many
What is a diploid organism?
organism that carries 2 alleles per gene
What is a dominant allele?
allele whose characteristic will always appear in the phenotype, whether 1 or 2 are present
What is recessive allele?
allele whose characteristics only appears in the phenotype if no dominant allele is present
What are codominant alleles?
2 dominant alleles that both contribute to the phenotype, either by showing a blend of characteristics, or characteristics appearing together
What is meant by homozygous?
when both alleles dominant or both recessive
What is meant by heterozygous?
when one alleles is dominant and one recessive
What is meant by monohybrid inheritance?
when one phenotypic characteristic is controlled by a single gene
What 2 ratios does a monohybrid cross produce?
3:1
1:2:1 due to codominance
Is brown eyes phenotype, genotype, or gamete?
phenotype
Is Bb phenotype, genotype, or gamete?
genotype
Is B phenotype, genotype, or gamete?
gamete
What is meant by dihybrid inheritance?
where 2 phenotypic characteristics are determined by 2 different genes present on 2 different chromosomes at the same time
What are the 4 ratios that can result from a dihybrid cross punnet square?
9:3:3:1
3:1 due to linkage
9:3:4 due to epistasis
12:3:1 due to epistasis
What is sex-linkage?
where an allele is located on 1 of the sex chromosomes, meaning its expression depends on the individual’s sex
Which chromosome is the sex chromosome?
23rd chromosome
Why are males more likely to express recessive sex-linked allele?
most sex-linked alleles are located on the X chromosome, therefore males only get one copy of the allele, so will express this characteristics even if it’s recessive - females get 2 alleles so this is less likely
Which parents do males inherit sex-linked characteristics from and why?
their mother since the Y chromosome can only come from their father, therefore if mother is heterozygous for sex-linked alleles - she is a carrier and may pass the trait on
What is autosomal linkage?
where 2 or more genes are located on the same non-sex chromosome
Which are the non-sex chromosomes?
the first 22 chromosomes
What is epistasis?
where 2 non-linked genes interact, with one gene either masking or suppressing the other gene
What are the 2 types of epistasis?
recessive epistasis
dominant epistasis
What is recessive epistasis?
where 2 homozygous recessive alleles mask the expression of another allele
What is dominant epistasis?
where 1 dominant allele masks the expression of multiple other alleles
What is the chi-squared test?
statistical test to find out whether the difference between observed and expected data is due to chance or a real effect
What are the 4 criteria for chi-squared test?
- categorical data
- large sample
- only raw count data allowed (e.g. not percentages)
- no data values = 0
What are the 2 steps in performing a chi-squared test?
1) formula results in a number
2) compare number to critical value for the corresponding degree of freedom
If the p is less than or equal to 0.05, what does this mean?
significant difference
not due to chance
reject null hypothesis
If the p is more than 0.05, what does this mean?
no significant difference
due to chance
accept null hypothesis
How can the chi-squared test be used for investigating inheritance?
we can compare expected ratios with observed ratios to test our understanding of how different genes and alleles are inherited
